static int asf_write_trailer(AVFormatContext *s)
{
    ASFContext *asf = s->priv_data;
    int64_t file_size,data_size;

    /* flush the current packet */
    if (asf->pb.buf_ptr > asf->pb.buffer)
        flush_packet(s);

    /* write index */
    data_size = url_ftell(s->pb);
    if ((!asf->is_streamed) && (asf->nb_index_count != 0)) {
        asf_write_index(s, asf->index_ptr, asf->maximum_packet, asf->nb_index_count);
    }
    put_flush_packet(s->pb);

    if (asf->is_streamed || url_is_streamed(s->pb)) {
        put_chunk(s, 0x4524, 0, 0); /* end of stream */
    } else {
        /* rewrite an updated header */
        file_size = url_ftell(s->pb);
        url_fseek(s->pb, 0, SEEK_SET);
        asf_write_header1(s, file_size, data_size - asf->data_offset);
    }

    put_flush_packet(s->pb);
    av_free(asf->index_ptr);
    return 0;
}

static int gxf_write_trailer(AVFormatContext *s)
{
    GXFContext *gxf = s->priv_data;
    ByteIOContext *pb = s->pb;
    int64_t end;
    int i;

    ff_audio_interleave_close(s);

    gxf_write_eos_packet(pb);
    end = url_ftell(pb);
    url_fseek(pb, 0, SEEK_SET);
    /* overwrite map, flt and umf packets with new values */
    gxf_write_map_packet(s, 1);
    gxf_write_flt_packet(s);
    gxf_write_umf_packet(s);
    put_flush_packet(pb);
    /* update duration in all map packets */
    for (i = 1; i < gxf->map_offsets_nb; i++) {
        url_fseek(pb, gxf->map_offsets[i], SEEK_SET);
        gxf_write_map_packet(s, 1);
        put_flush_packet(pb);
    }

    url_fseek(pb, end, SEEK_SET);

    av_freep(&gxf->flt_entries);
    av_freep(&gxf->map_offsets);

    return 0;
}

static int wav_write_trailer(AVFormatContext *s)
{
    ByteIOContext *pb  = s->pb;
    WAVContext    *wav = s->priv_data;
    int64_t file_size;

    put_flush_packet(pb);

    if (!url_is_streamed(s->pb)) {
        ff_end_tag(pb, wav->data);

        /* update file size */
        file_size = url_ftell(pb);
        url_fseek(pb, 4, SEEK_SET);
        put_le32(pb, (uint32_t)(file_size - 8));
        url_fseek(pb, file_size, SEEK_SET);

        put_flush_packet(pb);

        if(s->streams[0]->codec->codec_tag != 0x01) {
            /* Update num_samps in fact chunk */
            int number_of_samples;
            number_of_samples = av_rescale(wav->maxpts - wav->minpts + wav->last_duration,
                                           s->streams[0]->codec->sample_rate * (int64_t)s->streams[0]->time_base.num,
                                           s->streams[0]->time_base.den);
            url_fseek(pb, wav->data-12, SEEK_SET);
            put_le32(pb, number_of_samples);
            url_fseek(pb, file_size, SEEK_SET);
            put_flush_packet(pb);
        }
    }
    return 0;
}

/* We set AVOutputFormat->write_trailer to this function for mpeg1. That way,
 * the mpeg1 video gets a proper trailer when it is closed.
 */
static int mpeg1_write_trailer(AVFormatContext *s)
{
#if LIBAVFORMAT_BUILD >= (52<<16) 
    put_buffer(s->pb, mpeg1_trailer, 4);
    put_flush_packet(s->pb);    
#else
    put_buffer(&s->pb, mpeg1_trailer, 4);
    put_flush_packet(&s->pb);
#endif /* LIBAVFORMAT_BUILD >= (52<<16) */

    return 0; /* success */
}

/**
 * mpeg1_write_trailer
 *      We set AVOutputFormat->write_trailer to this function for mpeg1. That way,
 *      the mpeg1 video gets a proper trailer when it is closed.
 *
 *  Returns 0
 *
 */
static int mpeg1_write_trailer(AVFormatContext *s)
{
#if defined FF_API_NEW_AVIO
    avio_write(s->pb, mpeg1_trailer, 4);
    avio_flush(s->pb);
#elif LIBAVFORMAT_BUILD >= (52<<16)
    put_buffer(s->pb, mpeg1_trailer, 4);
    put_flush_packet(s->pb);
#else
    put_buffer(&s->pb, mpeg1_trailer, 4);
    put_flush_packet(&s->pb);
#endif /* FF_API_NEW_AVIO -- LIBAVFORMAT_BUILD >= (52<<16) */

    return 0; /* success */
}

static int img_write_packet(AVFormatContext *s, AVPacket *pkt)
{
    VideoData *img = s->priv_data;
    ByteIOContext pb1, *pb;
    char filename[1024];

    if (!img->is_pipe) {
        if (get_frame_filename(filename, sizeof(filename), 
                               img->path, img->img_number) < 0 && img->img_number>1)
            return AVERROR_IO;
        pb = &pb1;
        if (url_fopen(pb, filename, URL_WRONLY) < 0)
            return AVERROR_IO;
    } else {
        pb = &s->pb;
    }

    put_buffer(pb, pkt->data, pkt->size);
    put_flush_packet(pb);
    if (!img->is_pipe) {
        url_fclose(pb);
    }

    img->img_number++;
    return 0;
}

static int asf_write_header(AVFormatContext *s)
{
    ASFContext *asf = s->priv_data;

    asf->packet_size = PACKET_SIZE;
    asf->nb_packets = 0;

    asf->last_indexed_pts = 0;
    asf->index_ptr = (ASFIndex*)av_malloc( sizeof(ASFIndex) * ASF_INDEX_BLOCK );
    asf->nb_index_memory_alloc = ASF_INDEX_BLOCK;
    asf->nb_index_count = 0;
    asf->maximum_packet = 0;

    if (asf_write_header1(s, 0, 50) < 0) {
        //av_free(asf);
        return -1;
    }

    put_flush_packet(&s->pb);

    asf->packet_nb_payloads = 0;
    asf->prev_packet_sent_time = 0;
    asf->packet_timestamp_start = -1;
    asf->packet_timestamp_end = -1;
    init_put_byte(&asf->pb, asf->packet_buf, asf->packet_size, 1,
                  NULL, NULL, NULL, NULL);

    return 0;
}

static int asf_write_header(AVFormatContext *s)
{
    ASFContext *asf = s->priv_data;

    asf->packet_size = PACKET_SIZE;
    asf->nb_packets = 0;

    asf->last_indexed_pts = 0;
    asf->index_ptr = av_malloc( sizeof(ASFIndex) * ASF_INDEX_BLOCK );
    asf->nb_index_memory_alloc = ASF_INDEX_BLOCK;
    asf->nb_index_count = 0;
    asf->maximum_packet = 0;

    /* the data-chunk-size has to be 50, which is data_size - asf->data_offset
     *  at the moment this function is done. It is needed to use asf as
     *  streamable format. */
    if (asf_write_header1(s, 0, 50) < 0) {
        //av_free(asf);
        return -1;
    }

    put_flush_packet(s->pb);

    asf->packet_nb_payloads = 0;
    asf->packet_timestamp_start = -1;
    asf->packet_timestamp_end = -1;
    init_put_byte(&asf->pb, asf->packet_buf, asf->packet_size, 1,
                  NULL, NULL, NULL, NULL);

    return 0;
}

static int swf_write_trailer(AVFormatContext *s)
{
    SWFContext *swf = s->priv_data;
    ByteIOContext *pb = s->pb;
    AVCodecContext *enc, *video_enc;
    int file_size, i;

    video_enc = NULL;
    for(i=0;i<s->nb_streams;i++) {
        enc = s->streams[i]->codec;
        if (enc->codec_type == CODEC_TYPE_VIDEO)
            video_enc = enc;
        else
            av_fifo_free(&swf->audio_fifo);
    }

    put_swf_tag(s, TAG_END);
    put_swf_end_tag(s);

    put_flush_packet(s->pb);

