3 * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
4 * Copyright (c) 2004 Maarten Daniels
6 * This file is part of FFmpeg.
8 * FFmpeg is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU Lesser General Public
10 * License as published by the Free Software Foundation; either
11 * version 2.1 of the License, or (at your option) any later version.
13 * FFmpeg is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * Lesser General Public License for more details.
18 * You should have received a copy of the GNU Lesser General Public
19 * License along with FFmpeg; if not, write to the Free Software
20 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
28 #include "libavutil/avassert.h"
31 #include "mpegutils.h"
32 #include "mpegvideo.h"
37 #define H261_MBA_VLC_BITS 9
38 #define H261_MTYPE_VLC_BITS 6
39 #define H261_MV_VLC_BITS 7
40 #define H261_CBP_VLC_BITS 9
41 #define TCOEFF_VLC_BITS 9
42 #define MBA_STUFFING 33
43 #define MBA_STARTCODE 34
45 static VLC h261_mba_vlc;
46 static VLC h261_mtype_vlc;
47 static VLC h261_mv_vlc;
48 static VLC h261_cbp_vlc;
50 static av_cold void h261_decode_init_vlc(H261Context *h)
56 INIT_VLC_STATIC(&h261_mba_vlc, H261_MBA_VLC_BITS, 35,
57 ff_h261_mba_bits, 1, 1,
58 ff_h261_mba_code, 1, 1, 662);
59 INIT_VLC_STATIC(&h261_mtype_vlc, H261_MTYPE_VLC_BITS, 10,
60 ff_h261_mtype_bits, 1, 1,
61 ff_h261_mtype_code, 1, 1, 80);
62 INIT_VLC_STATIC(&h261_mv_vlc, H261_MV_VLC_BITS, 17,
63 &ff_h261_mv_tab[0][1], 2, 1,
64 &ff_h261_mv_tab[0][0], 2, 1, 144);
65 INIT_VLC_STATIC(&h261_cbp_vlc, H261_CBP_VLC_BITS, 63,
66 &ff_h261_cbp_tab[0][1], 2, 1,
67 &ff_h261_cbp_tab[0][0], 2, 1, 512);
68 INIT_VLC_RL(ff_h261_rl_tcoeff, 552);
72 static av_cold int h261_decode_init(AVCodecContext *avctx)
74 H261Context *h = avctx->priv_data;
75 MpegEncContext *const s = &h->s;
78 ff_MPV_decode_defaults(s);
80 s->width = s->avctx->coded_width;
81 s->height = s->avctx->coded_height;
82 s->codec_id = s->avctx->codec->id;
83 s->out_format = FMT_H261;
85 avctx->pix_fmt = AV_PIX_FMT_YUV420P;
86 s->codec_id = avctx->codec->id;
88 ff_h261_common_init();
89 h261_decode_init_vlc(h);
91 h->gob_start_code_skipped = 0;
97 * Decode the group of blocks header or slice header.
98 * @return <0 if an error occurred
100 static int h261_decode_gob_header(H261Context *h)
103 MpegEncContext *const s = &h->s;
105 if (!h->gob_start_code_skipped) {
106 /* Check for GOB Start Code */
107 val = show_bits(&s->gb, 15);
112 skip_bits(&s->gb, 16);
115 h->gob_start_code_skipped = 0;
117 h->gob_number = get_bits(&s->gb, 4); /* GN */
118 s->qscale = get_bits(&s->gb, 5); /* GQUANT */
120 /* Check if gob_number is valid */
121 if (s->mb_height == 18) { // CIF
122 if ((h->gob_number <= 0) || (h->gob_number > 12))
125 if ((h->gob_number != 1) && (h->gob_number != 3) &&
126 (h->gob_number != 5))
131 if (skip_1stop_8data_bits(&s->gb) < 0)
132 return AVERROR_INVALIDDATA;
134 if (s->qscale == 0) {
135 av_log(s->avctx, AV_LOG_ERROR, "qscale has forbidden 0 value\n");
136 if (s->avctx->err_recognition & (AV_EF_BITSTREAM | AV_EF_COMPLIANT))
140 /* For the first transmitted macroblock in a GOB, MBA is the absolute
141 * address. For subsequent macroblocks, MBA is the difference between
142 * the absolute addresses of the macroblock and the last transmitted
151 * Decode the group of blocks / video packet header.
152 * @return <0 if no resync found
154 static int h261_resync(H261Context *h)
156 MpegEncContext *const s = &h->s;
159 if (h->gob_start_code_skipped) {
160 ret = h261_decode_gob_header(h);
164 if (show_bits(&s->gb, 15) == 0) {
165 ret = h261_decode_gob_header(h);
169 // OK, it is not where it is supposed to be ...
170 s->gb = s->last_resync_gb;
171 align_get_bits(&s->gb);
172 left = get_bits_left(&s->gb);
174 for (; left > 15 + 1 + 4 + 5; left -= 8) {
175 if (show_bits(&s->gb, 15) == 0) {
176 GetBitContext bak = s->gb;
178 ret = h261_decode_gob_header(h);
184 skip_bits(&s->gb, 8);
192 * Decode skipped macroblocks.
195 static int h261_decode_mb_skipped(H261Context *h, int mba1, int mba2)
197 MpegEncContext *const s = &h->s;
202 for (i = mba1; i < mba2; i++) {
205 s->mb_x = ((h->gob_number - 1) % 2) * 11 + i % 11;
206 s->mb_y = ((h->gob_number - 1) / 2) * 3 + i / 11;
207 xy = s->mb_x + s->mb_y * s->mb_stride;
208 ff_init_block_index(s);
209 ff_update_block_index(s);
211 for (j = 0; j < 6; j++)
212 s->block_last_index[j] = -1;
214 s->mv_dir = MV_DIR_FORWARD;
215 s->mv_type = MV_TYPE_16X16;
216 s->current_picture.mb_type[xy] = MB_TYPE_SKIP | MB_TYPE_16x16 | MB_TYPE_L0;
220 h->mtype &= ~MB_TYPE_H261_FIL;
222 ff_MPV_decode_mb(s, s->block);
228 static const int mvmap[17] = {
229 0, -1, -2, -3, -4, -5, -6, -7, -8, -9, -10, -11, -12, -13, -14, -15, -16
232 static int decode_mv_component(GetBitContext *gb, int v)
234 int mv_diff = get_vlc2(gb, h261_mv_vlc.table, H261_MV_VLC_BITS, 2);
236 /* check if mv_diff is valid */
240 mv_diff = mvmap[mv_diff];
242 if (mv_diff && !get_bits1(gb))
255 * Decode a macroblock.
256 * @return <0 if an error occurred
258 static int h261_decode_block(H261Context *h, int16_t *block, int n, int coded)
260 MpegEncContext *const s = &h->s;
261 int code, level, i, j, run;
262 RLTable *rl = &ff_h261_rl_tcoeff;
263 const uint8_t *scan_table;
265 /* For the variable length encoding there are two code tables, one being
266 * used for the first transmitted LEVEL in INTER, INTER + MC and
267 * INTER + MC + FIL blocks, the second for all other LEVELs except the
268 * first one in INTRA blocks which is fixed length coded with 8 bits.
269 * NOTE: The two code tables only differ in one VLC so we handle that
271 scan_table = s->intra_scantable.permutated;
274 level = get_bits(&s->gb, 8);
275 // 0 (00000000b) and -128 (10000000b) are FORBIDDEN
276 if ((level & 0x7F) == 0) {
277 av_log(s->avctx, AV_LOG_ERROR, "illegal dc %d at %d %d\n",
278 level, s->mb_x, s->mb_y);
281 /* The code 1000 0000 is not used, the reconstruction level of 1024
282 * being coded as 1111 1111. */
289 // EOB Not possible for first level when cbp is available (that's why the table is different)
292 int check = show_bits(&s->gb, 2);
295 skip_bits(&s->gb, 2);
296 block[0] = (check & 0x1) ? -1 : 1;
303 s->block_last_index[n] = i - 1;
307 code = get_vlc2(&s->gb, rl->vlc.table, TCOEFF_VLC_BITS, 2);
309 av_log(s->avctx, AV_LOG_ERROR, "illegal ac vlc code at %dx%d\n",
315 /* The remaining combinations of (run, level) are encoded with a
316 * 20-bit word consisting of 6 bits escape, 6 bits run and 8 bits
318 run = get_bits(&s->gb, 6);
319 level = get_sbits(&s->gb, 8);
320 } else if (code == 0) {
323 run = rl->table_run[code];
324 level = rl->table_level[code];
325 if (get_bits1(&s->gb))
330 av_log(s->avctx, AV_LOG_ERROR, "run overflow at %dx%d\n",
338 s->block_last_index[n] = i - 1;
342 static int h261_decode_mb(H261Context *h)
344 MpegEncContext *const s = &h->s;
350 h->mba_diff = get_vlc2(&s->gb, h261_mba_vlc.table,
351 H261_MBA_VLC_BITS, 2);
353 /* Check for slice end */
354 /* NOTE: GOB can be empty (no MB data) or exist only of MBA_stuffing */
355 if (h->mba_diff == MBA_STARTCODE) { // start code
356 h->gob_start_code_skipped = 1;
359 } while (h->mba_diff == MBA_STUFFING); // stuffing
361 if (h->mba_diff < 0) {
362 if (get_bits_left(&s->gb) <= 7)
365 av_log(s->avctx, AV_LOG_ERROR, "illegal mba at %d %d\n", s->mb_x, s->mb_y);
370 h->current_mba += h->mba_diff;
372 if (h->current_mba > MBA_STUFFING)
375 s->mb_x = ((h->gob_number - 1) % 2) * 11 + ((h->current_mba - 1) % 11);
376 s->mb_y = ((h->gob_number - 1) / 2) * 3 + ((h->current_mba - 1) / 11);
377 xy = s->mb_x + s->mb_y * s->mb_stride;
378 ff_init_block_index(s);
379 ff_update_block_index(s);
382 h->mtype = get_vlc2(&s->gb, h261_mtype_vlc.table, H261_MTYPE_VLC_BITS, 2);
384 av_log(s->avctx, AV_LOG_ERROR, "Invalid mtype index %d\n",
388 av_assert0(h->mtype < FF_ARRAY_ELEMS(ff_h261_mtype_map));
389 h->mtype = ff_h261_mtype_map[h->mtype];
392 if (IS_QUANT(h->mtype))
393 ff_set_qscale(s, get_bits(&s->gb, 5));
395 s->mb_intra = IS_INTRA4x4(h->mtype);
398 if (IS_16X16(h->mtype)) {
399 /* Motion vector data is included for all MC macroblocks. MVD is
400 * obtained from the macroblock vector by subtracting the vector
401 * of the preceding macroblock. For this calculation the vector
402 * of the preceding macroblock is regarded as zero in the
403 * following three situations:
404 * 1) evaluating MVD for macroblocks 1, 12 and 23;
405 * 2) evaluating MVD for macroblocks in which MBA does not represent a difference of 1;
406 * 3) MTYPE of the previous macroblock was not MC. */
407 if ((h->current_mba == 1) || (h->current_mba == 12) ||
408 (h->current_mba == 23) || (h->mba_diff != 1)) {
413 h->current_mv_x = decode_mv_component(&s->gb, h->current_mv_x);
414 h->current_mv_y = decode_mv_component(&s->gb, h->current_mv_y);
421 if (HAS_CBP(h->mtype))
422 cbp = get_vlc2(&s->gb, h261_cbp_vlc.table, H261_CBP_VLC_BITS, 2) + 1;
425 s->current_picture.mb_type[xy] = MB_TYPE_INTRA;
430 s->mv_dir = MV_DIR_FORWARD;
431 s->mv_type = MV_TYPE_16X16;
432 s->current_picture.mb_type[xy] = MB_TYPE_16x16 | MB_TYPE_L0;
433 s->mv[0][0][0] = h->current_mv_x * 2; // gets divided by 2 in motion compensation
434 s->mv[0][0][1] = h->current_mv_y * 2;
436 if (s->current_picture.motion_val[0]) {
437 int b_stride = 2*s->mb_width + 1;
438 int b_xy = 2 * s->mb_x + (2 * s->mb_y) * b_stride;
439 s->current_picture.motion_val[0][b_xy][0] = s->mv[0][0][0];
440 s->current_picture.motion_val[0][b_xy][1] = s->mv[0][0][1];
444 /* decode each block */
445 if (s->mb_intra || HAS_CBP(h->mtype)) {
446 s->bdsp.clear_blocks(s->block[0]);
447 for (i = 0; i < 6; i++) {
448 if (h261_decode_block(h, s->block[i], i, cbp & 32) < 0)
453 for (i = 0; i < 6; i++)
454 s->block_last_index[i] = -1;
457 ff_MPV_decode_mb(s, s->block);
463 * Decode the H.261 picture header.
