Question

当我尝试在组件中的Web浏览器上播放视频时遇到问题，该文件根本无法播放。该文件是使用MediaRecorder和MediaProjection在Android设备上捕获的，并试图记录屏幕。这是我初始化MediaRecorder的代码：

public class ScreenRecordService extends Service {

private static final String TAG = ScreenRecordService.class.getSimpleName();

private static final SparseIntArray ORIENTATIONS = new SparseIntArray();
private static final int DISPLAY_WIDTH = 960;
private static final int DISPLAY_HEIGHT = 540;

private float mDensity;
private int mRotation;
private boolean mIsRecording;

private MediaProjectionManager mProjectionManager;
private MediaProjection mMediaProjection;
private VirtualDisplay mVirtualDisplay;
private MediaProjectionCallback mMediaProjectionCallback;
private MediaRecorder mMediaRecorder;
private String mFilePath;

static {
    ORIENTATIONS.append(Surface.ROTATION_0, 90);
    ORIENTATIONS.append(Surface.ROTATION_90, 0);
    ORIENTATIONS.append(Surface.ROTATION_180, 270);
    ORIENTATIONS.append(Surface.ROTATION_270, 180);
}

private class MediaProjectionCallback extends MediaProjection.Callback {
    @Override
    public void onStop() {
        try {
            if (mIsRecording) {
                mIsRecording = false;
                mMediaRecorder.stop();
                mMediaRecorder.reset();
            }
            mMediaProjection = null;
            stopScreenSharing();

            HermesEventBus.getDefault().post(new EventRecorder.Server(EventRecorder.SERVER_STOP_SUCCESS));
        } catch (Exception e) {
            e.printStackTrace();
            HermesEventBus.getDefault().post(new EventRecorder.Server(EventRecorder.SERVER_STOP_FAIL));
        }
    }
}

@Subscribe(threadMode = ThreadMode.MAIN)
public void onStopCall(EventRecorder.Client clientEvent) {
    if (clientEvent.messageType == EventRecorder.CLIENT_STOP_RECORD) {
        stopRecording();
    }
}

@Nullable
@Override
public IBinder onBind(Intent intent) {
    return null;
}

@Override
public void onCreate() {
    super.onCreate();
    HermesEventBus.getDefault().register(this);
    AppManager.getInstance().addService(this);
    mProjectionManager = (MediaProjectionManager) getSystemService(MEDIA_PROJECTION_SERVICE);
    mMediaProjectionCallback = new MediaProjectionCallback();
}

@Override
public int onStartCommand(Intent intent, int flags, int startId) {
    if (mProjectionManager == null) {
        mProjectionManager = (MediaProjectionManager) getSystemService(MEDIA_PROJECTION_SERVICE);
    }
    if (intent != null) {
        mDensity = intent.getFloatExtra("density", 0f);
        mRotation = intent.getIntExtra("rotation", 0);
        mFilePath = intent.getStringExtra(Const.Intent.INFO);
        JLog.d(TAG, mFilePath);

        startRecording(intent);
    }
    return START_NOT_STICKY;
}

@Override
public void onDestroy() {
    super.onDestroy();
    AppManager.getInstance().removeService(this);
}

private void startRecording(Intent intent) {
    try {
        if (!mIsRecording) {
            mMediaProjection = mProjectionManager.getMediaProjection(RESULT_OK, intent);
            mMediaProjection.registerCallback(mMediaProjectionCallback, null);
            initRecorder();
            mVirtualDisplay = createVirtualDisplay();
            mMediaRecorder.start();
            mIsRecording = true;

            HermesEventBus.getDefault().post(new EventRecorder.Server(EventRecorder.SERVER_START_SUCCESS));
        }
    } catch (Exception e) {
        e.printStackTrace();
        mIsRecording = false;
        HermesEventBus.getDefault().post(new EventRecorder.Server(EventRecorder.SERVER_START_FAIL));
    }
}

private void stopRecording() {
    try {
        if (mIsRecording) {
            mMediaRecorder.stop();
            mMediaRecorder.reset();
            stopScreenSharing();

            HermesEventBus.getDefault().post(new EventRecorder.Server(EventRecorder.SERVER_STOP_SUCCESS));
        }
    } catch (Exception e) {
        e.printStackTrace();
        mIsRecording = false;
        if (mMediaRecorder != null) {
            mMediaRecorder.reset();
        }
        stopScreenSharing();
        HermesEventBus.getDefault().post(new EventRecorder.Server(EventRecorder.SERVER_STOP_FAIL));
    }
}

private VirtualDisplay createVirtualDisplay() {
    return mMediaProjection.createVirtualDisplay(getString(R.string.video_record), DISPLAY_WIDTH, DISPLAY_HEIGHT, (int) mDensity,
            DisplayManager.VIRTUAL_DISPLAY_FLAG_AUTO_MIRROR, mMediaRecorder.getSurface(), null, null);
}

private void stopScreenSharing() {
    if (mVirtualDisplay == null) {
        return;
    }
    mVirtualDisplay.release();
    destroyMediaProjection();
    mIsRecording = false;
}

