/*
* The simplest AC-3 encoder
* Copyright (c) 2000 Fabrice Bellard
+ * Copyright (c) 2006-2010 Justin Ruggles <justin.ruggles@gmail.com>
+ * Copyright (c) 2006-2010 Prakash Punnoor <prakash@punnoor.de>
*
* This file is part of FFmpeg.
*
* @file
* The simplest AC-3 encoder.
*/
+
//#define DEBUG
-//#define DEBUG_BITALLOC
+
#include "libavcore/audioconvert.h"
#include "libavutil/crc.h"
#include "avcodec.h"
-#include "libavutil/common.h" /* for av_reverse */
#include "put_bits.h"
+#include "dsputil.h"
#include "ac3.h"
#include "audioconvert.h"
+
+/** Maximum number of exponent groups. +1 for separate DC exponent. */
+#define AC3_MAX_EXP_GROUPS 85
+
+/** Scale a float value by 2^bits and convert to an integer. */
+#define SCALE_FLOAT(a, bits) lrintf((a) * (float)(1 << (bits)))
+
+typedef int16_t SampleType;
+typedef int32_t CoefType;
+
+#define SCALE_COEF(a) (a)
+
+/** Scale a float value by 2^15, convert to an integer, and clip to range -32767..32767. */
+#define FIX15(a) av_clip(SCALE_FLOAT(a, 15), -32767, 32767)
+
+
+/**
+ * Compex number.
+ * Used in fixed-point MDCT calculation.
+ */
+typedef struct IComplex {
+ int16_t re,im;
+} IComplex;
+
+typedef struct AC3MDCTContext {
+ const int16_t *window; ///< MDCT window function
+ int nbits; ///< log2(transform size)
+ int16_t *costab; ///< FFT cos table
+ int16_t *sintab; ///< FFT sin table
+ int16_t *xcos1; ///< MDCT cos table
+ int16_t *xsin1; ///< MDCT sin table
+ int16_t *rot_tmp; ///< temp buffer for pre-rotated samples
+ IComplex *cplx_tmp; ///< temp buffer for complex pre-rotated samples
+} AC3MDCTContext;
+
+/**
+ * Data for a single audio block.
+ */
+typedef struct AC3Block {
+ uint8_t **bap; ///< bit allocation pointers (bap)
+ CoefType **mdct_coef; ///< MDCT coefficients
+ uint8_t **exp; ///< original exponents
+ uint8_t **grouped_exp; ///< grouped exponents
+ int16_t **psd; ///< psd per frequency bin
+ int16_t **band_psd; ///< psd per critical band
+ int16_t **mask; ///< masking curve
+ uint16_t **qmant; ///< quantized mantissas
+ uint8_t exp_strategy[AC3_MAX_CHANNELS]; ///< exponent strategies
+ int8_t exp_shift[AC3_MAX_CHANNELS]; ///< exponent shift values
+} AC3Block;
+
+/**
+ * AC-3 encoder private context.
+ */
typedef struct AC3EncodeContext {
- PutBitContext pb;
-
- int bitstream_id;
- int bitstream_mode;
-
- int bit_rate;
- int sample_rate;
- int sr_shift;
- int sr_code; /* frequency */
-
- int frame_size_min; /* minimum frame size in case rounding is necessary */
- int frame_size; /* current frame size in words */
- int frame_size_code;
- int bits_written;
- int samples_written;
-
- int fbw_channels;
- int channels;
- int lfe_on;
- int lfe_channel;
- int channel_mode;
- const uint8_t *channel_map;
-
- int bandwidth_code[AC3_MAX_CHANNELS];
+ PutBitContext pb; ///< bitstream writer context
+ DSPContext dsp;
+ AC3MDCTContext mdct; ///< MDCT context
+
+ AC3Block blocks[AC3_MAX_BLOCKS]; ///< per-block info
+
+ int bitstream_id; ///< bitstream id (bsid)
+ int bitstream_mode; ///< bitstream mode (bsmod)
+
+ int bit_rate; ///< target bit rate, in bits-per-second
+ int sample_rate; ///< sampling frequency, in Hz
+
+ int frame_size_min; ///< minimum frame size in case rounding is necessary
+ int frame_size; ///< current frame size in bytes
+ int frame_size_code; ///< frame size code (frmsizecod)
+ uint16_t crc_inv[2];
+ int bits_written; ///< bit count (used to avg. bitrate)
+ int samples_written; ///< sample count (used to avg. bitrate)
+
+ int fbw_channels; ///< number of full-bandwidth channels (nfchans)
+ int channels; ///< total number of channels (nchans)
+ int lfe_on; ///< indicates if there is an LFE channel (lfeon)
+ int lfe_channel; ///< channel index of the LFE channel
+ int channel_mode; ///< channel mode (acmod)
+ const uint8_t *channel_map; ///< channel map used to reorder channels
+
+ int cutoff; ///< user-specified cutoff frequency, in Hz
+ int bandwidth_code[AC3_MAX_CHANNELS]; ///< bandwidth code (0 to 60) (chbwcod)
int nb_coefs[AC3_MAX_CHANNELS];
/* bitrate allocation control */
- int slow_gain_code, slow_decay_code, fast_decay_code, db_per_bit_code, floor_code;
- AC3BitAllocParameters bit_alloc;
- int coarse_snr_offset;
- int fast_gain_code[AC3_MAX_CHANNELS];
- int fine_snr_offset[AC3_MAX_CHANNELS];
+ int slow_gain_code; ///< slow gain code (sgaincod)
+ int slow_decay_code; ///< slow decay code (sdcycod)
+ int fast_decay_code; ///< fast decay code (fdcycod)
+ int db_per_bit_code; ///< dB/bit code (dbpbcod)
+ int floor_code; ///< floor code (floorcod)
+ AC3BitAllocParameters bit_alloc; ///< bit allocation parameters
+ int coarse_snr_offset; ///< coarse SNR offsets (csnroffst)
+ int fast_gain_code[AC3_MAX_CHANNELS]; ///< fast gain codes (signal-to-mask ratio) (fgaincod)
+ int fine_snr_offset[AC3_MAX_CHANNELS]; ///< fine SNR offsets (fsnroffst)
+ int frame_bits_fixed; ///< number of non-coefficient bits for fixed parameters
+ int frame_bits; ///< all frame bits except exponents and mantissas
+ int exponent_bits; ///< number of bits used for exponents
/* mantissa encoding */
- int mant1_cnt, mant2_cnt, mant4_cnt;
-
- int16_t last_samples[AC3_MAX_CHANNELS][256];
+ int mant1_cnt, mant2_cnt, mant4_cnt; ///< mantissa counts for bap=1,2,4
+ uint16_t *qmant1_ptr, *qmant2_ptr, *qmant4_ptr; ///< mantissa pointers for bap=1,2,4
+
+ int16_t **planar_samples;
+ uint8_t *bap_buffer;
+ uint8_t *bap1_buffer;
+ CoefType *mdct_coef_buffer;
+ uint8_t *exp_buffer;
+ uint8_t *grouped_exp_buffer;
+ int16_t *psd_buffer;
+ int16_t *band_psd_buffer;
+ int16_t *mask_buffer;
+ uint16_t *qmant_buffer;
+
+ DECLARE_ALIGNED(16, SampleType, windowed_samples)[AC3_WINDOW_SIZE];
} AC3EncodeContext;
-static int16_t costab[64];
-static int16_t sintab[64];
-static int16_t xcos1[128];
-static int16_t xsin1[128];
-#define MDCT_NBITS 9
-#define N (1 << MDCT_NBITS)
+/**
+ * LUT for number of exponent groups.
+ * exponent_group_tab[exponent strategy-1][number of coefficients]
+ */
+static uint8_t exponent_group_tab[3][256];
+
+
+/**
+ * List of supported channel layouts.
+ */
+static const int64_t ac3_channel_layouts[] = {
+ AV_CH_LAYOUT_MONO,
+ AV_CH_LAYOUT_STEREO,
+ AV_CH_LAYOUT_2_1,
+ AV_CH_LAYOUT_SURROUND,
+ AV_CH_LAYOUT_2_2,
+ AV_CH_LAYOUT_QUAD,
+ AV_CH_LAYOUT_4POINT0,
+ AV_CH_LAYOUT_5POINT0,
+ AV_CH_LAYOUT_5POINT0_BACK,
+ (AV_CH_LAYOUT_MONO | AV_CH_LOW_FREQUENCY),
+ (AV_CH_LAYOUT_STEREO | AV_CH_LOW_FREQUENCY),
+ (AV_CH_LAYOUT_2_1 | AV_CH_LOW_FREQUENCY),
+ (AV_CH_LAYOUT_SURROUND | AV_CH_LOW_FREQUENCY),
+ (AV_CH_LAYOUT_2_2 | AV_CH_LOW_FREQUENCY),
+ (AV_CH_LAYOUT_QUAD | AV_CH_LOW_FREQUENCY),
+ (AV_CH_LAYOUT_4POINT0 | AV_CH_LOW_FREQUENCY),
+ AV_CH_LAYOUT_5POINT1,
+ AV_CH_LAYOUT_5POINT1_BACK,
+ 0
+};
+
+
+/**
+ * Adjust the frame size to make the average bit rate match the target bit rate.
+ * This is only needed for 11025, 22050, and 44100 sample rates.
+ */
+static void adjust_frame_size(AC3EncodeContext *s)
+{
+ while (s->bits_written >= s->bit_rate && s->samples_written >= s->sample_rate) {
+ s->bits_written -= s->bit_rate;
+ s->samples_written -= s->sample_rate;
+ }
+ s->frame_size = s->frame_size_min +
+ 2 * (s->bits_written * s->sample_rate < s->samples_written * s->bit_rate);
+ s->bits_written += s->frame_size * 8;
+ s->samples_written += AC3_FRAME_SIZE;
+}
-/* new exponents are sent if their Norm 1 exceed this number */
-#define EXP_DIFF_THRESHOLD 1000
-static inline int16_t fix15(float a)
+/**
+ * Deinterleave input samples.
+ * Channels are reordered from FFmpeg's default order to AC-3 order.
+ */
+static void deinterleave_input_samples(AC3EncodeContext *s,
+ const SampleType *samples)
{
- int v;
- v = (int)(a * (float)(1 << 15));
- if (v < -32767)
- v = -32767;
- else if (v > 32767)
- v = 32767;
- return v;
+ int ch, i;
+
+ /* deinterleave and remap input samples */
+ for (ch = 0; ch < s->channels; ch++) {
+ const SampleType *sptr;
+ int sinc;
+
+ /* copy last 256 samples of previous frame to the start of the current frame */
+ memcpy(&s->planar_samples[ch][0], &s->planar_samples[ch][AC3_FRAME_SIZE],
+ AC3_BLOCK_SIZE * sizeof(s->planar_samples[0][0]));
+
+ /* deinterleave */
+ sinc = s->channels;
+ sptr = samples + s->channel_map[ch];
+ for (i = AC3_BLOCK_SIZE; i < AC3_FRAME_SIZE+AC3_BLOCK_SIZE; i++) {
+ s->planar_samples[ch][i] = *sptr;
+ sptr += sinc;
+ }
+ }
}
-typedef struct IComplex {
- int16_t re,im;
-} IComplex;
-static av_cold void fft_init(int ln)
+/**
+ * Finalize MDCT and free allocated memory.
+ */
+static av_cold void mdct_end(AC3MDCTContext *mdct)
+{
+ mdct->nbits = 0;
+ av_freep(&mdct->costab);
+ av_freep(&mdct->sintab);
+ av_freep(&mdct->xcos1);
+ av_freep(&mdct->xsin1);
+ av_freep(&mdct->rot_tmp);
+ av_freep(&mdct->cplx_tmp);
+}
+
+
+/**
+ * Initialize FFT tables.
+ * @param ln log2(FFT size)
+ */
+static av_cold int fft_init(AVCodecContext *avctx, AC3MDCTContext *mdct, int ln)
{
- int i, n;
+ int i, n, n2;
float alpha;
- n = 1 << ln;
+ n = 1 << ln;
+ n2 = n >> 1;
+
+ FF_ALLOC_OR_GOTO(avctx, mdct->costab, n2 * sizeof(*mdct->costab), fft_alloc_fail);
+ FF_ALLOC_OR_GOTO(avctx, mdct->sintab, n2 * sizeof(*mdct->sintab), fft_alloc_fail);
+
+ for (i = 0; i < n2; i++) {
+ alpha = 2.0 * M_PI * i / n;
+ mdct->costab[i] = FIX15(cos(alpha));
+ mdct->sintab[i] = FIX15(sin(alpha));
+ }
+
+ return 0;
+fft_alloc_fail:
+ mdct_end(mdct);
+ return AVERROR(ENOMEM);
+}
+
+
+/**
+ * Initialize MDCT tables.
