/* * H.261 decoder * Copyright (c) 2002-2004 Michael Niedermayer * Copyright (c) 2004 Maarten Daniels * * This file is part of FFmpeg. * * FFmpeg is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public * License as published by the Free Software Foundation; either * version 2.1 of the License, or (at your option) any later version. * * FFmpeg is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with FFmpeg; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */ /** * @file * H.261 decoder. */ #include "libavutil/avassert.h" #include "libavutil/thread.h" #include "avcodec.h" #include "codec_internal.h" #include "decode.h" #include "mpeg_er.h" #include "mpegutils.h" #include "mpegvideo.h" #include "mpegvideodec.h" #include "h261.h" #define H261_MBA_VLC_BITS 8 #define H261_MTYPE_VLC_BITS 6 #define H261_MV_VLC_BITS 7 #define H261_CBP_VLC_BITS 9 #define TCOEFF_VLC_BITS 9 #define MBA_STUFFING 33 #define MBA_STARTCODE 34 static VLCElem h261_mba_vlc[540]; static VLCElem h261_mtype_vlc[80]; static VLCElem h261_mv_vlc[144]; static VLCElem h261_cbp_vlc[512]; typedef struct H261DecContext { MpegEncContext s; H261Context common; int current_mba; int mba_diff; int current_mv_x; int current_mv_y; int gob_number; int gob_start_code_skipped; // 1 if gob start code is already read before gob header is read } H261DecContext; static av_cold void h261_decode_init_static(void) { VLC_INIT_STATIC_TABLE(h261_mba_vlc, H261_MBA_VLC_BITS, 35, ff_h261_mba_bits, 1, 1, ff_h261_mba_code, 1, 1, 0); VLC_INIT_STATIC_SPARSE_TABLE(h261_mtype_vlc, H261_MTYPE_VLC_BITS, 10, ff_h261_mtype_bits, 1, 1, ff_h261_mtype_code, 1, 1, ff_h261_mtype_map, 2, 2, 0); VLC_INIT_STATIC_TABLE(h261_mv_vlc, H261_MV_VLC_BITS, 17, &ff_h261_mv_tab[0][1], 2, 1, &ff_h261_mv_tab[0][0], 2, 1, 0); VLC_INIT_STATIC_TABLE(h261_cbp_vlc, H261_CBP_VLC_BITS, 63, &ff_h261_cbp_tab[0][1], 2, 1, &ff_h261_cbp_tab[0][0], 2, 1, 0); INIT_FIRST_VLC_RL(ff_h261_rl_tcoeff, 552); } static av_cold int h261_decode_init(AVCodecContext *avctx) { static AVOnce init_static_once = AV_ONCE_INIT; H261DecContext *const h = avctx->priv_data; MpegEncContext *const s = &h->s; int ret; s->private_ctx = &h->common; // set defaults ret = ff_mpv_decode_init(s, avctx); if (ret < 0) return ret; s->out_format = FMT_H261; s->low_delay = 1; avctx->pix_fmt = AV_PIX_FMT_YUV420P; ff_thread_once(&init_static_once, h261_decode_init_static); return 0; } static inline void h261_init_dest(MpegEncContext *s) { const unsigned block_size = 8 >> s->avctx->lowres; ff_init_block_index(s); s->dest[0] += 2 * block_size; s->dest[1] += block_size; s->dest[2] += block_size; } /** * Decode the group of blocks header or slice header. * @return <0 if an error occurred */ static int h261_decode_gob_header(H261DecContext *h) { unsigned int val; MpegEncContext *const s = &h->s; if (!h->gob_start_code_skipped) { /* Check for GOB Start Code */ val = show_bits(&s->gb, 15); if (val) return -1; /* We have a GBSC */ skip_bits(&s->gb, 16); } h->gob_start_code_skipped = 0; h->gob_number = get_bits(&s->gb, 4); /* GN */ s->qscale = get_bits(&s->gb, 5); /* GQUANT */ /* Check if gob_number is valid */ if (s->mb_height == 18) { // CIF if ((h->gob_number <= 0) || (h->gob_number > 12)) return -1; } else { // QCIF if ((h->gob_number != 1) && (h->gob_number != 3) && (h->gob_number != 5)) return -1; } /* GEI */ if (skip_1stop_8data_bits(&s->gb) < 0) return AVERROR_INVALIDDATA; if (s->qscale == 0) { av_log(s->avctx, AV_LOG_ERROR, "qscale has forbidden 0 value\n"); if (s->avctx->err_recognition & (AV_EF_BITSTREAM | AV_EF_COMPLIANT)) return -1; } /* For the first transmitted macroblock in a GOB, MBA is the absolute * address. For subsequent macroblocks, MBA is the difference between * the absolute addresses of the macroblock and the last transmitted * macroblock. */ h->current_mba = 0; h->mba_diff = 0; return 0; } /** * Decode skipped macroblocks. * @return 0 */ static int h261_decode_mb_skipped(H261DecContext *h, int mba1, int mba2) { MpegEncContext *const s = &h->s; int i; s->mb_intra = 0; for (i = mba1; i < mba2; i++) { int j, xy; s->mb_x = ((h->gob_number - 1) % 2) * 11 + i % 11; s->mb_y = ((h->gob_number - 1) / 2) * 3 + i / 11; xy = s->mb_x + s->mb_y * s->mb_stride; h261_init_dest(s); for (j = 0; j < 6; j++) s->block_last_index[j] = -1; s->mv_dir = MV_DIR_FORWARD; s->mv_type = MV_TYPE_16X16; s->cur_pic.mb_type[xy] = MB_TYPE_SKIP | MB_TYPE_16x16 | MB_TYPE_FORWARD_MV; s->mv[0][0][0] = 0; s->mv[0][0][1] = 0; s->mb_skipped = 1; h->common.mtype &= ~MB_TYPE_H261_FIL; if (s->cur_pic.motion_val[0]) { int b_stride = 2*s->mb_width + 1; int b_xy = 2 * s->mb_x + (2 * s->mb_y) * b_stride; s->cur_pic.motion_val[0][b_xy][0] = s->mv[0][0][0]; s->cur_pic.motion_val[0][b_xy][1] = s->mv[0][0][1]; } ff_mpv_reconstruct_mb(s, s->block); } return 0; } static const int mvmap[17] = { 0, -1, -2, -3, -4, -5, -6, -7, -8, -9, -10, -11, -12, -13, -14, -15, -16 }; static int decode_mv_component(GetBitContext *gb, int v) { int mv_diff = get_vlc2(gb, h261_mv_vlc, H261_MV_VLC_BITS, 2); /* check if mv_diff is valid */ if (mv_diff < 0) return v; mv_diff = mvmap[mv_diff]; if (mv_diff && !get_bits1(gb)) mv_diff = -mv_diff; v += mv_diff; if (v <= -16) v += 32; else if (v >= 16) v -= 32; return v; } /** * Decode a macroblock. * @return <0 if an error occurred */ static int h261_decode_block(H261DecContext *h, int16_t *block, int n, int coded) { MpegEncContext *const s = &h->s; int level, i, j, run; const RLTable *rl = &ff_h261_rl_tcoeff; const uint8_t *scan_table; const int qmul = s->qscale << 1, qadd = (s->qscale - 1) | 1; /* For the variable length encoding there are two code tables, one being * used for the first transmitted LEVEL in INTER, INTER + MC and * INTER + MC + FIL blocks, the second for all other LEVELs except the * first one in INTRA blocks which is fixed length coded with 8 bits. * NOTE: The two code tables only differ in one VLC so we handle that * manually. */ scan_table = s->intra_scantable.permutated; if (s->mb_intra) { /* DC coef */ level = get_bits(&s->gb, 