ffmpeg.c

    if (!subtitle.num_rects)
        goto out;

    ist->frames_decoded++;

    for (i = 0; i < nb_output_streams; i++) {
        OutputStream *ost = output_streams[i];

        if (!check_output_constraints(ist, ost) || !ost->encoding_needed
            || ost->enc->type != AVMEDIA_TYPE_SUBTITLE)
            continue;

        do_subtitle_out(output_files[ost->file_index]->ctx, ost, ist, &subtitle);
    }

out:
    avsubtitle_free(&subtitle);
    return ret;
}

/* pkt = NULL means EOF (needed to flush decoder buffers) */
static int output_packet(InputStream *ist, const AVPacket *pkt)
{
    int ret = 0, i;
    int got_output = 0;

    AVPacket avpkt;
    if (!ist->saw_first_ts) {
        ist->dts = ist->st->avg_frame_rate.num ? - ist->dec_ctx->has_b_frames * AV_TIME_BASE / av_q2d(ist->st->avg_frame_rate) : 0;
        ist->pts = 0;
        if (pkt != NULL && pkt->pts != AV_NOPTS_VALUE && !ist->decoding_needed) {
            ist->dts += av_rescale_q(pkt->pts, ist->st->time_base, AV_TIME_BASE_Q);
            ist->pts = ist->dts; //unused but better to set it to a value thats not totally wrong
        }
        ist->saw_first_ts = 1;
    }

    if (ist->next_dts == AV_NOPTS_VALUE)
        ist->next_dts = ist->dts;
    if (ist->next_pts == AV_NOPTS_VALUE)
        ist->next_pts = ist->pts;

    if (pkt == NULL) {
        /* EOF handling */
        av_init_packet(&avpkt);
        avpkt.data = NULL;
        avpkt.size = 0;
        goto handle_eof;
    } else {
        avpkt = *pkt;
    }

    if (pkt->dts != AV_NOPTS_VALUE) {
        ist->next_dts = ist->dts = av_rescale_q(pkt->dts, ist->st->time_base, AV_TIME_BASE_Q);
        if (ist->dec_ctx->codec_type != AVMEDIA_TYPE_VIDEO || !ist->decoding_needed)
            ist->next_pts = ist->pts = ist->dts;
    }

    // while we have more to decode or while the decoder did output something on EOF
    while (ist->decoding_needed && (avpkt.size > 0 || (!pkt && got_output))) {
        int duration;
    handle_eof:

        ist->pts = ist->next_pts;
        ist->dts = ist->next_dts;

        if (avpkt.size && avpkt.size != pkt->size &&
            !(ist->dec->capabilities & CODEC_CAP_SUBFRAMES)) {
            av_log(NULL, ist->showed_multi_packet_warning ? AV_LOG_VERBOSE : AV_LOG_WARNING,
                   "Multiple frames in a packet from stream %d\n", pkt->stream_index);
            ist->showed_multi_packet_warning = 1;
        }

        switch (ist->dec_ctx->codec_type) {
        case AVMEDIA_TYPE_AUDIO:
            ret = decode_audio    (ist, &avpkt, &got_output);
            break;
        case AVMEDIA_TYPE_VIDEO:
            ret = decode_video    (ist, &avpkt, &got_output);
            if (avpkt.duration) {
                duration = av_rescale_q(avpkt.duration, ist->st->time_base, AV_TIME_BASE_Q);
            } else if(ist->dec_ctx->time_base.num != 0 && ist->dec_ctx->time_base.den != 0) {
                int ticks= ist->st->parser ? ist->st->parser->repeat_pict+1 : ist->dec_ctx->ticks_per_frame;
                duration = ((int64_t)AV_TIME_BASE *
                                ist->dec_ctx->time_base.num * ticks) /
                                ist->dec_ctx->time_base.den;
            } else
                duration = 0;

            if(ist->dts != AV_NOPTS_VALUE && duration) {
                ist->next_dts += duration;
            }else
                ist->next_dts = AV_NOPTS_VALUE;

            if (got_output)
                ist->next_pts += duration; //FIXME the duration is not correct in some cases
            break;
        case AVMEDIA_TYPE_SUBTITLE:
            ret = transcode_subtitles(ist, &avpkt, &got_output);
            break;
        default:
            return -1;
        }

        if (ret < 0)
            return ret;

        avpkt.dts=
        avpkt.pts= AV_NOPTS_VALUE;

        // touch data and size only if not EOF
        if (pkt) {
            if(ist->dec_ctx->codec_type != AVMEDIA_TYPE_AUDIO)
                ret = avpkt.size;
            avpkt.data += ret;
            avpkt.size -= ret;
        }
        if (!got_output) {
            continue;
        }
    }

