static void write_packet(AVFormatContext *s, AVPacket *pkt, OutputStream *ost)
{
    AVStream *st = ost->st;
    int ret;

    if ((st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO && video_sync_method == VSYNC_DROP) ||
        (st->codecpar->codec_type == AVMEDIA_TYPE_AUDIO && audio_sync_method < 0))
        pkt->pts = pkt->dts = AV_NOPTS_VALUE;

    /*
     * Audio encoders may split the packets --  #frames in != #packets out.
     * But there is no reordering, so we can limit the number of output packets
     * by simply dropping them here.
     * Counting encoded video frames needs to be done separately because of
     * reordering, see do_video_out()
     */
    if (!(st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO && ost->encoding_needed)) {
        if (ost->frame_number >= ost->max_frames) {
            av_packet_unref(pkt);
            return;
        }
        ost->frame_number++;
    }
    if (st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
        int i;
        uint8_t *sd = av_packet_get_side_data(pkt, AV_PKT_DATA_QUALITY_STATS,
                                              NULL);
        ost->quality = sd ? AV_RL32(sd) : -1;
        ost->pict_type = sd ? sd[4] : AV_PICTURE_TYPE_NONE;

        for (i = 0; i<FF_ARRAY_ELEMS(ost->error); i++) {
            if (sd && i < sd[5])
                ost->error[i] = AV_RL64(sd + 8 + 8*i);
            else
                ost->error[i] = -1;
        }

        if (ost->frame_rate.num && ost->is_cfr) {
            if (pkt->duration > 0)
                av_log(NULL, AV_LOG_WARNING, "Overriding packet duration by frame rate, this should not happen\n");
            pkt->duration = av_rescale_q(1, av_inv_q(ost->frame_rate),
                                         ost->st->time_base);
        }
    }

    if (!(s->oformat->flags & AVFMT_NOTIMESTAMPS)) {
        if (pkt->dts != AV_NOPTS_VALUE &&
            pkt->pts != AV_NOPTS_VALUE &&
            pkt->dts > pkt->pts) {
            av_log(s, AV_LOG_WARNING, "Invalid DTS: %"PRId64" PTS: %"PRId64" in output stream %d:%d, replacing by guess\n",
                   pkt->dts, pkt->pts,
                   ost->file_index, ost->st->index);
            pkt->pts =
            pkt->dts = pkt->pts + pkt->dts + ost->last_mux_dts + 1
                     - FFMIN3(pkt->pts, pkt->dts, ost->last_mux_dts + 1)
                     - FFMAX3(pkt->pts, pkt->dts, ost->last_mux_dts + 1);
        }
        if ((st->codecpar->codec_type == AVMEDIA_TYPE_AUDIO || st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) &&
            pkt->dts != AV_NOPTS_VALUE &&
            !(st->codecpar->codec_id == AV_CODEC_ID_VP9 && ost->stream_copy) &&
            ost->last_mux_dts != AV_NOPTS_VALUE) {
            int64_t max = ost->last_mux_dts + !(s->oformat->flags & AVFMT_TS_NONSTRICT);
            if (pkt->dts < max) {
                int loglevel = max - pkt->dts > 2 || st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO ? AV_LOG_WARNING : AV_LOG_DEBUG;
                av_log(s, loglevel, "Non-monotonous DTS in output stream "
                       "%d:%d; previous: %"PRId64", current: %"PRId64"; ",
                       ost->file_index, ost->st->index, ost->last_mux_dts, pkt->dts);
                if (exit_on_error) {
                    av_log(NULL, AV_LOG_FATAL, "aborting.\n");
                    exit_program(1);
                }
                av_log(s, loglevel, "changing to %"PRId64". This may result "
                       "in incorrect timestamps in the output file.\n",
                       max);
                if (pkt->pts >= pkt->dts)
                    pkt->pts = FFMAX(pkt->pts, max);
                pkt->dts = max;
            }
        }
    }
    ost->last_mux_dts = pkt->dts;

    ost->data_size += pkt->size;
    ost->packets_written++;

    pkt->stream_index = ost->index;

    if (debug_ts) {
        av_log(NULL, AV_LOG_INFO, "muxer <- type:%s "
                "pkt_pts:%s pkt_pts_time:%s pkt_dts:%s pkt_dts_time:%s size:%d\n",
                av_get_media_type_string(ost->enc_ctx->codec_type),
                av_ts2str(pkt->pts), av_ts2timestr(pkt->pts, &ost->st->time_base),
                av_ts2str(pkt->dts), av_ts2timestr(pkt->dts, &ost->st->time_base),
                pkt->size
              );
    }

    ret = av_interleaved_write_frame(s, pkt);
    if (ret < 0) {
        print_error("av_interleaved_write_frame()", ret);
        main_return_code = 1;
        close_all_output_streams(ost, MUXER_FINISHED | ENCODER_FINISHED, ENCODER_FINISHED);
    }
    av_packet_unref(pkt);
}