464 * @return <0 if no startcode found
466 static int h261_decode_picture_header(H261Context *h)
468 MpegEncContext *const s = &h->s;
470 uint32_t startcode = 0;
472 for (i = get_bits_left(&s->gb); i > 24; i -= 1) {
473 startcode = ((startcode << 1) | get_bits(&s->gb, 1)) & 0x000FFFFF;
475 if (startcode == 0x10)
479 if (startcode != 0x10) {
480 av_log(s->avctx, AV_LOG_ERROR, "Bad picture start code\n");
484 /* temporal reference */
485 i = get_bits(&s->gb, 5); /* picture timestamp */
486 if (i < (s->picture_number & 31))
488 s->picture_number = (s->picture_number & ~31) + i;
490 s->avctx->time_base = (AVRational) { 1001, 30000 };
492 /* PTYPE starts here */
493 skip_bits1(&s->gb); /* split screen off */
494 skip_bits1(&s->gb); /* camera off */
495 skip_bits1(&s->gb); /* freeze picture release off */
497 format = get_bits1(&s->gb);
499 // only 2 formats possible
500 if (format == 0) { // QCIF
512 s->mb_num = s->mb_width * s->mb_height;
514 skip_bits1(&s->gb); /* still image mode off */
515 skip_bits1(&s->gb); /* Reserved */
518 if (skip_1stop_8data_bits(&s->gb) < 0)
519 return AVERROR_INVALIDDATA;
521 /* H.261 has no I-frames, but if we pass AV_PICTURE_TYPE_I for the first
522 * frame, the codec crashes if it does not contain all I-blocks
523 * (e.g. when a packet is lost). */
524 s->pict_type = AV_PICTURE_TYPE_P;
530 static int h261_decode_gob(H261Context *h)
532 MpegEncContext *const s = &h->s;
534 ff_set_qscale(s, s->qscale);
537 while (h->current_mba <= MBA_STUFFING) {
540 ret = h261_decode_mb(h);
542 if (ret == SLICE_END) {
543 h261_decode_mb_skipped(h, h->current_mba, 33);
546 av_log(s->avctx, AV_LOG_ERROR, "Error at MB: %d\n",
547 s->mb_x + s->mb_y * s->mb_stride);
551 h261_decode_mb_skipped(h,
552 h->current_mba - h->mba_diff,
560 * returns the number of bytes consumed for building the current frame
562 static int get_consumed_bytes(MpegEncContext *s, int buf_size)
564 int pos = get_bits_count(&s->gb) >> 3;
566 pos = 1; // avoid infinite loops (i doubt that is needed but ...)
567 if (pos + 10 > buf_size)
568 pos = buf_size; // oops ;)
573 static int h261_decode_frame(AVCodecContext *avctx, void *data,
574 int *got_frame, AVPacket *avpkt)
576 const uint8_t *buf = avpkt->data;
577 int buf_size = avpkt->size;
578 H261Context *h = avctx->priv_data;
579 MpegEncContext *s = &h->s;
581 AVFrame *pict = data;
583 av_dlog(avctx, "*****frame %d size=%d\n", avctx->frame_number, buf_size);
584 av_dlog(avctx, "bytes=%x %x %x %x\n", buf[0], buf[1], buf[2], buf[3]);
585 s->flags = avctx->flags;
586 s->flags2 = avctx->flags2;
588 h->gob_start_code_skipped = 0;
591 init_get_bits(&s->gb, buf, buf_size * 8);
593 if (!s->context_initialized)
594 // we need the IDCT permutaton for reading a custom matrix
595 if (ff_MPV_common_init(s) < 0)
598 ret = h261_decode_picture_header(h);
600 /* skip if the header was thrashed */
602 av_log(s->avctx, AV_LOG_ERROR, "header damaged\n");
606 if (s->width != avctx->coded_width || s->height != avctx->coded_height) {
607 ParseContext pc = s->parse_context; // FIXME move this demuxing hack to libavformat
608 s->parse_context.buffer = 0;
609 ff_MPV_common_end(s);
610 s->parse_context = pc;
612 if (!s->context_initialized) {
613 ret = ff_set_dimensions(avctx, s->width, s->height);
620 // for skipping the frame
621 s->current_picture.f->pict_type = s->pict_type;
622 s->current_picture.f->key_frame = s->pict_type == AV_PICTURE_TYPE_I;
624 if ((avctx->skip_frame >= AVDISCARD_NONREF && s->pict_type == AV_PICTURE_TYPE_B) ||
625 (avctx->skip_frame >= AVDISCARD_NONKEY && s->pict_type != AV_PICTURE_TYPE_I) ||
626 avctx->skip_frame >= AVDISCARD_ALL)
627 return get_consumed_bytes(s, buf_size);
629 if (ff_MPV_frame_start(s, avctx) < 0)
632 ff_mpeg_er_frame_start(s);
634 /* decode each macroblock */
638 while (h->gob_number < (s->mb_height == 18 ? 12 : 5)) {
639 if (h261_resync(h) < 0)
645 av_assert0(s->current_picture.f->pict_type == s->current_picture_ptr->f->pict_type);
646 av_assert0(s->current_picture.f->pict_type == s->pict_type);
648 if ((ret = av_frame_ref(pict, s->current_picture_ptr->f)) < 0)
650 ff_print_debug_info(s, s->current_picture_ptr, pict);
654 return get_consumed_bytes(s, buf_size);
657 static av_cold int h261_decode_end(AVCodecContext *avctx)
659 H261Context *h = avctx->priv_data;
660 MpegEncContext *s = &h->s;
662 ff_MPV_common_end(s);
666 AVCodec ff_h261_decoder = {
668 .long_name = NULL_IF_CONFIG_SMALL("H.261"),
669 .type = AVMEDIA_TYPE_VIDEO,
670 .id = AV_CODEC_ID_H261,
671 .priv_data_size = sizeof(H261Context),
672 .init = h261_decode_init,
673 .close = h261_decode_end,
674 .decode = h261_decode_frame,
675 .capabilities = CODEC_CAP_DR1,