ffmpeg.c

ffmpeg的完整源代码和作者自己写的文档。不但有在Linux的工程哦

    for(i=0;i<nb_istreams;i++) {
        ist = av_mallocz(sizeof(AVInputStream));
        if (!ist)
            goto fail;
        ist_table[i] = ist;
    }
    j = 0;
    for(i=0;i<nb_input_files;i++) {
        is = input_files[i];
        for(k=0;k<is->nb_streams;k++) {
            ist = ist_table[j++];
            ist->st = is->streams[k];
            ist->file_index = i;
            ist->index = k;
            ist->discard = 1; /* the stream is discarded by default
                                 (changed later) */

            if (ist->st->codec->rate_emu) {
                ist->start = av_gettime();
                ist->frame = 0;
            }
        }
    }

    /* output stream init */
    nb_ostreams = 0;
    for(i=0;i<nb_output_files;i++) {
        os = output_files[i];
        if (!os->nb_streams) {
            fprintf(stderr, "Output file does not contain any stream\n");
            exit(1);
        }
        nb_ostreams += os->nb_streams;
    }
    if (nb_stream_maps > 0 && nb_stream_maps != nb_ostreams) {
        fprintf(stderr, "Number of stream maps must match number of output streams\n");
        exit(1);
    }

    /* Sanity check the mapping args -- do the input files & streams exist? */
    for(i=0;i<nb_stream_maps;i++) {
        int fi = stream_maps[i].file_index;
        int si = stream_maps[i].stream_index;

        if (fi < 0 || fi > nb_input_files - 1 ||
            si < 0 || si > file_table[fi].nb_streams - 1) {
            fprintf(stderr,"Could not find input stream #%d.%d\n", fi, si);
            exit(1);
        }
        fi = stream_maps[i].sync_file_index;
        si = stream_maps[i].sync_stream_index;
        if (fi < 0 || fi > nb_input_files - 1 ||
            si < 0 || si > file_table[fi].nb_streams - 1) {
            fprintf(stderr,"Could not find sync stream #%d.%d\n", fi, si);
            exit(1);
        }
    }

    ost_table = av_mallocz(sizeof(AVOutputStream *) * nb_ostreams);
    if (!ost_table)
        goto fail;
    for(i=0;i<nb_ostreams;i++) {
        ost = av_mallocz(sizeof(AVOutputStream));
        if (!ost)
            goto fail;
        ost_table[i] = ost;
    }

    n = 0;
    for(k=0;k<nb_output_files;k++) {
        os = output_files[k];
        for(i=0;i<os->nb_streams;i++) {
            int found;
            ost = ost_table[n++];
            ost->file_index = k;
            ost->index = i;
            ost->st = os->streams[i];
            if (nb_stream_maps > 0) {
                ost->source_index = file_table[stream_maps[n-1].file_index].ist_index +
                    stream_maps[n-1].stream_index;

                /* Sanity check that the stream types match */
                if (ist_table[ost->source_index]->st->codec->codec_type != ost->st->codec->codec_type) {
                    fprintf(stderr, "Codec type mismatch for mapping #%d.%d -> #%d.%d\n",
                        stream_maps[n-1].file_index, stream_maps[n-1].stream_index,
                        ost->file_index, ost->index);
                    exit(1);
                }

            } else {
                /* get corresponding input stream index : we select the first one with the right type */
                found = 0;
                for(j=0;j<nb_istreams;j++) {
                    ist = ist_table[j];
                    if (ist->discard &&
                        ist->st->codec->codec_type == ost->st->codec->codec_type) {
                        ost->source_index = j;
                        found = 1;
                        break;
                    }
                }

                if (!found) {
                    /* try again and reuse existing stream */
                    for(j=0;j<nb_istreams;j++) {
                        ist = ist_table[j];
                        if (ist->st->codec->codec_type == ost->st->codec->codec_type) {
                            ost->source_index = j;
                            found = 1;
                        }
                    }
                    if (!found) {
                        fprintf(stderr, "Could not find input stream matching output stream #%d.%d\n",
                                ost->file_index, ost->index);
                        exit(1);
                    }
                }
            }
            ist = ist_table[ost->source_index];
            ist->discard = 0;
            ost->sync_ist = (nb_stream_maps > 0) ?
                ist_table[file_table[stream_maps[n-1].sync_file_index].ist_index +
                         stream_maps[n-1].sync_stream_index] : ist;
        }
    }