    /* patch file size and number of frames if not streamed */
    if (!url_is_streamed(s->pb) && video_enc) {
        file_size = url_ftell(pb);
        url_fseek(pb, 4, SEEK_SET);
        put_le32(pb, file_size);
        url_fseek(pb, swf->duration_pos, SEEK_SET);
        put_le16(pb, swf->video_frame_number);
        url_fseek(pb, swf->vframes_pos, SEEK_SET);
        put_le16(pb, swf->video_frame_number);
        url_fseek(pb, file_size, SEEK_SET);
    }
    return 0;
}

static int rm_write_audio(AVFormatContext *s, const uint8_t *buf, int size, int flags)
{
    uint8_t *buf1;
    RMMuxContext *rm = s->priv_data;
    ByteIOContext *pb = s->pb;
    StreamInfo *stream = rm->audio_stream;
    int i;

    /* XXX: suppress this malloc */
    buf1= (uint8_t*) av_malloc( size * sizeof(uint8_t) );

    write_packet_header(s, stream, size, !!(flags & AV_PKT_FLAG_KEY));

    if (stream->enc->codec_id == CODEC_ID_AC3) {
        /* for AC-3, the words seem to be reversed */
        for(i=0;i<size;i+=2) {
            buf1[i] = buf[i+1];
            buf1[i+1] = buf[i];
        }
        put_buffer(pb, buf1, size);
    } else {
        put_buffer(pb, buf, size);
    }
    put_flush_packet(pb);
    stream->nb_frames++;
    av_free(buf1);
    return 0;
}

static int flv_write_packet(AVFormatContext *s, AVPacket *pkt)
{
    ByteIOContext *pb = &s->pb;
    AVCodecContext *enc = s->streams[pkt->stream_index]->codec;
    FLVContext *flv = s->priv_data;
    int size= pkt->size;
    int flags;

//    av_log(s, AV_LOG_DEBUG, "type:%d pts: %"PRId64" size:%d\n", enc->codec_type, timestamp, size);

    if (enc->codec_type == CODEC_TYPE_VIDEO) {
        put_byte(pb, 9);
        flags = 2; // choose h263
        flags |= pkt->flags & PKT_FLAG_KEY ? 0x10 : 0x20; // add keyframe indicator
    } else {
        assert(enc->codec_type == CODEC_TYPE_AUDIO);
        flags = get_audio_flags(enc);

        assert(size);

        put_byte(pb, 8);
    }

    put_be24(pb,size+1); // include flags
    put_be24(pb,pkt->pts);
    put_be32(pb,flv->reserved);
    put_byte(pb,flags);
    put_buffer(pb, pkt->data, size);
    put_be32(pb,size+1+11); // previous tag size
    flv->duration = pkt->pts + pkt->duration;

    put_flush_packet(pb);
    return 0;
}

static void flush_packet(AVFormatContext *s)
{
    FFMContext *ffm = s->priv_data;
    int fill_size, h;
    ByteIOContext *pb = s->pb;

    fill_size = ffm->packet_end - ffm->packet_ptr;
    memset(ffm->packet_ptr, 0, fill_size);

    if (url_ftell(pb) % ffm->packet_size)
        av_abort();

    /* put header */
    put_be16(pb, PACKET_ID);
    put_be16(pb, fill_size);
    put_be64(pb, ffm->dts);
    h = ffm->frame_offset;
    if (ffm->first_packet)
        h |= 0x8000;
    put_be16(pb, h);
    put_buffer(pb, ffm->packet, ffm->packet_end - ffm->packet);
    put_flush_packet(pb);

    /* prepare next packet */
    ffm->frame_offset = 0; /* no key frame */
    ffm->packet_ptr = ffm->packet;
    ffm->first_packet = 0;
}

static int write_header(AVFormatContext *s)
{
    ASSContext *ass = s->priv_data;
    AVCodecContext *avctx= s->streams[0]->codec;
    uint8_t *last= NULL;

    if(s->nb_streams != 1 || avctx->codec_id != CODEC_ID_SSA){
        av_log(s, AV_LOG_ERROR, "Exactly one ASS/SSA stream is needed.\n");
        return -1;
    }

    while(ass->extra_index < avctx->extradata_size){
        uint8_t *p  = avctx->extradata + ass->extra_index;
        uint8_t *end= strchr(p, '\n');
        if(!end) end= avctx->extradata + avctx->extradata_size;
        else     end++;

        put_buffer(s->pb, p, end-p);
        ass->extra_index += end-p;

        if(last && !memcmp(last, "[Events]", 8))
            break;
        last=p;
    }

    put_flush_packet(s->pb);

    return 0;
}

static int aiff_write_trailer(AVFormatContext *s)
{
    ByteIOContext *pb = s->pb;
    AIFFOutputContext *aiff = s->priv_data;
    AVCodecContext *enc = s->streams[0]->codec;

