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_FIRST_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_init(s, avctx);
80 s->out_format = FMT_H261;
82 avctx->pix_fmt = AV_PIX_FMT_YUV420P;
84 ff_h261_common_init();
85 h261_decode_init_vlc(h);
87 h->gob_start_code_skipped = 0;
93 * Decode the group of blocks header or slice header.
94 * @return <0 if an error occurred
96 static int h261_decode_gob_header(H261Context *h)
99 MpegEncContext *const s = &h->s;
101 if (!h->gob_start_code_skipped) {
102 /* Check for GOB Start Code */
103 val = show_bits(&s->gb, 15);
108 skip_bits(&s->gb, 16);
111 h->gob_start_code_skipped = 0;
113 h->gob_number = get_bits(&s->gb, 4); /* GN */
114 s->qscale = get_bits(&s->gb, 5); /* GQUANT */
116 /* Check if gob_number is valid */
117 if (s->mb_height == 18) { // CIF
118 if ((h->gob_number <= 0) || (h->gob_number > 12))
121 if ((h->gob_number != 1) && (h->gob_number != 3) &&
122 (h->gob_number != 5))
127 if (skip_1stop_8data_bits(&s->gb) < 0)
128 return AVERROR_INVALIDDATA;
130 if (s->qscale == 0) {
131 av_log(s->avctx, AV_LOG_ERROR, "qscale has forbidden 0 value\n");
132 if (s->avctx->err_recognition & (AV_EF_BITSTREAM | AV_EF_COMPLIANT))
136 /* For the first transmitted macroblock in a GOB, MBA is the absolute
137 * address. For subsequent macroblocks, MBA is the difference between
138 * the absolute addresses of the macroblock and the last transmitted
147 * Decode the group of blocks / video packet header.
148 * @return <0 if no resync found
150 static int h261_resync(H261Context *h)
152 MpegEncContext *const s = &h->s;
155 if (h->gob_start_code_skipped) {
156 ret = h261_decode_gob_header(h);
160 if (show_bits(&s->gb, 15) == 0) {
161 ret = h261_decode_gob_header(h);
165 // OK, it is not where it is supposed to be ...
166 s->gb = s->last_resync_gb;
167 align_get_bits(&s->gb);
168 left = get_bits_left(&s->gb);
170 for (; left > 15 + 1 + 4 + 5; left -= 8) {
171 if (show_bits(&s->gb, 15) == 0) {
172 GetBitContext bak = s->gb;
174 ret = h261_decode_gob_header(h);
180 skip_bits(&s->gb, 8);
188 * Decode skipped macroblocks.
191 static int h261_decode_mb_skipped(H261Context *h, int mba1, int mba2)
193 MpegEncContext *const s = &h->s;
198 for (i = mba1; i < mba2; i++) {
201 s->mb_x = ((h->gob_number - 1) % 2) * 11 + i % 11;
202 s->mb_y = ((h->gob_number - 1) / 2) * 3 + i / 11;
203 xy = s->mb_x + s->mb_y * s->mb_stride;
204 ff_init_block_index(s);
205 ff_update_block_index(s);
207 for (j = 0; j < 6; j++)
208 s->block_last_index[j] = -1;
210 s->mv_dir = MV_DIR_FORWARD;
211 s->mv_type = MV_TYPE_16X16;
212 s->current_picture.mb_type[xy] = MB_TYPE_SKIP | MB_TYPE_16x16 | MB_TYPE_L0;
216 h->mtype &= ~MB_TYPE_H261_FIL;
218 if (s->current_picture.motion_val[0]) {
219 int b_stride = 2*s->mb_width + 1;
220 int b_xy = 2 * s->mb_x + (2 * s->mb_y) * b_stride;
221 s->current_picture.motion_val[0][b_xy][0] = s->mv[0][0][0];
222 s->current_picture.motion_val[0][b_xy][1] = s->mv[0][0][1];
225 ff_mpv_reconstruct_mb(s, s->block);
231 static const int mvmap[17] = {
232 0, -1, -2, -3, -4, -5, -6, -7, -8, -9, -10, -11, -12, -13, -14, -15, -16
235 static int decode_mv_component(GetBitContext *gb, int v)
237 int mv_diff = get_vlc2(gb, h261_mv_vlc.table, H261_MV_VLC_BITS, 2);
239 /* check if mv_diff is valid */
243 mv_diff = mvmap[mv_diff];
245 if (mv_diff && !get_bits1(gb))
258 * Decode a macroblock.