private void initRecorder() {
    int bitRateQuality = PrefsUtils.getInstance(this, Const.Pref.FILE_COMMON).getInt(Const.Pref.KEY_RECORD_BITRATE, Const.Setting.QUALITY_MID);
    int bitRate;
    if (bitRateQuality == Const.Setting.QUALITY_HIGH) {
        bitRate = 1536000;
    } else if (bitRateQuality == Const.Setting.QUALITY_MID) {
        bitRate = 1024 * 1024;
    } else {
        bitRate = 512000;
    }
    if (mMediaRecorder == null) {
        mMediaRecorder = new MediaRecorder();
    }
    try {
        mMediaRecorder.setVideoSource(MediaRecorder.VideoSource.SURFACE);
        mMediaRecorder.setOutputFormat(MediaRecorder.OutputFormat.MPEG_4); //THREE_GPP
        mMediaRecorder.setOutputFile(mFilePath);
        mMediaRecorder.setVideoSize(DISPLAY_WIDTH, DISPLAY_HEIGHT);
        mMediaRecorder.setVideoEncoder(MediaRecorder.VideoEncoder.H264);
        mMediaRecorder.setVideoFrameRate(8); // 30
        mMediaRecorder.setVideoEncodingBitRate(bitRate);
        int orientation = ORIENTATIONS.get(mRotation + 90);
        mMediaRecorder.setOrientationHint(orientation);
        mMediaRecorder.prepare();
        mMediaRecorder.setOnInfoListener((mr, what, extra) -> {
            if (what == MEDIA_RECORDER_INFO_MAX_FILESIZE_REACHED) {
                stopRecording();
            }
        });
    } catch (IOException e) {
        e.printStackTrace();
    }
}

private void destroyMediaProjection() {
    if (mMediaProjection != null) {
        mMediaProjection.unregisterCallback(mMediaProjectionCallback);
        mMediaProjection.stop();
        mMediaProjection = null;
    }
    JLog.i(TAG, "MediaProjection Stopped");
}

}

这是我上传的文件。

http://eachdoctorvideotest.oss-cn-shenzhen.aliyuncs.com/1103/videoRecord/input/ali_TVM1103vRecordIn20190212154904841.mp4

只需将URL粘贴到任何浏览器（我使用Chrome，Chrome无法播放，但是Safari可以播放），您会发现该文件无法播放。但是您可以在PC上的任何第三方媒体播放器上播放它。那么，该文件无法在浏览器中播放的确切问题是什么？

此视频文件最初是由两个文件（视频轨道和音频轨道）生成的。我使用mp4parser合并了曲目，您可能会在这里看到该库：

https://github.com/sannies/mp4parser

这是我用来组合它们的关键代码：

    public boolean muxAacMp4(String mp4Path, String aacPath, String outPath) {
    boolean flag = false;
    try {
        AACTrackImpl aacTrack = new AACTrackImpl(new FileDataSourceImpl(aacPath));
        Movie videoMovie = MovieCreator.build(mp4Path);
        Track videoTracks = null;
        for (Track videoMovieTrack : videoMovie.getTracks()) {
            if ("vide".equals(videoMovieTrack.getHandler())) {
                videoTracks = videoMovieTrack;
            }
        }

        Movie resultMovie = new Movie();
        resultMovie.addTrack(videoTracks);
        resultMovie.addTrack(aacTrack);

        Container out = new DefaultMp4Builder().build(resultMovie);
        FileOutputStream fos = new FileOutputStream(new File(outPath));
        out.writeContainer(fos.getChannel());
        fos.close();
        flag = true;
        Log.e("update_tag", "merge finish");
    } catch (Exception e) {
        e.printStackTrace();
        flag = false;
    }
    return flag;
}

Answer 1

如果在HTML5视频元素上放置'error'处理程序，则可以看到此文件产生以下错误（Chrome 71）：

Error 3; details: PIPELINE_ERROR_DECODE: Failed to send audio packet for decoding: timestamp=0 duration=32000 size=2 side_data_size=0 is_key_frame=1 encrypted=0 discard_padding (us)=(0, 0)

（仅供参考：在github here上讨论了类似的错误）。

2字节对于音频样本来说有点小。稍作挖掘就会发现，它实际上是您的音轨的“音频特定配置”的副本，这很奇怪，因为该信息已经存在于.mp4标头中。它正在复制到时间戳0的样本（第一个样本）中；我不确定为什么。

您可能想看看setAudioEncoder()的文档；您尚未调用它，并且文档状态为：

如果未调用此方法，则输出文件将不包含音轨。

但是，您的文件包含一个音轨。因此，这可能需要进一步调查。

编辑

鉴于对您的问题有了新的了解，看来最方便的解决方案是强行从AAC流中删除第一个样本。也可以使用您的“组合”代码来完成。我会像这样子化AACTrackImpl：

AACTrackImpl aacTrack = new AACTrackImpl(new FileDataSourceImpl(aacPath)) {
    boolean mAltered = false;
    @Override
    List<Sample> getSamples() {
        List<Samples> samples = super.getSamples();
        if(!mAltered)
        {
            samples.remove(0);
            mAltered=true;
        }
        return samples;
    }
};

我尚未测试此代码。确实是一个很糟糕的解决方案，它取决于许多假设。它利用了AAC轨道中的所有样本都具有相同的“持续时间”这一事实。否则，您也必须使用类似的技术来覆盖getSampleDurations()。

由于我们删除了一个采样但未更改时间戳，因此这会将您的所有音频偏移约23ms。在这种情况下，由于我们不完全知道为什么音频编码器首先会表现出这种行为，因此这可以解释为造成时序问题或解决问题。

从Android屏幕录像机捕获的视频无法在Web浏览器上播放

1 个答案: