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 h261_decode_init_vlc(h);
86 h->gob_start_code_skipped = 0;
92 * Decode the group of blocks header or slice header.
93 * @return <0 if an error occurred
95 static int h261_decode_gob_header(H261Context *h)
98 MpegEncContext *const s = &h->s;
100 if (!h->gob_start_code_skipped) {
101 /* Check for GOB Start Code */
102 val = show_bits(&s->gb, 15);
107 skip_bits(&s->gb, 16);
110 h->gob_start_code_skipped = 0;
112 h->gob_number = get_bits(&s->gb, 4); /* GN */
113 s->qscale = get_bits(&s->gb, 5); /* GQUANT */
115 /* Check if gob_number is valid */
116 if (s->mb_height == 18) { // CIF
117 if ((h->gob_number <= 0) || (h->gob_number > 12))
120 if ((h->gob_number != 1) && (h->gob_number != 3) &&
121 (h->gob_number != 5))
126 if (skip_1stop_8data_bits(&s->gb) < 0)
127 return AVERROR_INVALIDDATA;
129 if (s->qscale == 0) {
130 av_log(s->avctx, AV_LOG_ERROR, "qscale has forbidden 0 value\n");
131 if (s->avctx->err_recognition & (AV_EF_BITSTREAM | AV_EF_COMPLIANT))
135 /* For the first transmitted macroblock in a GOB, MBA is the absolute
136 * address. For subsequent macroblocks, MBA is the difference between
137 * the absolute addresses of the macroblock and the last transmitted
146 * Decode the group of blocks / video packet header.
147 * @return <0 if no resync found
149 static int h261_resync(H261Context *h)
151 MpegEncContext *const s = &h->s;
154 if (h->gob_start_code_skipped) {
155 ret = h261_decode_gob_header(h);
159 if (show_bits(&s->gb, 15) == 0) {
160 ret = h261_decode_gob_header(h);
164 // OK, it is not where it is supposed to be ...
165 s->gb = s->last_resync_gb;
166 align_get_bits(&s->gb);
167 left = get_bits_left(&s->gb);
169 for (; left > 15 + 1 + 4 + 5; left -= 8) {
170 if (show_bits(&s->gb, 15) == 0) {
171 GetBitContext bak = s->gb;
173 ret = h261_decode_gob_header(h);
179 skip_bits(&s->gb, 8);
187 * Decode skipped macroblocks.
190 static int h261_decode_mb_skipped(H261Context *h, int mba1, int mba2)
192 MpegEncContext *const s = &h->s;
197 for (i = mba1; i < mba2; i++) {
200 s->mb_x = ((h->gob_number - 1) % 2) * 11 + i % 11;
201 s->mb_y = ((h->gob_number - 1) / 2) * 3 + i / 11;
202 xy = s->mb_x + s->mb_y * s->mb_stride;
203 ff_init_block_index(s);
204 ff_update_block_index(s);
206 for (j = 0; j < 6; j++)
207 s->block_last_index[j] = -1;
209 s->mv_dir = MV_DIR_FORWARD;
210 s->mv_type = MV_TYPE_16X16;
211 s->current_picture.mb_type[xy] = MB_TYPE_SKIP | MB_TYPE_16x16 | MB_TYPE_L0;
215 h->mtype &= ~MB_TYPE_H261_FIL;
217 if (s->current_picture.motion_val[0]) {
218 int b_stride = 2*s->mb_width + 1;
219 int b_xy = 2 * s->mb_x + (2 * s->mb_y) * b_stride;
220 s->current_picture.motion_val[0][b_xy][0] = s->mv[0][0][0];
221 s->current_picture.motion_val[0][b_xy][1] = s->mv[0][0][1];
224 ff_mpv_reconstruct_mb(s, s->block);
230 static const int mvmap[17] = {
231 0, -1, -2, -3, -4, -5, -6, -7, -8, -9, -10, -11, -12, -13, -14, -15, -16
234 static int decode_mv_component(GetBitContext *gb, int v)
236 int mv_diff = get_vlc2(gb, h261_mv_vlc.table, H261_MV_VLC_BITS, 2);
238 /* check if mv_diff is valid */
242 mv_diff = mvmap[mv_diff];
244 if (mv_diff && !get_bits1(gb))
257 * Decode a macroblock.