259 * @return <0 if an error occurred
261 static int h261_decode_block(H261Context *h, int16_t *block, int n, int coded)
263 MpegEncContext *const s = &h->s;
264 int level, i, j, run;
265 RLTable *rl = &ff_h261_rl_tcoeff;
266 const uint8_t *scan_table;
268 /* For the variable length encoding there are two code tables, one being
269 * used for the first transmitted LEVEL in INTER, INTER + MC and
270 * INTER + MC + FIL blocks, the second for all other LEVELs except the
271 * first one in INTRA blocks which is fixed length coded with 8 bits.
272 * NOTE: The two code tables only differ in one VLC so we handle that
274 scan_table = s->intra_scantable.permutated;
277 level = get_bits(&s->gb, 8);
278 // 0 (00000000b) and -128 (10000000b) are FORBIDDEN
279 if ((level & 0x7F) == 0) {
280 av_log(s->avctx, AV_LOG_ERROR, "illegal dc %d at %d %d\n",
281 level, s->mb_x, s->mb_y);
284 /* The code 1000 0000 is not used, the reconstruction level of 1024
285 * being coded as 1111 1111. */
292 // EOB Not possible for first level when cbp is available (that's why the table is different)
295 int check = show_bits(&s->gb, 2);
298 skip_bits(&s->gb, 2);
299 block[0] = (check & 0x1) ? -1 : 1;
306 s->block_last_index[n] = i - 1;
310 OPEN_READER(re, &s->gb);
311 i--; // offset by -1 to allow direct indexing of scan_table
313 UPDATE_CACHE(re, &s->gb);
314 GET_RL_VLC(level, run, re, &s->gb, rl->rl_vlc[0], TCOEFF_VLC_BITS, 2, 0);
317 CLOSE_READER(re, &s->gb);
318 av_log(s->avctx, AV_LOG_ERROR, "illegal ac vlc code at %dx%d\n",
323 /* The remaining combinations of (run, level) are encoded with a
324 * 20-bit word consisting of 6 bits escape, 6 bits run and 8 bits
326 run = SHOW_UBITS(re, &s->gb, 6) + 1;
327 SKIP_CACHE(re, &s->gb, 6);
328 level = SHOW_SBITS(re, &s->gb, 8);
329 SKIP_COUNTER(re, &s->gb, 6 + 8);
330 } else if (level == 0) {
333 if (SHOW_UBITS(re, &s->gb, 1))
335 SKIP_COUNTER(re, &s->gb, 1);
339 CLOSE_READER(re, &s->gb);
340 av_log(s->avctx, AV_LOG_ERROR, "run overflow at %dx%d\n",
347 CLOSE_READER(re, &s->gb);
349 s->block_last_index[n] = i;
353 static int h261_decode_mb(H261Context *h)
355 MpegEncContext *const s = &h->s;
361 h->mba_diff = get_vlc2(&s->gb, h261_mba_vlc.table,
362 H261_MBA_VLC_BITS, 2);
364 /* Check for slice end */
365 /* NOTE: GOB can be empty (no MB data) or exist only of MBA_stuffing */
366 if (h->mba_diff == MBA_STARTCODE) { // start code
367 h->gob_start_code_skipped = 1;
370 } while (h->mba_diff == MBA_STUFFING); // stuffing
372 if (h->mba_diff < 0) {
373 if (get_bits_left(&s->gb) <= 7)
376 av_log(s->avctx, AV_LOG_ERROR, "illegal mba at %d %d\n", s->mb_x, s->mb_y);
381 h->current_mba += h->mba_diff;
383 if (h->current_mba > MBA_STUFFING)
386 s->mb_x = ((h->gob_number - 1) % 2) * 11 + ((h->current_mba - 1) % 11);
387 s->mb_y = ((h->gob_number - 1) / 2) * 3 + ((h->current_mba - 1) / 11);
388 xy = s->mb_x + s->mb_y * s->mb_stride;
389 ff_init_block_index(s);
390 ff_update_block_index(s);
393 h->mtype = get_vlc2(&s->gb, h261_mtype_vlc.table, H261_MTYPE_VLC_BITS, 2);
395 av_log(s->avctx, AV_LOG_ERROR, "Invalid mtype index %d\n",
399 av_assert0(h->mtype < FF_ARRAY_ELEMS(ff_h261_mtype_map));
400 h->mtype = ff_h261_mtype_map[h->mtype];
403 if (IS_QUANT(h->mtype))
404 ff_set_qscale(s, get_bits(&s->gb, 5));
406 s->mb_intra = IS_INTRA4x4(h->mtype);
409 if (IS_16X16(h->mtype)) {
410 /* Motion vector data is included for all MC macroblocks. MVD is
411 * obtained from the macroblock vector by subtracting the vector
412 * of the preceding macroblock. For this calculation the vector
