int avcodec_close(AVCodecContext *avctx)
{
    /* If there is a user-supplied mutex locking routine, call it. */
    if (ff_lockmgr_cb) {
        if ((*ff_lockmgr_cb)(&codec_mutex, AV_LOCK_OBTAIN))
            return -1;
    }

    entangled_thread_counter++;
    if(entangled_thread_counter != 1){
        av_log(avctx, AV_LOG_ERROR, "insufficient thread locking around avcodec_open/close()\n");
        entangled_thread_counter--;
        return -1;
    }

    if (avcodec_is_open(avctx)) {
        if (avctx->internal->frame_thread_encoder && avctx->thread_count > 1) {
            entangled_thread_counter --;
            ff_frame_thread_encoder_free(avctx);
            entangled_thread_counter ++;
        }
        if (HAVE_THREADS && avctx->thread_opaque)
            ff_thread_free(avctx);
        if (avctx->codec && avctx->codec->close)
            avctx->codec->close(avctx);
        avcodec_default_free_buffers(avctx);
        avctx->coded_frame = NULL;
        avctx->internal->byte_buffer_size = 0;
        av_freep(&avctx->internal->byte_buffer);
        av_freep(&avctx->internal);
    }

    if (avctx->priv_data && avctx->codec && avctx->codec->priv_class)
        av_opt_free(avctx->priv_data);
    av_opt_free(avctx);
    av_freep(&avctx->priv_data);
    if (av_codec_is_encoder(avctx->codec))
        av_freep(&avctx->extradata);
    avctx->codec = NULL;
    avctx->active_thread_type = 0;
    entangled_thread_counter--;

    /* Release any user-supplied mutex. */
    if (ff_lockmgr_cb) {
        (*ff_lockmgr_cb)(&codec_mutex, AV_LOCK_RELEASE);
    }
    return 0;
}