    /* handle stream copy */
    if (!ist->decoding_needed) {
        ist->dts = ist->next_dts;
        switch (ist->dec_ctx->codec_type) {
        case AVMEDIA_TYPE_AUDIO:
            ist->next_dts += ((int64_t)AV_TIME_BASE * ist->dec_ctx->frame_size) /
                             ist->dec_ctx->sample_rate;
            break;
        case AVMEDIA_TYPE_VIDEO:
            if (ist->framerate.num) {
                // TODO: Remove work-around for c99-to-c89 issue 7
                AVRational time_base_q = AV_TIME_BASE_Q;
                int64_t next_dts = av_rescale_q(ist->next_dts, time_base_q, av_inv_q(ist->framerate));
                ist->next_dts = av_rescale_q(next_dts + 1, av_inv_q(ist->framerate), time_base_q);
            } else if (pkt->duration) {
                ist->next_dts += av_rescale_q(pkt->duration, ist->st->time_base, AV_TIME_BASE_Q);
            } else if(ist->dec_ctx->time_base.num != 0) {
                int ticks= ist->st->parser ? ist->st->parser->repeat_pict + 1 : ist->dec_ctx->ticks_per_frame;
                ist->next_dts += ((int64_t)AV_TIME_BASE *
                                  ist->dec_ctx->time_base.num * ticks) /
                                  ist->dec_ctx->time_base.den;
            }
            break;
        }
        ist->pts = ist->dts;
        ist->next_pts = ist->next_dts;
    }
    for (i = 0; pkt && i < nb_output_streams; i++) {
        OutputStream *ost = output_streams[i];

        if (!check_output_constraints(ist, ost) || ost->encoding_needed)
            continue;

        do_streamcopy(ist, ost, pkt);
    }

    return 0;
}

static void print_sdp(void)
{
    char sdp[16384];
    int i;
    AVFormatContext **avc = av_malloc_array(nb_output_files, sizeof(*avc));

    if (!avc)
        exit_program(1);
    for (i = 0; i < nb_output_files; i++)
        avc[i] = output_files[i]->ctx;

    av_sdp_create(avc, nb_output_files, sdp, sizeof(sdp));
    printf("SDP:\n%s\n", sdp);
    fflush(stdout);
    av_freep(&avc);
}

static const HWAccel *get_hwaccel(enum AVPixelFormat pix_fmt)
{
    int i;
    for (i = 0; hwaccels[i].name; i++)
        if (hwaccels[i].pix_fmt == pix_fmt)
            return &hwaccels[i];
    return NULL;
}

static enum AVPixelFormat get_format(AVCodecContext *s, const enum AVPixelFormat *pix_fmts)
{
    InputStream *ist = s->opaque;
    const enum AVPixelFormat *p;
    int ret;

    for (p = pix_fmts; *p != -1; p++) {
        const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(*p);
        const HWAccel *hwaccel;

        if (!(desc->flags & AV_PIX_FMT_FLAG_HWACCEL))
            break;

        hwaccel = get_hwaccel(*p);
        if (!hwaccel ||
            (ist->active_hwaccel_id && ist->active_hwaccel_id != hwaccel->id) ||
            (ist->hwaccel_id != HWACCEL_AUTO && ist->hwaccel_id != hwaccel->id))
            continue;

        ret = hwaccel->init(s);
        if (ret < 0) {
            if (ist->hwaccel_id == hwaccel->id) {
                av_log(NULL, AV_LOG_FATAL,
                       "%s hwaccel requested for input stream #%d:%d, "
                       "but cannot be initialized.\n", hwaccel->name,
                       ist->file_index, ist->st->index);
                exit_program(1);
            }
            continue;
        }
        ist->active_hwaccel_id = hwaccel->id;
        ist->hwaccel_pix_fmt   = *p;
        break;
    }

    return *p;
}

static int get_buffer(AVCodecContext *s, AVFrame *frame, int flags)
{
    InputStream *ist = s->opaque;

    if (ist->hwaccel_get_buffer && frame->format == ist->hwaccel_pix_fmt)
        return ist->hwaccel_get_buffer(s, frame, flags);

    return avcodec_default_get_buffer2(s, frame, flags);
}

static int init_input_stream(int ist_index, char *error, int error_len)
{
    int ret;
    InputStream *ist = input_streams[ist_index];

    if (ist->decoding_needed) {
        AVCodec *codec = ist->dec;
        if (!codec) {
            snprintf(error, error_len, "Decoder (codec %s) not found for input stream #%d:%d",
                    avcodec_get_name(ist->dec_ctx->codec_id), ist->file_index, ist->st->index);
            return AVERROR(EINVAL);
        }

        ist->dec_ctx->opaque                = ist;
        ist->dec_ctx->get_format            = get_format;
        ist->dec_ctx->get_buffer2           = get_buffer;
        ist->dec_ctx->thread_safe_callbacks = 1;

        av_opt_set_int(ist->dec_ctx, "refcounted_frames", 1, 0);

        if (!av_dict_get(ist->decoder_opts, "threads", NULL, 0))
            av_dict_set(&ist->decoder_opts, "threads", "auto", 0);
        if ((ret = avcodec_open2(ist->dec_ctx, codec, &ist->decoder_opts)) < 0) {
            if (ret == AVERROR_EXPERIMENTAL)
                abort_codec_experimental(codec, 0);

            snprintf(error, error_len,
                     "Error while opening decoder for input stream "
                     "#%d:%d : %s",
                     ist->file_index, ist->st->index, av_err2str(ret));
            return ret;
        }
        assert_avoptions(ist->decoder_opts);
    }

    ist->next_pts = AV_NOPTS_VALUE;
    ist->next_dts = AV_NOPTS_VALUE;

    return 0;
}

static InputStream *get_input_stream(OutputStream *ost)
{
    if (ost->source_index >= 0)
        return input_streams[ost->source_index];
    return NULL;
}