258 * @return <0 if an error occurred
260 static int h261_decode_block(H261Context *h, int16_t *block, int n, int coded)
262 MpegEncContext *const s = &h->s;
263 int level, i, j, run;
264 RLTable *rl = &ff_h261_rl_tcoeff;
265 const uint8_t *scan_table;
267 /* For the variable length encoding there are two code tables, one being
268 * used for the first transmitted LEVEL in INTER, INTER + MC and
269 * INTER + MC + FIL blocks, the second for all other LEVELs except the
270 * first one in INTRA blocks which is fixed length coded with 8 bits.
271 * NOTE: The two code tables only differ in one VLC so we handle that
273 scan_table = s->intra_scantable.permutated;
276 level = get_bits(&s->gb, 8);
277 // 0 (00000000b) and -128 (10000000b) are FORBIDDEN
278 if ((level & 0x7F) == 0) {
279 av_log(s->avctx, AV_LOG_ERROR, "illegal dc %d at %d %d\n",
280 level, s->mb_x, s->mb_y);
283 /* The code 1000 0000 is not used, the reconstruction level of 1024
284 * being coded as 1111 1111. */
291 // EOB Not possible for first level when cbp is available (that's why the table is different)
294 int check = show_bits(&s->gb, 2);
297 skip_bits(&s->gb, 2);
298 block[0] = (check & 0x1) ? -1 : 1;
305 s->block_last_index[n] = i - 1;
309 OPEN_READER(re, &s->gb);
310 i--; // offset by -1 to allow direct indexing of scan_table
312 UPDATE_CACHE(re, &s->gb);
313 GET_RL_VLC(level, run, re, &s->gb, rl->rl_vlc[0], TCOEFF_VLC_BITS, 2, 0);
316 CLOSE_READER(re, &s->gb);
317 av_log(s->avctx, AV_LOG_ERROR, "illegal ac vlc code at %dx%d\n",
322 /* The remaining combinations of (run, level) are encoded with a
323 * 20-bit word consisting of 6 bits escape, 6 bits run and 8 bits
325 run = SHOW_UBITS(re, &s->gb, 6) + 1;
326 SKIP_CACHE(re, &s->gb, 6);
327 level = SHOW_SBITS(re, &s->gb, 8);
328 SKIP_COUNTER(re, &s->gb, 6 + 8);
329 } else if (level == 0) {
332 if (SHOW_UBITS(re, &s->gb, 1))
334 SKIP_COUNTER(re, &s->gb, 1);
338 CLOSE_READER(re, &s->gb);
339 av_log(s->avctx, AV_LOG_ERROR, "run overflow at %dx%d\n",
346 CLOSE_READER(re, &s->gb);
348 s->block_last_index[n] = i;
352 static int h261_decode_mb(H261Context *h)
354 MpegEncContext *const s = &h->s;
360 h->mba_diff = get_vlc2(&s->gb, h261_mba_vlc.table,
361 H261_MBA_VLC_BITS, 2);
363 /* Check for slice end */
364 /* NOTE: GOB can be empty (no MB data) or exist only of MBA_stuffing */
365 if (h->mba_diff == MBA_STARTCODE) { // start code
366 h->gob_start_code_skipped = 1;
369 } while (h->mba_diff == MBA_STUFFING); // stuffing
371 if (h->mba_diff < 0) {
372 if (get_bits_left(&s->gb) <= 7)
375 av_log(s->avctx, AV_LOG_ERROR, "illegal mba at %d %d\n", s->mb_x, s->mb_y);
380 h->current_mba += h->mba_diff;
382 if (h->current_mba > MBA_STUFFING)
385 s->mb_x = ((h->gob_number - 1) % 2) * 11 + ((h->current_mba - 1) % 11);
386 s->mb_y = ((h->gob_number - 1) / 2) * 3 + ((h->current_mba - 1) / 11);
387 xy = s->mb_x + s->mb_y * s->mb_stride;
388 ff_init_block_index(s);
389 ff_update_block_index(s);
392 h->mtype = get_vlc2(&s->gb, h261_mtype_vlc.table, H261_MTYPE_VLC_BITS, 2);
394 av_log(s->avctx, AV_LOG_ERROR, "Invalid mtype index %d\n",
398 av_assert0(h->mtype < FF_ARRAY_ELEMS(ff_h261_mtype_map));
399 h->mtype = ff_h261_mtype_map[h->mtype];
402 if (IS_QUANT(h->mtype))
403 ff_set_qscale(s, get_bits(&s->gb, 5));
405 s->mb_intra = IS_INTRA4x4(h->mtype);
408 if (IS_16X16(h->mtype)) {
409 /* Motion vector data is included for all MC macroblocks. MVD is
410 * obtained from the macroblock vector by subtracting the vector
411 * of the preceding macroblock. For this calculation the vector
412 * of the preceding macroblock is regarded as zero in the
413 * following three situations:
414 * 1) evaluating MVD for macroblocks 1, 12 and 23;
415 * 2) evaluating MVD for macroblocks in which MBA does not represent a difference of 1;
416 * 3) MTYPE of the previous macroblock was not MC. */
417 if ((h->current_mba == 1) || (h->current_mba == 12) ||
418 (h->current_mba == 23) || (h->mba_diff != 1)) {
423 h->current_mv_x = decode_mv_component(&s->gb, h->current_mv_x);
424 h->current_mv_y = decode_mv_component(&s->gb, h->current_mv_y);
431 if (HAS_CBP(h->mtype))
432 cbp = get_vlc2(&s->gb, h261_cbp_vlc.table, H261_CBP_VLC_BITS, 1) + 1;
435 s->current_picture.mb_type[xy] = MB_TYPE_INTRA;
440 s->mv_dir = MV_DIR_FORWARD;
441 s->mv_type = MV_TYPE_16X16;
442 s->current_picture.mb_type[xy] = MB_TYPE_16x16 | MB_TYPE_L0;
443 s->mv[0][0][0] = h->current_mv_x * 2; // gets divided by 2 in motion compensation
444 s->mv[0][0][1] = h->current_mv_y * 2;
446 if (s->current_picture.motion_val[0]) {
447 int b_stride = 2*s->mb_width + 1;
448 int b_xy = 2 * s->mb_x + (2 * s->mb_y) * b_stride;
449 s->current_picture.motion_val[0][b_xy][0] = s->mv[0][0][0];
450 s->current_picture.motion_val[0][b_xy][1] = s->mv[0][0][1];
454 /* decode each block */
455 if (s->mb_intra || HAS_CBP(h->mtype)) {
456 s->bdsp.clear_blocks(s->block[0]);
457 for (i = 0; i < 6; i++) {
458 if (h261_decode_block(h, s->block[i], i, cbp & 32) < 0)
463 for (i = 0; i < 6; i++)
464 s->block_last_index[i] = -1;
467 ff_mpv_reconstruct_mb(s, s->block);
473 * Decode the H.261 picture header.
474 * @return <0 if no startcode found
476 static int h261_decode_picture_header(H261Context *h)
478 MpegEncContext *const s = &h->s;
480 uint32_t startcode = 0;
482 for (i = get_bits_left(&s->gb); i > 24; i -= 1) {
483 startcode = ((startcode << 1) | get_bits(&s->gb, 1)) & 0x000FFFFF;
485 if (startcode == 0x10)
489 if (startcode != 0x10) {
490 av_log(s->avctx, AV_LOG_ERROR, "Bad picture start code\n");
494 /* temporal reference */
495 i = get_bits(&s->gb, 5); /* picture timestamp */
496 if (i < (s->picture_number & 31))
498 s->picture_number = (s->picture_number & ~31) + i;
500 s->avctx->framerate = (AVRational) { 30000, 1001 };
502 /* PTYPE starts here */
503 skip_bits1(&s->gb); /* split screen off */
504 skip_bits1(&s->gb); /* camera off */
505 skip_bits1(&s->gb); /* freeze picture release off */
507 format = get_bits1(&s->gb);
509 // only 2 formats possible
510 if (format == 0) { // QCIF
522 s->mb_num = s->mb_width * s->mb_height;
524 skip_bits1(&s->gb); /* still image mode off */
525 skip_bits1(&s->gb); /* Reserved */
528 if (skip_1stop_8data_bits(&s->gb) < 0)
529 return AVERROR_INVALIDDATA;
531 /* H.261 has no I-frames, but if we pass AV_PICTURE_TYPE_I for the first
532 * frame, the codec crashes if it does not contain all I-blocks
533 * (e.g. when a packet is lost). */
534 s->pict_type = AV_PICTURE_TYPE_P;
540 static int h261_decode_gob(H261Context *h)
542 MpegEncContext *const s = &h->s;
544 ff_set_qscale(s, s->qscale);
547 while (h->current_mba <= MBA_STUFFING) {
550 ret = h261_decode_mb(h);
552 if (ret == SLICE_END) {
553 h261_decode_mb_skipped(h, h->current_mba, 33);
556 av_log(s->avctx, AV_LOG_ERROR, "Error at MB: %d\n",
557 s->mb_x + s->mb_y * s->mb_stride);
561 h261_decode_mb_skipped(h,
562 h->current_mba - h->mba_diff,
570 * returns the number of bytes consumed for building the current frame
572 static int get_consumed_bytes(MpegEncContext *s, int buf_size)
574 int pos = get_bits_count(&s->gb) >> 3;
576 pos = 1; // avoid infinite loops (i doubt that is needed but ...)