8); // 0 (00000000b) and -128 (10000000b) are FORBIDDEN if ((level & 0x7F) == 0) { av_log(s->avctx, AV_LOG_ERROR, "illegal dc %d at %d %d\n", level, s->mb_x, s->mb_y); return -1; } /* The code 1000 0000 is not used, the reconstruction level of 1024 * being coded as 1111 1111. */ if (level == 255) level = 128; block[0] = level * s->y_dc_scale; i = 1; } else if (coded) { // Run Level Code // EOB Not possible for first level when cbp is available (that's why the table is different) // 0 1 1s // * * 0* int check = show_bits(&s->gb, 2); i = 0; if (check & 0x2) { skip_bits(&s->gb, 2); block[0] = qmul + qadd; block[0] *= (check & 0x1) ? -1 : 1; i = 1; } } else { i = 0; } if (!coded) { s->block_last_index[n] = i - 1; return 0; } { OPEN_READER(re, &s->gb); i--; // offset by -1 to allow direct indexing of scan_table for (;;) { UPDATE_CACHE(re, &s->gb); GET_RL_VLC(level, run, re, &s->gb, rl->rl_vlc[0], TCOEFF_VLC_BITS, 2, 0); if (run == 66) { if (level) { CLOSE_READER(re, &s->gb); av_log(s->avctx, AV_LOG_ERROR, "illegal ac vlc code at %dx%d\n", s->mb_x, s->mb_y); return -1; } /* escape */ /* The remaining combinations of (run, level) are encoded with a * 20-bit word consisting of 6 bits escape, 6 bits run and 8 bits * level. */ run = SHOW_UBITS(re, &s->gb, 6) + 1; SKIP_CACHE(re, &s->gb, 6); level = SHOW_SBITS(re, &s->gb, 8); if (level > 0) level = level * qmul + qadd; else if (level < 0) level = level * qmul - qadd; SKIP_COUNTER(re, &s->gb, 6 + 8); } else if (level == 0) { break; } else { level = level * qmul + qadd; if (SHOW_UBITS(re, &s->gb, 1)) level = -level; SKIP_COUNTER(re, &s->gb, 1); } i += run; if (i >= 64) { CLOSE_READER(re, &s->gb); av_log(s->avctx, AV_LOG_ERROR, "run overflow at %dx%d\n", s->mb_x, s->mb_y); return -1; } j = scan_table[i]; block[j] = level; } CLOSE_READER(re, &s->gb); } s->block_last_index[n] = i; return 0; } static int h261_decode_mb(H261DecContext *h) { MpegEncContext *const s = &h->s; H261Context *const com = &h->common; int i, cbp, xy; cbp = 63; // Read mba do { h->mba_diff = get_vlc2(&s->gb, h261_mba_vlc, H261_MBA_VLC_BITS, 2); /* Check for slice end */ /* NOTE: GOB can be empty (no MB data) or exist only of MBA_stuffing */ if (h->mba_diff == MBA_STARTCODE) { // start code h->gob_start_code_skipped = 1; return SLICE_END; } } while (h->mba_diff == MBA_STUFFING); // stuffing if (h->mba_diff < 0) { if (get_bits_left(&s->gb) <= 7) return SLICE_END; av_log(s->avctx, AV_LOG_ERROR, "illegal mba at %d %d\n", s->mb_x, s->mb_y); return SLICE_ERROR; } h->mba_diff += 1; h->current_mba += h->mba_diff; if (h->current_mba > MBA_STUFFING) return SLICE_ERROR; s->mb_x = ((h->gob_number - 1) % 2) * 11 + ((h->current_mba - 1) % 11); s->mb_y = ((h->gob_number - 1) / 2) * 3 + ((h->current_mba - 1) / 11); xy = s->mb_x + s->mb_y * s->mb_stride; h261_init_dest(s); // Read mtype com->mtype = get_vlc2(&s->gb, h261_mtype_vlc, H261_MTYPE_VLC_BITS, 2); if (com->mtype < 0) { av_log(s->avctx, AV_LOG_ERROR, "Invalid mtype index\n"); return SLICE_ERROR; } // Read