static int compare_int64(const void *a, const void *b)
{
    int64_t va = *(int64_t *)a, vb = *(int64_t *)b;
    return va < vb ? -1 : va > vb ? +1 : 0;
}

static void parse_forced_key_frames(char *kf, OutputStream *ost,
                                    AVCodecContext *avctx)
{
    char *p;
    int n = 1, i, size, index = 0;
    int64_t t, *pts;

    for (p = kf; *p; p++)
        if (*p == ',')
            n++;
    size = n;
    pts = av_malloc_array(size, sizeof(*pts));
    if (!pts) {
        av_log(NULL, AV_LOG_FATAL, "Could not allocate forced key frames array.\n");
        exit_program(1);
    }

    p = kf;
    for (i = 0; i < n; i++) {
        char *next = strchr(p, ',');

        if (next)
            *next++ = 0;

        if (!memcmp(p, "chapters", 8)) {

            AVFormatContext *avf = output_files[ost->file_index]->ctx;
            int j;

            if (avf->nb_chapters > INT_MAX - size ||
                !(pts = av_realloc_f(pts, size += avf->nb_chapters - 1,
                                     sizeof(*pts)))) {
                av_log(NULL, AV_LOG_FATAL,
                       "Could not allocate forced key frames array.\n");
                exit_program(1);
            }
            t = p[8] ? parse_time_or_die("force_key_frames", p + 8, 1) : 0;
            t = av_rescale_q(t, AV_TIME_BASE_Q, avctx->time_base);

            for (j = 0; j < avf->nb_chapters; j++) {
                AVChapter *c = avf->chapters[j];
                av_assert1(index < size);
                pts[index++] = av_rescale_q(c->start, c->time_base,
                                            avctx->time_base) + t;
            }

        } else {

            t = parse_time_or_die("force_key_frames", p, 1);
            av_assert1(index < size);
            pts[index++] = av_rescale_q(t, AV_TIME_BASE_Q, avctx->time_base);

        }

        p = next;
    }

    av_assert0(index == size);
    qsort(pts, size, sizeof(*pts), compare_int64);
    ost->forced_kf_count = size;
    ost->forced_kf_pts   = pts;
}

static void report_new_stream(int input_index, AVPacket *pkt)
{
    InputFile *file = input_files[input_index];
    AVStream *st = file->ctx->streams[pkt->stream_index];

    if (pkt->stream_index < file->nb_streams_warn)
        return;
    av_log(file->ctx, AV_LOG_WARNING,
           "New %s stream %d:%d at pos:%"PRId64" and DTS:%ss\n",
           av_get_media_type_string(st->codec->codec_type),
           input_index, pkt->stream_index,
           pkt->pos, av_ts2timestr(pkt->dts, &st->time_base));
    file->nb_streams_warn = pkt->stream_index + 1;
}

static void set_encoder_id(OutputFile *of, OutputStream *ost)
{
    AVDictionaryEntry *e;

    uint8_t *encoder_string;
    int encoder_string_len;
    int format_flags = 0;
    int codec_flags = 0;

    if (av_dict_get(ost->st->metadata, "encoder",  NULL, 0))
        return;

    e = av_dict_get(of->opts, "fflags", NULL, 0);
    if (e) {
        const AVOption *o = av_opt_find(of->ctx, "fflags", NULL, 0, 0);
        if (!o)
            return;
        av_opt_eval_flags(of->ctx, o, e->value, &format_flags);
    }
    e = av_dict_get(ost->encoder_opts, "flags", NULL, 0);
    if (e) {
        const AVOption *o = av_opt_find(ost->st->codec, "flags", NULL, 0, 0);
        if (!o)
            return;
        av_opt_eval_flags(ost->st->codec, o, e->value, &codec_flags);
    }

    encoder_string_len = sizeof(LIBAVCODEC_IDENT) + strlen(ost->enc->name) + 2;
    encoder_string     = av_mallocz(encoder_string_len);
    if (!encoder_string)
        exit_program(1);

    if (!(format_flags & AVFMT_FLAG_BITEXACT) && !(codec_flags & CODEC_FLAG_BITEXACT))
        av_strlcpy(encoder_string, LIBAVCODEC_IDENT " ", encoder_string_len);
    else
        av_strlcpy(encoder_string, "Lavc ", encoder_string_len);
    av_strlcat(encoder_string, ost->enc->name, encoder_string_len);
    av_dict_set(&ost->st->metadata, "encoder",  encoder_string,
                AV_DICT_DONT_STRDUP_VAL | AV_DICT_DONT_OVERWRITE);
}

static int transcode_init(void)
{
    int ret = 0, i, j, k;
    AVFormatContext *oc;
    OutputStream *ost;
    InputStream *ist;
    char error[1024];
    int want_sdp = 1;

    for (i = 0; i < nb_filtergraphs; i++) {
        FilterGraph *fg = filtergraphs[i];
        for (j = 0; j < fg->nb_outputs; j++) {
            OutputFilter *ofilter = fg->outputs[j];
            if (!ofilter->ost || ofilter->ost->source_index >= 0)
                continue;
            if (fg->nb_inputs != 1)
                continue;
            for (k = nb_input_streams-1; k >= 0 ; k--)
                if (fg->inputs[0]->ist == input_streams[k])
                    break;
            ofilter->ost->source_index = k;
        }
    }