413 * of the preceding macroblock is regarded as zero in the
414 * following three situations:
415 * 1) evaluating MVD for macroblocks 1, 12 and 23;
416 * 2) evaluating MVD for macroblocks in which MBA does not represent a difference of 1;
417 * 3) MTYPE of the previous macroblock was not MC. */
418 if ((h->current_mba == 1) || (h->current_mba == 12) ||
419 (h->current_mba == 23) || (h->mba_diff != 1)) {
424 h->current_mv_x = decode_mv_component(&s->gb, h->current_mv_x);
425 h->current_mv_y = decode_mv_component(&s->gb, h->current_mv_y);
432 if (HAS_CBP(h->mtype))
433 cbp = get_vlc2(&s->gb, h261_cbp_vlc.table, H261_CBP_VLC_BITS, 1) + 1;
436 s->current_picture.mb_type[xy] = MB_TYPE_INTRA;
441 s->mv_dir = MV_DIR_FORWARD;
442 s->mv_type = MV_TYPE_16X16;
443 s->current_picture.mb_type[xy] = MB_TYPE_16x16 | MB_TYPE_L0;
444 s->mv[0][0][0] = h->current_mv_x * 2; // gets divided by 2 in motion compensation
445 s->mv[0][0][1] = h->current_mv_y * 2;
447 if (s->current_picture.motion_val[0]) {
448 int b_stride = 2*s->mb_width + 1;
449 int b_xy = 2 * s->mb_x + (2 * s->mb_y) * b_stride;
450 s->current_picture.motion_val[0][b_xy][0] = s->mv[0][0][0];
451 s->current_picture.motion_val[0][b_xy][1] = s->mv[0][0][1];
455 /* decode each block */
456 if (s->mb_intra || HAS_CBP(h->mtype)) {
457 s->bdsp.clear_blocks(s->block[0]);
458 for (i = 0; i < 6; i++) {
459 if (h261_decode_block(h, s->block[i], i, cbp & 32) < 0)
464 for (i = 0; i < 6; i++)
465 s->block_last_index[i] = -1;
468 ff_mpv_reconstruct_mb(s, s->block);
474 * Decode the H.261 picture header.
475 * @return <0 if no startcode found
477 static int h261_decode_picture_header(H261Context *h)
479 MpegEncContext *const s = &h->s;
481 uint32_t startcode = 0;
483 for (i = get_bits_left(&s->gb); i > 24; i -= 1) {
484 startcode = ((startcode << 1) | get_bits(&s->gb, 1)) & 0x000FFFFF;
486 if (startcode == 0x10)
490 if (startcode != 0x10) {
491 av_log(s->avctx, AV_LOG_ERROR, "Bad picture start code\n");
495 /* temporal reference */
496 i = get_bits(&s->gb, 5); /* picture timestamp */
497 if (i < (s->picture_number & 31))
499 s->picture_number = (s->picture_number & ~31) + i;
501 s->avctx->framerate = (AVRational) { 30000, 1001 };
503 /* PTYPE starts here */
504 skip_bits1(&s->gb); /* split screen off */
505 skip_bits1(&s->gb); /* camera off */
506 skip_bits1(&s->gb); /* freeze picture release off */
508 format = get_bits1(&s->gb);
510 // only 2 formats possible
511 if (format == 0) { // QCIF
523 s->mb_num = s->mb_width * s->mb_height;
525 skip_bits1(&s->gb); /* still image mode off */
526 skip_bits1(&s->gb); /* Reserved */
529 if (skip_1stop_8data_bits(&s->gb) < 0)
530 return AVERROR_INVALIDDATA;
532 /* H.261 has no I-frames, but if we pass AV_PICTURE_TYPE_I for the first
533 * frame, the codec crashes if it does not contain all I-blocks
534 * (e.g. when a packet is lost). */
535 s->pict_type = AV_PICTURE_TYPE_P;
541 static int h261_decode_gob(H261Context *h)
543 MpegEncContext *const s = &h->s;
545 ff_set_qscale(s, s->qscale);
548 while (h->current_mba <= MBA_STUFFING) {
551 ret = h261_decode_mb(h);
553 if (ret == SLICE_END) {
554 h261_decode_mb_skipped(h, h->current_mba, 33);
557 av_log(s->avctx, AV_LOG_ERROR, "Error at MB: %d\n",
558 s->mb_x + s->mb_y * s->mb_stride);
562 h261_decode_mb_skipped(h,
563 h->current_mba - h->mba_diff,
571 * returns the number of bytes consumed for building the current frame
573 static int get_consumed_bytes(MpegEncContext *s, int buf_size)
575 int pos = get_bits_count(&s->gb) >> 3;
577 pos = 1; // avoid infinite loops (i doubt that is needed but ...)
