static int decode_frame(AVCodecContext *avctx, void *data,
                        int *got_frame, AVPacket *avpkt)
{
    const uint8_t *buf = avpkt->data;
    int buf_size       = avpkt->size;
    H264Context *h     = avctx->priv_data;
    AVFrame *pict      = data;
    int buf_index      = 0;
    Picture *out;
    int i, out_idx;
    int ret;

    h->flags = avctx->flags;

    /* end of stream, output what is still in the buffers */
    if (buf_size == 0) {
 out:

        h->cur_pic_ptr = NULL;
        h->first_field = 0;

        // FIXME factorize this with the output code below
        out     = h->delayed_pic[0];
        out_idx = 0;
        for (i = 1;
             h->delayed_pic[i] &&
             !h->delayed_pic[i]->f.key_frame &&
             !h->delayed_pic[i]->mmco_reset;
             i++)
            if (h->delayed_pic[i]->poc < out->poc) {
                out     = h->delayed_pic[i];
                out_idx = i;
            }

        for (i = out_idx; h->delayed_pic[i]; i++)
            h->delayed_pic[i] = h->delayed_pic[i + 1];

        if (out) {
            out->reference &= ~DELAYED_PIC_REF;
            ret = output_frame(h, pict, out);
            if (ret < 0)
                return ret;
            *got_frame = 1;
        }

        return buf_index;
    }
    if(h->is_avc && buf_size >= 9 && buf[0]==1 && buf[2]==0 && (buf[4]&0xFC)==0xFC && (buf[5]&0x1F) && buf[8]==0x67){
        int cnt= buf[5]&0x1f;
        const uint8_t *p= buf+6;
        while(cnt--){
            int nalsize= AV_RB16(p) + 2;
            if(nalsize > buf_size - (p-buf) || p[2]!=0x67)
                goto not_extra;
            p += nalsize;
        }
        cnt = *(p++);
        if(!cnt)
            goto not_extra;
        while(cnt--){
            int nalsize= AV_RB16(p) + 2;
            if(nalsize > buf_size - (p-buf) || p[2]!=0x68)
                goto not_extra;
            p += nalsize;
        }

        return ff_h264_decode_extradata(h, buf, buf_size);
    }
not_extra:

    buf_index = decode_nal_units(h, buf, buf_size, 0);
    if (buf_index < 0)
        return AVERROR_INVALIDDATA;

    if (!h->cur_pic_ptr && h->nal_unit_type == NAL_END_SEQUENCE) {
        av_assert0(buf_index <= buf_size);
        goto out;
    }

    if (!(avctx->flags2 & CODEC_FLAG2_CHUNKS) && !h->cur_pic_ptr) {
        if (avctx->skip_frame >= AVDISCARD_NONREF ||
            buf_size >= 4 && !memcmp("Q264", buf, 4))
            return buf_size;
        av_log(avctx, AV_LOG_ERROR, "no frame!\n");
        return AVERROR_INVALIDDATA;
    }

    if (!(avctx->flags2 & CODEC_FLAG2_CHUNKS) ||
        (h->mb_y >= h->mb_height && h->mb_height)) {
        if (avctx->flags2 & CODEC_FLAG2_CHUNKS)
            decode_postinit(h, 1);

        field_end(h, 0);

        /* Wait for second field. */
        *got_frame = 0;
        if (h->next_output_pic && (h->next_output_pic->sync || h->sync>1)) {
            ret = output_frame(h, pict, h->next_output_pic);
            if (ret < 0)
                return ret;
            *got_frame = 1;
            if (CONFIG_MPEGVIDEO) {
                ff_print_debug_info2(h->avctx, h->next_output_pic, pict, h->er.mbskip_table,
                                    &h->low_delay,
                                    h->mb_width, h->mb_height, h->mb_stride, 1);
            }
        }
    }

    assert(pict->data[0] || !*got_frame);

    return get_consumed_bytes(buf_index, buf_size);
}