2 * ALAC (Apple Lossless Audio Codec) decoder
3 * Copyright (c) 2005 David Hammerton
5 * This file is part of FFmpeg.
7 * FFmpeg is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Lesser General Public
9 * License as published by the Free Software Foundation; either
10 * version 2.1 of the License, or (at your option) any later version.
12 * FFmpeg is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * Lesser General Public License for more details.
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with FFmpeg; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
24 * ALAC (Apple Lossless Audio Codec) decoder
25 * @author 2005 David Hammerton
26 * @see http://crazney.net/programs/itunes/alac.html
28 * Note: This decoder expects a 36-byte QuickTime atom to be
29 * passed through the extradata[_size] fields. This atom is tacked onto
30 * the end of an 'alac' stsd atom and has the following format:
33 * 32 bits tag ("alac")
34 * 32 bits tag version (0)
35 * 32 bits samples per frame (used when not set explicitly in the frames)
36 * 8 bits compatible version (0)
38 * 8 bits history mult (40)
39 * 8 bits initial history (10)
40 * 8 bits rice param limit (14)
42 * 16 bits maxRun (255)
43 * 32 bits max coded frame size (0 means unknown)
44 * 32 bits average bitrate (0 means unknown)
50 #include "libavutil/channel_layout.h"
51 #include "libavutil/opt.h"
54 #include "bytestream.h"
59 #include "alac_data.h"
62 #define ALAC_EXTRADATA_SIZE 36
64 typedef struct ALACContext {
66 AVCodecContext *avctx;
70 int32_t *predict_error_buffer[2];
71 int32_t *output_samples_buffer[2];
72 int32_t *extra_bits_buffer[2];
74 uint32_t max_samples_per_frame;
76 uint8_t rice_history_mult;
77 uint8_t rice_initial_history;
81 int extra_bits; /**< number of extra bits beyond 16-bit */
82 int nb_samples; /**< number of samples in the current frame */
90 static inline unsigned int decode_scalar(GetBitContext *gb, int k, int bps)
92 unsigned int x = get_unary_0_9(gb);
94 if (x > 8) { /* RICE THRESHOLD */
95 /* use alternative encoding */
96 x = get_bits_long(gb, bps);
98 int extrabits = show_bits(gb, k);
100 /* multiply x by 2^k - 1, as part of their strange algorithm */
107 skip_bits(gb, k - 1);
112 static int rice_decompress(ALACContext *alac, int32_t *output_buffer,
113 int nb_samples, int bps, int rice_history_mult)
116 unsigned int history = alac->rice_initial_history;
117 int sign_modifier = 0;
119 for (i = 0; i < nb_samples; i++) {
123 if(get_bits_left(&alac->gb) <= 0)
124 return AVERROR_INVALIDDATA;
126 /* calculate rice param and decode next value */
127 k = av_log2((history >> 9) + 3);
128 k = FFMIN(k, alac->rice_limit);
129 x = decode_scalar(&alac->gb, k, bps);
132 output_buffer[i] = (x >> 1) ^ -(x & 1);
134 /* update the history */
138 history += x * rice_history_mult -
139 ((history * rice_history_mult) >> 9);
141 /* special case: there may be compressed blocks of 0 */
142 if ((history < 128) && (i + 1 < nb_samples)) {
145 /* calculate rice param and decode block size */
146 k = 7 - av_log2(history) + ((history + 16) >> 6);
147 k = FFMIN(k, alac->rice_limit);
148 block_size = decode_scalar(&alac->gb, k, 16);