    /* for each output stream, we compute the right encoding parameters */
    for(i=0;i<nb_ostreams;i++) {
        ost = ost_table[i];
        os = output_files[ost->file_index];
        ist = ist_table[ost->source_index];

        codec = ost->st->codec;
        icodec = ist->st->codec;

        if (!ost->st->language[0])
            av_strlcpy(ost->st->language, ist->st->language,
                       sizeof(ost->st->language));

        if (ost->st->stream_copy) {
            /* if stream_copy is selected, no need to decode or encode */
            codec->codec_id = icodec->codec_id;
            codec->codec_type = icodec->codec_type;

            if(!codec->codec_tag){
                if(   !os->oformat->codec_tag
                   || av_codec_get_id (os->oformat->codec_tag, icodec->codec_tag) > 0
                   || av_codec_get_tag(os->oformat->codec_tag, icodec->codec_id) <= 0)
                    codec->codec_tag = icodec->codec_tag;
            }

            codec->bit_rate = icodec->bit_rate;
            codec->extradata= icodec->extradata;
            codec->extradata_size= icodec->extradata_size;
            if(av_q2d(icodec->time_base) > av_q2d(ist->st->time_base) && av_q2d(ist->st->time_base) < 1.0/1000)
                codec->time_base = icodec->time_base;
            else
                codec->time_base = ist->st->time_base;
            switch(codec->codec_type) {
            case CODEC_TYPE_AUDIO:
                codec->sample_rate = icodec->sample_rate;
                codec->channels = icodec->channels;
                codec->frame_size = icodec->frame_size;
                codec->block_align= icodec->block_align;
                if(codec->block_align == 1 && codec->codec_id == CODEC_ID_MP3)
                    codec->block_align= 0;
                break;
            case CODEC_TYPE_VIDEO:
                if(using_vhook) {
                    fprintf(stderr,"-vcodec copy and -vhook are incompatible (frames are not decoded)\n");
                    exit(1);
                }
                codec->pix_fmt = icodec->pix_fmt;
                codec->width = icodec->width;
                codec->height = icodec->height;
                codec->has_b_frames = icodec->has_b_frames;
                break;
            case CODEC_TYPE_SUBTITLE:
                break;
            default:
                abort();
            }
        } else {
            switch(codec->codec_type) {
            case CODEC_TYPE_AUDIO:
                if (av_fifo_init(&ost->fifo, 2 * MAX_AUDIO_PACKET_SIZE))
                    goto fail;

                if (codec->channels == icodec->channels &&
                    codec->sample_rate == icodec->sample_rate) {
                    ost->audio_resample = 0;
                } else {
                    if (codec->channels != icodec->channels &&
                        (icodec->codec_id == CODEC_ID_AC3 ||
                         icodec->codec_id == CODEC_ID_DTS)) {
                        /* Special case for 5:1 AC3 and DTS input */
                        /* and mono or stereo output      */
                        /* Request specific number of channels */
                        icodec->channels = codec->channels;
                        if (codec->sample_rate == icodec->sample_rate)
                            ost->audio_resample = 0;
                        else {
                            ost->audio_resample = 1;
                        }
                    } else {
                        ost->audio_resample = 1;
                    }
                }
                if(audio_sync_method>1)
                    ost->audio_resample = 1;

