int ff_h2645_packet_split(H2645Packet *pkt, const uint8_t *buf, int length,
                          void *logctx, int is_nalff, int nal_length_size,
                          enum AVCodecID codec_id)
{
    int consumed, ret = 0;
    const uint8_t *next_avc = buf + (is_nalff ? 0 : length);

    pkt->nb_nals = 0;
    while (length >= 4) {
        H2645NAL *nal;
        int extract_length = 0;
        int skip_trailing_zeros = 1;

        /*
         * Only parse an AVC1 length field if one is expected at the current
         * buffer position. There are unfortunately streams with multiple
         * NAL units covered by the length field. Those NAL units are delimited
         * by Annex B start code prefixes. ff_h2645_extract_rbsp() detects it
         * correctly and consumes only the first NAL unit. The additional NAL
         * units are handled here in the Annex B parsing code.
         */
        if (buf == next_avc) {
            int i;
            for (i = 0; i < nal_length_size; i++)
                extract_length = (extract_length << 8) | buf[i];

            if (extract_length > length) {
                av_log(logctx, AV_LOG_ERROR,
                       "Invalid NAL unit size (%d > %d).\n",
                       extract_length, length);
                return AVERROR_INVALIDDATA;
            }
            buf     += nal_length_size;
            length  -= nal_length_size;
            // keep track of the next AVC1 length field
            next_avc = buf + extract_length;
        } else {
            /*
             * expected to return immediately except for streams with mixed
             * NAL unit coding
             */
            int buf_index = find_next_start_code(buf, next_avc);

            buf    += buf_index;
            length -= buf_index;

            /*
             * break if an AVC1 length field is expected at the current buffer
             * position
             */
            if (buf == next_avc)
                continue;

            if (length > 0) {
                extract_length = length;
            } else if (pkt->nb_nals == 0) {
                av_log(logctx, AV_LOG_ERROR, "No NAL unit found\n");
                return AVERROR_INVALIDDATA;
            } else {
                break;
            }
        }

        if (pkt->nals_allocated < pkt->nb_nals + 1) {
            int new_size = pkt->nals_allocated + 1;
            H2645NAL *tmp = av_realloc_array(pkt->nals, new_size, sizeof(*tmp));
            if (!tmp)
                return AVERROR(ENOMEM);

            pkt->nals = tmp;
            memset(pkt->nals + pkt->nals_allocated, 0,
                   (new_size - pkt->nals_allocated) * sizeof(*tmp));
            pkt->nals_allocated = new_size;
        }
        nal = &pkt->nals[pkt->nb_nals++];

        consumed = ff_h2645_extract_rbsp(buf, extract_length, nal);
        if (consumed < 0)
            return consumed;

        /* see commit 3566042a0 */
        if (consumed < length - 3 &&
            buf[consumed]     == 0x00 && buf[consumed + 1] == 0x00 &&
            buf[consumed + 2] == 0x01 && buf[consumed + 3] == 0xE0)
            skip_trailing_zeros = 0;

        nal->size_bits = get_bit_length(nal, skip_trailing_zeros);

        ret = init_get_bits(&nal->gb, nal->data, nal->size_bits);
        if (ret < 0)
            return ret;

        if (codec_id == AV_CODEC_ID_HEVC)
            ret = hevc_parse_nal_header(nal, logctx);
        else
            ret = h264_parse_nal_header(nal, logctx);
        if (ret <= 0) {
            if (ret < 0) {
                av_log(logctx, AV_LOG_ERROR, "Invalid NAL unit %d, skipping.\n",
                       nal->type);
            }
            pkt->nb_nals--;
        }

        buf    += consumed;
        length -= consumed;
    }

    return 0;
}