150 if (block_size > 0) {
151 if (block_size >= nb_samples - i) {
152 av_log(alac->avctx, AV_LOG_ERROR,
153 "invalid zero block size of %d %d %d\n", block_size,
155 block_size = nb_samples - i - 1;
157 memset(&output_buffer[i + 1], 0,
158 block_size * sizeof(*output_buffer));
161 if (block_size <= 0xffff)
169 static inline int sign_only(int v)
171 return v ? FFSIGN(v) : 0;
174 static void lpc_prediction(int32_t *error_buffer, uint32_t *buffer_out,
175 int nb_samples, int bps, int16_t *lpc_coefs,
176 int lpc_order, int lpc_quant)
179 uint32_t *pred = buffer_out;
181 /* first sample always copies */
182 *buffer_out = *error_buffer;
188 memcpy(&buffer_out[1], &error_buffer[1],
189 (nb_samples - 1) * sizeof(*buffer_out));
193 if (lpc_order == 31) {
194 /* simple 1st-order prediction */
195 for (i = 1; i < nb_samples; i++) {
196 buffer_out[i] = sign_extend(buffer_out[i - 1] + error_buffer[i],
202 /* read warm-up samples */
203 for (i = 1; i <= lpc_order && i < nb_samples; i++)
204 buffer_out[i] = sign_extend(buffer_out[i - 1] + error_buffer[i], bps);
206 /* NOTE: 4 and 8 are very common cases that could be optimized. */
208 for (; i < nb_samples; i++) {
211 unsigned error_val = error_buffer[i];
216 for (j = 0; j < lpc_order; j++)
217 val += (pred[j] - d) * lpc_coefs[j];
218 val = (val + (1LL << (lpc_quant - 1))) >> lpc_quant;
219 val += d + error_val;
220 buffer_out[i] = sign_extend(val, bps);
222 /* adapt LPC coefficients */
223 error_sign = sign_only(error_val);
225 for (j = 0; j < lpc_order && (int)(error_val * error_sign) > 0; j++) {
228 sign = sign_only(val) * error_sign;
229 lpc_coefs[j] -= sign;
230 val *= (unsigned)sign;
231 error_val -= (val >> lpc_quant) * (j + 1U);
237 static int decode_element(AVCodecContext *avctx, AVFrame *frame, int ch_index,
240 ALACContext *alac = avctx->priv_data;
241 int has_size, bps, is_compressed, decorr_shift, decorr_left_weight, ret;
242 uint32_t output_samples;
245 skip_bits(&alac->gb, 4); /* element instance tag */
246 skip_bits(&alac->gb, 12); /* unused header bits */
248 /* the number of output samples is stored in the frame */
249 has_size = get_bits1(&alac->gb);
251 alac->extra_bits = get_bits(&alac->gb, 2) << 3;
252 bps = alac->sample_size - alac->extra_bits + channels - 1;
254 avpriv_report_missing_feature(avctx, "bps %d", bps);
255 return AVERROR_PATCHWELCOME;
258 return AVERROR_INVALIDDATA;
260 /* whether the frame is compressed */
261 is_compressed = !get_bits1(&alac->gb);
264 output_samples = get_bits_long(&alac->gb, 32);
266 output_samples = alac->max_samples_per_frame;
267 if (!output_samples || output_samples > alac->max_samples_per_frame) {
268 av_log(avctx, AV_LOG_ERROR, "invalid samples per frame: %"PRIu32"\n",
270 return AVERROR_INVALIDDATA;
272 if (!alac->nb_samples) {
273 ThreadFrame tframe = { .f = frame };
274 /* get output buffer */
275 frame->nb_samples = output_samples;
276 if ((ret = ff_thread_get_buffer(avctx, &tframe, 0)) < 0)
278 } else if (output_samples != alac->nb_samples) {
279 av_log(avctx, AV_LOG_ERROR, "sample count mismatch: %"PRIu32" != %d\n",
280 output_samples, alac->nb_samples);
281 return AVERROR_INVALIDDATA;