mquant if (IS_QUANT(com->mtype)) ff_set_qscale(s, get_bits(&s->gb, 5)); s->mb_intra = IS_INTRA4x4(com->mtype); // Read mv if (IS_16X16(com->mtype)) { /* Motion vector data is included for all MC macroblocks. MVD is * obtained from the macroblock vector by subtracting the vector * of the preceding macroblock. For this calculation the vector * of the preceding macroblock is regarded as zero in the * following three situations: * 1) evaluating MVD for macroblocks 1, 12 and 23; * 2) evaluating MVD for macroblocks in which MBA does not represent a difference of 1; * 3) MTYPE of the previous macroblock was not MC. */ if ((h->current_mba == 1) || (h->current_mba == 12) || (h->current_mba == 23) || (h->mba_diff != 1)) { h->current_mv_x = 0; h->current_mv_y = 0; } h->current_mv_x = decode_mv_component(&s->gb, h->current_mv_x); h->current_mv_y = decode_mv_component(&s->gb, h->current_mv_y); } else { h->current_mv_x = 0; h->current_mv_y = 0; } // Read cbp if (HAS_CBP(com->mtype)) cbp = get_vlc2(&s->gb, h261_cbp_vlc, H261_CBP_VLC_BITS, 1) + 1; if (s->mb_intra) { s->cur_pic.mb_type[xy] = MB_TYPE_INTRA; goto intra; } //set motion vectors s->mv_dir = MV_DIR_FORWARD; s->mv_type = MV_TYPE_16X16; s->cur_pic.mb_type[xy] = MB_TYPE_16x16 | MB_TYPE_FORWARD_MV; s->mv[0][0][0] = h->current_mv_x * 2; // gets divided by 2 in motion compensation s->mv[0][0][1] = h->current_mv_y * 2; if (s->cur_pic.motion_val[0]) { int b_stride = 2*s->mb_width + 1; int b_xy = 2 * s->mb_x + (2 * s->mb_y) * b_stride; s->cur_pic.motion_val[0][b_xy][0] = s->mv[0][0][0]; s->cur_pic.motion_val[0][b_xy][1] = s->mv[0][0][1]; } intra: /* decode each block */ if (s->mb_intra || HAS_CBP(com->mtype)) { s->bdsp.clear_blocks(s->block[0]); for (i = 0; i < 6; i++) { if (h261_decode_block(h, s->block[i], i, cbp & 32) < 0) return SLICE_ERROR; cbp += cbp; } } else { for (i = 0; i < 6; i++) s->block_last_index[i] = -1; } ff_mpv_reconstruct_mb(s, s->block); return SLICE_OK; } /** * Decode the H.261 picture header. * @return <0 if no startcode found */ static int h261_decode_picture_header(H261DecContext *h) { MpegEncContext *const s = &h->s; int format, i; uint32_t startcode = 0; for (i = get_bits_left(&s->gb); i > 24; i -= 1) { startcode = ((startcode << 1) | get_bits(&s->gb, 1)) & 0x000FFFFF; if (startcode == 0x10) break; } if (startcode != 0x10) { av_log(s->avctx, AV_LOG_ERROR, "Bad picture start code\n"); return -1; } /* temporal reference */ skip_bits(&s->gb, 5); /* picture timestamp */ s->avctx->framerate = (AVRational) { 30000, 1001 }; /* PTYPE starts here */ skip_bits1(&s->gb); /* split screen off */ skip_bits1(&s->gb); /* camera off */ skip_bits1(&s->gb); /* freeze picture release off */ format = get_bits1(&s->gb); // only 2 formats possible if (format == 0) { // QCIF s->width = 176; s->height = 144; } else { // CIF s->width = 352; s->height = 288; } skip_bits1(&s->gb); /* still image mode off */ skip_bits1(&s->gb); /* Reserved */ /* PEI */ if (skip_1stop_8data_bits(&s->gb) < 0) return AVERROR_INVALIDDATA; /* H.261 