+ * @param nbits log2(MDCT size)
+ */
+static av_cold int mdct_init(AVCodecContext *avctx, AC3MDCTContext *mdct,
+ int nbits)
+{
+ int i, n, n4, ret;
+
+ n = 1 << nbits;
+ n4 = n >> 2;
+
+ mdct->nbits = nbits;
- for(i=0;i<(n/2);i++) {
- alpha = 2 * M_PI * (float)i / (float)n;
- costab[i] = fix15(cos(alpha));
- sintab[i] = fix15(sin(alpha));
+ ret = fft_init(avctx, mdct, nbits - 2);
+ if (ret)
+ return ret;
+
+ mdct->window = ff_ac3_window;
+
+ FF_ALLOC_OR_GOTO(avctx, mdct->xcos1, n4 * sizeof(*mdct->xcos1), mdct_alloc_fail);
+ FF_ALLOC_OR_GOTO(avctx, mdct->xsin1, n4 * sizeof(*mdct->xsin1), mdct_alloc_fail);
+ FF_ALLOC_OR_GOTO(avctx, mdct->rot_tmp, n * sizeof(*mdct->rot_tmp), mdct_alloc_fail);
+ FF_ALLOC_OR_GOTO(avctx, mdct->cplx_tmp, n4 * sizeof(*mdct->cplx_tmp), mdct_alloc_fail);
+
+ for (i = 0; i < n4; i++) {
+ float alpha = 2.0 * M_PI * (i + 1.0 / 8.0) / n;
+ mdct->xcos1[i] = FIX15(-cos(alpha));
+ mdct->xsin1[i] = FIX15(-sin(alpha));
}
+
+ return 0;
+mdct_alloc_fail:
+ mdct_end(mdct);
+ return AVERROR(ENOMEM);
}
-/* butter fly op */
-#define BF(pre, pim, qre, qim, pre1, pim1, qre1, qim1) \
-{\
- int ax, ay, bx, by;\
- bx=pre1;\
- by=pim1;\
- ax=qre1;\
- ay=qim1;\
- pre = (bx + ax) >> 1;\
- pim = (by + ay) >> 1;\
- qre = (bx - ax) >> 1;\
- qim = (by - ay) >> 1;\
+
+/** Butterfly op */
+#define BF(pre, pim, qre, qim, pre1, pim1, qre1, qim1) \
+{ \
+ int ax, ay, bx, by; \
+ bx = pre1; \
+ by = pim1; \
+ ax = qre1; \
+ ay = qim1; \
+ pre = (bx + ax) >> 1; \
+ pim = (by + ay) >> 1; \
+ qre = (bx - ax) >> 1; \
+ qim = (by - ay) >> 1; \
}
-#define CMUL(pre, pim, are, aim, bre, bim) \
-{\
- pre = (MUL16(are, bre) - MUL16(aim, bim)) >> 15;\
- pim = (MUL16(are, bim) + MUL16(bre, aim)) >> 15;\
+
+/** Complex multiply */
+#define CMUL(pre, pim, are, aim, bre, bim) \
+{ \
+ pre = (MUL16(are, bre) - MUL16(aim, bim)) >> 15; \
+ pim = (MUL16(are, bim) + MUL16(bre, aim)) >> 15; \
}
-/* do a 2^n point complex fft on 2^ln points. */
-static void fft(IComplex *z, int ln)
+/**
+ * Calculate a 2^n point complex FFT on 2^ln points.
+ * @param z complex input/output samples
+ * @param ln log2(FFT size)
+ */
+static void fft(AC3MDCTContext *mdct, IComplex *z, int ln)
{
- int j, l, np, np2;
- int nblocks, nloops;
+ int j, l, np, np2;
+ int nblocks, nloops;
register IComplex *p,*q;
int tmp_re, tmp_im;
np = 1 << ln;
/* reverse */
- for(j=0;j<np;j++) {
+ for (j = 0; j < np; j++) {
int k = av_reverse[j] >> (8 - ln);
if (k < j)
FFSWAP(IComplex, z[k], z[j]);
/* pass 0 */
- p=&z[0];
- j=(np >> 1);
+ p = &z[0];
+ j = np >> 1;
do {
BF(p[0].re, p[0].im, p[1].re, p[1].im,
p[0].re, p[0].im, p[1].re, p[1].im);
- p+=2;
- } while (--j != 0);
+ p += 2;
+ } while (--j);
/* pass 1 */
- p=&z[0];
- j=np >> 2;
+ p = &z[0];
+ j = np >> 2;
do {
- BF(p[0].re, p[0].im, p[2].re, p[2].im,
- p[0].re, p[0].im, p[2].re, p[2].im);
- BF(p[1].re, p[1].im, p[3].re, p[3].im,
+ BF(p[0].re, p[0].im, p[2].re, p[2].im,
+ p[0].re, p[0].im, p[2].re, p[2].im);
+ BF(p[1].re, p[1].im, p[3].re, p[3].im,
p[1].re, p[1].im, p[3].im, -p[3].re);
p+=4;
- } while (--j != 0);
+ } while (--j);
/* pass 2 .. ln-1 */
nblocks = np >> 3;
- nloops = 1 << 2;
- np2 = np >> 1;
+ nloops = 1 << 2;
+ np2 = np >> 1;
do {
p = z;
q = z + nloops;
- for (j = 0; j < nblocks; ++j) {
-
+ for (j = 0; j < nblocks; j++) {
BF(p->re, p->im, q->re, q->im,
p->re, p->im, q->re, q->im);
-
p++;
q++;
for(l = nblocks; l < np2; l += nblocks) {
- CMUL(tmp_re, tmp_im, costab[l], -sintab[l], q->re, q->im);
- BF(p->re, p->im, q->re, q->im,
+ CMUL(tmp_re, tmp_im, mdct->costab[l], -mdct->sintab[l], q->re, q->im);
+ BF(p->re, p->im, q->re, q->im,
p->re, p->im, tmp_re, tmp_im);
p++;
q++;
q += nloops;
}
nblocks = nblocks >> 1;
- nloops = nloops << 1;
- } while (nblocks != 0);
+ nloops = nloops << 1;
+ } while (nblocks);
}
-/* do a 512 point mdct */
-static void mdct512(int32_t *out, int16_t *in)
+
+/**
+ * Calculate a 512-point MDCT
+ * @param out 256 output frequency coefficients
+ * @param in 512 windowed input audio samples
+ */
+static void mdct512(AC3MDCTContext *mdct, int32_t *out, int16_t *in)
{
- int i, re, im, re1, im1;
- int16_t rot[N];
- IComplex x[N/4];
+ int i, re, im, n, n2, n4;
+ int16_t *rot = mdct->rot_tmp;
+ IComplex *x = mdct->cplx_tmp;
+
+ n = 1 << mdct->nbits;
+ n2 = n >> 1;
+ n4 = n >> 2;
/* shift to simplify computations */
- for(i=0;i<N/4;i++)
- rot[i] = -in[i + 3*N/4];
- for(i=N/4;i<N;i++)
- rot[i] = in[i - N/4];
+ for (i = 0; i <n4; i++)
+ rot[i] = -in[i + 3*n4];
+ memcpy(&rot[n4], &in[0], 3*n4*sizeof(*in));
/* pre rotation */
- for(i=0;i<N/4;i++) {
- re = ((int)rot[2*i] - (int)rot[N-1-2*i]) >> 1;
- im = -((int)rot[N/2+2*i] - (int)rot[N/2-1-2*i]) >> 1;
- CMUL(x[i].re, x[i].im, re, im, -xcos1[i], xsin1[i]);
+ for (i = 0; i < n4; i++) {
+ re = ((int)rot[ 2*i] - (int)rot[ n-1-2*i]) >> 1;
+ im = -((int)rot[n2+2*i] - (int)rot[n2-1-2*i]) >> 1;
+ CMUL(x[i].re, x[i].im, re, im, -mdct->xcos1[i], mdct->xsin1[i]);
}
- fft(x, MDCT_NBITS - 2);
+ fft(mdct, x, mdct->nbits - 2);
/* post rotation */
- for(i=0;i<N/4;i++) {
+ for (i = 0; i < n4; i++) {
re = x[i].re;
im = x[i].im;
- CMUL(re1, im1, re, im, xsin1[i], xcos1[i]);
- out[2*i] = im1;
- out[N/2-1-2*i] = re1;
+ CMUL(out[n2-1-2*i], out[2*i], re, im, mdct->xsin1[i], mdct->xcos1[i]);
+ }
+}
+
+
+/**
+ * Apply KBD window to input samples prior to MDCT.
+ */
+static void apply_window(int16_t *output, const int16_t *input,
+ const int16_t *window, int n)
+{
+ int i;
+ int n2 = n >> 1;
+
+ for (i = 0; i < n2; i++) {
+ output[i] = MUL16(input[i], window[i]) >> 15;
+ output[n-i-1] = MUL16(input[n-i-1], window[i]) >> 15;
+ }
+}
+
+
+/**
+ * Calculate the log2() of the maximum absolute value in an array.
+ * @param tab input array
+ * @param n number of values in the array
+ * @return log2(max(abs(tab[])))
+ */
+static int log2_tab(int16_t *tab, int n)
+{
+ int i, v;
+
+ v = 0;
+ for (i = 0; i < n; i++)
+ v |= abs(tab[i]);
+
+ return av_log2(v);
+}
+
+
+/**
+ * Left-shift each value in an array by a specified amount.
+ * @param tab input array
+ * @param n number of values in the array
+ * @param lshift left shift amount. a negative value means right shift.
+ */
+static void lshift_tab(int16_t *tab, int n, int lshift)
+{
+ int i;
+
+ if (lshift > 0) {
+ for (i = 0; i < n; i++)
+ tab[i] <<= lshift;
+ } else if (lshift < 0) {
+ lshift = -lshift;
+ for (i = 0; i < n; i++)
+ tab[i] >>= lshift;
+ }
+}
+
+
+/**
+ * Normalize the input samples to use the maximum available precision.
+ * This assumes signed 16-bit input samples. Exponents are reduced by 9 to
+ * match the 24-bit internal precision for MDCT coefficients.
+ *
+ * @return exponent shift
+ */
+static int normalize_samples(AC3EncodeContext *s)
+{
+ int v = 14 - log2_tab(s->windowed_samples, AC3_WINDOW_SIZE);
+ v = FFMAX(0, v);
+ lshift_tab(s->windowed_samples, AC3_WINDOW_SIZE, v);
+ return v - 9;
+}
+
+
+/**
+ * Apply the MDCT to input samples to generate frequency coefficients.
+ * This applies the KBD window and normalizes the input to reduce precision
+ * loss due to fixed-point calculations.
+ */
+static void apply_mdct(AC3EncodeContext *s)
+{
+ int blk, ch;
+
+ for (ch = 0; ch < s->channels; ch++) {
+ for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
+ AC3Block *block = &s->blocks[blk];
+ const SampleType *input_samples = &s->planar_samples[ch][blk * AC3_BLOCK_SIZE];
+
+ apply_window(s->windowed_samples, input_samples, s->mdct.window, AC3_WINDOW_SIZE);
+
+ block->exp_shift[ch] = normalize_samples(s);
+
+ mdct512(&s->mdct, block->mdct_coef[ch], s->windowed_samples);
+ }
+ }
+}
+
+
+/**
+ * Initialize exponent tables.
+ */
+static av_cold void exponent_init(AC3EncodeContext *s)
+{
+ int i;
+ for (i = 73; i < 256; i++) {
+ exponent_group_tab[0][i] = (i - 1) / 3;
+ exponent_group_tab[1][i] = (i + 2) / 6;
+ exponent_group_tab[2][i] = (i + 8) / 12;
}
+ /* LFE */
+ exponent_group_tab[0][7] = 2;
}
-/* XXX: use another norm ? */
-static int calc_exp_diff(uint8_t *exp1, uint8_t *exp2, int n)
+
+/**
+ * Extract exponents from the MDCT coefficients.
+ * This takes into account the normalization that was done to the input samples
+ * by adjusting the exponents by the exponent shift values.
+ */
+static void extract_exponents(AC3EncodeContext *s)
{
- int sum, i;
- sum = 0;
- for(i=0;i<n;i++) {
- sum += abs(exp1[i] - exp2[i]);
+ int blk, ch, i;
+
+ for (ch = 0; ch < s->channels; ch++) {
+ for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
+ AC3Block *block = &s->blocks[blk];
+ for (i = 0; i < AC3_MAX_COEFS; i++) {
+ int e;
+ int v = abs(SCALE_COEF(block->mdct_coef[ch][i]));
+ if (v == 0)
+ e = 24;
+ else {
+ e = 23 - av_log2(v) + block->exp_shift[ch];
+ if (e >= 24) {
+ e = 24;
+ block->mdct_coef[ch][i] = 0;
+ }
+ }
+ block->exp[ch][i] = e;
+ }
+ }
}
- return sum;
}
-static void compute_exp_strategy(uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS],
- uint8_t exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
- int ch, int is_lfe)
+
+/**
+ * Exponent Difference Threshold.
+ * New exponents are sent if their SAD exceed this number.
+ */
+#define EXP_DIFF_THRESHOLD 1000
+
+
+/**
+ * Calculate exponent strategies for all blocks in a single channel.
+ */
+static void compute_exp_strategy_ch(AC3EncodeContext *s, uint8_t *exp_strategy,
+ uint8_t **exp)
{
- int i, j;
+ int blk, blk1;
int exp_diff;
/* estimate if the exponent variation & decide if they should be
reused in the next frame */
- exp_strategy[0][ch] = EXP_NEW;
- for(i=1;i<NB_BLOCKS;i++) {
- exp_diff = calc_exp_diff(exp[i][ch], exp[i-1][ch], N/2);
- dprintf(NULL, "exp_diff=%d\n", exp_diff);
+ exp_strategy[0] = EXP_NEW;
+ for (blk = 1; blk < AC3_MAX_BLOCKS; blk++) {
+ exp_diff = s->dsp.sad[0](NULL, exp[blk], exp[blk-1], 16, 16);
if (exp_diff > EXP_DIFF_THRESHOLD)
- exp_strategy[i][ch] = EXP_NEW;
+ exp_strategy[blk] = EXP_NEW;
else
- exp_strategy[i][ch] = EXP_REUSE;
+ exp_strategy[blk] = EXP_REUSE;
}
- if (is_lfe)
- return;
+ emms_c();
/* now select the encoding strategy type : if exponents are often
recoded, we use a coarse encoding */
- i = 0;
- while (i < NB_BLOCKS) {
- j = i + 1;
- while (j < NB_BLOCKS && exp_strategy[j][ch] == EXP_REUSE)
- j++;
- switch(j - i) {
- case 1:
- exp_strategy[i][ch] = EXP_D45;
- break;
+ blk = 0;
+ while (blk < AC3_MAX_BLOCKS) {
+ blk1 = blk + 1;
+ while (blk1 < AC3_MAX_BLOCKS && exp_strategy[blk1] == EXP_REUSE)
+ blk1++;
+ switch (blk1 - blk) {
+ case 1: exp_strategy[blk] = EXP_D45; break;
case 2:
- case 3:
- exp_strategy[i][ch] = EXP_D25;
- break;
- default:
- exp_strategy[i][ch] = EXP_D15;
- break;
+ case 3: exp_strategy[blk] = EXP_D25; break;
+ default: exp_strategy[blk] = EXP_D15; break;
}
- i = j;
+ blk = blk1;
}
}
-/* set exp[i] to min(exp[i], exp1[i]) */
-static void exponent_min(uint8_t exp[N/2], uint8_t exp1[N/2], int n)
+
+/**
+ * Calculate exponent strategies for all channels.