283 alac->nb_samples = output_samples;
284 if (alac->direct_output) {
285 for (ch = 0; ch < channels; ch++)
286 alac->output_samples_buffer[ch] = (int32_t *)frame->extended_data[ch_index + ch];
290 int16_t lpc_coefs[2][32];
292 int prediction_type[2];
294 int rice_history_mult[2];
296 if (!alac->rice_limit) {
297 avpriv_request_sample(alac->avctx,
298 "Compression with rice limit 0");
299 return AVERROR(ENOSYS);
302 decorr_shift = get_bits(&alac->gb, 8);
303 decorr_left_weight = get_bits(&alac->gb, 8);
305 for (ch = 0; ch < channels; ch++) {
306 prediction_type[ch] = get_bits(&alac->gb, 4);
307 lpc_quant[ch] = get_bits(&alac->gb, 4);
308 rice_history_mult[ch] = get_bits(&alac->gb, 3);
309 lpc_order[ch] = get_bits(&alac->gb, 5);
311 if (lpc_order[ch] >= alac->max_samples_per_frame || !lpc_quant[ch])
312 return AVERROR_INVALIDDATA;
314 /* read the predictor table */
315 for (i = lpc_order[ch] - 1; i >= 0; i--)
316 lpc_coefs[ch][i] = get_sbits(&alac->gb, 16);
319 if (alac->extra_bits) {
320 for (i = 0; i < alac->nb_samples; i++) {
321 if(get_bits_left(&alac->gb) <= 0)
322 return AVERROR_INVALIDDATA;
323 for (ch = 0; ch < channels; ch++)
324 alac->extra_bits_buffer[ch][i] = get_bits(&alac->gb, alac->extra_bits);
327 for (ch = 0; ch < channels; ch++) {
328 int ret=rice_decompress(alac, alac->predict_error_buffer[ch],
329 alac->nb_samples, bps,
330 rice_history_mult[ch] * alac->rice_history_mult / 4);
334 /* adaptive FIR filter */
335 if (prediction_type[ch] == 15) {
336 /* Prediction type 15 runs the adaptive FIR twice.
337 * The first pass uses the special-case coef_num = 31, while
338 * the second pass uses the coefs from the bitstream.
340 * However, this prediction type is not currently used by the
343 lpc_prediction(alac->predict_error_buffer[ch],
344 alac->predict_error_buffer[ch],
345 alac->nb_samples, bps, NULL, 31, 0);
346 } else if (prediction_type[ch] > 0) {
347 av_log(avctx, AV_LOG_WARNING, "unknown prediction type: %i\n",
348 prediction_type[ch]);
350 lpc_prediction(alac->predict_error_buffer[ch],
351 alac->output_samples_buffer[ch], alac->nb_samples,
352 bps, lpc_coefs[ch], lpc_order[ch], lpc_quant[ch]);
355 /* not compressed, easy case */
356 for (i = 0; i < alac->nb_samples; i++) {
357 if(get_bits_left(&alac->gb) <= 0)
358 return AVERROR_INVALIDDATA;
359 for (ch = 0; ch < channels; ch++) {
360 alac->output_samples_buffer[ch][i] =
361 get_sbits_long(&alac->gb, alac->sample_size);
364 alac->extra_bits = 0;
366 decorr_left_weight = 0;
370 if (alac->extra_bits && alac->extra_bit_bug) {
371 alac->dsp.append_extra_bits[1](alac->output_samples_buffer, alac->extra_bits_buffer,
372 alac->extra_bits, channels, alac->nb_samples);
375 if (decorr_left_weight) {
376 alac->dsp.decorrelate_stereo(alac->output_samples_buffer, alac->nb_samples,
377 decorr_shift, decorr_left_weight);
380 if (alac->extra_bits && !alac->extra_bit_bug) {
381 alac->dsp.append_extra_bits[1](alac->output_samples_buffer, alac->extra_bits_buffer,
382 alac->extra_bits, channels, alac->nb_samples);
384 } else if (alac->extra_bits) {
385 alac->dsp.append_extra_bits[0](alac->output_samples_buffer, alac->extra_bits_buffer,
386 alac->extra_bits, channels, alac->nb_samples);
389 switch(alac->sample_size) {
391 for (ch = 0; ch < channels; ch++) {
392 int16_t *outbuffer = (int16_t *)frame->extended_data[ch_index + ch];
393 for (i = 0; i < alac->nb_samples; i++)
394 *outbuffer++ = alac->output_samples_buffer[ch][i];
398 for (ch = 0; ch < channels; ch++) {
399 for (i = 0; i < alac->nb_samples; i++)
400 alac->output_samples_buffer[ch][i] *= 1 << 12;
404 for (ch = 0; ch < channels; ch++) {
405 for (i = 0; i < alac->nb_samples; i++)
406 alac->output_samples_buffer[ch][i] *= 1 << 8;
414 static int alac_decode_frame(AVCodecContext *avctx, void *data,
415 int *got_frame_ptr, AVPacket *avpkt)
417 ALACContext *alac = avctx->priv_data;
418 AVFrame *frame = data;
419 enum AlacRawDataBlockType element;
421 int ch, ret, got_end;
423 if ((ret = init_get_bits8(&alac->gb, avpkt->data, avpkt->size)) < 0)
427 alac->nb_samples = 0;
429 while (get_bits_left(&alac->gb) >= 3) {
430 element = get_bits(&alac->gb, 3);
431 if (element == TYPE_END) {
435 if (element > TYPE_CPE && element != TYPE_LFE) {
436 avpriv_report_missing_feature(avctx, "Syntax element %d", element);
437 return AVERROR_PATCHWELCOME;
440 channels = (element == TYPE_CPE) ? 2 : 1;
441 if (ch + channels > alac->channels ||
442 ff_alac_channel_layout_offsets[alac->channels - 1][ch] + channels > alac->channels) {
443 av_log(avctx, AV_LOG_ERROR, "invalid element channel count\n");
444 return AVERROR_INVALIDDATA;
447 ret = decode_element(avctx, frame,
448 ff_alac_channel_layout_offsets[alac->channels - 1][ch],
450 if (ret < 0 && get_bits_left(&alac->gb))
456 av_log(avctx, AV_LOG_ERROR, "no end tag found. incomplete packet.\n");
457 return AVERROR_INVALIDDATA;
460 if (avpkt->size * 8 - get_bits_count(&alac->gb) > 8) {
461 av_log(avctx, AV_LOG_ERROR, "Error : %d bits left\n",
462 avpkt->size * 8 - get_bits_count(&alac->gb));
465 if (alac->channels == ch && alac->nb_samples)
468 av_log(avctx, AV_LOG_WARNING, "Failed to decode all channels\n");
473 static av_cold int alac_decode_close(AVCodecContext *avctx)
475 ALACContext *alac = avctx->priv_data;
478 for (ch = 0; ch < FFMIN(alac->channels, 2); ch++) {
479 av_freep(&alac->predict_error_buffer[ch]);
480 if (!alac->direct_output)
481 av_freep(&alac->output_samples_buffer[ch]);
482 av_freep(&alac->extra_bits_buffer[ch]);
488 static int allocate_buffers(ALACContext *alac)
491 unsigned buf_size = alac->max_samples_per_frame * sizeof(int32_t);
493 for (ch = 0; ch < 2; ch++) {
494 alac->predict_error_buffer[ch] = NULL;
495 alac->output_samples_buffer[ch] = NULL;
496 alac->extra_bits_buffer[ch] = NULL;
499 for (ch = 0; ch < FFMIN(alac->channels, 2); ch++) {
500 FF_ALLOC_OR_GOTO(alac->avctx, alac->predict_error_buffer[ch],
501 buf_size, buf_alloc_fail);
503 alac->direct_output = alac->sample_size > 16;
504 if (!alac->direct_output) {
505 FF_ALLOC_OR_GOTO(alac->avctx, alac->output_samples_buffer[ch],
506 buf_size + AV_INPUT_BUFFER_PADDING_SIZE, buf_alloc_fail);
509 FF_ALLOC_OR_GOTO(alac->avctx, alac->extra_bits_buffer[ch],
510 buf_size + AV_INPUT_BUFFER_PADDING_SIZE, buf_alloc_fail);
514 alac_decode_close(alac->avctx);
515 return AVERROR(ENOMEM);
518 static int alac_set_info(ALACContext *alac)
522 bytestream2_init(&gb, alac->avctx->extradata,
523 alac->avctx->extradata_size);
525 bytestream2_skipu(&gb, 12); // size:4, alac:4, version:4
527 alac->max_samples_per_frame = bytestream2_get_be32u(&gb);
528 if (!alac->max_samples_per_frame ||
529 alac->max_samples_per_frame > 4096 * 4096) {
530 av_log(alac->avctx, AV_LOG_ERROR,
531 "max samples per frame invalid: %"PRIu32"\n",
532 alac->max_samples_per_frame);
533 return AVERROR_INVALIDDATA;
535 bytestream2_skipu(&gb, 1); // compatible version
536 alac->sample_size = bytestream2_get_byteu(&gb);
537 alac->rice_history_mult = bytestream2_get_byteu(&gb);
538 alac->rice_initial_history = bytestream2_get_byteu(&gb);
539 alac->rice_limit = bytestream2_get_byteu(&gb);
540 alac->channels = bytestream2_get_byteu(&gb);
541 bytestream2_get_be16u(&gb); // maxRun
542 bytestream2_get_be32u(&gb); // max coded frame size
543 bytestream2_get_be32u(&gb); // average bitrate
544 alac->sample_rate = bytestream2_get_be32u(&gb);
549 static av_cold int alac_decode_init(AVCodecContext * avctx)
552 ALACContext *alac = avctx->priv_data;
555 /* initialize from the extradata */
556 if (alac->avctx->extradata_size < ALAC_EXTRADATA_SIZE) {
557 av_log(avctx, AV_LOG_ERROR, "extradata is too small\n");
558 return AVERROR_INVALIDDATA;
560 if ((ret = alac_set_info(alac)) < 0) {
561 av_log(avctx, AV_LOG_ERROR, "set_info failed\n");
565 switch (alac->sample_size) {
566 case 16: avctx->sample_fmt = AV_SAMPLE_FMT_S16P;
570 case 32: avctx->sample_fmt = AV_SAMPLE_FMT_S32P;
572 default: avpriv_request_sample(avctx, "Sample depth %d", alac->sample_size);
573 return AVERROR_PATCHWELCOME;
575 avctx->bits_per_raw_sample = alac->sample_size;
576 avctx->sample_rate = alac->sample_rate;
578 if (alac->channels < 1) {
579 av_log(avctx, AV_LOG_WARNING, "Invalid channel count\n");
580 alac->channels = avctx->channels;
582 if (alac->channels > ALAC_MAX_CHANNELS)
583 alac->channels = avctx->channels;
585 avctx->channels = alac->channels;
587 if (avctx->channels > ALAC_MAX_CHANNELS || avctx->channels <= 0 ) {
588 avpriv_report_missing_feature(avctx, "Channel count %d",
590 return AVERROR_PATCHWELCOME;
592 avctx->channel_layout = ff_alac_channel_layouts[alac->channels - 1];
594 if ((ret = allocate_buffers(alac)) < 0) {
595 av_log(avctx, AV_LOG_ERROR, "Error allocating buffers\n");
599 ff_alacdsp_init(&alac->dsp);
604 static const AVOption options[] = {
605 { "extra_bits_bug", "Force non-standard decoding process",
606 offsetof(ALACContext, extra_bit_bug), AV_OPT_TYPE_BOOL, { .i64 = 0 },
607 0, 1, AV_OPT_FLAG_AUDIO_PARAM | AV_OPT_FLAG_DECODING_PARAM },
611 static const AVClass alac_class = {
612 .class_name = "alac",
613 .item_name = av_default_item_name,
615 .version = LIBAVUTIL_VERSION_INT,
618 AVCodec ff_alac_decoder = {
620 .long_name = NULL_IF_CONFIG_SMALL("ALAC (Apple Lossless Audio Codec)"),
621 .type = AVMEDIA_TYPE_AUDIO,
622 .id = AV_CODEC_ID_ALAC,
623 .priv_data_size = sizeof(ALACContext),
624 .init = alac_decode_init,
625 .close = alac_decode_close,
626 .decode = alac_decode_frame,
627 .capabilities = AV_CODEC_CAP_DR1 | AV_CODEC_CAP_FRAME_THREADS,
628 .priv_class = &alac_class