while (av_read_frame(pFormatCtx, packet) >= 0){
    EnterCriticalSection(&cs) ;
    if (packet->stream_index == videoindex){
        ret = avcodec_decode_video2(pCodecCtx, pFrame, &got_picture, packet);
        if (ret < 0){
            printf("Decode Error.\n");
            return -1;
        }
        if (got_picture){

            pFrame->pts = av_frame_get_best_effort_timestamp(pFrame);

            if (filter_change)
                apply_filters(pFormatCtx);
            filter_change = 0;
            /* push the decoded frame into the filtergraph */
            if (av_buffersrc_add_frame(buffersrc_ctx, pFrame) < 0) {
                printf("Error while feeding the filtergraph\n");
                break;
            }
            picref = av_frame_alloc();

            while (1) {
                ret = av_buffersink_get_frame_flags(buffersink_ctx, picref, 0);
                if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
                    break;
                if (ret < 0)
                    return ret;

                if (picref) {
                    img_convert_ctx = sws_getContext(picref->width, picref->height, (AVPixelFormat)picref->format, pCodecCtx->width, pCodecCtx->hei