/* * H261 decoder * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at> * Copyright (c) 2004 Maarten Daniels * * This file is part of Libav. * * Libav 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. * * Libav 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 Libav; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */ /** * @file * H.261 decoder. */ #include "avcodec.h" #include "mpegvideo.h" #include "h263.h" #include "h261.h" #define H261_MBA_VLC_BITS 9 #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 VLC h261_mba_vlc; static VLC h261_mtype_vlc; static VLC h261_mv_vlc; static VLC h261_cbp_vlc; static av_cold void h261_decode_init_vlc(H261Context *h) { static int done = 0; if (!done) { done = 1; INIT_VLC_STATIC(&h261_mba_vlc, H261_MBA_VLC_BITS, 35, ff_h261_mba_bits, 1, 1, ff_h261_mba_code, 1, 1, 662); INIT_VLC_STATIC(&h261_mtype_vlc, H261_MTYPE_VLC_BITS, 10, ff_h261_mtype_bits, 1, 1, ff_h261_mtype_code, 1, 1, 80); INIT_VLC_STATIC(&h261_mv_vlc, H261_MV_VLC_BITS, 17, &ff_h261_mv_tab[0][1], 2, 1, &ff_h261_mv_tab[0][0], 2, 1, 144); INIT_VLC_STATIC(&h261_cbp_vlc, H261_CBP_VLC_BITS, 63, &ff_h261_cbp_tab[0][1], 2, 1, &ff_h261_cbp_tab[0][0], 2, 1, 512); INIT_VLC_RL(ff_h261_rl_tcoeff, 552); } } static av_cold int h261_decode_init(AVCodecContext *avctx) { H261Context *h = avctx->priv_data; MpegEncContext *const s = &h->s; // set defaults ff_MPV_decode_defaults(s); s->avctx = avctx; s->width = s->avctx->coded_width; s->height = s->avctx->coded_height; s->codec_id = s->avctx->codec->id; s->out_format = FMT_H261; s->low_delay = 1; avctx->pix_fmt = AV_PIX_FMT_YUV420P; s->codec_id = avctx->codec->id; ff_h261_common_init(); h261_decode_init_vlc(h); h->gob_start_code_skipped = 0; return 0; } /** * Decode the group of blocks header or slice header. * @return <0 if an error occurred */ static int h261_decode_gob_header(H261Context *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 */ while (get_bits1(&s->gb) != 0) skip_bits(&s->gb, 8); 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) 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 the group of blocks / video packet header. * @return <0 if no resync found */ static int h261_resync(H261Context *h) { MpegEncContext *const s = &h->s; int left, ret; if (h->gob_start_code_skipped) { ret = h261_decode_gob_header(h); if (ret >= 0) return 0; } else { if (show_bits(&s->gb, 15) == 0) { ret = h261_decode_gob_header(h); if (ret >= 0) return 0; } // OK, it is not where it is supposed to be ... s->gb = s->last_resync_gb; align_get_bits(&s->gb); left = get_bits_left(&s->gb); for (; left > 15 + 1 + 4 + 5; left -= 8) { if (show_bits(&s->gb, 15) == 0) { GetBitContext bak = s->gb; ret = h261_decode_gob_header(h); if (ret >= 0) return 0; s->gb = bak; } skip_bits(&s->gb, 8); } } return -1; } /** * Decode skipped macroblocks. * @return 0 */ static int h261_decode_mb_skipped(H261Context *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; ff_init_block_index(s); ff_update_block_index(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->current_picture.mb_type[xy] = MB_TYPE_SKIP | MB_TYPE_16x16 | MB_TYPE_L0; s->mv[0][0][0] = 0; s->mv[0][0][1] = 0; s->mb_skipped = 1; h->mtype &= ~MB_TYPE_H261_FIL; ff_MPV_decode_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.table, 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(H261Context *h, int16_t *block, int n, int coded) { MpegEncContext *const s = &h->s; int code, level, i, j, run; RLTable *rl = &ff_h261_rl_tcoeff; const uint8_t *scan_table; /* 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; 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] = (check & 0x1) ? -1 : 1; i = 1; } } else { i = 0; } if (!coded) { s->block_last_index[n] = i - 1; return 0; } for (;;) { code = get_vlc2(&s->gb, rl->vlc.table, TCOEFF_VLC_BITS, 2); if (code < 0) { av_log(s->avctx, AV_LOG_ERROR, "illegal ac vlc code at %dx%d\n", s->mb_x, s->mb_y); return -1; } if (code == rl->n) { /* 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 = get_bits(&s->gb, 6); level = get_sbits(&s->gb, 8); } else if (code == 0) { break; } else { run = rl->table_run[code]; level = rl->table_level[code]; if (get_bits1(&s->gb)) level = -level; } i += run; if (i >= 64) { 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; i++; } s->block_last_index[n] = i - 1; return 0; } static int h261_decode_mb(H261Context *h) { MpegEncContext *const s = &h->s; int i, cbp, xy; cbp = 63; // Read mba do { h->mba_diff = get_vlc2(&s->gb, h261_mba_vlc.table, 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; ff_init_block_index(s); ff_update_block_index(s); // Read mtype h->mtype = get_vlc2(&s->gb, h261_mtype_vlc.table, H261_MTYPE_VLC_BITS, 2); if (h->mtype < 0 || h->mtype >= FF_ARRAY_ELEMS(ff_h261_mtype_map)) { av_log(s->avctx, AV_LOG_ERROR, "Invalid mtype index %d\n", h->mtype); return SLICE_ERROR; } h->mtype = ff_h261_mtype_map[h->mtype]; // Read mquant if (IS_QUANT(h->mtype)) ff_set_qscale(s, get_bits(&s->gb, 5)); s->mb_intra = IS_INTRA4x4(h->mtype); // Read mv if (IS_16X16(h->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(h->mtype)) cbp = get_vlc2(&s->gb, h261_cbp_vlc.table, H261_CBP_VLC_BITS, 2) + 1; if (s->mb_intra) { s->current_picture.mb_type[xy] = MB_TYPE_INTRA; goto intra; } //set motion vectors s->mv_dir = MV_DIR_FORWARD; s->mv_type = MV_TYPE_16X16; s->current_picture.mb_type[xy] = MB_TYPE_16x16 | MB_TYPE_L0; 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; intra: /* decode each block */ if (s->mb_intra || HAS_CBP(h->mtype)) { s->dsp.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_decode_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(H261Context *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 */ i = get_bits(&s->gb, 5); /* picture timestamp */ if (i < (s->picture_number & 31)) i += 32; s->picture_number = (s->picture_number & ~31) + i; s->avctx->time_base = (AVRational) { 1001, 30000 }; s->current_picture.f.pts = s->picture_number; /* 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; s->mb_width = 11; s->mb_height = 9; } else { // CIF s->width = 352; s->height = 288; s->mb_width = 22; s->mb_height = 18; } s->mb_num = s->mb_width * s->mb_height; skip_bits1(&s->gb); /* still image mode off */ skip_bits1(&s->gb); /* Reserved */ /* PEI */ while (get_bits1(&s->gb) != 0) skip_bits(&s->gb, 8); /* 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(H261Context *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, void *data, int *got_frame, AVPacket *avpkt) { const uint8_t *buf = avpkt->data; int buf_size = avpkt->size; H261Context *h = avctx->priv_data; MpegEncContext *s = &h->s; int ret; AVFrame *pict = data; av_dlog(avctx, "*****frame %d size=%d\n", avctx->frame_number, buf_size); av_dlog(avctx, "bytes=%x %x %x %x\n", buf[0], buf[1], buf[2], buf[3]); s->flags = avctx->flags; s->flags2 = avctx->flags2; h->gob_start_code_skipped = 0; retry: init_get_bits(&s->gb, buf, buf_size * 8); if (!s->context_initialized) // we need the IDCT permutaton for reading a custom matrix if (ff_MPV_common_init(s) < 0) return -1; /* We need to set current_picture_ptr before reading the header, * otherwise we cannot store anything in there. */ if (s->current_picture_ptr == NULL || s->current_picture_ptr->f.data[0]) { int i = ff_find_unused_picture(s, 0); if (i < 0) return i; s->current_picture_ptr = &s->picture[i]; } 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) { ParseContext pc = s->parse_context; // FIXME move this demuxing hack to libavformat s->parse_context.buffer = 0; ff_MPV_common_end(s); s->parse_context = pc; } if (!s->context_initialized) { avcodec_set_dimensions(avctx, s->width, s->height); goto retry; } // for skipping the frame s->current_picture.f.pict_type = s->pict_type; s->current_picture.f.key_frame = s->pict_type == AV_PICTURE_TYPE_I; 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 get_consumed_bytes(s, 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_resync(h) < 0) break; h261_decode_gob(h); } ff_MPV_frame_end(s); assert(s->current_picture.f.pict_type == s->current_picture_ptr->f.pict_type); assert(s->current_picture.f.pict_type == s->pict_type); if ((ret = av_frame_ref(pict, &s->current_picture_ptr->f)) < 0) return ret; ff_print_debug_info(s, s->current_picture_ptr); *got_frame = 1; return get_consumed_bytes(s, buf_size); } static av_cold int h261_decode_end(AVCodecContext *avctx) { H261Context *h = avctx->priv_data; MpegEncContext *s = &h->s; ff_MPV_common_end(s); return 0; } AVCodec ff_h261_decoder = { .name = "h261", .long_name = NULL_IF_CONFIG_SMALL("H.261"), .type = AVMEDIA_TYPE_VIDEO, .id = AV_CODEC_ID_H261, .priv_data_size = sizeof(H261Context), .init = h261_decode_init, .close = h261_decode_end, .decode = h261_decode_frame, .capabilities = CODEC_CAP_DR1, };