static int mov_write_single_packet(AVFormatContext *s, AVPacket *pkt)
{
        MOVMuxContext *mov = s->priv_data;
        MOVTrack *trk = &mov->tracks[pkt->stream_index];
        AVCodecParameters *par = trk->par;
        int64_t frag_duration = 0;
        int size = pkt->size;

        int ret = check_pkt(s, pkt);
        if (ret < 0)
            return ret;

        if (mov->flags & FF_MOV_FLAG_FRAG_DISCONT) {
            int i;
            for (i = 0; i < s->nb_streams; i++)
                mov->tracks[i].frag_discont = 1;
            mov->flags &= ~FF_MOV_FLAG_FRAG_DISCONT;
        }

        if (!pkt->size) {
            if (trk->start_dts == AV_NOPTS_VALUE && trk->frag_discont) {
                trk->start_dts = pkt->dts;
                if (pkt->pts != AV_NOPTS_VALUE)
                    trk->start_cts = pkt->pts - pkt->dts;
                else
                    trk->start_cts = 0;
            }

            if (trk->par->codec_id == AV_CODEC_ID_MP4ALS) {
                int side_size = 0;
                uint8_t *side = av_packet_get_side_data(pkt, AV_PKT_DATA_NEW_EXTRADATA, &side_size);
                if (side && side_size > 0 && (side_size != par->extradata_size || memcmp(side, par->extradata, side_size))) {
                    void *newextra = av_mallocz(side_size + AV_INPUT_BUFFER_PADDING_SIZE);
                    if (!newextra)
                        return AVERROR(ENOMEM);
                    av_free(par->extradata);
                    par->extradata = newextra;
                    memcpy(par->extradata, side, side_size);
                    par->extradata_size = side_size;
                    mov->need_rewrite_extradata = 1;
                }
            }

            return 0;             /* Discard 0 sized packets */
        }

        if (trk->entry && pkt->stream_index < s->nb_streams)
            frag_duration = av_rescale_q(pkt->dts - trk->cluster[0].dts,
                                         s->streams[pkt->stream_index]->time_base,
                                         AV_TIME_BASE_Q);
        if ((mov->max_fragment_duration &&
             frag_duration >= mov->max_fragment_duration) ||
             (mov->max_fragment_size && mov->mdat_size + size >= mov->max_fragment_size) ||
             (mov->flags & FF_MOV_FLAG_FRAG_KEYFRAME &&
              par->codec_type == AVMEDIA_TYPE_VIDEO &&
              trk->entry && pkt->flags & AV_PKT_FLAG_KEY)) {
            if (frag_duration >= mov->min_fragment_duration) {
                // Set the duration of this track to line up with the next
                // sample in this track. This avoids relying on AVPacket
                // duration, but only helps for this particular track, not
                // for the other ones that are flushed at the same time.
                trk->track_duration = pkt->dts - trk->start_dts;
                if (pkt->pts != AV_NOPTS_VALUE)
                    trk->end_pts = pkt->pts;
                else
                    trk->end_pts = pkt->dts;
                trk->end_reliable = 1;
                mov_auto_flush_fragment(s, 0);
            }
        }

        return ff_mov_write_packet(s, pkt);
}
Unknown