/* * H261 decoder * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at> * 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 h261dec.c * H.261 decoder. */ #include "dsputil.h" #include "avcodec.h" #include "mpegvideo.h" #include "h261.h" #include "h261data.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 extern uint8_t ff_h261_rl_table_store[2][2*MAX_RUN + MAX_LEVEL + 3]; static VLC h261_mba_vlc; static VLC h261_mtype_vlc; static VLC h261_mv_vlc; static VLC h261_cbp_vlc; static int h261_decode_block(H261Context * h, DCTELEM * block, int n, int coded); static av_cold void h261_decode_init_vlc(H261Context *h){ static int done = 0; if(!done){ done = 1; init_vlc(&h261_mba_vlc, H261_MBA_VLC_BITS, 35, h261_mba_bits, 1, 1, h261_mba_code, 1, 1, 1); init_vlc(&h261_mtype_vlc, H261_MTYPE_VLC_BITS, 10, h261_mtype_bits, 1, 1, h261_mtype_code, 1, 1, 1); init_vlc(&h261_mv_vlc, H261_MV_VLC_BITS, 17, &h261_mv_tab[0][1], 2, 1, &h261_mv_tab[0][0], 2, 1, 1); init_vlc(&h261_cbp_vlc, H261_CBP_VLC_BITS, 63, &h261_cbp_tab[0][1], 2, 1, &h261_cbp_tab[0][0], 2, 1, 1); init_rl(&h261_rl_tcoeff, ff_h261_rl_table_store); init_vlc_rl(&h261_rl_tcoeff, 1); } } static av_cold int h261_decode_init(AVCodecContext *avctx){ H261Context *h= avctx->priv_data; MpegEncContext * const s = &h->s; // set defaults 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= PIX_FMT_YUV420P; s->codec_id= avctx->codec->id; h261_decode_init_vlc(h); h->gob_start_code_skipped = 0; return 0; } /** * decodes 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) 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; } /** * decodes the group of blocks / video packet header. * @return <0 if no resync found */ static int ff_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= s->gb.size_in_bits - get_bits_count(&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; } /** * decodes 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; MPV_decode_mb(s, s->block); } return 0; } 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; } 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_count(&s->gb) + 7 >= s->gb.size_in_bits ) 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); h->mtype = 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; } MPV_decode_mb(s, s->block); return SLICE_OK; } /** * decodes a macroblock * @return <0 if an error occurred */ static int h261_decode_block(H261Context * h, DCTELEM * block, int n, int coded) { MpegEncContext * const s = &h->s; int code, level, i, j, run; RLTable *rl = &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; } /** * decodes the H261 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= s->gb.size_in_bits - get_bits_count(&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.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); } // h261 has no I-FRAMES, but if we pass FF_I_TYPE 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 = FF_P_TYPE; 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 *data_size, const uint8_t *buf, int buf_size) { H261Context *h= avctx->priv_data; MpegEncContext *s = &h->s; int ret; AVFrame *pict = data; #ifdef DEBUG av_log(avctx, AV_LOG_DEBUG, "*****frame %d size=%d\n", avctx->frame_number, buf_size); av_log(avctx, AV_LOG_DEBUG, "bytes=%x %x %x %x\n", buf[0], buf[1], buf[2], buf[3]); #endif 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){ if (MPV_common_init(s) < 0) //we need the idct permutaton for reading a custom matrix return -1; } //we need to set current_picture_ptr before reading the header, otherwise we cannot store anyting im there if(s->current_picture_ptr==NULL || s->current_picture_ptr->data[0]){ int i= ff_find_unused_picture(s, 0); 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; MPV_common_end(s); s->parse_context= pc; } if (!s->context_initialized) { avcodec_set_dimensions(avctx, s->width, s->height); goto retry; } // for hurry_up==5 s->current_picture.pict_type= s->pict_type; s->current_picture.key_frame= s->pict_type == FF_I_TYPE; /* skip everything if we are in a hurry>=5 */ if(avctx->hurry_up>=5) return get_consumed_bytes(s, buf_size); if( (avctx->skip_frame >= AVDISCARD_NONREF && s->pict_type==FF_B_TYPE) ||(avctx->skip_frame >= AVDISCARD_NONKEY && s->pict_type!=FF_I_TYPE) || avctx->skip_frame >= AVDISCARD_ALL) return get_consumed_bytes(s, buf_size); if(MPV_frame_start(s, avctx) < 0) return -1; ff_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(ff_h261_resync(h)<0) break; h261_decode_gob(h); } MPV_frame_end(s); assert(s->current_picture.pict_type == s->current_picture_ptr->pict_type); assert(s->current_picture.pict_type == s->pict_type); *pict= *(AVFrame*)s->current_picture_ptr; ff_print_debug_info(s, pict); *data_size = sizeof(AVFrame); 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; MPV_common_end(s); return 0; } AVCodec h261_decoder = { "h261", CODEC_TYPE_VIDEO, CODEC_ID_H261, sizeof(H261Context), h261_decode_init, NULL, h261_decode_end, h261_decode_frame, CODEC_CAP_DR1, };