+ * Array arrangement is reversed to simplify the per-channel calculation.
+ */
+static void compute_exp_strategy(AC3EncodeContext *s)
{
- int i;
+ uint8_t *exp1[AC3_MAX_CHANNELS][AC3_MAX_BLOCKS];
+ uint8_t exp_str1[AC3_MAX_CHANNELS][AC3_MAX_BLOCKS];
+ int ch, blk;
+
+ for (ch = 0; ch < s->fbw_channels; ch++) {
+ for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
+ exp1[ch][blk] = s->blocks[blk].exp[ch];
+ exp_str1[ch][blk] = s->blocks[blk].exp_strategy[ch];
+ }
+
+ compute_exp_strategy_ch(s, exp_str1[ch], exp1[ch]);
+
+ for (blk = 0; blk < AC3_MAX_BLOCKS; blk++)
+ s->blocks[blk].exp_strategy[ch] = exp_str1[ch][blk];
+ }
+ if (s->lfe_on) {
+ ch = s->lfe_channel;
+ s->blocks[0].exp_strategy[ch] = EXP_D15;
+ for (blk = 1; blk < AC3_MAX_BLOCKS; blk++)
+ s->blocks[blk].exp_strategy[ch] = EXP_REUSE;
+ }
+}
- for(i=0;i<n;i++) {
+
+/**
+ * Set each encoded exponent in a block to the minimum of itself and the
+ * exponent in the same frequency bin of a following block.
+ * exp[i] = min(exp[i], exp1[i]
+ */
+static void exponent_min(uint8_t *exp, uint8_t *exp1, int n)
+{
+ int i;
+ for (i = 0; i < n; i++) {
if (exp1[i] < exp[i])
exp[i] = exp1[i];
}
}
-/* update the exponents so that they are the ones the decoder will
- decode. Return the number of bits used to code the exponents */
-static int encode_exp(uint8_t encoded_exp[N/2],
- uint8_t exp[N/2],
- int nb_exps,
- int exp_strategy)
+
+/**
+ * Update the exponents so that they are the ones the decoder will decode.
+ */
+static void encode_exponents_blk_ch(uint8_t *exp, int nb_exps, int exp_strategy)
{
- int group_size, nb_groups, i, j, k, exp_min;
- uint8_t exp1[N/2];
+ int nb_groups, i, k;
+ nb_groups = exponent_group_tab[exp_strategy-1][nb_exps] * 3;
+
+ /* for each group, compute the minimum exponent */
switch(exp_strategy) {
- case EXP_D15:
- group_size = 1;
- break;
case EXP_D25:
- group_size = 2;
+ for (i = 1, k = 1; i <= nb_groups; i++) {
+ uint8_t exp_min = exp[k];
+ if (exp[k+1] < exp_min)
+ exp_min = exp[k+1];
+ exp[i] = exp_min;
+ k += 2;
+ }
break;
- default:
case EXP_D45:
- group_size = 4;
- break;
- }
- nb_groups = ((nb_exps + (group_size * 3) - 4) / (3 * group_size)) * 3;
-
- /* for each group, compute the minimum exponent */
- exp1[0] = exp[0]; /* DC exponent is handled separately */
- k = 1;
- for(i=1;i<=nb_groups;i++) {
- exp_min = exp[k];
- assert(exp_min >= 0 && exp_min <= 24);
- for(j=1;j<group_size;j++) {
- if (exp[k+j] < exp_min)
- exp_min = exp[k+j];
+ for (i = 1, k = 1; i <= nb_groups; i++) {
+ uint8_t exp_min = exp[k];
+ if (exp[k+1] < exp_min)
+ exp_min = exp[k+1];
+ if (exp[k+2] < exp_min)
+ exp_min = exp[k+2];
+ if (exp[k+3] < exp_min)
+ exp_min = exp[k+3];
+ exp[i] = exp_min;
+ k += 4;
}
- exp1[i] = exp_min;
- k += group_size;
+ break;
}
/* constraint for DC exponent */
- if (exp1[0] > 15)
- exp1[0] = 15;
+ if (exp[0] > 15)
+ exp[0] = 15;
- /* Decrease the delta between each groups to within 2
- * so that they can be differentially encoded */
- for (i=1;i<=nb_groups;i++)
- exp1[i] = FFMIN(exp1[i], exp1[i-1] + 2);
- for (i=nb_groups-1;i>=0;i--)
- exp1[i] = FFMIN(exp1[i], exp1[i+1] + 2);
+ /* decrease the delta between each groups to within 2 so that they can be
+ differentially encoded */
+ for (i = 1; i <= nb_groups; i++)
+ exp[i] = FFMIN(exp[i], exp[i-1] + 2);
+ i--;
+ while (--i >= 0)
+ exp[i] = FFMIN(exp[i], exp[i+1] + 2);
/* now we have the exponent values the decoder will see */
- encoded_exp[0] = exp1[0];
- k = 1;
- for(i=1;i<=nb_groups;i++) {
- for(j=0;j<group_size;j++) {
- encoded_exp[k+j] = exp1[i];
+ switch (exp_strategy) {
+ case EXP_D25:
+ for (i = nb_groups, k = nb_groups * 2; i > 0; i--) {
+ uint8_t exp1 = exp[i];
+ exp[k--] = exp1;
+ exp[k--] = exp1;
}
- k += group_size;
- }
-
-#if defined(DEBUG)
- av_log(NULL, AV_LOG_DEBUG, "exponents: strategy=%d\n", exp_strategy);
- for(i=0;i<=nb_groups * group_size;i++) {
- av_log(NULL, AV_LOG_DEBUG, "%d ", encoded_exp[i]);
+ break;
+ case EXP_D45:
+ for (i = nb_groups, k = nb_groups * 4; i > 0; i--) {
+ exp[k] = exp[k-1] = exp[k-2] = exp[k-3] = exp[i];
+ k -= 4;
+ }
+ break;
}
- av_log(NULL, AV_LOG_DEBUG, "\n");
-#endif
-
- return 4 + (nb_groups / 3) * 7;
}
-/* return the size in bits taken by the mantissa */
-static int compute_mantissa_size(AC3EncodeContext *s, uint8_t *m, int nb_coefs)
+
+/**
+ * Encode exponents from original extracted form to what the decoder will see.
+ * This copies and groups exponents based on exponent strategy and reduces
+ * deltas between adjacent exponent groups so that they can be differentially
+ * encoded.
+ */
+static void encode_exponents(AC3EncodeContext *s)
{
- int bits, mant, i;
+ int blk, blk1, blk2, ch;
+ AC3Block *block, *block1, *block2;
- bits = 0;
- for(i=0;i<nb_coefs;i++) {
- mant = m[i];
- switch(mant) {
- case 0:
- /* nothing */
- break;
- case 1:
- /* 3 mantissa in 5 bits */
- if (s->mant1_cnt == 0)
- bits += 5;
- if (++s->mant1_cnt == 3)
- s->mant1_cnt = 0;
- break;
- case 2:
- /* 3 mantissa in 7 bits */
- if (s->mant2_cnt == 0)
- bits += 7;
- if (++s->mant2_cnt == 3)
- s->mant2_cnt = 0;
- break;
- case 3:
- bits += 3;
- break;
- case 4:
- /* 2 mantissa in 7 bits */
- if (s->mant4_cnt == 0)
- bits += 7;
- if (++s->mant4_cnt == 2)
- s->mant4_cnt = 0;
- break;
- case 14:
- bits += 14;
- break;
- case 15:
- bits += 16;
- break;
- default:
- bits += mant - 1;
- break;
+ for (ch = 0; ch < s->channels; ch++) {
+ blk = 0;
+ block = &s->blocks[0];
+ while (blk < AC3_MAX_BLOCKS) {
+ blk1 = blk + 1;
+ block1 = block + 1;
+ /* for the EXP_REUSE case we select the min of the exponents */
+ while (blk1 < AC3_MAX_BLOCKS && block1->exp_strategy[ch] == EXP_REUSE) {
+ exponent_min(block->exp[ch], block1->exp[ch], s->nb_coefs[ch]);
+ blk1++;
+ block1++;
+ }
+ encode_exponents_blk_ch(block->exp[ch], s->nb_coefs[ch],
+ block->exp_strategy[ch]);
+ /* copy encoded exponents for reuse case */
+ block2 = block + 1;
+ for (blk2 = blk+1; blk2 < blk1; blk2++, block2++) {
+ memcpy(block2->exp[ch], block->exp[ch],
+ s->nb_coefs[ch] * sizeof(uint8_t));
+ }
+ blk = blk1;
+ block = block1;
}
}
- return bits;
}
-static void bit_alloc_masking(AC3EncodeContext *s,
- uint8_t encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
- uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS],
- int16_t psd[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
- int16_t mask[NB_BLOCKS][AC3_MAX_CHANNELS][50])
+/**
+ * Group exponents.
+ * 3 delta-encoded exponents are in each 7-bit group. The number of groups
+ * varies depending on exponent strategy and bandwidth.
+ */
+static void group_exponents(AC3EncodeContext *s)
{
- int blk, ch;
- int16_t band_psd[NB_BLOCKS][AC3_MAX_CHANNELS][50];
+ int blk, ch, i;
+ int group_size, nb_groups, bit_count;
+ uint8_t *p;
+ int delta0, delta1, delta2;
+ int exp0, exp1;
- for(blk=0; blk<NB_BLOCKS; blk++) {
- for(ch=0;ch<s->channels;ch++) {
- if(exp_strategy[blk][ch] == EXP_REUSE) {
- memcpy(psd[blk][ch], psd[blk-1][ch], (N/2)*sizeof(int16_t));
- memcpy(mask[blk][ch], mask[blk-1][ch], 50*sizeof(int16_t));
- } else {
- ff_ac3_bit_alloc_calc_psd(encoded_exp[blk][ch], 0,
- s->nb_coefs[ch],
- psd[blk][ch], band_psd[blk][ch]);
- ff_ac3_bit_alloc_calc_mask(&s->bit_alloc, band_psd[blk][ch],
- 0, s->nb_coefs[ch],
- ff_ac3_fast_gain_tab[s->fast_gain_code[ch]],
- ch == s->lfe_channel,
- DBA_NONE, 0, NULL, NULL, NULL,
- mask[blk][ch]);
+ bit_count = 0;
+ for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
+ AC3Block *block = &s->blocks[blk];
+ for (ch = 0; ch < s->channels; ch++) {
+ if (block->exp_strategy[ch] == EXP_REUSE) {
+ continue;
+ }
+ group_size = block->exp_strategy[ch] + (block->exp_strategy[ch] == EXP_D45);
+ nb_groups = exponent_group_tab[block->exp_strategy[ch]-1][s->nb_coefs[ch]];
+ bit_count += 4 + (nb_groups * 7);
+ p = block->exp[ch];
+
+ /* DC exponent */
+ exp1 = *p++;
+ block->grouped_exp[ch][0] = exp1;
+
+ /* remaining exponents are delta encoded */
+ for (i = 1; i <= nb_groups; i++) {
+ /* merge three delta in one code */
+ exp0 = exp1;
+ exp1 = p[0];
+ p += group_size;
+ delta0 = exp1 - exp0 + 2;
+
+ exp0 = exp1;
+ exp1 = p[0];
+ p += group_size;
+ delta1 = exp1 - exp0 + 2;
+
+ exp0 = exp1;
+ exp1 = p[0];
+ p += group_size;
+ delta2 = exp1 - exp0 + 2;
+
+ block->grouped_exp[ch][i] = ((delta0 * 5 + delta1) * 5) + delta2;
}
}
}
+
+ s->exponent_bits = bit_count;
}
-static int bit_alloc(AC3EncodeContext *s,
- int16_t mask[NB_BLOCKS][AC3_MAX_CHANNELS][50],
- int16_t psd[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
- uint8_t bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
- int frame_bits, int coarse_snr_offset, int fine_snr_offset)
+
+/**
+ * Calculate final exponents from the supplied MDCT coefficients and exponent shift.
+ * Extract exponents from MDCT coefficients, calculate exponent strategies,
+ * and encode final exponents.
+ */
+static void process_exponents(AC3EncodeContext *s)
{
- int i, ch;
- int snr_offset;
-
- snr_offset = (((coarse_snr_offset - 15) << 4) + fine_snr_offset) << 2;
-
- /* compute size */
- for(i=0;i<NB_BLOCKS;i++) {
- s->mant1_cnt = 0;
- s->mant2_cnt = 0;
- s->mant4_cnt = 0;
- for(ch=0;ch<s->channels;ch++) {
- ff_ac3_bit_alloc_calc_bap(mask[i][ch], psd[i][ch], 0,
- s->nb_coefs[ch], snr_offset,
- s->bit_alloc.floor, ff_ac3_bap_tab,
- bap[i][ch]);
- frame_bits += compute_mantissa_size(s, bap[i][ch],
- s->nb_coefs[ch]);
- }
- }
-#if 0
- printf("csnr=%d fsnr=%d frame_bits=%d diff=%d\n",
- coarse_snr_offset, fine_snr_offset, frame_bits,
- 16 * s->frame_size - ((frame_bits + 7) & ~7));
-#endif
- return 16 * s->frame_size - frame_bits;
+ extract_exponents(s);
+
+ compute_exp_strategy(s);
+
+ encode_exponents(s);
+
+ group_exponents(s);
}
-#define SNR_INC1 4
-static int compute_bit_allocation(AC3EncodeContext *s,
- uint8_t bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
- uint8_t encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2],
- uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS],
- int frame_bits)
+/**
+ * Count frame bits that are based solely on fixed parameters.
+ * This only has to be run once when the encoder is initialized.