    /* Chunks sizes must be even */
    int64_t file_size, end_size;
    end_size = file_size = url_ftell(pb);
    if (file_size & 1) {
        put_byte(pb, 0);
        end_size++;
    }

    if (!url_is_streamed(s->pb)) {
        /* File length */
        url_fseek(pb, aiff->form, SEEK_SET);
        put_be32(pb, file_size - aiff->form - 4);

        /* Number of sample frames */
        url_fseek(pb, aiff->frames, SEEK_SET);
        put_be32(pb, (file_size-aiff->ssnd-12)/enc->block_align);

        /* Sound Data chunk size */
        url_fseek(pb, aiff->ssnd, SEEK_SET);
        put_be32(pb, file_size - aiff->ssnd - 4);

        /* return to the end */
        url_fseek(pb, end_size, SEEK_SET);

        put_flush_packet(pb);
    }

    return 0;
}

static int gif_write_video(AVFormatContext *s,
                           AVCodecContext *enc, const uint8_t *buf, int size)
{
    ByteIOContext *pb = s->pb;
    GIFContext *gif = s->priv_data;
    int jiffies;
    int64_t delay;

    /* graphic control extension block */
    put_byte(pb, 0x21);
    put_byte(pb, 0xf9);
    put_byte(pb, 0x04); /* block size */
    put_byte(pb, 0x04); /* flags */

    /* 1 jiffy is 1/70 s */
    /* the delay_time field indicates the number of jiffies - 1 */
    delay = gif->file_time - gif->time;

    /* XXX: should use delay, in order to be more accurate */
    /* instead of using the same rounded value each time */
    /* XXX: don't even remember if I really use it for now */
    jiffies = (70*enc->time_base.num/enc->time_base.den) - 1;

    put_le16(pb, jiffies);

    put_byte(pb, 0x1f); /* transparent color index */
    put_byte(pb, 0x00);

    gif_image_write_image(pb, 0, 0, enc->width, enc->height,
                          buf, enc->width * 3, PIX_FMT_RGB24);

    put_flush_packet(s->pb);
    return 0;
}

static int rso_write_trailer(AVFormatContext *s)
{
    ByteIOContext *pb = s->pb;
    int64_t file_size;
    uint16_t coded_file_size;

    file_size = url_ftell(pb);

    if (file_size < 0)
        return file_size;

    if (file_size > 0xffff + RSO_HEADER_SIZE) {
        av_log(s, AV_LOG_WARNING,
               "Output file is too big (%"PRId64" bytes >= 64kB)\n", file_size);
        coded_file_size = 0xffff;
    } else {
        coded_file_size = file_size - RSO_HEADER_SIZE;
    }

    /* update file size */
    url_fseek(pb, 2, SEEK_SET);
    put_be16(pb, coded_file_size);
    url_fseek(pb, file_size, SEEK_SET);

    put_flush_packet(pb);

    return 0;
}

/* send an rtcp sender report packet */
static void rtcp_send_sr(AVFormatContext *s1, int64_t ntp_time)
{
    RTPMuxContext *s = s1->priv_data;
    uint32_t rtp_ts;
#ifdef _MSC_VER
	AVRational rational = {1, 1000000};
#endif

    dprintf(s1, "RTCP: %02x %"PRIx64" %x\n", s->payload_type, ntp_time, s->timestamp);

    s->last_rtcp_ntp_time = ntp_time;
#ifdef _MSC_VER
    rtp_ts = av_rescale_q(ntp_time - s->first_rtcp_ntp_time, rational,
                          s1->streams[0]->time_base) + s->base_timestamp;
#else
    rtp_ts = av_rescale_q(ntp_time - s->first_rtcp_ntp_time, (AVRational){1, 1000000},
                          s1->streams[0]->time_base) + s->base_timestamp;
#endif
    put_byte(s1->pb, (RTP_VERSION << 6));
    put_byte(s1->pb, RTCP_SR);
    put_be16(s1->pb, 6); /* length in words - 1 */
    put_be32(s1->pb, s->ssrc);
    put_be32(s1->pb, ntp_time / 1000000);
    put_be32(s1->pb, ((ntp_time % 1000000) << 32) / 1000000);
    put_be32(s1->pb, rtp_ts);
    put_be32(s1->pb, s->packet_count);
    put_be32(s1->pb, s->octet_count);
    put_flush_packet(s1->pb);
}

static void flush_packet(AVFormatContext *s)
{
    ASFContext *asf = s->priv_data;
    int packet_hdr_size, packet_filled_size;

    assert(asf->packet_timestamp_end >= asf->packet_timestamp_start);

    if (asf->is_streamed) {
        put_chunk(s, 0x4424, asf->packet_size, 0);
    }

    packet_hdr_size = put_payload_parsing_info(
                            s,
                            asf->packet_timestamp_start,
                            asf->packet_timestamp_end - asf->packet_timestamp_start,
                            asf->packet_nb_payloads,
                            asf->packet_size_left
                        );

    packet_filled_size = PACKET_SIZE - asf->packet_size_left;
    assert(packet_hdr_size <= asf->packet_size_left);
    memset(asf->packet_buf + packet_filled_size, 0, asf->packet_size_left);

    put_buffer(s->pb, asf->packet_buf, asf->packet_size - packet_hdr_size);

    put_flush_packet(s->pb);
    asf->nb_packets++;
    asf->packet_nb_payloads = 0;
    asf->packet_timestamp_start = -1;
    asf->packet_timestamp_end = -1;
    init_put_byte(&asf->pb, asf->packet_buf, asf->packet_size, 1,
                  NULL, NULL, NULL, NULL);
}

static int ogg_write_page(AVFormatContext *s, const uint8_t *data, int size,
                          int64_t granule, int stream_index, int flags)
{
    OGGStreamContext *oggstream = s->streams[stream_index]->priv_data;
    int64_t crc_offset;
    int page_segments, i;

    if (size >= 255*255) {
        granule = -1;
        size = 255*255;
    } else if (oggstream->eos)
        flags |= 4;

    page_segments = FFMIN((size/255)+!!size, 255);

    init_checksum(s->pb, ff_crc04C11DB7_update, 0);
    put_tag(s->pb, "OggS");
    put_byte(s->pb, 0);
    put_byte(s->pb, flags);
    put_le64(s->pb, granule);
    put_le32(s->pb, stream_index);
    put_le32(s->pb, oggstream->page_counter++);
    crc_offset = url_ftell(s->pb);
    put_le32(s->pb, 0); // crc
    put_byte(s->pb, page_segments);
    for (i = 0; i < page_segments-1; i++)
        put_byte(s->pb, 255);
    if (size) {
        put_byte(s->pb, size - (page_segments-1)*255);
        put_buffer(s->pb, data, size);
    }
    ogg_update_checksum(s, crc_offset);
    put_flush_packet(s->pb);
    return size;
}

static int write_trailer(AVFormatContext *s)
{
    int i;

    write_tags(s->pb, s->metadata);

    for (i = 0; i < s->nb_streams; i++) {
        put_tag(s->pb, ID_STREAM);
        put_byte(s->pb, '\n');
        write_tags(s->pb, s->streams[i]->metadata);
    }

    for (i = 0; i < s->nb_chapters; i++) {
        AVChapter *ch = s->chapters[i];
        put_tag(s->pb, ID_CHAPTER);
        put_byte(s->pb, '\n');
        url_fprintf(s->pb, "TIMEBASE=%d/%d\n", ch->time_base.num, ch->time_base.den);
        url_fprintf(s->pb, "START=%"PRId64"\n", ch->start);
        url_fprintf(s->pb, "END=%"PRId64"\n",   ch->end);
        write_tags(s->pb, ch->metadata);
    }

    put_flush_packet(s->pb);

    return 0;
}