1/* 2 * H.261 decoder 3 * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at> 4 * Copyright (c) 2004 Maarten Daniels 5 * 6 * This file is part of FFmpeg. 7 * 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. 12 * 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. 17 * 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 21 */ 22 23/** 24 * @file 25 * H.261 decoder. 26 */ 27 28#include "libavutil/avassert.h" 29#include "libavutil/thread.h" 30#include "avcodec.h" 31#include "codec_internal.h" 32#include "mpeg_er.h" 33#include "mpegutils.h" 34#include "mpegvideo.h" 35#include "mpegvideodec.h" 36#include "h261.h" 37#include "internal.h" 38 39#define H261_MBA_VLC_BITS 8 40#define H261_MTYPE_VLC_BITS 6 41#define H261_MV_VLC_BITS 7 42#define H261_CBP_VLC_BITS 9 43#define TCOEFF_VLC_BITS 9 44#define MBA_STUFFING 33 45#define MBA_STARTCODE 34 46 47static VLC h261_mba_vlc; 48static VLC h261_mtype_vlc; 49static VLC h261_mv_vlc; 50static VLC h261_cbp_vlc; 51 52typedef struct H261DecContext { 53 MpegEncContext s; 54 55 H261Context common; 56 57 int current_mba; 58 int mba_diff; 59 int current_mv_x; 60 int current_mv_y; 61 int gob_number; 62 int gob_start_code_skipped; // 1 if gob start code is already read before gob header is read 63} H261DecContext; 64 65static av_cold void h261_decode_init_static(void) 66{ 67 INIT_VLC_STATIC(&h261_mba_vlc, H261_MBA_VLC_BITS, 35, 68 ff_h261_mba_bits, 1, 1, 69 ff_h261_mba_code, 1, 1, 540); 70 INIT_VLC_STATIC(&h261_mtype_vlc, H261_MTYPE_VLC_BITS, 10, 71 ff_h261_mtype_bits, 1, 1, 72 ff_h261_mtype_code, 1, 1, 80); 73 INIT_VLC_STATIC(&h261_mv_vlc, H261_MV_VLC_BITS, 17, 74 &ff_h261_mv_tab[0][1], 2, 1, 75 &ff_h261_mv_tab[0][0], 2, 1, 144); 76 INIT_VLC_STATIC(&h261_cbp_vlc, H261_CBP_VLC_BITS, 63, 77 &ff_h261_cbp_tab[0][1], 2, 1, 78 &ff_h261_cbp_tab[0][0], 2, 1, 512); 79 INIT_FIRST_VLC_RL(ff_h261_rl_tcoeff, 552); 80} 81 82static av_cold int h261_decode_init(AVCodecContext *avctx) 83{ 84 static AVOnce init_static_once = AV_ONCE_INIT; 85 H261DecContext *const h = avctx->priv_data; 86 MpegEncContext *const s = &h->s; 87 88 s->private_ctx = &h->common; 89 // set defaults 90 ff_mpv_decode_init(s, avctx); 91 92 s->out_format = FMT_H261; 93 s->low_delay = 1; 94 avctx->pix_fmt = AV_PIX_FMT_YUV420P; 95 96 h->gob_start_code_skipped = 0; 97 ff_mpv_idct_init(s); 98 99 ff_thread_once(&init_static_once, h261_decode_init_static); 100 101 return 0; 102} 103 104/** 105 * Decode the group of blocks header or slice header. 106 * @return <0 if an error occurred 107 */ 108static int h261_decode_gob_header(H261DecContext *h) 109{ 110 unsigned int val; 111 MpegEncContext *const s = &h->s; 112 113 if (!h->gob_start_code_skipped) { 114 /* Check for GOB Start Code */ 115 val = show_bits(&s->gb, 15); 116 if (val) 117 return -1; 118 119 /* We have a GBSC */ 120 skip_bits(&s->gb, 16); 121 } 122 123 h->gob_start_code_skipped = 0; 124 125 h->gob_number = get_bits(&s->gb, 4); /* GN */ 126 s->qscale = get_bits(&s->gb, 5); /* GQUANT */ 127 128 /* Check if gob_number is valid */ 129 if (s->mb_height == 18) { // CIF 130 if ((h->gob_number <= 0) || (h->gob_number > 12)) 131 return -1; 132 } else { // QCIF 133 if ((h->gob_number != 1) && (h->gob_number != 3) && 134 (h->gob_number != 5)) 135 return -1; 136 } 137 138 /* GEI */ 139 if (skip_1stop_8data_bits(&s->gb) < 0) 140 return AVERROR_INVALIDDATA; 141 142 if (s->qscale == 0) { 143 av_log(s->avctx, AV_LOG_ERROR, "qscale has forbidden 0 value\n"); 144 if (s->avctx->err_recognition & (AV_EF_BITSTREAM | AV_EF_COMPLIANT)) 145 return -1; 146 } 147 148 /* For the first transmitted macroblock in a GOB, MBA is the absolute 149 * address. For subsequent macroblocks, MBA is the difference between 150 * the absolute addresses of the macroblock and the last transmitted 151 * macroblock. */ 152 h->current_mba = 0; 153 h->mba_diff = 0; 154 155 return 0; 156} 157 158/** 159 * Decode the group of blocks / video packet header. 160 * @return <0 if no resync found 161 */ 162static int h261_resync(H261DecContext *h) 163{ 164 MpegEncContext *const s = &h->s; 165 int left, ret; 166 167 if (h->gob_start_code_skipped) { 168 ret = h261_decode_gob_header(h); 169 if (ret >= 0) 170 return 0; 171 } else { 172 if (show_bits(&s->gb, 15) == 0) { 173 ret = h261_decode_gob_header(h); 174 if (ret >= 0) 175 return 0; 176 } 177 // OK, it is not where it is supposed to be ... 178 s->gb = s->last_resync_gb; 179 align_get_bits(&s->gb); 180 left = get_bits_left(&s->gb); 181 182 for (; left > 15 + 1 + 4 + 5; left -= 8) { 183 if (show_bits(&s->gb, 15) == 0) { 184 GetBitContext bak = s->gb; 185 186 ret = h261_decode_gob_header(h); 187 if (ret >= 0) 188 return 0; 189 190 s->gb = bak; 191 } 192 skip_bits(&s->gb, 8); 193 } 194 } 195 196 return -1; 197} 198 199/** 200 * Decode skipped macroblocks. 201 * @return 0 202 */ 203static int h261_decode_mb_skipped(H261DecContext *h, int mba1, int mba2) 204{ 205 MpegEncContext *const s = &h->s; 206 int i; 207 208 s->mb_intra = 0; 209 210 for (i = mba1; i < mba2; i++) { 211 int j, xy; 212 213 s->mb_x = ((h->gob_number - 1) % 2) * 11 + i % 11; 214 s->mb_y = ((h->gob_number - 1) / 2) * 3 + i / 11; 215 xy = s->mb_x + s->mb_y * s->mb_stride; 216 ff_init_block_index(s); 217 ff_update_block_index(s); 218 219 for (j = 0; j < 6; j++) 220 s->block_last_index[j] = -1; 221 222 s->mv_dir = MV_DIR_FORWARD; 223 s->mv_type = MV_TYPE_16X16; 224 s->current_picture.mb_type[xy] = MB_TYPE_SKIP | MB_TYPE_16x16 | MB_TYPE_L0; 225 s->mv[0][0][0] = 0; 226 s->mv[0][0][1] = 0; 227 s->mb_skipped = 1; 228 h->common.mtype &= ~MB_TYPE_H261_FIL; 229 230 if (s->current_picture.motion_val[0]) { 231 int b_stride = 2*s->mb_width + 1; 232 int b_xy = 2 * s->mb_x + (2 * s->mb_y) * b_stride; 233 s->current_picture.motion_val[0][b_xy][0] = s->mv[0][0][0]; 234 s->current_picture.motion_val[0][b_xy][1] = s->mv[0][0][1]; 235 } 236 237 ff_mpv_reconstruct_mb(s, s->block); 238 } 239 240 return 0; 241} 242 243static const int mvmap[17] = { 244 0, -1, -2, -3, -4, -5, -6, -7, -8, -9, -10, -11, -12, -13, -14, -15, -16 245}; 246 247static int decode_mv_component(GetBitContext *gb, int v) 248{ 249 int mv_diff = get_vlc2(gb, h261_mv_vlc.table, H261_MV_VLC_BITS, 2); 250 251 /* check if mv_diff is valid */ 252 if (mv_diff < 0) 253 return v; 254 255 mv_diff = mvmap[mv_diff]; 256 257 if (mv_diff && !get_bits1(gb)) 258 mv_diff = -mv_diff; 259 260 v += mv_diff; 261 if (v <= -16) 262 v += 32; 263 else if (v >= 16) 264 v -= 32; 265 266 return v; 267} 268 269/** 270 * Decode a macroblock. 