    /* init framerate emulation */
    for (i = 0; i < nb_input_files; i++) {
        InputFile *ifile = input_files[i];
        if (ifile->rate_emu)
            for (j = 0; j < ifile->nb_streams; j++)
                input_streams[j + ifile->ist_index]->start = av_gettime_relative();
    }

    /* output stream init */
    for (i = 0; i < nb_output_files; i++) {
        oc = output_files[i]->ctx;
        if (!oc->nb_streams && !(oc->oformat->flags & AVFMT_NOSTREAMS)) {
            av_dump_format(oc, i, oc->filename, 1);
            av_log(NULL, AV_LOG_ERROR, "Output file #%d does not contain any stream\n", i);
            return AVERROR(EINVAL);
        }
    }

    /* init complex filtergraphs */
    for (i = 0; i < nb_filtergraphs; i++)
        if ((ret = avfilter_graph_config(filtergraphs[i]->graph, NULL)) < 0)
            return ret;

    /* for each output stream, we compute the right encoding parameters */
    for (i = 0; i < nb_output_streams; i++) {
        AVCodecContext *enc_ctx;
        AVCodecContext *dec_ctx = NULL;
        ost = output_streams[i];
        oc  = output_files[ost->file_index]->ctx;
        ist = get_input_stream(ost);

        if (ost->attachment_filename)
            continue;

        enc_ctx = ost->enc_ctx;

        if (ist) {
            dec_ctx = ist->dec_ctx;

            ost->st->disposition          = ist->st->disposition;
            enc_ctx->bits_per_raw_sample    = dec_ctx->bits_per_raw_sample;
            enc_ctx->chroma_sample_location = dec_ctx->chroma_sample_location;
        } else {
            for (j=0; j<oc->nb_streams; j++) {
                AVStream *st = oc->streams[j];
                if (st != ost->st && st->codec->codec_type == enc_ctx->codec_type)
                    break;
            }
            if (j == oc->nb_streams)
                if (enc_ctx->codec_type == AVMEDIA_TYPE_AUDIO || enc_ctx->codec_type == AVMEDIA_TYPE_VIDEO)
                    ost->st->disposition = AV_DISPOSITION_DEFAULT;
        }

        if (ost->stream_copy) {
            AVRational sar;
            uint64_t extra_size;

            av_assert0(ist && !ost->filter);

            extra_size = (uint64_t)dec_ctx->extradata_size + FF_INPUT_BUFFER_PADDING_SIZE;

            if (extra_size > INT_MAX) {
                return AVERROR(EINVAL);
            }

            /* if stream_copy is selected, no need to decode or encode */
            enc_ctx->codec_id   = dec_ctx->codec_id;
            enc_ctx->codec_type = dec_ctx->codec_type;

            if (!enc_ctx->codec_tag) {
                unsigned int codec_tag;
                if (!oc->oformat->codec_tag ||
                     av_codec_get_id (oc->oformat->codec_tag, dec_ctx->codec_tag) == enc_ctx->codec_id ||
                     !av_codec_get_tag2(oc->oformat->codec_tag, dec_ctx->codec_id, &codec_tag))
                    enc_ctx->codec_tag = dec_ctx->codec_tag;
            }

            enc_ctx->bit_rate       = dec_ctx->bit_rate;
            enc_ctx->rc_max_rate    = dec_ctx->rc_max_rate;
            enc_ctx->rc_buffer_size = dec_ctx->rc_buffer_size;
            enc_ctx->field_order    = dec_ctx->field_order;
            enc_ctx->extradata      = av_mallocz(extra_size);
            if (!enc_ctx->extradata) {
                return AVERROR(ENOMEM);
            }
            memcpy(enc_ctx->extradata, dec_ctx->extradata, dec_ctx->extradata_size);
            enc_ctx->extradata_size= dec_ctx->extradata_size;
            enc_ctx->bits_per_coded_sample  = dec_ctx->bits_per_coded_sample;

            enc_ctx->time_base = ist->st->time_base;
            /*
             * Avi is a special case here because it supports variable fps but
             * having the fps and timebase differe significantly adds quite some
             * overhead
             */
            if(!strcmp(oc->oformat->name, "avi")) {
                if ( copy_tb<0 && av_q2d(ist->st->r_frame_rate) >= av_q2d(ist->st->avg_frame_rate)
                               && 0.5/av_q2d(ist->st->r_frame_rate) > av_q2d(ist->st->time_base)
                               && 0.5/av_q2d(ist->st->r_frame_rate) > av_q2d(dec_ctx->time_base)
                               && av_q2d(ist->st->time_base) < 1.0/500 && av_q2d(dec_ctx->time_base) < 1.0/500
                     || copy_tb==2){
                    enc_ctx->time_base.num = ist->st->r_frame_rate.den;
                    enc_ctx->time_base.den = 2*ist->st->r_frame_rate.num;
                    enc_ctx->ticks_per_frame = 2;
                } else if (   copy_tb<0 && av_q2d(dec_ctx->time_base)*dec_ctx->ticks_per_frame > 2*av_q2d(ist->st->time_base)
                                 && av_q2d(ist->st->time_base) < 1.0/500
                    || copy_tb==0){
                    enc_ctx->time_base = dec_ctx->time_base;
                    enc_ctx->time_base.num *= dec_ctx->ticks_per_frame;
                    enc_ctx->time_base.den *= 2;
                    enc_ctx->ticks_per_frame = 2;
                }
            } else if(!(oc->oformat->flags & AVFMT_VARIABLE_FPS)
                      && strcmp(oc->oformat->name, "mov") && strcmp(oc->oformat->name, "mp4") && strcmp(oc->oformat->name, "3gp")
                      && strcmp(oc->oformat->name, "3g2") && strcmp(oc->oformat->name, "psp") && strcmp(oc->oformat->name, "ipod")
                      && strcmp(oc->oformat->name, "f4v")
            ) {
                if(   copy_tb<0 && dec_ctx->time_base.den
                                && av_q2d(dec_ctx->time_base)*dec_ctx->ticks_per_frame > av_q2d(ist->st->time_base)
                                && av_q2d(ist->st->time_base) < 1.0/500
                   || copy_tb==0){
                    enc_ctx->time_base = dec_ctx->time_base;
                    enc_ctx->time_base.num *= dec_ctx->ticks_per_frame;
                }
            }
            if (   enc_ctx->codec_tag == AV_RL32("tmcd")
                && dec_ctx->time_base.num < dec_ctx->time_base.den
                && dec_ctx->time_base.num > 0
                && 121LL*dec_ctx->time_base.num > dec_ctx->time_base.den) {
                enc_ctx->time_base = dec_ctx->time_base;
            }