578 if (pos + 10 > buf_size)
579 pos = buf_size; // oops ;)
584 static int h261_decode_frame(AVCodecContext *avctx, void *data,
585 int *got_frame, AVPacket *avpkt)
587 const uint8_t *buf = avpkt->data;
588 int buf_size = avpkt->size;
589 H261Context *h = avctx->priv_data;
590 MpegEncContext *s = &h->s;
592 AVFrame *pict = data;
594 ff_dlog(avctx, "*****frame %d size=%d\n", avctx->frame_number, buf_size);
595 ff_dlog(avctx, "bytes=%x %x %x %x\n", buf[0], buf[1], buf[2], buf[3]);
597 h->gob_start_code_skipped = 0;
600 init_get_bits(&s->gb, buf, buf_size * 8);
602 if (!s->context_initialized)
603 // we need the IDCT permutation for reading a custom matrix
606 ret = h261_decode_picture_header(h);
608 /* skip if the header was thrashed */
610 av_log(s->avctx, AV_LOG_ERROR, "header damaged\n");
614 if (s->width != avctx->coded_width || s->height != avctx->coded_height) {
615 ParseContext pc = s->parse_context; // FIXME move this demuxing hack to libavformat
616 s->parse_context.buffer = 0;
617 ff_mpv_common_end(s);
618 s->parse_context = pc;
621 if (!s->context_initialized) {
622 if ((ret = ff_mpv_common_init(s)) < 0)
625 ret = ff_set_dimensions(avctx, s->width, s->height);
632 // for skipping the frame
633 s->current_picture.f->pict_type = s->pict_type;
634 s->current_picture.f->key_frame = s->pict_type == AV_PICTURE_TYPE_I;
636 if ((avctx->skip_frame >= AVDISCARD_NONREF && s->pict_type == AV_PICTURE_TYPE_B) ||
637 (avctx->skip_frame >= AVDISCARD_NONKEY && s->pict_type != AV_PICTURE_TYPE_I) ||
638 avctx->skip_frame >= AVDISCARD_ALL)
639 return get_consumed_bytes(s, buf_size);
641 if (ff_mpv_frame_start(s, avctx) < 0)
644 ff_mpeg_er_frame_start(s);
646 /* decode each macroblock */
650 while (h->gob_number < (s->mb_height == 18 ? 12 : 5)) {
651 if (h261_resync(h) < 0)
657 av_assert0(s->current_picture.f->pict_type == s->current_picture_ptr->f->pict_type);
658 av_assert0(s->current_picture.f->pict_type == s->pict_type);
660 if ((ret = av_frame_ref(pict, s->current_picture_ptr->f)) < 0)
662 ff_print_debug_info(s, s->current_picture_ptr, pict);
666 return get_consumed_bytes(s, buf_size);
669 static av_cold int h261_decode_end(AVCodecContext *avctx)
671 H261Context *h = avctx->priv_data;
672 MpegEncContext *s = &h->s;
674 ff_mpv_common_end(s);
678 AVCodec ff_h261_decoder = {
680 .long_name = NULL_IF_CONFIG_SMALL("H.261"),
681 .type = AVMEDIA_TYPE_VIDEO,
682 .id = AV_CODEC_ID_H261,
683 .priv_data_size = sizeof(H261Context),
684 .init = h261_decode_init,
685 .close = h261_decode_end,
686 .decode = h261_decode_frame,
687 .capabilities = AV_CODEC_CAP_DR1,
688 .caps_internal = FF_CODEC_CAP_INIT_CLEANUP,