+ */
+static void count_frame_bits_fixed(AC3EncodeContext *s)
{
- int i, ch;
- int coarse_snr_offset, fine_snr_offset;
- uint8_t bap1[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
- int16_t psd[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
- int16_t mask[NB_BLOCKS][AC3_MAX_CHANNELS][50];
static const int frame_bits_inc[8] = { 0, 0, 2, 2, 2, 4, 2, 4 };
+ int blk;
+ int frame_bits;
- /* init default parameters */
- s->slow_decay_code = 2;
- s->fast_decay_code = 1;
- s->slow_gain_code = 1;
- s->db_per_bit_code = 2;
- s->floor_code = 4;
- for(ch=0;ch<s->channels;ch++)
- s->fast_gain_code[ch] = 4;
-
- /* compute real values */
- s->bit_alloc.sr_code = s->sr_code;
- s->bit_alloc.sr_shift = s->sr_shift;
- s->bit_alloc.slow_decay = ff_ac3_slow_decay_tab[s->slow_decay_code] >> s->sr_shift;
- s->bit_alloc.fast_decay = ff_ac3_fast_decay_tab[s->fast_decay_code] >> s->sr_shift;
- s->bit_alloc.slow_gain = ff_ac3_slow_gain_tab[s->slow_gain_code];
- s->bit_alloc.db_per_bit = ff_ac3_db_per_bit_tab[s->db_per_bit_code];
- s->bit_alloc.floor = ff_ac3_floor_tab[s->floor_code];
+ /* assumptions:
+ * no dynamic range codes
+ * no channel coupling
+ * no rematrixing
+ * bit allocation parameters do not change between blocks
+ * SNR offsets do not change between blocks
+ * no delta bit allocation
+ * no skipped data
+ * no auxilliary data
+ */
/* header size */
- frame_bits += 65;
- // if (s->channel_mode == 2)
- // frame_bits += 2;
+ frame_bits = 65;
frame_bits += frame_bits_inc[s->channel_mode];
/* audio blocks */
- for(i=0;i<NB_BLOCKS;i++) {
+ for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
frame_bits += s->fbw_channels * 2 + 2; /* blksw * c, dithflag * c, dynrnge, cplstre */
if (s->channel_mode == AC3_CHMODE_STEREO) {
frame_bits++; /* rematstr */
- if(i==0) frame_bits += 4;
+ if (!blk)
+ frame_bits += 4;
}
frame_bits += 2 * s->fbw_channels; /* chexpstr[2] * c */
if (s->lfe_on)
frame_bits++; /* lfeexpstr */
- for(ch=0;ch<s->fbw_channels;ch++) {
- if (exp_strategy[i][ch] != EXP_REUSE)
- frame_bits += 6 + 2; /* chbwcod[6], gainrng[2] */
- }
frame_bits++; /* baie */
frame_bits++; /* snr */
frame_bits += 2; /* delta / skip */
/* CRC */
frame_bits += 16;
- /* calculate psd and masking curve before doing bit allocation */
- bit_alloc_masking(s, encoded_exp, exp_strategy, psd, mask);
-
- /* now the big work begins : do the bit allocation. Modify the snr
- offset until we can pack everything in the requested frame size */
-
- coarse_snr_offset = s->coarse_snr_offset;
- while (coarse_snr_offset >= 0 &&
- bit_alloc(s, mask, psd, bap, frame_bits, coarse_snr_offset, 0) < 0)
- coarse_snr_offset -= SNR_INC1;
- if (coarse_snr_offset < 0) {
- av_log(NULL, AV_LOG_ERROR, "Bit allocation failed. Try increasing the bitrate.\n");
- return -1;
- }
- while ((coarse_snr_offset + SNR_INC1) <= 63 &&
- bit_alloc(s, mask, psd, bap1, frame_bits,
- coarse_snr_offset + SNR_INC1, 0) >= 0) {
- coarse_snr_offset += SNR_INC1;
- memcpy(bap, bap1, sizeof(bap1));
- }
- while ((coarse_snr_offset + 1) <= 63 &&
- bit_alloc(s, mask, psd, bap1, frame_bits, coarse_snr_offset + 1, 0) >= 0) {
- coarse_snr_offset++;
- memcpy(bap, bap1, sizeof(bap1));
- }
-
- fine_snr_offset = 0;
- while ((fine_snr_offset + SNR_INC1) <= 15 &&
- bit_alloc(s, mask, psd, bap1, frame_bits,
- coarse_snr_offset, fine_snr_offset + SNR_INC1) >= 0) {
- fine_snr_offset += SNR_INC1;
- memcpy(bap, bap1, sizeof(bap1));
- }
- while ((fine_snr_offset + 1) <= 15 &&
- bit_alloc(s, mask, psd, bap1, frame_bits,
- coarse_snr_offset, fine_snr_offset + 1) >= 0) {
- fine_snr_offset++;
- memcpy(bap, bap1, sizeof(bap1));
- }
-
- s->coarse_snr_offset = coarse_snr_offset;
- for(ch=0;ch<s->channels;ch++)
- s->fine_snr_offset[ch] = fine_snr_offset;
-#if defined(DEBUG_BITALLOC)
- {
- int j;
-
- for(i=0;i<6;i++) {
- for(ch=0;ch<s->channels;ch++) {
- printf("Block #%d Ch%d:\n", i, ch);
- printf("bap=");
- for(j=0;j<s->nb_coefs[ch];j++) {
- printf("%d ",bap[i][ch][j]);
- }
- printf("\n");
- }
- }
- }
-#endif
- return 0;
+ s->frame_bits_fixed = frame_bits;
}
-static av_cold int set_channel_info(AC3EncodeContext *s, int channels,
- int64_t *channel_layout)
+
+/**
+ * Initialize bit allocation.
+ * Set default parameter codes and calculate parameter values.
+ */
+static void bit_alloc_init(AC3EncodeContext *s)
{
- int ch_layout;
+ int ch;
- if (channels < 1 || channels > AC3_MAX_CHANNELS)
- return -1;
- if ((uint64_t)*channel_layout > 0x7FF)
- return -1;
- ch_layout = *channel_layout;
- if (!ch_layout)
- ch_layout = avcodec_guess_channel_layout(channels, CODEC_ID_AC3, NULL);
- if (av_get_channel_layout_nb_channels(ch_layout) != channels)
- return -1;
+ /* init default parameters */
+ s->slow_decay_code = 2;
+ s->fast_decay_code = 1;
+ s->slow_gain_code = 1;
+ s->db_per_bit_code = 3;
+ s->floor_code = 4;
+ for (ch = 0; ch < s->channels; ch++)
+ s->fast_gain_code[ch] = 4;
- s->lfe_on = !!(ch_layout & AV_CH_LOW_FREQUENCY);
- s->channels = channels;
- s->fbw_channels = channels - s->lfe_on;
- s->lfe_channel = s->lfe_on ? s->fbw_channels : -1;
- if (s->lfe_on)
- ch_layout -= AV_CH_LOW_FREQUENCY;
+ /* initial snr offset */
+ s->coarse_snr_offset = 40;
- switch (ch_layout) {
- case AV_CH_LAYOUT_MONO: s->channel_mode = AC3_CHMODE_MONO; break;
- case AV_CH_LAYOUT_STEREO: s->channel_mode = AC3_CHMODE_STEREO; break;
- case AV_CH_LAYOUT_SURROUND: s->channel_mode = AC3_CHMODE_3F; break;
- case AV_CH_LAYOUT_2_1: s->channel_mode = AC3_CHMODE_2F1R; break;
- case AV_CH_LAYOUT_4POINT0: s->channel_mode = AC3_CHMODE_3F1R; break;
- case AV_CH_LAYOUT_QUAD:
- case AV_CH_LAYOUT_2_2: s->channel_mode = AC3_CHMODE_2F2R; break;
- case AV_CH_LAYOUT_5POINT0:
- case AV_CH_LAYOUT_5POINT0_BACK: s->channel_mode = AC3_CHMODE_3F2R; break;
- default:
- return -1;
+ /* compute real values */
+ /* currently none of these values change during encoding, so we can just
+ set them once at initialization */
+ s->bit_alloc.slow_decay = ff_ac3_slow_decay_tab[s->slow_decay_code] >> s->bit_alloc.sr_shift;
+ s->bit_alloc.fast_decay = ff_ac3_fast_decay_tab[s->fast_decay_code] >> s->bit_alloc.sr_shift;
+ s->bit_alloc.slow_gain = ff_ac3_slow_gain_tab[s->slow_gain_code];
+ s->bit_alloc.db_per_bit = ff_ac3_db_per_bit_tab[s->db_per_bit_code];
+ s->bit_alloc.floor = ff_ac3_floor_tab[s->floor_code];
+
+ count_frame_bits_fixed(s);
+}
+
+
+/**
+ * Count the bits used to encode the frame, minus exponents and mantissas.
+ * Bits based on fixed parameters have already been counted, so now we just
+ * have to add the bits based on parameters that change during encoding.
+ */
+static void count_frame_bits(AC3EncodeContext *s)
+{
+ int blk, ch;
+ int frame_bits = 0;
+
+ for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
+ uint8_t *exp_strategy = s->blocks[blk].exp_strategy;
+ for (ch = 0; ch < s->fbw_channels; ch++) {
+ if (exp_strategy[ch] != EXP_REUSE)
+ frame_bits += 6 + 2; /* chbwcod[6], gainrng[2] */
+ }
}
+ s->frame_bits = s->frame_bits_fixed + frame_bits;
+}
- s->channel_map = ff_ac3_enc_channel_map[s->channel_mode][s->lfe_on];
- *channel_layout = ch_layout;
- if (s->lfe_on)
- *channel_layout |= AV_CH_LOW_FREQUENCY;
- return 0;
+/**
+ * Calculate the number of bits needed to encode a set of mantissas.
+ */
+static int compute_mantissa_size(int mant_cnt[5], uint8_t *bap, int nb_coefs)
+{
+ int bits, b, i;
+
+ bits = 0;
+ for (i = 0; i < nb_coefs; i++) {
+ b = bap[i];
+ if (b <= 4) {
+ // bap=1 to bap=4 will be counted in compute_mantissa_size_final
+ mant_cnt[b]++;
+ } else if (b <= 13) {
+ // bap=5 to bap=13 use (bap-1) bits
+ bits += b - 1;
+ } else {
+ // bap=14 uses 14 bits and bap=15 uses 16 bits
+ bits += (b == 14) ? 14 : 16;
+ }
+ }
+ return bits;
}
-static av_cold int AC3_encode_init(AVCodecContext *avctx)
+
+/**
+ * Finalize the mantissa bit count by adding in the grouped mantissas.
+ */
+static int compute_mantissa_size_final(int mant_cnt[5])
{
- int freq = avctx->sample_rate;
- int bitrate = avctx->bit_rate;
- AC3EncodeContext *s = avctx->priv_data;
- int i, j, ch;
- float alpha;
- int bw_code;
+ // bap=1 : 3 mantissas in 5 bits
+ int bits = (mant_cnt[1] / 3) * 5;
+ // bap=2 : 3 mantissas in 7 bits
+ // bap=4 : 2 mantissas in 7 bits
+ bits += ((mant_cnt[2] / 3) + (mant_cnt[4] >> 1)) * 7;
+ // bap=3 : each mantissa is 3 bits
+ bits += mant_cnt[3] * 3;
+ return bits;
+}
- avctx->frame_size = AC3_FRAME_SIZE;
- ac3_common_init();
+/**
+ * Calculate masking curve based on the final exponents.
+ * Also calculate the power spectral densities to use in future calculations.
+ */
+static void bit_alloc_masking(AC3EncodeContext *s)
+{
+ int blk, ch;
- if (!avctx->channel_layout) {
- av_log(avctx, AV_LOG_WARNING, "No channel layout specified. The "
- "encoder will guess the layout, but it "
- "might be incorrect.\n");
+ for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
+ AC3Block *block = &s->blocks[blk];
+ for (ch = 0; ch < s->channels; ch++) {
+ /* We only need psd and mask for calculating bap.
+ Since we currently do not calculate bap when exponent
+ strategy is EXP_REUSE we do not need to calculate psd or mask. */
+ if (block->exp_strategy[ch] != EXP_REUSE) {
+ ff_ac3_bit_alloc_calc_psd(block->exp[ch], 0,
+ s->nb_coefs[ch],
+ block->psd[ch], block->band_psd[ch]);
+ ff_ac3_bit_alloc_calc_mask(&s->bit_alloc, block->band_psd[ch],
+ 0, s->nb_coefs[ch],
+ ff_ac3_fast_gain_tab[s->fast_gain_code[ch]],
+ ch == s->lfe_channel,
+ DBA_NONE, 0, NULL, NULL, NULL,
+ block->mask[ch]);
+ }
+ }
}
- if (set_channel_info(s, avctx->channels, &avctx->channel_layout)) {
- av_log(avctx, AV_LOG_ERROR, "invalid channel layout\n");
- return -1;
+}
+
+
+/**
+ * Ensure that bap for each block and channel point to the current bap_buffer.
+ * They may have been switched during the bit allocation search.
+ */
+static void reset_block_bap(AC3EncodeContext *s)
+{
+ int blk, ch;
+ if (s->blocks[0].bap[0] == s->bap_buffer)
+ return;
+ for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
+ for (ch = 0; ch < s->channels; ch++) {
+ s->blocks[blk].bap[ch] = &s->bap_buffer[AC3_MAX_COEFS * (blk * s->channels + ch)];
+ }
}
+}
+
- /* frequency */
- for(i=0;i<3;i++) {
- for(j=0;j<3;j++)
- if ((ff_ac3_sample_rate_tab[j] >> i) == freq)
- goto found;
+/**
+ * Run the bit allocation with a given SNR offset.
+ * This calculates the bit allocation pointers that will be used to determine
+ * the quantization of each mantissa.
+ * @return the number of bits needed for mantissas if the given SNR offset is
+ * is used.