271 * @return <0 if an error occurred 272 */ 273static int h261_decode_block(H261DecContext *h, int16_t *block, int n, int coded) 274{ 275 MpegEncContext *const s = &h->s; 276 int level, i, j, run; 277 RLTable *rl = &ff_h261_rl_tcoeff; 278 const uint8_t *scan_table; 279 280 /* For the variable length encoding there are two code tables, one being 281 * used for the first transmitted LEVEL in INTER, INTER + MC and 282 * INTER + MC + FIL blocks, the second for all other LEVELs except the 283 * first one in INTRA blocks which is fixed length coded with 8 bits. 284 * NOTE: The two code tables only differ in one VLC so we handle that 285 * manually. */ 286 scan_table = s->intra_scantable.permutated; 287 if (s->mb_intra) { 288 /* DC coef */ 289 level = get_bits(&s->gb, 8); 290 // 0 (00000000b) and -128 (10000000b) are FORBIDDEN 291 if ((level & 0x7F) == 0) { 292 av_log(s->avctx, AV_LOG_ERROR, "illegal dc %d at %d %d\n", 293 level, s->mb_x, s->mb_y); 294 return -1; 295 } 296 /* The code 1000 0000 is not used, the reconstruction level of 1024 297 * being coded as 1111 1111. */ 298 if (level == 255) 299 level = 128; 300 block[0] = level; 301 i = 1; 302 } else if (coded) { 303 // Run Level Code 304 // EOB Not possible for first level when cbp is available (that's why the table is different) 305 // 0 1 1s 306 // * * 0* 307 int check = show_bits(&s->gb, 2); 308 i = 0; 309 if (check & 0x2) { 310 skip_bits(&s->gb, 2); 311 block[0] = (check & 0x1) ? -1 : 1; 312 i = 1; 313 } 314 } else { 315 i = 0; 316 } 317 if (!coded) { 318 s->block_last_index[n] = i - 1; 319 return 0; 320 } 321 { 322 OPEN_READER(re, &s->gb); 323 i--; // offset by -1 to allow direct indexing of scan_table 324 for (;;) { 325 UPDATE_CACHE(re, &s->gb); 326 GET_RL_VLC(level, run, re, &s->gb, rl->rl_vlc[0], TCOEFF_VLC_BITS, 2, 0); 327 if (run == 66) { 328 if (level) { 329 CLOSE_READER(re, &s->gb); 330 av_log(s->avctx, AV_LOG_ERROR, "illegal ac vlc code at %dx%d\n", 331 s->mb_x, s->mb_y); 332 return -1; 333 } 334 /* escape */ 335 /* The remaining combinations of (run, level) are encoded with a 336 * 20-bit word consisting of 6 bits escape, 6 bits run and 8 bits 337 * level. */ 338 run = SHOW_UBITS(re, &s->gb, 6) + 1; 339 SKIP_CACHE(re, &s->gb, 6); 340 level = SHOW_SBITS(re, &s->gb, 8); 341 SKIP_COUNTER(re, &s->gb, 6 + 8); 342 } else if (level == 0) { 343 break; 344 } else { 345 if (SHOW_UBITS(re, &s->gb, 1)) 346 level = -level; 347 SKIP_COUNTER(re, &s->gb, 1); 348 } 349 i += run; 350 if (i >= 64) { 351 CLOSE_READER(re, &s->gb); 352 av_log(s->avctx, AV_LOG_ERROR, "run overflow at %dx%d\n", 353 s->mb_x, s->mb_y); 354 return -1; 355 } 356 j = scan_table[i]; 357 block[j] = level; 358 } 359 CLOSE_READER(re, &s->gb); 360 } 361 s->block_last_index[n] = i; 362 return 0; 363} 364 365static int h261_decode_mb(H261DecContext *h) 366{ 367 