            if (ist && !ost->frame_rate.num)
                ost->frame_rate = ist->framerate;
            if(ost->frame_rate.num)
                enc_ctx->time_base = av_inv_q(ost->frame_rate);

            av_reduce(&enc_ctx->time_base.num, &enc_ctx->time_base.den,
                        enc_ctx->time_base.num, enc_ctx->time_base.den, INT_MAX);

            ost->parser = av_parser_init(enc_ctx->codec_id);

            switch (enc_ctx->codec_type) {
            case AVMEDIA_TYPE_AUDIO:
                if (audio_volume != 256) {
                    av_log(NULL, AV_LOG_FATAL, "-acodec copy and -vol are incompatible (frames are not decoded)\n");
                    exit_program(1);
                }
                enc_ctx->channel_layout     = dec_ctx->channel_layout;
                enc_ctx->sample_rate        = dec_ctx->sample_rate;
                enc_ctx->channels           = dec_ctx->channels;
                enc_ctx->frame_size         = dec_ctx->frame_size;
                enc_ctx->audio_service_type = dec_ctx->audio_service_type;
                enc_ctx->block_align        = dec_ctx->block_align;
                enc_ctx->delay              = dec_ctx->delay;
                if((enc_ctx->block_align == 1 || enc_ctx->block_align == 1152 || enc_ctx->block_align == 576) && enc_ctx->codec_id == AV_CODEC_ID_MP3)
                    enc_ctx->block_align= 0;
                if(enc_ctx->codec_id == AV_CODEC_ID_AC3)
                    enc_ctx->block_align= 0;
                break;
            case AVMEDIA_TYPE_VIDEO:
                enc_ctx->pix_fmt            = dec_ctx->pix_fmt;
                enc_ctx->width              = dec_ctx->width;
                enc_ctx->height             = dec_ctx->height;
                enc_ctx->has_b_frames       = dec_ctx->has_b_frames;
                if (ost->frame_aspect_ratio.num) { // overridden by the -aspect cli option
                    sar =
                        av_mul_q(ost->frame_aspect_ratio,
                                 (AVRational){ enc_ctx->height, enc_ctx->width });
                    av_log(NULL, AV_LOG_WARNING, "Overriding aspect ratio "
                           "with stream copy may produce invalid files\n");
                }
                else if (ist->st->sample_aspect_ratio.num)
                    sar = ist->st->sample_aspect_ratio;
                else
                    sar = dec_ctx->sample_aspect_ratio;
                ost->st->sample_aspect_ratio = enc_ctx->sample_aspect_ratio = sar;
                ost->st->avg_frame_rate = ist->st->avg_frame_rate;
                break;
            case AVMEDIA_TYPE_SUBTITLE:
                enc_ctx->width  = dec_ctx->width;
                enc_ctx->height = dec_ctx->height;
                break;
            case AVMEDIA_TYPE_DATA:
            case AVMEDIA_TYPE_ATTACHMENT:
                break;
            default:
                abort();
            }
        } else {
            if (!ost->enc)
                ost->enc = avcodec_find_encoder(enc_ctx->codec_id);
            if (!ost->enc) {
                /* should only happen when a default codec is not present. */
                snprintf(error, sizeof(error), "Encoder (codec %s) not found for output stream #%d:%d",
                         avcodec_get_name(ost->st->codec->codec_id), ost->file_index, ost->index);
                ret = AVERROR(EINVAL);
                goto dump_format;
            }

            if (ist)
                ist->decoding_needed++;
            ost->encoding_needed = 1;

            set_encoder_id(output_files[ost->file_index], ost);

            if (!ost->filter &&
                (enc_ctx->codec_type == AVMEDIA_TYPE_VIDEO ||
                 enc_ctx->codec_type == AVMEDIA_TYPE_AUDIO)) {
                    FilterGraph *fg;
                    fg = init_simple_filtergraph(ist, ost);
                    if (configure_filtergraph(fg)) {
                        av_log(NULL, AV_LOG_FATAL, "Error opening filters!\n");
                        exit_program(1);
                    }
            }

