public void stop() throws Exception {
        if (oc != null) {
            try {
                synchronized (oc) {
                    /* flush all the buffers */
                    while (video_st != null && ifmt_ctx == null && recordImage(0, 0, 0, 0, 0, AV_PIX_FMT_NONE, (Buffer[])null));
                    while (audio_st != null && ifmt_ctx == null && recordSamples(0, 0, (Buffer[])null));

                    if (interleaved && video_st != null && audio_st != null) {
                        av_interleaved_write_frame(oc, null);
                    } else {
                        av_write_frame(oc, null);   <--- app crash here
                    }

                    /* write the trailer, if any */
                    av_write_trailer(oc);
                }
            } finally {
                release();
            }
        }
    }