static int compat_decode(AVCodecContext *avctx, AVFrame *frame,
                         int *got_frame, const AVPacket *pkt)
{
    AVCodecInternal *avci = avctx->internal;
    int ret = 0;

    av_assert0(avci->compat_decode_consumed == 0);

    *got_frame = 0;
    avci->compat_decode = 1;

    if (avci->compat_decode_partial_size > 0 &&
        avci->compat_decode_partial_size != pkt->size) {
        av_log(avctx, AV_LOG_ERROR,
               "Got unexpected packet size after a partial decode\n");
        ret = AVERROR(EINVAL);
        goto finish;
    }

    if (!avci->compat_decode_partial_size) {
        ret = avcodec_send_packet(avctx, pkt);
        if (ret == AVERROR_EOF)
            ret = 0;
        else if (ret == AVERROR(EAGAIN)) {
            /* we fully drain all the output in each decode call, so this should not
             * ever happen */
            ret = AVERROR_BUG;
            goto finish;
        } else if (ret < 0)
            goto finish;
    }

    while (ret >= 0) {
        ret = avcodec_receive_frame(avctx, frame);
        if (ret < 0) {
            if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
                ret = 0;
            goto finish;
        }

        if (frame != avci->compat_decode_frame) {
            if (!avctx->refcounted_frames) {
                ret = unrefcount_frame(avci, frame);
                if (ret < 0)
                    goto finish;
            }

            *got_frame = 1;
            frame = avci->compat_decode_frame;
        } else {
            if (!avci->compat_decode_warned) {
                av_log(avctx, AV_LOG_WARNING, "The deprecated avcodec_decode_* "
                       "API cannot return all the frames for this decoder. "
                       "Some frames will be dropped. Update your code to the "
                       "new decoding API to fix this.\n");
                avci->compat_decode_warned = 1;
            }
        }

        if (avci->draining || (!avctx->codec->bsfs && avci->compat_decode_consumed < pkt->size))
            break;
    }

finish:
    if (ret == 0) {
        /* if there are any bsfs then assume full packet is always consumed */
        if (avctx->codec->bsfs)
            ret = pkt->size;
        else
            ret = FFMIN(avci->compat_decode_consumed, pkt->size);
    }
    avci->compat_decode_consumed = 0;
    avci->compat_decode_partial_size = (ret >= 0) ? pkt->size - ret : 0;

    return ret;
}