Question

我正在开发一个使用mp4parser库（isoparser-1.0-RC-27.jar和aspectjrt-1.8.0.jar）合并mp4剪辑的应用程序。合并两个剪辑时，它们会成为一个剪辑，但随着更多剪辑被添加到其中，输出mp4会在视频后面显示音频。

以下是代码：

    Movie[] clips = new Movie[2];

    //location of the movie clip storage
    File mediaStorageDir = new File(Environment.getExternalStoragePublicDirectory(
            Environment.DIRECTORY_PICTURES), "TestMerge");

    //Build the two clips into movies
    Movie firstClip = MovieCreator.build(first);
    Movie secondClip = MovieCreator.build(second);

    //Add both movie clips
    clips[0] = firstClip;
    clips[1] = secondClip;

    //List for audio and video tracks
    List<Track> videoTracks = new LinkedList<Track>();
    List<Track> audioTracks = new LinkedList<Track>();

    //Iterate all the movie clips and find the audio and videos
    for (Movie movie: clips) {
        for (Track track : movie.getTracks()) {
            if (track.getHandler().equals("soun")) 
                audioTracks.add(track);                
            if (track.getHandler().equals("vide"))
                videoTracks.add(track);
        }
    }

    //Result movie from putting the audio and video together from the two clips
    Movie result = new Movie();

    //Append all audio and video
    if (videoTracks.size() > 0)
        result.addTrack(new AppendTrack(videoTracks.toArray(new Track[videoTracks.size()])));

    if (audioTracks.size() > 0) 
        result.addTrack(new AppendTrack(audioTracks.toArray(new Track[audioTracks.size()])));

    //Output the resulting movie to a new mp4 file
    String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss").format(new Date());
    String outputLocation = mediaStorageDir.getPath()+timeStamp;
    Container out = new DefaultMp4Builder().build(result);
    FileChannel fc = new RandomAccessFile(String.format(outputLocation), "rw").getChannel();
    out.writeContainer(fc);
    fc.close();

    //Now set the active URL to play as the combined videos!
    setURL(outputLocation);
}

我的猜测是，随着更多剪辑被添加，视频与音频的同步正在混乱，因为如果合并两个更长的剪辑，那么音频/视频就可以了。反正是为了防止多个较小的剪辑中的视频和音频的这种差的同步，还是有人找到了使用mp4parser这样做的解决方案？ FFMpeg是我正在考虑的另一个解决方案，但没有找到其他人使用它来做到这一点

编辑：我发现音频通常比视频长，因此，当添加越来越多的剪辑来创建一个剪辑时，这就是导致最终结果视频偏移的原因。我将通过切断音频样本来解决问题

Answer 1

将代码放到卢卡斯的答案上面：

1

LinkedList<Track> videoTracks = new LinkedList<>();
            LinkedList<Track> audioTracks = new LinkedList<>();
            double[] audioDuration = {0}, videoDuration = {0};
            for (Movie m : clips) {
                for (Track t : m.getTracks()) {
                    if (t.getHandler().equals("soun")) {
                        for (long a : t.getSampleDurations()) audioDuration[0] += ((double) a) / t.getTrackMetaData().getTimescale();
                        audioTracks.add(t);
                    } else if (t.getHandler().equals("vide")) {
                        for (long v : t.getSampleDurations()) videoDuration[0] += ((double) v) / t.getTrackMetaData().getTimescale();
                        videoTracks.add(t);
                    }
                }

                adjustDurations(videoTracks, audioTracks, videoDuration, audioDuration);
            }

2

private void adjustDurations(LinkedList<Track> videoTracks, LinkedList<Track> audioTracks, double[] videoDuration, double[] audioDuration) {
    double diff = audioDuration[0] - videoDuration[0];

    //nothing to do
    if (diff == 0) {
        return;
    }

    //audio is longer
    LinkedList<Track> tracks = audioTracks;

    //video is longer
    if (diff < 0) {
        tracks = videoTracks;
        diff *= -1;
    }

    Track track = tracks.getLast();
    long[] sampleDurations = track.getSampleDurations();
    long counter = 0;
    for (int i = sampleDurations.length - 1; i > -1; i--) {
        if (((double) (sampleDurations[i]) / track.getTrackMetaData().getTimescale()) > diff) {
            break;
        }
        diff -= ((double) (sampleDurations[i]) / track.getTrackMetaData().getTimescale());
        audioDuration[0] -= ((double) (sampleDurations[i]) / track.getTrackMetaData().getTimescale());
        counter++;
    }

    if (counter == 0) {
        return;
    }

    track = new CroppedTrack(track, 0, track.getSamples().size() - counter);

    //update the original reference
    tracks.removeLast();
    tracks.addLast(track);
}

Answer 2

通过使用上述编辑技术，我能够解决这个问题。诀窍是跟踪合并多少个剪辑，并从添加的最新剪辑的音轨末尾删除样本。随着产生的输出mp4随着更多剪辑而增长，你需要越来越多地去掉。这部分是由于音频和视频轨道的时序差异，因为音频轨道可能是1020ms而视频是1000ms，添加了5个剪辑，然后音频与视频长度的偏移量约为100ms。你必须弥补这一点。

将mp4剪辑与mp4parser合并可使视频背后的音频

2 个答案: