2 * Lagarith lossless decoder
3 * Copyright (c) 2009 Nathan Caldwell <saintdev (at) gmail.com>
5 * This file is part of FFmpeg.
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19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
24 * Lagarith lossless decoder
25 * @author Nathan Caldwell
32 #include "lagarithrac.h"
34 enum LagarithFrameType {
35 FRAME_RAW = 1, /**< uncompressed */
36 FRAME_U_RGB24 = 2, /**< unaligned RGB24 */
37 FRAME_ARITH_YUY2 = 3, /**< arithmetic coded YUY2 */
38 FRAME_ARITH_RGB24 = 4, /**< arithmetic coded RGB24 */
39 FRAME_SOLID_GRAY = 5, /**< solid grayscale color frame */
40 FRAME_SOLID_COLOR = 6, /**< solid non-grayscale color frame */
41 FRAME_OLD_ARITH_RGB = 7, /**< obsolete arithmetic coded RGB (no longer encoded by upstream since version 1.1.0) */
42 FRAME_ARITH_RGBA = 8, /**< arithmetic coded RGBA */
43 FRAME_SOLID_RGBA = 9, /**< solid RGBA color frame */
44 FRAME_ARITH_YV12 = 10, /**< arithmetic coded YV12 */
45 FRAME_REDUCED_RES = 11, /**< reduced resolution YV12 frame */
48 typedef struct LagarithContext {
49 AVCodecContext *avctx;
52 int zeros; /**< number of consecutive zero bytes encountered */
53 int zeros_rem; /**< number of zero bytes remaining to output */
57 * Compute the 52bit mantissa of 1/(double)denom.
58 * This crazy format uses floats in an entropy coder and we have to match x86
59 * rounding exactly, thus ordinary floats aren't portable enough.
60 * @param denom denominator
61 * @return 52bit mantissa
64 static uint64_t softfloat_reciprocal(uint32_t denom)
66 int shift = av_log2(denom - 1) + 1;
67 uint64_t ret = (1ULL << 52) / denom;
68 uint64_t err = (1ULL << 52) - ret * denom;
72 return ret + err / denom;
76 * (uint32_t)(x*f), where f has the given mantissa, and exponent 0
77 * Used in combination with softfloat_reciprocal computes x/(double)denom.
78 * @param x 32bit integer factor
79 * @param mantissa mantissa of f with exponent 0
80 * @return 32bit integer value (x*f)
81 * @see softfloat_reciprocal
83 static uint32_t softfloat_mul(uint32_t x, uint64_t mantissa)
85 uint64_t l = x * (mantissa & 0xffffffff);
86 uint64_t h = x * (mantissa >> 32);
89 l += 1 << av_log2(h >> 21);
94 static uint8_t lag_calc_zero_run(int8_t x)
96 return (x << 1) ^ (x >> 7);
99 static int lag_decode_prob(GetBitContext *gb, uint32_t *value)
101 static const uint8_t series[] = { 1, 2, 3, 5, 8, 13, 21 };
108 for (i = 0; i < 7; i++) {
117 if (bits < 0 || bits > 31) {
120 } else if (bits == 0) {
125 val = get_bits_long(gb, bits);
133 static int lag_read_prob_header(lag_rac *rac, GetBitContext *gb)
135 int i, j, scale_factor;
136 unsigned prob, cumulative_target;
137 unsigned cumul_prob = 0;
138 unsigned scaled_cumul_prob = 0;
141 rac->prob[257] = UINT_MAX;
142 /* Read probabilities from bitstream */
143 for (i = 1; i < 257; i++) {
144 if (lag_decode_prob(gb, &rac->prob[i]) < 0) {
145 av_log(rac->avctx, AV_LOG_ERROR, "Invalid probability encountered.\n");
148 if ((uint64_t)cumul_prob + rac->prob[i] > UINT_MAX) {
149 av_log(rac->avctx, AV_LOG_ERROR, "Integer overflow encountered in cumulative probability calculation.\n");
152 cumul_prob += rac->prob[i];
154 if (lag_decode_prob(gb, &prob)) {
155 av_log(rac->avctx, AV_LOG_ERROR, "Invalid probability run encountered.\n");
160 for (j = 0; j < prob; j++)
166 av_log(rac->avctx, AV_LOG_ERROR, "All probabilities are 0!\n");
170 /* Scale probabilities so cumulative probability is an even power of 2. */
171 scale_factor = av_log2(cumul_prob);
173 if (cumul_prob & (cumul_prob - 1)) {
174 uint64_t mul = softfloat_reciprocal(cumul_prob);
175 for (i = 1; i < 257; i++) {
176 rac->prob[i] = softfloat_mul(rac->prob[i], mul);
177 scaled_cumul_prob += rac->prob[i];
181 cumulative_target = 1 << scale_factor;
183 if (scaled_cumul_prob > cumulative_target) {
184 av_log(rac->avctx, AV_LOG_ERROR,
185 "Scaled probabilities are larger than target!\n");
189 scaled_cumul_prob = cumulative_target - scaled_cumul_prob;
191 for (i = 1; scaled_cumul_prob; i = (i & 0x7f) + 1) {
196 /* Comment from reference source:
197 * if (b & 0x80 == 0) { // order of operations is 'wrong'; it has been left this way
198 * // since the compression change is negligable and fixing it
199 * // breaks backwards compatibilty
200 * b =- (signed int)b;
210 rac->scale = scale_factor;
212 /* Fill probability array with cumulative probability for each symbol. */
213 for (i = 1; i < 257; i++)
214 rac->prob[i] += rac->prob[i - 1];
219 static void add_lag_median_prediction(uint8_t *dst, uint8_t *src1,
220 uint8_t *diff, int w, int *left,
223 /* This is almost identical to add_hfyu_median_prediction in dsputil.h.
224 * However the &0xFF on the gradient predictor yealds incorrect output
233 for (i = 0; i < w; i++) {
234 l = mid_pred(l, src1[i], l + src1[i] - lt) + diff[i];
243 static void lag_pred_line(LagarithContext *l, uint8_t *buf,
244 int width, int stride, int line)
249 /* Left prediction only for first line */
250 L = l->dsp.add_hfyu_left_prediction(buf + 1, buf + 1,
253 } else if (line == 1) {
254 /* Second line, left predict first pixel, the rest of the line is median predicted */
255 /* FIXME: In the case of RGB this pixel is top predicted */
258 /* Top left is 2 rows back, last pixel */
259 TL = buf[width - (2 * stride) - 1];
261 /* Left pixel is actually prev_row[width] */
262 L = buf[width - stride - 1];
264 add_lag_median_prediction(buf, buf - stride, buf,
268 static int lag_decode_line(LagarithContext *l, lag_rac *rac,
269 uint8_t *dst, int width, int stride,
278 /* Output any zeros remaining from the previous run */
281 int count = FFMIN(l->zeros_rem, width - i);
282 memset(dst + i, 0, count);
284 l->zeros_rem -= count;
288 dst[i] = lag_get_rac(rac);
297 if (l->zeros == esc_count) {
298 int index = lag_get_rac(rac);
303 l->zeros_rem = lag_calc_zero_run(index);
310 static int lag_decode_zero_run_line(LagarithContext *l, uint8_t *dst,
311 const uint8_t *src, int width,
316 uint8_t zero_run = 0;
317 const uint8_t *start = src;
318 uint8_t mask1 = -(esc_count < 2);
319 uint8_t mask2 = -(esc_count < 3);
320 uint8_t *end = dst + (width - 2);
324 count = FFMIN(l->zeros_rem, width - i);
325 memset(dst, 0, count);
326 l->zeros_rem -= count;
332 while (!zero_run && dst + i < end) {
335 !(src[i] | (src[i + 1] & mask1) | (src[i + 2] & mask2));
342 l->zeros_rem = lag_calc_zero_run(src[i]);
356 static int lag_decode_arith_plane(LagarithContext *l, uint8_t *dst,
357 int width, int height, int stride,
358 const uint8_t *src, int src_size)
364 int esc_count = src[0];
368 rac.avctx = l->avctx;
372 length = width * height;
373 if (esc_count && AV_RL32(src + 1) < length) {
374 length = AV_RL32(src + 1);
378 init_get_bits(&gb, src + offset, src_size * 8);
380 if (lag_read_prob_header(&rac, &gb) < 0)
383 lag_rac_init(&rac, &gb, length - stride);
385 for (i = 0; i < height; i++)
386 read += lag_decode_line(l, &rac, dst + (i * stride), width,
390 av_log(l->avctx, AV_LOG_WARNING,
391 "Output more bytes than length (%d of %d)\n", read,
393 } else if (esc_count < 8) {
396 /* Zero run coding only, no range coding. */
397 for (i = 0; i < height; i++)
398 src += lag_decode_zero_run_line(l, dst + (i * stride), src,
401 /* Plane is stored uncompressed */
402 for (i = 0; i < height; i++) {
403 memcpy(dst + (i * stride), src, width);
407 } else if (esc_count == 0xff) {
408 /* Plane is a solid run of given value */
409 for (i = 0; i < height; i++)
410 memset(dst + i * stride, src[1], width);
411 /* Do not apply prediction.