577 if (pos + 10 > buf_size)
578 pos = buf_size; // oops ;)
583 static int h261_decode_frame(AVCodecContext *avctx, void *data,
584 int *got_frame, AVPacket *avpkt)
586 const uint8_t *buf = avpkt->data;
587 int buf_size = avpkt->size;
588 H261Context *h = avctx->priv_data;
589 MpegEncContext *s = &h->s;
591 AVFrame *pict = data;
593 ff_dlog(avctx, "*****frame %d size=%d\n", avctx->frame_number, buf_size);
594 ff_dlog(avctx, "bytes=%x %x %x %x\n", buf[0], buf[1], buf[2], buf[3]);
596 h->gob_start_code_skipped = 0;
599 init_get_bits(&s->gb, buf, buf_size * 8);
601 if (!s->context_initialized)
602 // we need the IDCT permutation for reading a custom matrix
605 ret = h261_decode_picture_header(h);
607 /* skip if the header was thrashed */
609 av_log(s->avctx, AV_LOG_ERROR, "header damaged\n");
613 if (s->width != avctx->coded_width || s->height != avctx->coded_height) {
614 ParseContext pc = s->parse_context; // FIXME move this demuxing hack to libavformat
615 s->parse_context.buffer = 0;
616 ff_mpv_common_end(s);
617 s->parse_context = pc;
620 if (!s->context_initialized) {
621 if ((ret = ff_mpv_common_init(s)) < 0)
624 ret = ff_set_dimensions(avctx, s->width, s->height);
631 // for skipping the frame
632 s->current_picture.f->pict_type = s->pict_type;
633 s->current_picture.f->key_frame = s->pict_type == AV_PICTURE_TYPE_I;
635 if ((avctx->skip_frame >= AVDISCARD_NONREF && s->pict_type == AV_PICTURE_TYPE_B) ||
636 (avctx->skip_frame >= AVDISCARD_NONKEY && s->pict_type != AV_PICTURE_TYPE_I) ||
637 avctx->skip_frame >= AVDISCARD_ALL)
638 return get_consumed_bytes(s, buf_size);
640 if (ff_mpv_frame_start(s, avctx) < 0)
643 ff_mpeg_er_frame_start(s);
645 /* decode each macroblock */
649 while (h->gob_number < (s->mb_height == 18 ? 12 : 5)) {
650 if (h261_resync(h) < 0)
656 av_assert0(s->current_picture.f->pict_type == s->current_picture_ptr->f->pict_type);
657 av_assert0(s->current_picture.f->pict_type == s->pict_type);
659 if ((ret = av_frame_ref(pict, s->current_picture_ptr->f)) < 0)
661 ff_print_debug_info(s, s->current_picture_ptr, pict);
665 return get_consumed_bytes(s, buf_size);
668 static av_cold int h261_decode_end(AVCodecContext *avctx)
670 H261Context *h = avctx->priv_data;
671 MpegEncContext *s = &h->s;
673 ff_mpv_common_end(s);
677 AVCodec ff_h261_decoder = {
679 .long_name = NULL_IF_CONFIG_SMALL("H.261"),
680 .type = AVMEDIA_TYPE_VIDEO,
681 .id = AV_CODEC_ID_H261,
682 .priv_data_size = sizeof(H261Context),
683 .init = h261_decode_init,
684 .close = h261_decode_end,
685 .decode = h261_decode_frame,
686 .capabilities = AV_CODEC_CAP_DR1,
687 .caps_internal = FF_CODEC_CAP_INIT_CLEANUP,