static int mov_write_traf_tag(AVIOContext *pb, MOVMuxContext *mov,
                              MOVTrack *track, int64_t moof_offset,
                              int moof_size)
{
    int64_t pos = avio_tell(pb);
    int i, start = 0;
    avio_wb32(pb, 0); /* size placeholder */
    ffio_wfourcc(pb, "traf");

    mov_write_tfhd_tag(pb, mov, track, moof_offset);
    if (mov->mode != MODE_ISM)
        mov_write_tfdt_tag(pb, track);
    for (i = 1; i < track->entry; i++) {
        if (track->cluster[i].pos != track->cluster[i - 1].pos + track->cluster[i - 1].size) {
            mov_write_trun_tag(pb, mov, track, moof_size, start, i);
            start = i;
        }
    }
    mov_write_trun_tag(pb, mov, track, moof_size, start, track->entry);
    if (mov->mode == MODE_ISM) {
        mov_write_tfxd_tag(pb, track);

        if (mov->ism_lookahead) {
            int i, size = 16 + 4 + 1 + 16 * mov->ism_lookahead;

            if (track->nb_frag_info > 0) {
                MOVFragmentInfo *info = &track->frag_info[track->nb_frag_info - 1];
                if (!info->tfrf_offset)
                    info->tfrf_offset = avio_tell(pb);
            }
            avio_wb32(pb, 8 + size);
            ffio_wfourcc(pb, "free");
            for (i = 0; i < size; i++)
                avio_w8(pb, 0);
        }
    }

    return update_size(pb, pos);
}

The product divides a value by zero.