static int mov_text_decode_frame(AVCodecContext *avctx,
                            void *data, int *got_sub_ptr, AVPacket *avpkt)
{
    AVSubtitle *sub = data;
    int ret, ts_start, ts_end;
    AVBPrint buf;
    char *ptr = avpkt->data;
    char *end;
    //char *ptr_temp;
    int text_length, tsmb_type, style_entries, tsmb_size, tracksize;
    int **style_start = {0,};
    int **style_end = {0,};
    int **style_flags = {0,};
    const uint8_t *tsmb;
    int index, i;
    int *flag;
    int *style_pos;

    if (!ptr || avpkt->size < 2)
        return AVERROR_INVALIDDATA;

    /*
     * A packet of size two with value zero is an empty subtitle
     * used to mark the end of the previous non-empty subtitle.
     * We can just drop them here as we have duration information
     * already. If the value is non-zero, then it's technically a
     * bad packet.
     */
    if (avpkt->size == 2)
        return AV_RB16(ptr) == 0 ? 0 : AVERROR_INVALIDDATA;

    /*
     * The first two bytes of the packet are the length of the text string
     * In complex cases, there are style descriptors appended to the string
     * so we can't just assume the packet size is the string size.
     */
    text_length = AV_RB16(ptr);
    end = ptr + FFMIN(2 + text_length, avpkt->size);
    ptr += 2;

    ts_start = av_rescale_q(avpkt->pts,
                            avctx->time_base,
                            (AVRational){1,100});
    ts_end   = av_rescale_q(avpkt->pts + avpkt->duration,
                            avctx->time_base,
                            (AVRational){1,100});

    tsmb_size = 0;
    tracksize = 2 + text_length;
    // Note that the spec recommends lines be no longer than 2048 characters.
    av_bprint_init(&buf, 0, AV_BPRINT_SIZE_UNLIMITED);
    if (text_length + 2 != avpkt->size) {
        while (tracksize + 8 <= avpkt->size) {
            // A box is a minimum of 8 bytes.
            tsmb = ptr + tracksize - 2;
            tsmb_size = AV_RB32(tsmb);
            tsmb += 4;
            tsmb_type = AV_RB32(tsmb);
            tsmb += 4;

            if (tracksize + tsmb_size > avpkt->size)
                break;

            if (tsmb_type == MKBETAG('s','t','y','l')) {
                if (tracksize + 10 > avpkt->size)
                    break;
                style_entries = AV_RB16(tsmb);
                tsmb += 2;

                // A single style record is of length 12 bytes.
                if (tracksize + 10 + style_entries * 12 > avpkt->size)
                    break;

                for(i = 0; i < style_entries; i++) {
                    style_pos = av_malloc(4);
                    *style_pos = AV_RB16(tsmb);
                    index = i;
                    av_dynarray_add(&style_start, &index, style_pos);
                    tsmb += 2;
                    style_pos = av_malloc(4);
                    *style_pos = AV_RB16(tsmb);
                    index = i;
                    av_dynarray_add(&style_end, &index, style_pos);
                    tsmb += 2;
                    // fontID = AV_RB16(tsmb);
                    tsmb += 2;
                    flag = av_malloc(4);
                    *flag = AV_RB8(tsmb);
                    index = i;
                    av_dynarray_add(&style_flags, &index, flag);
                    //fontsize=AV_RB8(tsmb);
                    tsmb += 2;
                    // text-color-rgba
                    tsmb += 4;
                }
                text_to_ass(&buf, ptr, end, style_start, style_end, style_flags, style_entries);
                av_freep(&style_start);
                av_freep(&style_end);
                av_freep(&style_flags);
            }
            tracksize = tracksize + tsmb_size;
        }
    } else
        text_to_ass(&buf, ptr, end, NULL, NULL, 0, 0);

    ret = ff_ass_add_rect_bprint(sub, &buf, ts_start, ts_end - ts_start);
    av_bprint_finalize(&buf, NULL);
    if (ret < 0)
        return ret;
    *got_sub_ptr = sub->num_rects > 0;
    return avpkt->size;
}