MpegEncContext *const s = &h->s; 368 H261Context *const com = &h->common; 369 int i, cbp, xy; 370 371 cbp = 63; 372 // Read mba 373 do { 374 h->mba_diff = get_vlc2(&s->gb, h261_mba_vlc.table, 375 H261_MBA_VLC_BITS, 2); 376 377 /* Check for slice end */ 378 /* NOTE: GOB can be empty (no MB data) or exist only of MBA_stuffing */ 379 if (h->mba_diff == MBA_STARTCODE) { // start code 380 h->gob_start_code_skipped = 1; 381 return SLICE_END; 382 } 383 } while (h->mba_diff == MBA_STUFFING); // stuffing 384 385 if (h->mba_diff < 0) { 386 if (get_bits_left(&s->gb) <= 7) 387 return SLICE_END; 388 389 av_log(s->avctx, AV_LOG_ERROR, "illegal mba at %d %d\n", s->mb_x, s->mb_y); 390 return SLICE_ERROR; 391 } 392 393 h->mba_diff += 1; 394 h->current_mba += h->mba_diff; 395 396 if (h->current_mba > MBA_STUFFING) 397 return SLICE_ERROR; 398 399 s->mb_x = ((h->gob_number - 1) % 2) * 11 + ((h->current_mba - 1) % 11); 400 s->mb_y = ((h->gob_number - 1) / 2) * 3 + ((h->current_mba - 1) / 11); 401 xy = s->mb_x + s->mb_y * s->mb_stride; 402 ff_init_block_index(s); 403 ff_update_block_index(s); 404 405 // Read mtype 406 com->mtype = get_vlc2(&s->gb, h261_mtype_vlc.table, H261_MTYPE_VLC_BITS, 2); 407 if (com->mtype < 0) { 408 av_log(s->avctx, AV_LOG_ERROR, "Invalid mtype index %d\n", 409 com->mtype); 410 return SLICE_ERROR; 411 } 412 av_assert0(com->mtype < FF_ARRAY_ELEMS(ff_h261_mtype_map)); 413 com->mtype = ff_h261_mtype_map[com->mtype]; 414 415 // Read mquant 416 if (IS_QUANT(com->mtype)) 417 ff_set_qscale(s, get_bits(&s->gb, 5)); 418 419 s->mb_intra = IS_INTRA4x4(com->mtype); 420 421 // Read mv 422 if (IS_16X16(com->mtype)) { 423 /* Motion vector data is included for all MC macroblocks. MVD is 424 * obtained from the macroblock vector by subtracting the vector 425 * of the preceding macroblock. For this calculation the vector 426 * of the preceding macroblock is regarded as zero in the 427 * following three situations: 428 * 1) evaluating MVD for macroblocks 1, 12 and 23; 429 * 2) evaluating MVD for macroblocks in which MBA does not represent a difference of 1; 430 * 3) MTYPE of the previous macroblock was not MC. */ 431 if ((h->current_mba == 1) || (h->current_mba == 12) || 432 (h->current_mba == 23) || (h->mba_diff != 1)) { 433 h->current_mv_x = 0; 434 h->current_mv_y = 0; 435 } 436 437 h->current_mv_x = decode_mv_component(&s->gb, h->current_mv_x); 438 h->current_mv_y = decode_mv_component(&s->gb, h->current_mv_y); 439 } else { 440 h->current_mv_x = 0; 441 h->current_mv_y = 0; 442 } 443 444 // Read cbp 445 if (HAS_CBP(com->mtype)) 446 cbp = get_vlc2(&s->gb, h261_cbp_vlc.table, H261_CBP_VLC_BITS, 1) + 1; 447 448 if (s->mb_intra) { 449 s->current_picture.mb_type[xy] = MB_TYPE_INTRA; 450 goto intra; 451 } 452 453 //set motion vectors 454 s->mv_dir = MV_DIR_FORWARD; 455 s->mv_type = MV_TYPE_16X16; 456 s->current_picture.mb_type[xy] = MB_TYPE_16x16 | MB_TYPE_L0; 457 s->mv[0][0][0] = h->current_mv_x * 2; // gets divided by 2 in motion compensation 458 s->mv[0][0][1] = h->current_mv_y * 2; 459 460 if (s->current_picture.motion_val[0]) { 461 int b_stride = 2*s->mb_width + 1; 462 