                if(ost->audio_resample){
                    ost->resample = audio_resample_init(codec->channels, icodec->channels,
                                                    codec->sample_rate, icodec->sample_rate);
                    if(!ost->resample){
                        printf("Can't resample.  Aborting.\n");
                        abort();
                    }
                }
                ist->decoding_needed = 1;
                ost->encoding_needed = 1;
                break;
            case CODEC_TYPE_VIDEO:
                ost->video_crop = ((frame_leftBand + frame_rightBand + frame_topBand + frame_bottomBand) != 0);
                ost->video_pad = ((frame_padleft + frame_padright + frame_padtop + frame_padbottom) != 0);
                ost->video_resample = ((codec->width != icodec->width -
                                (frame_leftBand + frame_rightBand) +
                                (frame_padleft + frame_padright)) ||
                        (codec->height != icodec->height -
                                (frame_topBand  + frame_bottomBand) +
                                (frame_padtop + frame_padbottom)) ||
                        (codec->pix_fmt != icodec->pix_fmt));
                if (ost->video_crop) {
                    ost->topBand = frame_topBand;
                    ost->leftBand = frame_leftBand;
                }
                if (ost->video_pad) {
                    ost->padtop = frame_padtop;
                    ost->padleft = frame_padleft;
                    ost->padbottom = frame_padbottom;
                    ost->padright = frame_padright;
                    if (!ost->video_resample) {
                        avcodec_get_frame_defaults(&ost->pict_tmp);
                        if( avpicture_alloc( (AVPicture*)&ost->pict_tmp, codec->pix_fmt,
                                         codec->width, codec->height ) )
                            goto fail;
                    }
                }
                if (ost->video_resample) {
                    avcodec_get_frame_defaults(&ost->pict_tmp);
                    if( avpicture_alloc( (AVPicture*)&ost->pict_tmp, codec->pix_fmt,
                                         codec->width, codec->height ) ) {
                        fprintf(stderr, "Cannot allocate temp picture, check pix fmt\n");
                        exit(1);
                    }
                    sws_flags = av_get_int(sws_opts, "sws_flags", NULL);
                    ost->img_resample_ctx = sws_getContext(
                            icodec->width - (frame_leftBand + frame_rightBand),
                            icodec->height - (frame_topBand + frame_bottomBand),
                            icodec->pix_fmt,
                            codec->width - (frame_padleft + frame_padright),
                            codec->height - (frame_padtop + frame_padbottom),
                            codec->pix_fmt,
                            sws_flags, NULL, NULL, NULL);
                    if (ost->img_resample_ctx == NULL) {
                        fprintf(stderr, "Cannot get resampling context\n");
                        exit(1);
                    }
                    ost->resample_height = icodec->height - (frame_topBand + frame_bottomBand);
                }
                ost->encoding_needed = 1;
                ist->decoding_needed = 1;
                break;
            case CODEC_TYPE_SUBTITLE:
                ost->encoding_needed = 1;
                ist->decoding_needed = 1;
                break;
            default:
                abort();
                break;
            }
            /* two pass mode */
            if (ost->encoding_needed &&
                (codec->flags & (CODEC_FLAG_PASS1 | CODEC_FLAG_PASS2))) {
                char logfilename[1024];
                FILE *f;
                int size;
                char *logbuffer;

                snprintf(logfilename, sizeof(logfilename), "%s-%d.log",
                         pass_logfilename ?
                         pass_logfilename : DEFAULT_PASS_LOGFILENAME, i);
                if (codec->flags & CODEC_FLAG_PASS1) {
                    f = fopen(logfilename, "w");
                    if (!f) {
                        perror(logfilename);
                        exit(1);
                    }
                    ost->logfile = f;
                } else {
                    /* read the log file */
                    f = fopen(logfilename, "r");
                    if (!f) {
                        perror(logfilename);
                        exit(1);
                    }
                    fseek(f, 0, SEEK_END);
                    size = ftell(f);
                    fseek(f, 0, SEEK_SET);
                    logbuffer = av_malloc(size + 1);
                    if (!logbuffer) {
                        fprintf(stderr, "Could not allocate log buffer\n");
                        exit(1);
                    }
                    size = fread(logbuffer, 1, size, f);
                    fclose(f);
                    logbuffer[size] = '\0';
                    codec->stats_in = logbuffer;
                }
            }
        }
        if(codec->codec_type == CODEC_TYPE_VIDEO){
            int size= codec->width * codec->height;
            bit_buffer_size= FFMAX(bit_buffer_size, 4*size);
        }
    }

    if (!bit_buffer)
        bit_buffer = av_malloc(bit_buffer_size);
    if (!bit_buffer)
        goto fail;

    /* dump the file output parameters - cannot be done before in case
       of stream copy */
    for(i=0;i<nb_output_files;i++) {
        dump_format(output_files[i], i, output_files[i]->filename, 1);
    }

    /* dump the stream mapping */
    if (verbose >= 0) {
        fprintf(stderr, "Stream mapping:\n");
        for(i=0;i<nb_ostreams;i++) {
            ost = ost_table[i];