has no I-frames, but if we pass AV_PICTURE_TYPE_I for the first * frame, the codec crashes if it does not contain all I-blocks * (e.g. when a packet is lost). */ s->pict_type = AV_PICTURE_TYPE_P; h->gob_number = 0; return 0; } static int h261_decode_gob(H261DecContext *h) { MpegEncContext *const s = &h->s; ff_set_qscale(s, s->qscale); /* decode mb's */ while (h->current_mba <= MBA_STUFFING) { int ret; /* DCT & quantize */ ret = h261_decode_mb(h); if (ret < 0) { if (ret == SLICE_END) { h261_decode_mb_skipped(h, h->current_mba, 33); return 0; } av_log(s->avctx, AV_LOG_ERROR, "Error at MB: %d\n", s->mb_x + s->mb_y * s->mb_stride); return -1; } h261_decode_mb_skipped(h, h->current_mba - h->mba_diff, h->current_mba - 1); } return -1; } /** * returns the number of bytes consumed for building the current frame */ static int get_consumed_bytes(MpegEncContext *s, int buf_size) { int pos = get_bits_count(&s->gb) >> 3; if (pos == 0) pos = 1; // avoid infinite loops (i doubt that is needed but ...) if (pos + 10 > buf_size) pos = buf_size; // oops ;) return pos; } static int h261_decode_frame(AVCodecContext *avctx, AVFrame *pict, int *got_frame, AVPacket *avpkt) { H261DecContext *const h = avctx->priv_data; const uint8_t *buf = avpkt->data; int buf_size = avpkt->size; MpegEncContext *s = &h->s; int ret; ff_dlog(avctx, "*****frame %"PRId64" size=%d\n", avctx->frame_num, buf_size); ff_dlog(avctx, "bytes=%x %x %x %x\n", buf[0], buf[1], buf[2], buf[3]); h->gob_start_code_skipped = 0; init_get_bits(&s->gb, buf, buf_size * 8); ret = h261_decode_picture_header(h); /* skip if the header was thrashed */ if (ret < 0) { av_log(s->avctx, AV_LOG_ERROR, "header damaged\n"); return -1; } if (s->width != avctx->coded_width || s->height != avctx->coded_height) { ff_mpv_common_end(s); } if (!s->context_initialized) { if ((ret = ff_mpv_common_init(s)) < 0) return ret; ret = ff_set_dimensions(avctx, s->width, s->height); if (ret < 0) return ret; } if ((avctx->skip_frame >= AVDISCARD_NONREF && s->pict_type == AV_PICTURE_TYPE_B) || (avctx->skip_frame >= AVDISCARD_NONKEY && s->pict_type != AV_PICTURE_TYPE_I) || avctx->skip_frame >= AVDISCARD_ALL) return buf_size; if (ff_mpv_frame_start(s, avctx) < 0) return -1; ff_mpeg_er_frame_start(s); /* decode each macroblock */ s->mb_x = 0; s->mb_y = 0; while (h->gob_number < (s->mb_height == 18 ? 12 : 5)) { if (h261_decode_gob_header(h) < 0) break; h261_decode_gob(h); } ff_mpv_frame_end(s); av_assert0(s->pict_type == s->cur_pic.ptr->f->pict_type); if ((ret = av_frame_ref(pict, s->cur_pic.ptr->f)) < 0) return ret; ff_print_debug_info(s, s->cur_pic.ptr, pict); *got_frame = 1; return get_consumed_bytes(s, buf_size); } const FFCodec ff_h261_decoder = { .p.name = "h261", CODEC_LONG_NAME("H.261"), .p.type = AVMEDIA_TYPE_VIDEO, .p.id = AV_CODEC_ID_H261, .priv_data_size = sizeof(H261DecContext), .init = h261_decode_init, FF_CODEC_DECODE_CB(h261_decode_frame), .close = ff_mpv_decode_close, .p.capabilities = AV_CODEC_CAP_DR1, .p.max_lowres = 3, };