            if (enc_ctx->codec_type == AVMEDIA_TYPE_VIDEO) {
                if (ost->filter && !ost->frame_rate.num)
                    ost->frame_rate = av_buffersink_get_frame_rate(ost->filter->filter);
                if (ist && !ost->frame_rate.num)
                    ost->frame_rate = ist->framerate;
                if (ist && !ost->frame_rate.num)
                    ost->frame_rate = ist->st->r_frame_rate;
                if (ist && !ost->frame_rate.num) {
                    ost->frame_rate = (AVRational){25, 1};
                    av_log(NULL, AV_LOG_WARNING,
                           "No information "
                           "about the input framerate is available. Falling "
                           "back to a default value of 25fps for output stream #%d:%d. Use the -r option "
                           "if you want a different framerate.\n",
                           ost->file_index, ost->index);
                }
//                    ost->frame_rate = ist->st->avg_frame_rate.num ? ist->st->avg_frame_rate : (AVRational){25, 1};
                if (ost->enc && ost->enc->supported_framerates && !ost->force_fps) {
                    int idx = av_find_nearest_q_idx(ost->frame_rate, ost->enc->supported_framerates);
                    ost->frame_rate = ost->enc->supported_framerates[idx];
                }
                if (enc_ctx->codec_id == AV_CODEC_ID_MPEG4) {
                    av_reduce(&ost->frame_rate.num, &ost->frame_rate.den,
                              ost->frame_rate.num, ost->frame_rate.den, 65535);
                }
            }

            switch (enc_ctx->codec_type) {
            case AVMEDIA_TYPE_AUDIO:
                enc_ctx->sample_fmt     = ost->filter->filter->inputs[0]->format;
                enc_ctx->sample_rate    = ost->filter->filter->inputs[0]->sample_rate;
                enc_ctx->channel_layout = ost->filter->filter->inputs[0]->channel_layout;
                enc_ctx->channels       = avfilter_link_get_channels(ost->filter->filter->inputs[0]);
                enc_ctx->time_base      = (AVRational){ 1, enc_ctx->sample_rate };
                break;
            case AVMEDIA_TYPE_VIDEO:
                enc_ctx->time_base = av_inv_q(ost->frame_rate);
                if (ost->filter && !(enc_ctx->time_base.num && enc_ctx->time_base.den))
                    enc_ctx->time_base = ost->filter->filter->inputs[0]->time_base;
                if (   av_q2d(enc_ctx->time_base) < 0.001 && video_sync_method != VSYNC_PASSTHROUGH
                   && (video_sync_method == VSYNC_CFR || video_sync_method == VSYNC_VSCFR || (video_sync_method == VSYNC_AUTO && !(oc->oformat->flags & AVFMT_VARIABLE_FPS)))){
                    av_log(oc, AV_LOG_WARNING, "Frame rate very high for a muxer not efficiently supporting it.\n"
                                               "Please consider specifying a lower framerate, a different muxer or -vsync 2\n");
                }
                for (j = 0; j < ost->forced_kf_count; j++)
                    ost->forced_kf_pts[j] = av_rescale_q(ost->forced_kf_pts[j],
                                                         AV_TIME_BASE_Q,
                                                         enc_ctx->time_base);

                enc_ctx->width  = ost->filter->filter->inputs[0]->w;
                enc_ctx->height = ost->filter->filter->inputs[0]->h;
                enc_ctx->sample_aspect_ratio = ost->st->sample_aspect_ratio =
                    ost->frame_aspect_ratio.num ? // overridden by the -aspect cli option
                    av_mul_q(ost->frame_aspect_ratio, (AVRational){ enc_ctx->height, enc_ctx->width }) :
                    ost->filter->filter->inputs[0]->sample_aspect_ratio;
                if (!strncmp(ost->enc->name, "libx264", 7) &&
                    enc_ctx->pix_fmt == AV_PIX_FMT_NONE &&
                    ost->filter->filter->inputs[0]->format != AV_PIX_FMT_YUV420P)
                    av_log(NULL, AV_LOG_WARNING,
                           "No pixel format specified, %s for H.264 encoding chosen.\n"
                           "Use -pix_fmt yuv420p for compatibility with outdated media players.\n",
                           av_get_pix_fmt_name(ost->filter->filter->inputs[0]->format));
                if (!strncmp(ost->enc->name, "mpeg2video", 10) &&
                    enc_ctx->pix_fmt == AV_PIX_FMT_NONE &&
                    ost->filter->filter->inputs[0]->format != AV_PIX_FMT_YUV420P)
                    av_log(NULL, AV_LOG_WARNING,
                           "No pixel format specified, %s for MPEG-2 encoding chosen.\n"
                           "Use -pix_fmt yuv420p for compatibility with outdated media players.\n",
                           av_get_pix_fmt_name(ost->filter->filter->inputs[0]->format));
                enc_ctx->pix_fmt = ost->filter->filter->inputs[0]->format;

                ost->st->avg_frame_rate = ost->frame_rate;

                if (!dec_ctx ||
                    enc_ctx->width   != dec_ctx->width  ||
                    enc_ctx->height  != dec_ctx->height ||
                    enc_ctx->pix_fmt != dec_ctx->pix_fmt) {
                    enc_ctx->bits_per_raw_sample = frame_bits_per_raw_sample;
                }

