Can not work in thread pool?

[jiamo]

I got JVM assert (just crash). When I do use such sample code in thread pool.

public static SizeDuration get_duration(String fileName){
    // return duration, size
    SizeDuration errorLongs = new SizeDuration();
    try{
        final Demuxer demuxer = Demuxer.make();
        demuxer.open(fileName, null, false, true, null, null);

        errorLongs.duration = demuxer.getDuration() / 1000 ;
        errorLongs.size = demuxer.getFileSize();
    }catch (Exception e){
        e.printStackTrace();
        System.out.println(e);
    }
    return errorLongs;
}

When I move such code in main thread. All things done.