+ */
+static int bit_alloc(AC3EncodeContext *s, int snr_offset)
+{
+ int blk, ch;
+ int mantissa_bits;
+ int mant_cnt[5];
+
+ snr_offset = (snr_offset - 240) << 2;
+
+ reset_block_bap(s);
+ mantissa_bits = 0;
+ for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
+ AC3Block *block = &s->blocks[blk];
+ // initialize grouped mantissa counts. these are set so that they are
+ // padded to the next whole group size when bits are counted in
+ // compute_mantissa_size_final
+ mant_cnt[0] = mant_cnt[3] = 0;
+ mant_cnt[1] = mant_cnt[2] = 2;
+ mant_cnt[4] = 1;
+ for (ch = 0; ch < s->channels; ch++) {
+ /* Currently the only bit allocation parameters which vary across
+ blocks within a frame are the exponent values. We can take
+ advantage of that by reusing the bit allocation pointers
+ whenever we reuse exponents. */
+ if (block->exp_strategy[ch] == EXP_REUSE) {
+ memcpy(block->bap[ch], s->blocks[blk-1].bap[ch], AC3_MAX_COEFS);
+ } else {
+ ff_ac3_bit_alloc_calc_bap(block->mask[ch], block->psd[ch], 0,
+ s->nb_coefs[ch], snr_offset,
+ s->bit_alloc.floor, ff_ac3_bap_tab,
+ block->bap[ch]);
+ }
+ mantissa_bits += compute_mantissa_size(mant_cnt, block->bap[ch], s->nb_coefs[ch]);
+ }
+ mantissa_bits += compute_mantissa_size_final(mant_cnt);
}
- return -1;
- found:
- s->sample_rate = freq;
- s->sr_shift = i;
- s->sr_code = j;
- s->bitstream_id = 8 + s->sr_shift;
- s->bitstream_mode = 0; /* complete main audio service */
+ return mantissa_bits;
+}
- /* bitrate & frame size */
- for(i=0;i<19;i++) {
- if ((ff_ac3_bitrate_tab[i] >> s->sr_shift)*1000 == bitrate)
- break;
+
+/**
+ * Constant bitrate bit allocation search.
+ * Find the largest SNR offset that will allow data to fit in the frame.
+ */
+static int cbr_bit_allocation(AC3EncodeContext *s)
+{
+ int ch;
+ int bits_left;
+ int snr_offset, snr_incr;
+
+ bits_left = 8 * s->frame_size - (s->frame_bits + s->exponent_bits);
+
+ snr_offset = s->coarse_snr_offset << 4;
+
+ while (snr_offset >= 0 &&
+ bit_alloc(s, snr_offset) > bits_left) {
+ snr_offset -= 64;
}
- if (i == 19)
- return -1;
- s->bit_rate = bitrate;
- s->frame_size_code = i << 1;
- s->frame_size_min = ff_ac3_frame_size_tab[s->frame_size_code][s->sr_code];
- s->bits_written = 0;
- s->samples_written = 0;
- s->frame_size = s->frame_size_min;
+ if (snr_offset < 0)
+ return AVERROR(EINVAL);
+
+ FFSWAP(uint8_t *, s->bap_buffer, s->bap1_buffer);
+ for (snr_incr = 64; snr_incr > 0; snr_incr >>= 2) {
+ while (snr_offset + 64 <= 1023 &&
+ bit_alloc(s, snr_offset + snr_incr) <= bits_left) {
+ snr_offset += snr_incr;
+ FFSWAP(uint8_t *, s->bap_buffer, s->bap1_buffer);
+ }
+ }
+ FFSWAP(uint8_t *, s->bap_buffer, s->bap1_buffer);
+ reset_block_bap(s);
- /* bit allocation init */
- if(avctx->cutoff) {
- /* calculate bandwidth based on user-specified cutoff frequency */
- int cutoff = av_clip(avctx->cutoff, 1, s->sample_rate >> 1);
- int fbw_coeffs = cutoff * 512 / s->sample_rate;
- bw_code = av_clip((fbw_coeffs - 73) / 3, 0, 60);
- } else {
- /* use default bandwidth setting */
- /* XXX: should compute the bandwidth according to the frame
- size, so that we avoid annoying high frequency artifacts */
- bw_code = 50;
+ s->coarse_snr_offset = snr_offset >> 4;
+ for (ch = 0; ch < s->channels; ch++)
+ s->fine_snr_offset[ch] = snr_offset & 0xF;
+
+ return 0;
+}
+
+
+/**
+ * Downgrade exponent strategies to reduce the bits used by the exponents.
+ * This is a fallback for when bit allocation fails with the normal exponent
+ * strategies. Each time this function is run it only downgrades the
+ * strategy in 1 channel of 1 block.
+ * @return non-zero if downgrade was unsuccessful
+ */
+static int downgrade_exponents(AC3EncodeContext *s)
+{
+ int ch, blk;
+
+ for (ch = 0; ch < s->fbw_channels; ch++) {
+ for (blk = AC3_MAX_BLOCKS-1; blk >= 0; blk--) {
+ if (s->blocks[blk].exp_strategy[ch] == EXP_D15) {
+ s->blocks[blk].exp_strategy[ch] = EXP_D25;
+ return 0;
+ }
+ }
}
- for(ch=0;ch<s->fbw_channels;ch++) {
- /* bandwidth for each channel */
- s->bandwidth_code[ch] = bw_code;
- s->nb_coefs[ch] = bw_code * 3 + 73;
+ for (ch = 0; ch < s->fbw_channels; ch++) {
+ for (blk = AC3_MAX_BLOCKS-1; blk >= 0; blk--) {
+ if (s->blocks[blk].exp_strategy[ch] == EXP_D25) {
+ s->blocks[blk].exp_strategy[ch] = EXP_D45;
+ return 0;
+ }
+ }
}
- if (s->lfe_on) {
- s->nb_coefs[s->lfe_channel] = 7; /* fixed */
+ for (ch = 0; ch < s->fbw_channels; ch++) {
+ /* block 0 cannot reuse exponents, so only downgrade D45 to REUSE if
+ the block number > 0 */
+ for (blk = AC3_MAX_BLOCKS-1; blk > 0; blk--) {
+ if (s->blocks[blk].exp_strategy[ch] > EXP_REUSE) {
+ s->blocks[blk].exp_strategy[ch] = EXP_REUSE;
+ return 0;
+ }
+ }
}
- /* initial snr offset */
- s->coarse_snr_offset = 40;
+ return -1;
+}
- /* mdct init */
- fft_init(MDCT_NBITS - 2);
- for(i=0;i<N/4;i++) {
- alpha = 2 * M_PI * (i + 1.0 / 8.0) / (float)N;
- xcos1[i] = fix15(-cos(alpha));
- xsin1[i] = fix15(-sin(alpha));
- }
- avctx->coded_frame= avcodec_alloc_frame();
- avctx->coded_frame->key_frame= 1;
+/**
+ * Reduce the bandwidth to reduce the number of bits used for a given SNR offset.
+ * This is a second fallback for when bit allocation still fails after exponents
+ * have been downgraded.
+ * @return non-zero if bandwidth reduction was unsuccessful
+ */
+static int reduce_bandwidth(AC3EncodeContext *s, int min_bw_code)
+{
+ int ch;
- return 0;
+ if (s->bandwidth_code[0] > min_bw_code) {
+ for (ch = 0; ch < s->fbw_channels; ch++) {
+ s->bandwidth_code[ch]--;
+ s->nb_coefs[ch] = s->bandwidth_code[ch] * 3 + 73;
+ }
+ return 0;
+ }
+ return -1;
}
-/* output the AC-3 frame header */
-static void output_frame_header(AC3EncodeContext *s, unsigned char *frame)
+
+/**
+ * Perform bit allocation search.
+ * Finds the SNR offset value that maximizes quality and fits in the specified
+ * frame size. Output is the SNR offset and a set of bit allocation pointers
+ * used to quantize the mantissas.
+ */
+static int compute_bit_allocation(AC3EncodeContext *s)
{
- init_put_bits(&s->pb, frame, AC3_MAX_CODED_FRAME_SIZE);
+ int ret;
- put_bits(&s->pb, 16, 0x0b77); /* frame header */
- put_bits(&s->pb, 16, 0); /* crc1: will be filled later */
- put_bits(&s->pb, 2, s->sr_code);
- put_bits(&s->pb, 6, s->frame_size_code + (s->frame_size - s->frame_size_min));
- put_bits(&s->pb, 5, s->bitstream_id);
- put_bits(&s->pb, 3, s->bitstream_mode);
- put_bits(&s->pb, 3, s->channel_mode);
- if ((s->channel_mode & 0x01) && s->channel_mode != AC3_CHMODE_MONO)
- put_bits(&s->pb, 2, 1); /* XXX -4.5 dB */
- if (s->channel_mode & 0x04)
- put_bits(&s->pb, 2, 1); /* XXX -6 dB */
- if (s->channel_mode == AC3_CHMODE_STEREO)
- put_bits(&s->pb, 2, 0); /* surround not indicated */
- put_bits(&s->pb, 1, s->lfe_on); /* LFE */
- put_bits(&s->pb, 5, 31); /* dialog norm: -31 db */
- put_bits(&s->pb, 1, 0); /* no compression control word */
- put_bits(&s->pb, 1, 0); /* no lang code */
- put_bits(&s->pb, 1, 0); /* no audio production info */
- put_bits(&s->pb, 1, 0); /* no copyright */
- put_bits(&s->pb, 1, 1); /* original bitstream */
- put_bits(&s->pb, 1, 0); /* no time code 1 */
- put_bits(&s->pb, 1, 0); /* no time code 2 */
- put_bits(&s->pb, 1, 0); /* no additional bit stream info */
+ count_frame_bits(s);
+
+ bit_alloc_masking(s);
+
+ ret = cbr_bit_allocation(s);
+ while (ret) {
+ /* fallback 1: downgrade exponents */
+ if (!downgrade_exponents(s)) {
+ extract_exponents(s);
+ encode_exponents(s);
+ group_exponents(s);
+ ret = compute_bit_allocation(s);
+ continue;
+ }
+
+ /* fallback 2: reduce bandwidth */
+ /* only do this if the user has not specified a specific cutoff
+ frequency */
+ if (!s->cutoff && !reduce_bandwidth(s, 0)) {
+ process_exponents(s);
+ ret = compute_bit_allocation(s);
+ continue;
+ }
+
+ /* fallbacks were not enough... */
+ break;
+ }
+
+ return ret;
}
-/* symetric quantization on 'levels' levels */
+
+/**
+ * Symmetric quantization on 'levels' levels.
+ */
static inline int sym_quant(int c, int e, int levels)
{
int v;
v = (v + 1) >> 1;
v = (levels >> 1) - v;
}
- assert (v >= 0 && v < levels);
+ assert(v >= 0 && v < levels);
return v;
}
-/* asymetric quantization on 2^qbits levels */
+
+/**
+ * Asymmetric quantization on 2^qbits levels.
+ */
static inline int asym_quant(int c, int e, int qbits)
{
int lshift, m, v;
return v & ((1 << qbits)-1);
}
-/* Output one audio block. There are NB_BLOCKS audio blocks in one AC-3
- frame */
-static void output_audio_block(AC3EncodeContext *s,
- uint8_t exp_strategy[AC3_MAX_CHANNELS],
- uint8_t encoded_exp[AC3_MAX_CHANNELS][N/2],
- uint8_t bap[AC3_MAX_CHANNELS][N/2],
- int32_t mdct_coefs[AC3_MAX_CHANNELS][N/2],
- int8_t global_exp[AC3_MAX_CHANNELS],
- int block_num)
+
+/**
+ * Quantize a set of mantissas for a single channel in a single block.
+ */
+static void quantize_mantissas_blk_ch(AC3EncodeContext *s, CoefType *mdct_coef,
+ int8_t exp_shift, uint8_t *exp,
+ uint8_t *bap, uint16_t *qmant, int n)
+{
+ int i;
+
+ for (i = 0; i < n; i++) {
+ int v;
+ int c = SCALE_COEF(mdct_coef[i]);
+ int e = exp[i] - exp_shift;
+ int b = bap[i];
+ switch (b) {
+ case 0:
+ v = 0;
+ break;
+ case 1:
+ v = sym_quant(c, e, 3);
+ switch (s->mant1_cnt) {
+ case 0:
+ s->qmant1_ptr = &qmant[i];
+ v = 9 * v;
+ s->mant1_cnt = 1;
+ break;
+ case 1:
+ *s->qmant1_ptr += 3 * v;
+ s->mant1_cnt = 2;
+ v = 128;
+ break;
+ default:
+ *s->qmant1_ptr += v;
+ s->mant1_cnt = 0;
+ v = 128;
+ break;
+ }
+ break;
+ case 2:
+ v = sym_quant(c, e, 5);
+ switch (s->mant2_cnt) {
+ case 0:
+ s->qmant2_ptr = &qmant[i];
+ v = 25 * v;
+ s->mant2_cnt = 1;
+ break;
+ case 1:
+ *s->qmant2_ptr += 5 * v;
+ s->mant2_cnt = 2;
+ v = 128;
+ break;
+ default:
+ *s->qmant2_ptr += v;
+ s->mant2_cnt = 0;
+ v = 128;
+ break;
+ }
+ break;
+ case 3:
+ v = sym_quant(c, e, 7);
+ break;
+ case 4:
+ v = sym_quant(c, e, 11);
+ switch (s->mant4_cnt) {
+ case 0:
+ s->qmant4_ptr = &qmant[i];
+ v = 11 * v;
+ s->mant4_cnt = 1;
+ break;
+ default:
+ *s->qmant4_ptr += v;
+ s->mant4_cnt = 0;
+ v = 128;
+ break;
+ }
+ break;
+ case 5:
+ v = sym_quant(c, e, 15);
+ break;
+ case 14:
+ v = asym_quant(c, e, 14);
+ break;
+ case 15:
+ v = asym_quant(c, e, 16);
+ break;
+ default:
+ v = asym_quant(c, e, b - 1);
+ break;
+ }
+ qmant[i] = v;
+ }
+}
+
+
+/**
+ * Quantize mantissas using coefficients, exponents, and bit allocation pointers.
+ */
+static void quantize_mantissas(AC3EncodeContext *s)
+{
+ int blk, ch;
+
+
+ for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
+ AC3Block *block = &s->blocks[blk];
+ s->mant1_cnt = s->mant2_cnt = s->mant4_cnt = 0;
+ s->qmant1_ptr = s->qmant2_ptr = s->qmant4_ptr = NULL;
+
+ for (ch = 0; ch < s->channels; ch++) {
+ quantize_mantissas_blk_ch(s, block->mdct_coef[ch], block->exp_shift[ch],
+ block->exp[ch], block->bap[ch],
+ block->qmant[ch], s->nb_coefs[ch]);
+ }
+ }
+}
+
+
+/**
+ * Write the AC-3 frame header to the output bitstream.
+ */
+static void output_frame_header(AC3EncodeContext *s)
+{
+ put_bits(&s->pb, 16, 0x0b77); /* frame header */
+ put_bits(&s->pb, 16, 0); /* crc1: will be filled later */
+ put_bits(&s->pb, 2, s->bit_alloc.sr_code);
+ put_bits(&s->pb, 6, s->frame_size_code + (s->frame_size - s->frame_size_min) / 2);
+ put_bits(&s->pb, 5, s->bitstream_id);
+ put_bits(&s->pb, 3, s->bitstream_mode);
+ put_bits(&s->pb, 3, s->channel_mode);
+ if ((s->channel_mode & 0x01) && s->channel_mode != AC3_CHMODE_MONO)
+ put_bits(&s->pb, 2, 1); /* XXX -4.5 dB */
+ if (s->channel_mode & 0x04)
+ put_bits(&s->pb, 2, 1); /* XXX -6 dB */
+ if (s->channel_mode == AC3_CHMODE_STEREO)
+ put_bits(&s->pb, 2, 0); /* surround not indicated */
+ put_bits(&s->pb, 1, s->lfe_on); /* LFE */
+ put_bits(&s->pb, 5, 31); /* dialog norm: -31 db */
+ put_bits(&s->pb, 1, 0); /* no compression control word */
+ put_bits(&s->pb, 1, 0); /* no lang code */
+ put_bits(&s->pb, 1, 0); /* no audio production info */
+ put_bits(&s->pb, 1, 0); /* no copyright */
+ put_bits(&s->pb, 1, 1); /* original bitstream */
+ put_bits(&s->pb, 1, 0); /* no time code 1 */
+ put_bits(&s->pb, 1, 0); /* no time code 2 */
+ put_bits(&s->pb, 1, 0); /* no additional bit stream info */
+}
+
+
+/**
+ * Write one audio block to the output bitstream.
+ */
+static void output_audio_block(AC3EncodeContext *s, int block_num)
{
- int ch, nb_groups, group_size, i, baie, rbnd;
- uint8_t *p;
- uint16_t qmant[AC3_MAX_CHANNELS][N/2];
- int exp0, exp1;
- int mant1_cnt, mant2_cnt, mant4_cnt;
- uint16_t *qmant1_ptr, *qmant2_ptr, *qmant4_ptr;
- int delta0, delta1, delta2;
+ int ch, i, baie, rbnd;
+ AC3Block *block = &s->blocks[block_num];
+
+ /* block switching */
+ for (ch = 0; ch < s->fbw_channels; ch++)
+ put_bits(&s->pb, 1, 0);
- for(ch=0;ch<s->fbw_channels;ch++)
- put_bits(&s->pb, 1, 0); /* 512 point MDCT */
- for(ch=0;ch<s->fbw_channels;ch++)
- put_bits(&s->pb, 1, 1); /* no dither */
- put_bits(&s->pb, 1, 0); /* no dynamic range */
- if (block_num == 0) {
- /* for block 0, even if no coupling, we must say it. This is a
- waste of bit :-) */
+ /* dither flags */
+ for (ch = 0; ch < s->fbw_channels; ch++)
+ put_bits(&s->pb, 1, 1);
+
+ /* dynamic range codes */
+ put_bits(&s->pb, 1, 0);
+
+ /* channel coupling */
+ if (!block_num) {
put_bits(&s->pb, 1, 1); /* coupling strategy present */
put_bits(&s->pb, 1, 0); /* no coupling strategy */
} else {
put_bits(&s->pb, 1, 0); /* no new coupling strategy */
}
- if (s->channel_mode == AC3_CHMODE_STEREO)
- {
- if(block_num==0)
- {
- /* first block must define rematrixing (rematstr) */
+ /* stereo rematrixing */
+ if (s->channel_mode == AC3_CHMODE_STEREO) {
+ if (!block_num) {
+ /* first block must define rematrixing (rematstr) */
put_bits(&s->pb, 1, 1);
/* dummy rematrixing rematflg(1:4)=0 */
- for (rbnd=0;rbnd<4;rbnd++)
- put_bits(&s->pb, 1, 0);
- }
- else
- {
+ for (rbnd = 0; rbnd < 4; rbnd++)
+ put_bits(&s->pb, 1, 0);
+ } else {
/* no matrixing (but should be used in the future) */
put_bits(&s->pb, 1, 0);
- }
- }
-
-#if defined(DEBUG)
- {
- static int count = 0;
- av_log(NULL, AV_LOG_DEBUG, "Block #%d (%d)\n", block_num, count++);
- }
-#endif
- /* exponent strategy */
- for(ch=0;ch<s->fbw_channels;ch++) {
- put_bits(&s->pb, 2, exp_strategy[ch]);
+ }
}
- if (s->lfe_on) {
- put_bits(&s->pb, 1, exp_strategy[s->lfe_channel]);
- }
+ /* exponent strategy */
+ for (ch = 0; ch < s->fbw_channels; ch++)
+ put_bits(&s->pb, 2, block->exp_strategy[ch]);
+ if (s->lfe_on)
+ put_bits(&s->pb, 1, block->exp_strategy[s->lfe_channel]);
- for(ch=0;ch<s->fbw_channels;ch++) {
- if (exp_strategy[ch] != EXP_REUSE)
+ /* bandwidth */
+ for (ch = 0; ch < s->fbw_channels; ch++) {
+ if (block->exp_strategy[ch] != EXP_REUSE)
put_bits(&s->pb, 6, s->bandwidth_code[ch]);
}
/* exponents */
for (ch = 0; ch < s->channels; ch++) {
- switch(exp_strategy[ch]) {
- case EXP_REUSE:
+ int nb_groups;
+
+ if (block->exp_strategy[ch] == EXP_REUSE)
continue;
- case EXP_D15:
- group_size = 1;
- break;
- case EXP_D25:
- group_size = 2;
- break;
- default:
- case EXP_D45:
- group_size = 4;
- break;
- }
- nb_groups = (s->nb_coefs[ch] + (group_size * 3) - 4) / (3 * group_size);
- p = encoded_exp[ch];
-
- /* first exponent */
- exp1 = *p++;
- put_bits(&s->pb, 4, exp1);
-
- /* next ones are delta encoded */
- for(i=0;i<nb_groups;i++) {
- /* merge three delta in one code */
- exp0 = exp1;
- exp1 = p[0];
- p += group_size;
- delta0 = exp1 - exp0 + 2;
-
- exp0 = exp1;
- exp1 = p[0];
- p += group_size;
- delta1 = exp1 - exp0 + 2;
-
- exp0 = exp1;
- exp1 = p[0];
- p += group_size;
- delta2 = exp1 - exp0 + 2;
-
- put_bits(&s->pb, 7, ((delta0 * 5 + delta1) * 5) + delta2);
- }
+ /* DC exponent */
+ put_bits(&s->pb, 4, block->grouped_exp[ch][0]);
+
+ /* exponent groups */
+ nb_groups = exponent_group_tab[block->exp_strategy[ch]-1][s->nb_coefs[ch]];
+ for (i = 1; i <= nb_groups; i++)
+ put_bits(&s->pb, 7, block->grouped_exp[ch][i]);
+
+ /* gain range info */
if (ch != s->lfe_channel)
- put_bits(&s->pb, 2, 0); /* no gain range info */
+ put_bits(&s->pb, 2, 0);
}
/* bit allocation info */
}
/* snr offset */
- put_bits(&s->pb, 1, baie); /* always present with bai */
+ put_bits(&s->pb, 1, baie);
if (baie) {
put_bits(&s->pb, 6, s->coarse_snr_offset);
- for(ch=0;ch<s->channels;ch++) {
+ for (ch = 0; ch < s->channels; ch++) {
put_bits(&s->pb, 4, s->fine_snr_offset[ch]);
put_bits(&s->pb, 3, s->fast_gain_code[ch]);
}
put_bits(&s->pb, 1, 0); /* no delta bit allocation */
put_bits(&s->pb, 1, 0); /* no data to skip */
- /* mantissa encoding : we use two passes to handle the grouping. A
- one pass method may be faster, but it would necessitate to
- modify the output stream. */
-
- /* first pass: quantize */
- mant1_cnt = mant2_cnt = mant4_cnt = 0;
- qmant1_ptr = qmant2_ptr = qmant4_ptr = NULL;
-
- for (ch = 0; ch < s->channels; ch++) {
- int b, c, e, v;
-
- for(i=0;i<s->nb_coefs[ch];i++) {
- c = mdct_coefs[ch][i];
- e = encoded_exp[ch][i] - global_exp[ch];
- b = bap[ch][i];
- switch(b) {
- case 0:
- v = 0;
- break;
- case 1:
- v = sym_quant(c, e, 3);
- switch(mant1_cnt) {
- case 0:
- qmant1_ptr = &qmant[ch][i];
- v = 9 * v;
- mant1_cnt = 1;
- break;
- case 1:
- *qmant1_ptr += 3 * v;
- mant1_cnt = 2;
- v = 128;
- break;
- default:
- *qmant1_ptr += v;
- mant1_cnt = 0;
- v = 128;
- break;
- }
- break;
- case 2:
- v = sym_quant(c, e, 5);
- switch(mant2_cnt) {
- case 0:
- qmant2_ptr = &qmant[ch][i];
- v = 25 * v;
- mant2_cnt = 1;
- break;
- case 1:
- *qmant2_ptr += 5 * v;
- mant2_cnt = 2;
- v = 128;
- break;
- default:
- *qmant2_ptr += v;
- mant2_cnt = 0;
- v = 128;
- break;
- }
- break;
- case 3:
- v = sym_quant(c, e, 7);
- break;
- case 4:
- v = sym_quant(c, e, 11);
- switch(mant4_cnt) {
- case 0:
- qmant4_ptr = &qmant[ch][i];
- v = 11 * v;
- mant4_cnt = 1;
- break;
- default:
- *qmant4_ptr += v;
- mant4_cnt = 0;
- v = 128;
- break;
- }
- break;
- case 5:
- v = sym_quant(c, e, 15);
- break;
- case 14:
- v = asym_quant(c, e, 14);
- break;
- case 15:
- v = asym_quant(c, e, 16);
- break;
- default:
- v = asym_quant(c, e, b - 1);
- break;
- }
- qmant[ch][i] = v;
- }
- }
-
- /* second pass : output the values */
+ /* mantissas */
for (ch = 0; ch < s->channels; ch++) {
int b, q;
-
- for(i=0;i<s->nb_coefs[ch];i++) {
- q = qmant[ch][i];
- b = bap[ch][i];
- switch(b) {
- case 0:
- break;
- case 1:
- if (q != 128)
- put_bits(&s->pb, 5, q);
- break;
- case 2:
- if (q != 128)
- put_bits(&s->pb, 7, q);
- break;
- case 3:
- put_bits(&s->pb, 3, q);
- break;
- case 4:
- if (q != 128)
- put_bits(&s->pb, 7, q);
- break;
- case 14:
- put_bits(&s->pb, 14, q);
- break;
- case 15:
- put_bits(&s->pb, 16, q);
- break;
- default:
- put_bits(&s->pb, b - 1, q);
- break;
+ for (i = 0; i < s->nb_coefs[ch]; i++) {
+ q = block->qmant[ch][i];
+ b = block->bap[ch][i];
+ switch (b) {
+ case 0: break;
+ case 1: if (q != 128) put_bits(&s->pb, 5, q); break;
+ case 2: if (q != 128) put_bits(&s->pb, 7, q); break;
+ case 3: put_bits(&s->pb, 3, q); break;
+ case 4: if (q != 128) put_bits(&s->pb, 7, q); break;
+ case 14: put_bits(&s->pb, 14, q); break;
+ case 15: put_bits(&s->pb, 16, q); break;
+ default: put_bits(&s->pb, b-1, q); break;
}
}
}
}
+
+/** CRC-16 Polynomial */
#define CRC16_POLY ((1 << 0) | (1 << 2) | (1 << 15) | (1 << 16))
+
static unsigned int mul_poly(unsigned int a, unsigned int b, unsigned int poly)
{
unsigned int c;
return c;
}
+
static unsigned int pow_poly(unsigned int a, unsigned int n, unsigned int poly)
{
unsigned int r;
}
-/* compute log2(max(abs(tab[]))) */
-static int log2_tab(int16_t *tab, int n)
+/**
+ * Fill the end of the frame with 0's and compute the two CRCs.
+ */
+static void output_frame_end(AC3EncodeContext *s)
{
- int i, v;
+ const AVCRC *crc_ctx = av_crc_get_table(AV_CRC_16_ANSI);
+ int frame_size_58, pad_bytes, crc1, crc2_partial, crc2, crc_inv;
+ uint8_t *frame;
- v = 0;
- for(i=0;i<n;i++) {
- v |= abs(tab[i]);
+ frame_size_58 = ((s->frame_size >> 2) + (s->frame_size >> 4)) << 1;
+
+ /* pad the remainder of the frame with zeros */
+ flush_put_bits(&s->pb);
+ frame = s->pb.buf;
+ pad_bytes = s->frame_size - (put_bits_ptr(&s->pb) - frame) - 2;
+ assert(pad_bytes >= 0);
+ if (pad_bytes > 0)
+ memset(put_bits_ptr(&s->pb), 0, pad_bytes);
+
+ /* compute crc1 */
+ /* this is not so easy because it is at the beginning of the data... */
+ crc1 = av_bswap16(av_crc(crc_ctx, 0, frame + 4, frame_size_58 - 4));
+ crc_inv = s->crc_inv[s->frame_size > s->frame_size_min];
+ crc1 = mul_poly(crc_inv, crc1, CRC16_POLY);
+ AV_WB16(frame + 2, crc1);
+
+ /* compute crc2 */
+ crc2_partial = av_crc(crc_ctx, 0, frame + frame_size_58,
+ s->frame_size - frame_size_58 - 3);
+ crc2 = av_crc(crc_ctx, crc2_partial, frame + s->frame_size - 3, 1);
+ /* ensure crc2 does not match sync word by flipping crcrsv bit if needed */
+ if (crc2 == 0x770B) {
+ frame[s->frame_size - 3] ^= 0x1;
+ crc2 = av_crc(crc_ctx, crc2_partial, frame + s->frame_size - 3, 1);
}
- return av_log2(v);
+ crc2 = av_bswap16(crc2);
+ AV_WB16(frame + s->frame_size - 2, crc2);
}
-static void lshift_tab(int16_t *tab, int n, int lshift)
+
+/**
+ * Write the frame to the output bitstream.
+ */
+static void output_frame(AC3EncodeContext *s, unsigned char *frame)
{
- int i;
+ int blk;
- if (lshift > 0) {
- for(i=0;i<n;i++) {
- tab[i] <<= lshift;
- }
- } else if (lshift < 0) {
- lshift = -lshift;
- for(i=0;i<n;i++) {
- tab[i] >>= lshift;
- }
- }
+ init_put_bits(&s->pb, frame, AC3_MAX_CODED_FRAME_SIZE);
+
+ output_frame_header(s);
+
+ for (blk = 0; blk < AC3_MAX_BLOCKS; blk++)
+ output_audio_block(s, blk);
+
+ output_frame_end(s);
}
-/* fill the end of the frame and compute the two crcs */
-static int output_frame_end(AC3EncodeContext *s)
+
+/**
+ * Encode a single AC-3 frame.
+ */
+static int ac3_encode_frame(AVCodecContext *avctx, unsigned char *frame,
+ int buf_size, void *data)
{
- int frame_size, frame_size_58, n, crc1, crc2, crc_inv;
- uint8_t *frame;
+ AC3EncodeContext *s = avctx->priv_data;
+ const SampleType *samples = data;
+ int ret;
- frame_size = s->frame_size; /* frame size in words */
- /* align to 8 bits */
- flush_put_bits(&s->pb);
- /* add zero bytes to reach the frame size */
- frame = s->pb.buf;
- n = 2 * s->frame_size - (put_bits_ptr(&s->pb) - frame) - 2;
- assert(n >= 0);
- if(n>0)
- memset(put_bits_ptr(&s->pb), 0, n);
-
- /* Now we must compute both crcs : this is not so easy for crc1
- because it is at the beginning of the data... */
- frame_size_58 = (frame_size >> 1) + (frame_size >> 3);
- crc1 = av_bswap16(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0,
- frame + 4, 2 * frame_size_58 - 4));
- /* XXX: could precompute crc_inv */
- crc_inv = pow_poly((CRC16_POLY >> 1), (16 * frame_size_58) - 16, CRC16_POLY);
- crc1 = mul_poly(crc_inv, crc1, CRC16_POLY);
- AV_WB16(frame+2,crc1);
-
- crc2 = av_bswap16(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0,
- frame + 2 * frame_size_58,
- (frame_size - frame_size_58) * 2 - 2));
- AV_WB16(frame+2*frame_size-2,crc2);
-
- // printf("n=%d frame_size=%d\n", n, frame_size);
- return frame_size * 2;
+ if (s->bit_alloc.sr_code == 1)
+ adjust_frame_size(s);
+
+ deinterleave_input_samples(s, samples);
+
+ apply_mdct(s);
+
+ process_exponents(s);
+
+ ret = compute_bit_allocation(s);
+ if (ret) {
+ av_log(avctx, AV_LOG_ERROR, "Bit allocation failed. Try increasing the bitrate.\n");
+ return ret;
+ }
+
+ quantize_mantissas(s);
+
+ output_frame(s, frame);
+
+ return s->frame_size;
}
-static int AC3_encode_frame(AVCodecContext *avctx,
- unsigned char *frame, int buf_size, void *data)
+
+/**
+ * Finalize encoding and free any memory allocated by the encoder.
+ */
+static av_cold int ac3_encode_close(AVCodecContext *avctx)
{
+ int blk, ch;
AC3EncodeContext *s = avctx->priv_data;
- const int16_t *samples = data;
- int i, j, k, v, ch;
- int16_t input_samples[N];
- int32_t mdct_coef[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
- uint8_t exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
- uint8_t exp_strategy[NB_BLOCKS][AC3_MAX_CHANNELS];
- uint8_t encoded_exp[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
- uint8_t bap[NB_BLOCKS][AC3_MAX_CHANNELS][N/2];
- int8_t exp_samples[NB_BLOCKS][AC3_MAX_CHANNELS];
- int frame_bits;
- frame_bits = 0;
- for(ch=0;ch<s->channels;ch++) {
- int ich = s->channel_map[ch];
- /* fixed mdct to the six sub blocks & exponent computation */
- for(i=0;i<NB_BLOCKS;i++) {
- const int16_t *sptr;
- int sinc;
-
- /* compute input samples */
- memcpy(input_samples, s->last_samples[ich], N/2 * sizeof(int16_t));
- sinc = s->channels;
- sptr = samples + (sinc * (N/2) * i) + ich;
- for(j=0;j<N/2;j++) {
- v = *sptr;
- input_samples[j + N/2] = v;
- s->last_samples[ich][j] = v;
- sptr += sinc;
- }
+ for (ch = 0; ch < s->channels; ch++)
+ av_freep(&s->planar_samples[ch]);
+ av_freep(&s->planar_samples);
+ av_freep(&s->bap_buffer);
+ av_freep(&s->bap1_buffer);
+ av_freep(&s->mdct_coef_buffer);
+ av_freep(&s->exp_buffer);
+ av_freep(&s->grouped_exp_buffer);
+ av_freep(&s->psd_buffer);
+ av_freep(&s->band_psd_buffer);
+ av_freep(&s->mask_buffer);
+ av_freep(&s->qmant_buffer);
+ for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
+ AC3Block *block = &s->blocks[blk];
+ av_freep(&block->bap);
+ av_freep(&block->mdct_coef);
+ av_freep(&block->exp);
+ av_freep(&block->grouped_exp);
+ av_freep(&block->psd);
+ av_freep(&block->band_psd);
+ av_freep(&block->mask);
+ av_freep(&block->qmant);
+ }
- /* apply the MDCT window */
- for(j=0;j<N/2;j++) {
- input_samples[j] = MUL16(input_samples[j],
- ff_ac3_window[j]) >> 15;
- input_samples[N-j-1] = MUL16(input_samples[N-j-1],
- ff_ac3_window[j]) >> 15;
- }
+ mdct_end(&s->mdct);
- /* Normalize the samples to use the maximum available
- precision */
- v = 14 - log2_tab(input_samples, N);
- if (v < 0)
- v = 0;
- exp_samples[i][ch] = v - 9;
- lshift_tab(input_samples, N, v);
+ av_freep(&avctx->coded_frame);
+ return 0;
+}
- /* do the MDCT */
- mdct512(mdct_coef[i][ch], input_samples);
- /* compute "exponents". We take into account the
- normalization there */
- for(j=0;j<N/2;j++) {
- int e;
- v = abs(mdct_coef[i][ch][j]);
- if (v == 0)
- e = 24;
- else {
- e = 23 - av_log2(v) + exp_samples[i][ch];
- if (e >= 24) {
- e = 24;
- mdct_coef[i][ch][j] = 0;
- }
- }
- exp[i][ch][j] = e;
- }
- }
+/**
+ * Set channel information during initialization.
+ */
+static av_cold int set_channel_info(AC3EncodeContext *s, int channels,
+ int64_t *channel_layout)
+{
+ int ch_layout;
- compute_exp_strategy(exp_strategy, exp, ch, ch == s->lfe_channel);
-
- /* compute the exponents as the decoder will see them. The
- EXP_REUSE case must be handled carefully : we select the
- min of the exponents */
- i = 0;
- while (i < NB_BLOCKS) {
- j = i + 1;
- while (j < NB_BLOCKS && exp_strategy[j][ch] == EXP_REUSE) {
- exponent_min(exp[i][ch], exp[j][ch], s->nb_coefs[ch]);
- j++;
- }
- frame_bits += encode_exp(encoded_exp[i][ch],
- exp[i][ch], s->nb_coefs[ch],
- exp_strategy[i][ch]);
- /* copy encoded exponents for reuse case */
- for(k=i+1;k<j;k++) {
- memcpy(encoded_exp[k][ch], encoded_exp[i][ch],
- s->nb_coefs[ch] * sizeof(uint8_t));
- }
- i = j;
- }
+ if (channels < 1 || channels > AC3_MAX_CHANNELS)
+ return AVERROR(EINVAL);
+ if ((uint64_t)*channel_layout > 0x7FF)
+ return AVERROR(EINVAL);
+ ch_layout = *channel_layout;
+ if (!ch_layout)
+ ch_layout = avcodec_guess_channel_layout(channels, CODEC_ID_AC3, NULL);
+ if (av_get_channel_layout_nb_channels(ch_layout) != channels)
+ return AVERROR(EINVAL);
+
+ s->lfe_on = !!(ch_layout & AV_CH_LOW_FREQUENCY);
+ s->channels = channels;
+ s->fbw_channels = channels - s->lfe_on;
+ s->lfe_channel = s->lfe_on ? s->fbw_channels : -1;
+ if (s->lfe_on)
+ ch_layout -= AV_CH_LOW_FREQUENCY;
+
+ switch (ch_layout) {
+ case AV_CH_LAYOUT_MONO: s->channel_mode = AC3_CHMODE_MONO; break;
+ case AV_CH_LAYOUT_STEREO: s->channel_mode = AC3_CHMODE_STEREO; break;
+ case AV_CH_LAYOUT_SURROUND: s->channel_mode = AC3_CHMODE_3F; break;
+ case AV_CH_LAYOUT_2_1: s->channel_mode = AC3_CHMODE_2F1R; break;
+ case AV_CH_LAYOUT_4POINT0: s->channel_mode = AC3_CHMODE_3F1R; break;
+ case AV_CH_LAYOUT_QUAD:
+ case AV_CH_LAYOUT_2_2: s->channel_mode = AC3_CHMODE_2F2R; break;
+ case AV_CH_LAYOUT_5POINT0:
+ case AV_CH_LAYOUT_5POINT0_BACK: s->channel_mode = AC3_CHMODE_3F2R; break;
+ default:
+ return AVERROR(EINVAL);
}
- /* adjust for fractional frame sizes */
- while(s->bits_written >= s->bit_rate && s->samples_written >= s->sample_rate) {
- s->bits_written -= s->bit_rate;
- s->samples_written -= s->sample_rate;
+ s->channel_map = ff_ac3_enc_channel_map[s->channel_mode][s->lfe_on];
+ *channel_layout = ch_layout;
+ if (s->lfe_on)
+ *channel_layout |= AV_CH_LOW_FREQUENCY;
+
+ return 0;
+}
+
+
+static av_cold int validate_options(AVCodecContext *avctx, AC3EncodeContext *s)
+{
+ int i, ret;
+
+ /* validate channel layout */
+ if (!avctx->channel_layout) {
+ av_log(avctx, AV_LOG_WARNING, "No channel layout specified. The "
+ "encoder will guess the layout, but it "
+ "might be incorrect.\n");
}
- s->frame_size = s->frame_size_min + (s->bits_written * s->sample_rate < s->samples_written * s->bit_rate);
- s->bits_written += s->frame_size * 16;
- s->samples_written += AC3_FRAME_SIZE;
+ ret = set_channel_info(s, avctx->channels, &avctx->channel_layout);
+ if (ret) {
+ av_log(avctx, AV_LOG_ERROR, "invalid channel layout\n");
+ return ret;
+ }
+
+ /* validate sample rate */
+ for (i = 0; i < 9; i++) {
+ if ((ff_ac3_sample_rate_tab[i / 3] >> (i % 3)) == avctx->sample_rate)
+ break;
+ }
+ if (i == 9) {
+ av_log(avctx, AV_LOG_ERROR, "invalid sample rate\n");
+ return AVERROR(EINVAL);
+ }
+ s->sample_rate = avctx->sample_rate;
+ s->bit_alloc.sr_shift = i % 3;
+ s->bit_alloc.sr_code = i / 3;
+
+ /* validate bit rate */
+ for (i = 0; i < 19; i++) {
+ if ((ff_ac3_bitrate_tab[i] >> s->bit_alloc.sr_shift)*1000 == avctx->bit_rate)
+ break;
+ }
+ if (i == 19) {
+ av_log(avctx, AV_LOG_ERROR, "invalid bit rate\n");
+ return AVERROR(EINVAL);
+ }
+ s->bit_rate = avctx->bit_rate;
+ s->frame_size_code = i << 1;
+
+ /* validate cutoff */
+ if (avctx->cutoff < 0) {
+ av_log(avctx, AV_LOG_ERROR, "invalid cutoff frequency\n");
+ return AVERROR(EINVAL);
+ }
+ s->cutoff = avctx->cutoff;
+ if (s->cutoff > (s->sample_rate >> 1))
+ s->cutoff = s->sample_rate >> 1;
+
+ return 0;
+}
+
+
+/**
+ * Set bandwidth for all channels.
+ * The user can optionally supply a cutoff frequency. Otherwise an appropriate
+ * default value will be used.