412 Note: memset to 0 above, setting first value to src[1]
413 and applying prediction gives the same result. */
416 av_log(l->avctx, AV_LOG_ERROR,
417 "Invalid zero run escape code! (%#x)\n", esc_count);
421 for (i = 0; i < height; i++) {
422 lag_pred_line(l, dst, width, stride, i);
431 * @param avctx codec context
432 * @param data output AVFrame
433 * @param data_size size of output data or 0 if no picture is returned
434 * @param avpkt input packet
435 * @return number of consumed bytes on success or negative if decode fails
437 static int lag_decode_frame(AVCodecContext *avctx,
438 void *data, int *data_size, AVPacket *avpkt)
440 const uint8_t *buf = avpkt->data;
441 int buf_size = avpkt->size;
442 LagarithContext *l = avctx->priv_data;
443 AVFrame *const p = &l->picture;
444 uint8_t frametype = 0;
445 uint32_t offset_gu = 0, offset_bv = 0, offset_ry = 9;
447 AVFrame *picture = data;
450 avctx->release_buffer(avctx, p);
457 offset_gu = AV_RL32(buf + 1);
458 offset_bv = AV_RL32(buf + 5);
461 case FRAME_ARITH_YV12:
462 avctx->pix_fmt = PIX_FMT_YUV420P;
464 if (avctx->get_buffer(avctx, p) < 0) {
465 av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
469 lag_decode_arith_plane(l, p->data[0], avctx->width, avctx->height,
470 p->linesize[0], buf + offset_ry,
472 lag_decode_arith_plane(l, p->data[2], avctx->width / 2,
473 avctx->height / 2, p->linesize[2],
474 buf + offset_gu, buf_size);
475 lag_decode_arith_plane(l, p->data[1], avctx->width / 2,
476 avctx->height / 2, p->linesize[1],
477 buf + offset_bv, buf_size);
480 av_log(avctx, AV_LOG_ERROR,
481 "Unsupported Lagarith frame type: %#x\n", frametype);
486 *data_size = sizeof(AVFrame);
491 static av_cold int lag_decode_init(AVCodecContext *avctx)
493 LagarithContext *l = avctx->priv_data;
496 dsputil_init(&l->dsp, avctx);
501 static av_cold int lag_decode_end(AVCodecContext *avctx)
503 LagarithContext *l = avctx->priv_data;
505 if (l->picture.data[0])
506 avctx->release_buffer(avctx, &l->picture);
511 AVCodec ff_lagarith_decoder = {
513 .type = AVMEDIA_TYPE_VIDEO,
514 .id = CODEC_ID_LAGARITH,
515 .priv_data_size = sizeof(LagarithContext),
516 .init = lag_decode_init,
517 .close = lag_decode_end,
518 .decode = lag_decode_frame,
519 .capabilities = CODEC_CAP_DR1,
520 .long_name = NULL_IF_CONFIG_SMALL("Lagarith lossless"),