                if (ost->forced_keyframes) {
                    if (!strncmp(ost->forced_keyframes, "expr:", 5)) {
                        ret = av_expr_parse(&ost->forced_keyframes_pexpr, ost->forced_keyframes+5,
                                            forced_keyframes_const_names, NULL, NULL, NULL, NULL, 0, NULL);
                        if (ret < 0) {
                            av_log(NULL, AV_LOG_ERROR,
                                   "Invalid force_key_frames expression '%s'\n", ost->forced_keyframes+5);
                            return ret;
                        }
                        ost->forced_keyframes_expr_const_values[FKF_N] = 0;
                        ost->forced_keyframes_expr_const_values[FKF_N_FORCED] = 0;
                        ost->forced_keyframes_expr_const_values[FKF_PREV_FORCED_N] = NAN;
                        ost->forced_keyframes_expr_const_values[FKF_PREV_FORCED_T] = NAN;
                    } else {
                        parse_forced_key_frames(ost->forced_keyframes, ost, ost->enc_ctx);
                    }
                }
                break;
            case AVMEDIA_TYPE_SUBTITLE:
                enc_ctx->time_base = (AVRational){1, 1000};
                if (!enc_ctx->width) {
                    enc_ctx->width     = input_streams[ost->source_index]->st->codec->width;
                    enc_ctx->height    = input_streams[ost->source_index]->st->codec->height;
                }
                break;
            default:
                abort();
                break;
            }
            /* two pass mode */
            if (enc_ctx->flags & (CODEC_FLAG_PASS1 | CODEC_FLAG_PASS2)) {
                char logfilename[1024];
                FILE *f;

                snprintf(logfilename, sizeof(logfilename), "%s-%d.log",
                         ost->logfile_prefix ? ost->logfile_prefix :
                                               DEFAULT_PASS_LOGFILENAME_PREFIX,
                         i);
                if (!strcmp(ost->enc->name, "libx264")) {
                    av_dict_set(&ost->encoder_opts, "stats", logfilename, AV_DICT_DONT_OVERWRITE);
                } else {
                    if (enc_ctx->flags & CODEC_FLAG_PASS2) {
                        char  *logbuffer;
                        size_t logbuffer_size;
                        if (cmdutils_read_file(logfilename, &logbuffer, &logbuffer_size) < 0) {
                            av_log(NULL, AV_LOG_FATAL, "Error reading log file '%s' for pass-2 encoding\n",
                                   logfilename);
                            exit_program(1);
                        }
                        enc_ctx->stats_in = logbuffer;
                    }
                    if (enc_ctx->flags & CODEC_FLAG_PASS1) {
                        f = av_fopen_utf8(logfilename, "wb");
                        if (!f) {
                            av_log(NULL, AV_LOG_FATAL, "Cannot write log file '%s' for pass-1 encoding: %s\n",
                                logfilename, strerror(errno));
                            exit_program(1);
                        }
                        ost->logfile = f;
                    }
                }
            }
        }
    }

    /* open each encoder */
    for (i = 0; i < nb_output_streams; i++) {
        ost = output_streams[i];
        if (ost->encoding_needed) {
            AVCodec      *codec = ost->enc;
            AVCodecContext *dec = NULL;

            if ((ist = get_input_stream(ost)))
                dec = ist->dec_ctx;
            if (dec && dec->subtitle_header) {
                /* ASS code assumes this buffer is null terminated so add extra byte. */
                ost->enc_ctx->subtitle_header = av_mallocz(dec->subtitle_header_size + 1);
                if (!ost->enc_ctx->subtitle_header) {
                    ret = AVERROR(ENOMEM);
                    goto dump_format;
                }
                memcpy(ost->enc_ctx->subtitle_header, dec->subtitle_header, dec->subtitle_header_size);
                ost->enc_ctx->subtitle_header_size = dec->subtitle_header_size;
            }
            if (!av_dict_get(ost->encoder_opts, "threads", NULL, 0))
                av_dict_set(&ost->encoder_opts, "threads", "auto", 0);
            av_dict_set(&ost->encoder_opts, "side_data_only_packets", "1", 0);

            if ((ret = avcodec_open2(ost->enc_ctx, codec, &ost->encoder_opts)) < 0) {
                if (ret == AVERROR_EXPERIMENTAL)
                    abort_codec_experimental(codec, 1);
                snprintf(error, sizeof(error), "Error while opening encoder for output stream #%d:%d - maybe incorrect parameters such as bit_rate, rate, width or height",
                        ost->file_index, ost->index);
                goto dump_format;
            }
            if (ost->enc->type == AVMEDIA_TYPE_AUDIO &&
                !(ost->enc->capabilities & CODEC_CAP_VARIABLE_FRAME_SIZE))
                av_buffersink_set_frame_size(ost->filter->filter,
                                             ost->enc_ctx->frame_size);
            assert_avoptions(ost->encoder_opts);
            if (ost->enc_ctx->bit_rate && ost->enc_ctx->bit_rate < 1000)
                av_log(NULL, AV_LOG_WARNING, "The bitrate parameter is set too low."
                                             " It takes bits/s as argument, not kbits/s\n");
        } else {
            av_opt_set_dict(ost->enc_ctx, &ost->encoder_opts);
        }

        ret = avcodec_copy_context(ost->st->codec, ost->enc_ctx);
        if (ret < 0) {
            av_log(NULL, AV_LOG_FATAL,
                   "Error initializing the output stream codec context.\n");
            exit_program(1);
        }
    }