int b_xy = 2 * s->mb_x + (2 * s->mb_y) * b_stride; 463 s->current_picture.motion_val[0][b_xy][0] = s->mv[0][0][0]; 464 s->current_picture.motion_val[0][b_xy][1] = s->mv[0][0][1]; 465 } 466 467intra: 468 /* decode each block */ 469 if (s->mb_intra || HAS_CBP(com->mtype)) { 470 s->bdsp.clear_blocks(s->block[0]); 471 for (i = 0; i < 6; i++) { 472 if (h261_decode_block(h, s->block[i], i, cbp & 32) < 0) 473 return SLICE_ERROR; 474 cbp += cbp; 475 } 476 } else { 477 for (i = 0; i < 6; i++) 478 s->block_last_index[i] = -1; 479 } 480 481 ff_mpv_reconstruct_mb(s, s->block); 482 483 return SLICE_OK; 484} 485 486/** 487 * Decode the H.261 picture header. 488 * @return <0 if no startcode found 489 */ 490static int h261_decode_picture_header(H261DecContext *h) 491{ 492 MpegEncContext *const s = &h->s; 493 int format, i; 494 uint32_t startcode = 0; 495 496 for (i = get_bits_left(&s->gb); i > 24; i -= 1) { 497 startcode = ((startcode << 1) | get_bits(&s->gb, 1)) & 0x000FFFFF; 498 499 if (startcode == 0x10) 500 break; 501 } 502 503 if (startcode != 0x10) { 504 av_log(s->avctx, AV_LOG_ERROR, "Bad picture start code\n"); 505 return -1; 506 } 507 508 /* temporal reference */ 509 i = get_bits(&s->gb, 5); /* picture timestamp */ 510 if (i < (s->picture_number & 31)) 511 i += 32; 512 s->picture_number = (s->picture_number & ~31) + i; 513 514 s->avctx->framerate = (AVRational) { 30000, 1001 }; 515 516 /* PTYPE starts here */ 517 skip_bits1(&s->gb); /* split screen off */ 518 skip_bits1(&s->gb); /* camera off */ 519 skip_bits1(&s->gb); /* freeze picture release off */ 520 521 format = get_bits1(&s->gb); 522 523 // only 2 formats possible 524 if (format == 0) { // QCIF 525 s->width = 176; 526 s->height = 144; 527 s->mb_width = 11; 528 s->mb_height = 9; 529 } else { // CIF 530 s->width = 352; 531 s->height = 288; 532 s->mb_width = 22; 533 s->mb_height = 18; 534 } 535 536 s->mb_num = s->mb_width * s->mb_height; 537 538 skip_bits1(&s->gb); /* still image mode off */ 539 skip_bits1(&s->gb); /* Reserved */ 540 541 /* PEI */ 542 if (skip_1stop_8data_bits(&s->gb) < 0) 543 return AVERROR_INVALIDDATA; 544 545 /* H.261 has no I-frames, but if we pass AV_PICTURE_TYPE_I for the first 546 * frame, the codec crashes if it does not contain all I-blocks 547 * (e.g. when a packet is lost). */ 548 s->pict_type = AV_PICTURE_TYPE_P; 549 550 h->gob_number = 0; 551 return 0; 552} 553 554static int h261_decode_gob(H261DecContext *h) 555{ 556 MpegEncContext *const s = &h->s; 557 558 ff_set_qscale(s, s->qscale); 559 560 /* decode mb's */ 561 while (h->current_mba <= MBA_STUFFING) { 562 int ret; 563 /* DCT & quantize */ 564 ret = h261_decode_mb(h); 565 if (ret < 0) { 566 if (ret == SLICE_END) { 567 h261_decode_mb_skipped(h, h->current_mba, 33); 568 return 0; 569 } 570 av_log(s->avctx, AV_LOG_ERROR, "Error at MB: %d\n", 571 s->mb_x + s->mb_y * s->mb_stride); 572 return -1; 573 } 574 575 h261_decode_mb_skipped(h, 576 h->current_mba - h->mba_diff, 577 h->current_mba - 1); 578 } 579 580 return -1; 581} 582 583/** 584 * returns the number of bytes consumed for building the current frame 585 */ 586static int get_consumed_bytes(MpegEncContext *s, int buf_size) 587{ 588 int pos = get_bits_count(&s->gb) >> 3; 589 if (pos == 0) 590 pos = 1; // avoid infinite loops (i doubt that is needed but ...) 