+ */
+static av_cold void set_bandwidth(AC3EncodeContext *s)
+{
+ int ch, bw_code;
- compute_bit_allocation(s, bap, encoded_exp, exp_strategy, frame_bits);
- /* everything is known... let's output the frame */
- output_frame_header(s, frame);
+ if (s->cutoff) {
+ /* calculate bandwidth based on user-specified cutoff frequency */
+ int fbw_coeffs;
+ fbw_coeffs = s->cutoff * 2 * AC3_MAX_COEFS / s->sample_rate;
+ bw_code = av_clip((fbw_coeffs - 73) / 3, 0, 60);
+ } else {
+ /* use default bandwidth setting */
+ /* XXX: should compute the bandwidth according to the frame
+ size, so that we avoid annoying high frequency artifacts */
+ bw_code = 50;
+ }
- for(i=0;i<NB_BLOCKS;i++) {
- output_audio_block(s, exp_strategy[i], encoded_exp[i],
- bap[i], mdct_coef[i], exp_samples[i], i);
+ /* set number of coefficients for each channel */
+ for (ch = 0; ch < s->fbw_channels; ch++) {
+ s->bandwidth_code[ch] = bw_code;
+ s->nb_coefs[ch] = bw_code * 3 + 73;
}
- return output_frame_end(s);
+ if (s->lfe_on)
+ s->nb_coefs[s->lfe_channel] = 7; /* LFE channel always has 7 coefs */
}
-static av_cold int AC3_encode_close(AVCodecContext *avctx)
+
+static av_cold int allocate_buffers(AVCodecContext *avctx)
{
- av_freep(&avctx->coded_frame);
+ int blk, ch;
+ AC3EncodeContext *s = avctx->priv_data;
+
+ FF_ALLOC_OR_GOTO(avctx, s->planar_samples, s->channels * sizeof(*s->planar_samples),
+ alloc_fail);
+ for (ch = 0; ch < s->channels; ch++) {
+ FF_ALLOCZ_OR_GOTO(avctx, s->planar_samples[ch],
+ (AC3_FRAME_SIZE+AC3_BLOCK_SIZE) * sizeof(**s->planar_samples),
+ alloc_fail);
+ }
+ FF_ALLOC_OR_GOTO(avctx, s->bap_buffer, AC3_MAX_BLOCKS * s->channels *
+ AC3_MAX_COEFS * sizeof(*s->bap_buffer), alloc_fail);
+ FF_ALLOC_OR_GOTO(avctx, s->bap1_buffer, AC3_MAX_BLOCKS * s->channels *
+ AC3_MAX_COEFS * sizeof(*s->bap1_buffer), alloc_fail);
+ FF_ALLOC_OR_GOTO(avctx, s->mdct_coef_buffer, AC3_MAX_BLOCKS * s->channels *
+ AC3_MAX_COEFS * sizeof(*s->mdct_coef_buffer), alloc_fail);
+ FF_ALLOC_OR_GOTO(avctx, s->exp_buffer, AC3_MAX_BLOCKS * s->channels *
+ AC3_MAX_COEFS * sizeof(*s->exp_buffer), alloc_fail);
+ FF_ALLOC_OR_GOTO(avctx, s->grouped_exp_buffer, AC3_MAX_BLOCKS * s->channels *
+ 128 * sizeof(*s->grouped_exp_buffer), alloc_fail);
+ FF_ALLOC_OR_GOTO(avctx, s->psd_buffer, AC3_MAX_BLOCKS * s->channels *
+ AC3_MAX_COEFS * sizeof(*s->psd_buffer), alloc_fail);
+ FF_ALLOC_OR_GOTO(avctx, s->band_psd_buffer, AC3_MAX_BLOCKS * s->channels *
+ 64 * sizeof(*s->band_psd_buffer), alloc_fail);
+ FF_ALLOC_OR_GOTO(avctx, s->mask_buffer, AC3_MAX_BLOCKS * s->channels *
+ 64 * sizeof(*s->mask_buffer), alloc_fail);
+ FF_ALLOC_OR_GOTO(avctx, s->qmant_buffer, AC3_MAX_BLOCKS * s->channels *
+ AC3_MAX_COEFS * sizeof(*s->qmant_buffer), alloc_fail);
+ for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
+ AC3Block *block = &s->blocks[blk];
+ FF_ALLOC_OR_GOTO(avctx, block->bap, s->channels * sizeof(*block->bap),
+ alloc_fail);
+ FF_ALLOCZ_OR_GOTO(avctx, block->mdct_coef, s->channels * sizeof(*block->mdct_coef),
+ alloc_fail);
+ FF_ALLOCZ_OR_GOTO(avctx, block->exp, s->channels * sizeof(*block->exp),
+ alloc_fail);
+ FF_ALLOCZ_OR_GOTO(avctx, block->grouped_exp, s->channels * sizeof(*block->grouped_exp),
+ alloc_fail);
+ FF_ALLOCZ_OR_GOTO(avctx, block->psd, s->channels * sizeof(*block->psd),
+ alloc_fail);
+ FF_ALLOCZ_OR_GOTO(avctx, block->band_psd, s->channels * sizeof(*block->band_psd),
+ alloc_fail);
+ FF_ALLOCZ_OR_GOTO(avctx, block->mask, s->channels * sizeof(*block->mask),
+ alloc_fail);
+ FF_ALLOCZ_OR_GOTO(avctx, block->qmant, s->channels * sizeof(*block->qmant),
+ alloc_fail);
+
+ for (ch = 0; ch < s->channels; ch++) {
+ block->bap[ch] = &s->bap_buffer [AC3_MAX_COEFS * (blk * s->channels + ch)];
+ block->mdct_coef[ch] = &s->mdct_coef_buffer [AC3_MAX_COEFS * (blk * s->channels + ch)];
+ block->exp[ch] = &s->exp_buffer [AC3_MAX_COEFS * (blk * s->channels + ch)];
+ block->grouped_exp[ch] = &s->grouped_exp_buffer[128 * (blk * s->channels + ch)];
+ block->psd[ch] = &s->psd_buffer [AC3_MAX_COEFS * (blk * s->channels + ch)];
+ block->band_psd[ch] = &s->band_psd_buffer [64 * (blk * s->channels + ch)];
+ block->mask[ch] = &s->mask_buffer [64 * (blk * s->channels + ch)];
+ block->qmant[ch] = &s->qmant_buffer [AC3_MAX_COEFS * (blk * s->channels + ch)];
+ }
+ }
+
+ return 0;
+alloc_fail:
+ return AVERROR(ENOMEM);
+}
+
+
+/**
+ * Initialize the encoder.
+ */
+static av_cold int ac3_encode_init(AVCodecContext *avctx)
+{
+ AC3EncodeContext *s = avctx->priv_data;
+ int ret, frame_size_58;
+
+ avctx->frame_size = AC3_FRAME_SIZE;
+
+ ac3_common_init();
+
+ ret = validate_options(avctx, s);
+ if (ret)
+ return ret;
+
+ s->bitstream_id = 8 + s->bit_alloc.sr_shift;
+ s->bitstream_mode = 0; /* complete main audio service */
+
+ s->frame_size_min = 2 * ff_ac3_frame_size_tab[s->frame_size_code][s->bit_alloc.sr_code];
+ s->bits_written = 0;
+ s->samples_written = 0;
+ s->frame_size = s->frame_size_min;
+
+ /* calculate crc_inv for both possible frame sizes */
+ frame_size_58 = (( s->frame_size >> 2) + ( s->frame_size >> 4)) << 1;
+ s->crc_inv[0] = pow_poly((CRC16_POLY >> 1), (8 * frame_size_58) - 16, CRC16_POLY);
+ if (s->bit_alloc.sr_code == 1) {
+ frame_size_58 = (((s->frame_size+2) >> 2) + ((s->frame_size+2) >> 4)) << 1;
+ s->crc_inv[1] = pow_poly((CRC16_POLY >> 1), (8 * frame_size_58) - 16, CRC16_POLY);
+ }
+
+ set_bandwidth(s);
+
+ exponent_init(s);
+
+ bit_alloc_init(s);
+
+ ret = mdct_init(avctx, &s->mdct, 9);
+ if (ret)
+ goto init_fail;
+
+ ret = allocate_buffers(avctx);
+ if (ret)
+ goto init_fail;
+
+ avctx->coded_frame= avcodec_alloc_frame();
+
+ dsputil_init(&s->dsp, avctx);
+
return 0;
+init_fail:
+ ac3_encode_close(avctx);
+ return ret;
}
-#if 0
+
+#ifdef TEST
/*************************************************************************/
/* TEST */
-#undef random
-#define FN (N/4)
+#include "libavutil/lfg.h"
-void fft_test(void)
+#define MDCT_NBITS 9
+#define MDCT_SAMPLES (1 << MDCT_NBITS)
+#define FN (MDCT_SAMPLES/4)
+
+
+static void fft_test(AC3MDCTContext *mdct, AVLFG *lfg)
{
IComplex in[FN], in1[FN];
int k, n, i;
float sum_re, sum_im, a;
- /* FFT test */
-
- for(i=0;i<FN;i++) {
- in[i].re = random() % 65535 - 32767;
- in[i].im = random() % 65535 - 32767;
- in1[i] = in[i];
+ for (i = 0; i < FN; i++) {
+ in[i].re = av_lfg_get(lfg) % 65535 - 32767;
+ in[i].im = av_lfg_get(lfg) % 65535 - 32767;
+ in1[i] = in[i];
}
- fft(in, 7);
+ fft(mdct, in, 7);
/* do it by hand */
- for(k=0;k<FN;k++) {
+ for (k = 0; k < FN; k++) {
sum_re = 0;
sum_im = 0;
- for(n=0;n<FN;n++) {
+ for (n = 0; n < FN; n++) {
a = -2 * M_PI * (n * k) / FN;
sum_re += in1[n].re * cos(a) - in1[n].im * sin(a);
sum_im += in1[n].re * sin(a) + in1[n].im * cos(a);
}
- printf("%3d: %6d,%6d %6.0f,%6.0f\n",
+ av_log(NULL, AV_LOG_DEBUG, "%3d: %6d,%6d %6.0f,%6.0f\n",
k, in[k].re, in[k].im, sum_re / FN, sum_im / FN);
}
}
-void mdct_test(void)
+
+static void mdct_test(AC3MDCTContext *mdct, AVLFG *lfg)
{
- int16_t input[N];
- int32_t output[N/2];
- float input1[N];
- float output1[N/2];
+ int16_t input[MDCT_SAMPLES];
+ int32_t output[AC3_MAX_COEFS];
+ float input1[MDCT_SAMPLES];
+ float output1[AC3_MAX_COEFS];
float s, a, err, e, emax;
int i, k, n;
- for(i=0;i<N;i++) {
- input[i] = (random() % 65535 - 32767) * 9 / 10;
+ for (i = 0; i < MDCT_SAMPLES; i++) {
+ input[i] = (av_lfg_get(lfg) % 65535 - 32767) * 9 / 10;
input1[i] = input[i];
}
- mdct512(output, input);
+ mdct512(mdct, output, input);
/* do it by hand */
- for(k=0;k<N/2;k++) {
+ for (k = 0; k < AC3_MAX_COEFS; k++) {
s = 0;
- for(n=0;n<N;n++) {
- a = (2*M_PI*(2*n+1+N/2)*(2*k+1) / (4 * N));
+ for (n = 0; n < MDCT_SAMPLES; n++) {
+ a = (2*M_PI*(2*n+1+MDCT_SAMPLES/2)*(2*k+1) / (4 * MDCT_SAMPLES));
s += input1[n] * cos(a);
}
- output1[k] = -2 * s / N;
+ output1[k] = -2 * s / MDCT_SAMPLES;
}
- err = 0;
+ err = 0;
emax = 0;
- for(i=0;i<N/2;i++) {
- printf("%3d: %7d %7.0f\n", i, output[i], output1[i]);
+ for (i = 0; i < AC3_MAX_COEFS; i++) {
+ av_log(NULL, AV_LOG_DEBUG, "%3d: %7d %7.0f\n", i, output[i], output1[i]);
e = output[i] - output1[i];
if (e > emax)
emax = e;
err += e * e;
}
- printf("err2=%f emax=%f\n", err / (N/2), emax);
+ av_log(NULL, AV_LOG_DEBUG, "err2=%f emax=%f\n", err / AC3_MAX_COEFS, emax);
}
-void test_ac3(void)
+
+int main(void)
{
- AC3EncodeContext ctx;
- unsigned char frame[AC3_MAX_CODED_FRAME_SIZE];
- int16_t samples[AC3_FRAME_SIZE];
- int ret, i;
+ AVLFG lfg;
+ AC3MDCTContext mdct;
- AC3_encode_init(&ctx, 44100, 64000, 1);
+ mdct.avctx = NULL;
+ av_log_set_level(AV_LOG_DEBUG);
+ mdct_init(&mdct, 9);
- fft_test();
- mdct_test();
+ fft_test(&mdct, &lfg);
+ mdct_test(&mdct, &lfg);
- for(i=0;i<AC3_FRAME_SIZE;i++)
- samples[i] = (int)(sin(2*M_PI*i*1000.0/44100) * 10000);
- ret = AC3_encode_frame(&ctx, frame, samples);
- printf("ret=%d\n", ret);
+ return 0;
}
-#endif
+#endif /* TEST */
+
AVCodec ac3_encoder = {
"ac3",
AVMEDIA_TYPE_AUDIO,
CODEC_ID_AC3,
sizeof(AC3EncodeContext),
- AC3_encode_init,
- AC3_encode_frame,
- AC3_encode_close,
+ ac3_encode_init,
+ ac3_encode_frame,
+ ac3_encode_close,
NULL,
.sample_fmts = (const enum AVSampleFormat[]){AV_SAMPLE_FMT_S16,AV_SAMPLE_FMT_NONE},
.long_name = NULL_IF_CONFIG_SMALL("ATSC A/52A (AC-3)"),
- .channel_layouts = (const int64_t[]){
- AV_CH_LAYOUT_MONO,
- AV_CH_LAYOUT_STEREO,
- AV_CH_LAYOUT_2_1,
- AV_CH_LAYOUT_SURROUND,
- AV_CH_LAYOUT_2_2,
- AV_CH_LAYOUT_QUAD,
- AV_CH_LAYOUT_4POINT0,
- AV_CH_LAYOUT_5POINT0,
- AV_CH_LAYOUT_5POINT0_BACK,
- (AV_CH_LAYOUT_MONO | AV_CH_LOW_FREQUENCY),
- (AV_CH_LAYOUT_STEREO | AV_CH_LOW_FREQUENCY),
- (AV_CH_LAYOUT_2_1 | AV_CH_LOW_FREQUENCY),
- (AV_CH_LAYOUT_SURROUND | AV_CH_LOW_FREQUENCY),
- (AV_CH_LAYOUT_2_2 | AV_CH_LOW_FREQUENCY),
- (AV_CH_LAYOUT_QUAD | AV_CH_LOW_FREQUENCY),
- (AV_CH_LAYOUT_4POINT0 | AV_CH_LOW_FREQUENCY),
- AV_CH_LAYOUT_5POINT1,
- AV_CH_LAYOUT_5POINT1_BACK,
- 0 },
+ .channel_layouts = ac3_channel_layouts,
};