    /* init input streams */
    for (i = 0; i < nb_input_streams; i++)
        if ((ret = init_input_stream(i, error, sizeof(error))) < 0) {
            for (i = 0; i < nb_output_streams; i++) {
                ost = output_streams[i];
                avcodec_close(ost->enc_ctx);
            }
            goto dump_format;
        }

    /* discard unused programs */
    for (i = 0; i < nb_input_files; i++) {
        InputFile *ifile = input_files[i];
        for (j = 0; j < ifile->ctx->nb_programs; j++) {
            AVProgram *p = ifile->ctx->programs[j];
            int discard  = AVDISCARD_ALL;

            for (k = 0; k < p->nb_stream_indexes; k++)
                if (!input_streams[ifile->ist_index + p->stream_index[k]]->discard) {
                    discard = AVDISCARD_DEFAULT;
                    break;
                }
            p->discard = discard;
        }
    }

    /* open files and write file headers */
    for (i = 0; i < nb_output_files; i++) {
        oc = output_files[i]->ctx;
        oc->interrupt_callback = int_cb;
        if ((ret = avformat_write_header(oc, &output_files[i]->opts)) < 0) {
            snprintf(error, sizeof(error),
                     "Could not write header for output file #%d "
                     "(incorrect codec parameters ?): %s",
                     i, av_err2str(ret));
            ret = AVERROR(EINVAL);
            goto dump_format;
        }
//         assert_avoptions(output_files[i]->opts);
        if (strcmp(oc->oformat->name, "rtp")) {
            want_sdp = 0;
        }
    }

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

    /* dump the stream mapping */
    av_log(NULL, AV_LOG_INFO, "Stream mapping:\n");
    for (i = 0; i < nb_input_streams; i++) {
        ist = input_streams[i];

        for (j = 0; j < ist->nb_filters; j++) {
            if (ist->filters[j]->graph->graph_desc) {
                av_log(NULL, AV_LOG_INFO, "  Stream #%d:%d (%s) -> %s",
                       ist->file_index, ist->st->index, ist->dec ? ist->dec->name : "?",
                       ist->filters[j]->name);
                if (nb_filtergraphs > 1)
                    av_log(NULL, AV_LOG_INFO, " (graph %d)", ist->filters[j]->graph->index);
                av_log(NULL, AV_LOG_INFO, "\n");
            }
        }
    }

    for (i = 0; i < nb_output_streams; i++) {
        ost = output_streams[i];

        if (ost->attachment_filename) {
            /* an attached file */
            av_log(NULL, AV_LOG_INFO, "  File %s -> Stream #%d:%d\n",
                   ost->attachment_filename, ost->file_index, ost->index);
            continue;
        }

        if (ost->filter && ost->filter->graph->graph_desc) {
            /* output from a complex graph */
            av_log(NULL, AV_LOG_INFO, "  %s", ost->filter->name);
            if (nb_filtergraphs > 1)
                av_log(NULL, AV_LOG_INFO, " (graph %d)", ost->filter->graph->index);

            av_log(NULL, AV_LOG_INFO, " -> Stream #%d:%d (%s)\n", ost->file_index,
                   ost->index, ost->enc ? ost->enc->name : "?");
            continue;
        }

        av_log(NULL, AV_LOG_INFO, "  Stream #%d:%d -> #%d:%d",
               input_streams[ost->source_index]->file_index,
               input_streams[ost->source_index]->st->index,
               ost->file_index,
               ost->index);
        if (ost->sync_ist != input_streams[ost->source_index])
            av_log(NULL, AV_LOG_INFO, " [sync #%d:%d]",
                   ost->sync_ist->file_index,
                   ost->sync_ist->st->index);
        if (ost->stream_copy)
            av_log(NULL, AV_LOG_INFO, " (copy)");
        else
            av_log(NULL, AV_LOG_INFO, " (%s -> %s)", input_streams[ost->source_index]->dec ?
                   input_streams[ost->source_index]->dec->name : "?",
                   ost->enc ? ost->enc->name : "?");
        av_log(NULL, AV_LOG_INFO, "\n");
    }

    if (ret) {
        av_log(NULL, AV_LOG_ERROR, "%s\n", error);
        return ret;
    }

    if (want_sdp) {
        print_sdp();
    }

    transcode_init_done = 1;

    return 0;
}

/* Return 1 if there remain streams where more output is wanted, 0 otherwise. */
static int need_output(void)
{
    int i;

    for (i = 0; i < nb_output_streams; i++) {
        OutputStream *ost    = output_streams[i];
        OutputFile *of       = output_files[ost->file_index];
        AVFormatContext *os  = output_files[ost->file_index]->ctx;

        if (ost->finished ||
            (os->pb && avio_tell(os->pb) >= of->limit_filesize))
            continue;
        if (ost->frame_number >= ost->max_frames) {
            int j;
            for (j = 0; j < of->ctx->nb_streams; j++)
                close_output_stream(output_streams[of->ost_index + j]);
            continue;
        }

        return 1;
    }

    return 0;
}

/**
 * Select the output stream to process.
 *
 * @return  selected output stream, or NULL if none available
 */
static OutputStream *choose_output(void)
{
    int i;
    int64_t opts_min = INT64_MAX;