591 if (pos + 10 > buf_size) 592 pos = buf_size; // oops ;) 593 594 return pos; 595} 596 597static int h261_decode_frame(AVCodecContext *avctx, AVFrame *pict, 598 int *got_frame, AVPacket *avpkt) 599{ 600 H261DecContext *const h = avctx->priv_data; 601 const uint8_t *buf = avpkt->data; 602 int buf_size = avpkt->size; 603 MpegEncContext *s = &h->s; 604 int ret; 605 606 ff_dlog(avctx, "*****frame %d size=%d\n", avctx->frame_number, buf_size); 607 ff_dlog(avctx, "bytes=%x %x %x %x\n", buf[0], buf[1], buf[2], buf[3]); 608 609 h->gob_start_code_skipped = 0; 610 611retry: 612 init_get_bits(&s->gb, buf, buf_size * 8); 613 614 ret = h261_decode_picture_header(h); 615 616 /* skip if the header was thrashed */ 617 if (ret < 0) { 618 av_log(s->avctx, AV_LOG_ERROR, "header damaged\n"); 619 return -1; 620 } 621 622 if (s->width != avctx->coded_width || s->height != avctx->coded_height) { 623 ff_mpv_common_end(s); 624 } 625 626 if (!s->context_initialized) { 627 if ((ret = ff_mpv_common_init(s)) < 0) 628 return ret; 629 630 ret = ff_set_dimensions(avctx, s->width, s->height); 631 if (ret < 0) 632 return ret; 633 634 goto retry; 635 } 636 637 // for skipping the frame 638 s->current_picture.f->pict_type = s->pict_type; 639 s->current_picture.f->key_frame = s->pict_type == AV_PICTURE_TYPE_I; 640 641 if ((avctx->skip_frame >= AVDISCARD_NONREF && s->pict_type == AV_PICTURE_TYPE_B) || 642 (avctx->skip_frame >= AVDISCARD_NONKEY && s->pict_type != AV_PICTURE_TYPE_I) || 643 avctx->skip_frame >= AVDISCARD_ALL) 644 return get_consumed_bytes(s, buf_size); 645 646 if (ff_mpv_frame_start(s, avctx) < 0) 647 return -1; 648 649 ff_mpeg_er_frame_start(s); 650 651 /* decode each macroblock */ 652 s->mb_x = 0; 653 s->mb_y = 0; 654 655 while (h->gob_number < (s->mb_height == 18 ? 12 : 5)) { 656 if (h261_resync(h) < 0) 657 break; 658 h261_decode_gob(h); 659 } 660 ff_mpv_frame_end(s); 661 662 av_assert0(s->current_picture.f->pict_type == s->current_picture_ptr->f->pict_type); 663 av_assert0(s->current_picture.f->pict_type == s->pict_type); 664 665 if ((ret = av_frame_ref(pict, s->current_picture_ptr->f)) < 0) 666 return ret; 667 ff_print_debug_info(s, s->current_picture_ptr, pict); 668 669 *got_frame = 1; 670 671 return get_consumed_bytes(s, buf_size); 672} 673 674static av_cold int h261_decode_end(AVCodecContext *avctx) 675{ 676 H261DecContext *const h = avctx->priv_data; 677 MpegEncContext *s = &h->s; 678 679 ff_mpv_common_end(s); 680 return 0; 681} 682 683const FFCodec ff_h261_decoder = { 684 .p.name = "h261", 685 .p.long_name = NULL_IF_CONFIG_SMALL("H.261"), 686 .p.type = AVMEDIA_TYPE_VIDEO, 687 .p.id = AV_CODEC_ID_H261, 688 .priv_data_size = sizeof(H261DecContext), 689 .init = h261_decode_init, 690 .close = h261_decode_end, 691 FF_CODEC_DECODE_CB(h261_decode_frame), 692 .p.capabilities = AV_CODEC_CAP_DR1, 693 .caps_internal = FF_CODEC_CAP_INIT_THREADSAFE, 694 .p.max_lowres = 3, 695}; 696