android - 无法混合音频和视频

Question

我正在编写一个使用 MediaCodec 录制屏幕截图和音频的应用程序。我使用 MediaMuxer 来混合视频和音频以创建 mp4 文件。我成功地设法将视频和音频分开编写，但是当我尝试将它们实时混合在一起时，结果出乎意料。要么在没有视频的情况下播放音频，要么在音频之后播放视频。我的猜测是我在时间戳方面做错了，但我无法弄清楚到底是什么。我已经看过这些例子:https://github.com/OnlyInAmerica/HWEncoderExperiments/tree/audiotest/HWEncoderExperiments/src/main/java/net/openwatch/hwencoderexperiments以及 bigflake.com 上的那些，但无法找到答案。

这是我的媒体格式配置:

    mVideoFormat = createMediaFormat();

    private static MediaFormat createVideoFormat() {
    MediaFormat format = MediaFormat.createVideoFormat(
            Preferences.MIME_TYPE, mScreenWidth, mScreenHeight);
    format.setInteger(MediaFormat.KEY_COLOR_FORMAT,
            MediaCodecInfo.CodecCapabilities.COLOR_FormatSurface);
    format.setInteger(MediaFormat.KEY_BIT_RATE, Preferences.BIT_RATE);
    format.setInteger(MediaFormat.KEY_FRAME_RATE, Preferences.FRAME_RATE);
    format.setInteger(MediaFormat.KEY_I_FRAME_INTERVAL,
            Preferences.IFRAME_INTERVAL);
    return format;
}
    mAudioFormat = createAudioFormat();

    private static MediaFormat createAudioFormat() {
    MediaFormat format = new MediaFormat();
    format.setString(MediaFormat.KEY_MIME, "audio/mp4a-latm");
    format.setInteger(MediaFormat.KEY_AAC_PROFILE, MediaCodecInfo.CodecProfileLevel.AACObjectLC);
    format.setInteger(MediaFormat.KEY_SAMPLE_RATE, 44100);
    format.setInteger(MediaFormat.KEY_CHANNEL_COUNT, 1);
    format.setInteger(MediaFormat.KEY_BIT_RATE, 64000);
    return format;
}

音频和视频编码器、混合器:

      mVideoEncoder = MediaCodec.createEncoderByType(Preferences.MIME_TYPE);
    mVideoEncoder.configure(mVideoFormat, null, null,
            MediaCodec.CONFIGURE_FLAG_ENCODE);
    mInputSurface = new InputSurface(mVideoEncoder.createInputSurface(),
            mSavedEglContext);
    mVideoEncoder.start();
    if (recordAudio){
        audioBufferSize = AudioRecord.getMinBufferSize(44100, AudioFormat.CHANNEL_CONFIGURATION_MONO, 
        AudioFormat.ENCODING_PCM_16BIT);
        mAudioRecorder = new AudioRecord(MediaRecorder.AudioSource.MIC, 44100,
        AudioFormat.CHANNEL_CONFIGURATION_MONO, AudioFormat.ENCODING_PCM_16BIT, audioBufferSize);
        mAudioRecorder.startRecording();

        mAudioEncoder = MediaCodec.createEncoderByType("audio/mp4a-latm");
        mAudioEncoder.configure(mAudioFormat, null, null, MediaCodec.CONFIGURE_FLAG_ENCODE);
        mAudioEncoder.start();
    }
    try {
        String fileId = String.valueOf(System.currentTimeMillis());
        mMuxer = new MediaMuxer(dir.getPath() + "/Video"
                + fileId + ".mp4",
                MediaMuxer.OutputFormat.MUXER_OUTPUT_MPEG_4);
    } catch (IOException ioe) {
        throw new RuntimeException("MediaMuxer creation failed", ioe);
    }
    mVideoTrackIndex = -1;
    mAudioTrackIndex = -1;
    mMuxerStarted = false;

我用它来设置视频时间戳:

mInputSurface.setPresentationTime(mSurfaceTexture.getTimestamp());
drainVideoEncoder(false);

这是设置音频时间戳:

lastQueuedPresentationTimeStampUs = getNextQueuedPresentationTimeStampUs();

if(endOfStream)
    mAudioEncoder.queueInputBuffer(inputBufferIndex, 0, audioBuffer.length, lastQueuedPresentationTimeStampUs, MediaCodec.BUFFER_FLAG_END_OF_STREAM);
 else
     mAudioEncoder.queueInputBuffer(inputBufferIndex, 0, audioBuffer.length, lastQueuedPresentationTimeStampUs, 0);


  mAudioBufferInfo.presentationTimeUs = getNextDeQueuedPresentationTimeStampUs();
  mMuxer.writeSampleData(mAudioTrackIndex, encodedData,
                           mAudioBufferInfo);
  lastDequeuedPresentationTimeStampUs = mAudioBufferInfo.presentationTimeUs;


  private static long getNextQueuedPresentationTimeStampUs(){
    long nextQueuedPresentationTimeStampUs = (lastQueuedPresentationTimeStampUs > lastDequeuedPresentationTimeStampUs) 
            ? (lastQueuedPresentationTimeStampUs + 1) : (lastDequeuedPresentationTimeStampUs + 1);
    Log.i(TAG, "nextQueuedPresentationTimeStampUs: " + nextQueuedPresentationTimeStampUs);
    return nextQueuedPresentationTimeStampUs;
}


private static long getNextDeQueuedPresentationTimeStampUs(){
    Log.i(TAG, "nextDequeuedPresentationTimeStampUs: " + (lastDequeuedPresentationTimeStampUs + 1));
    lastDequeuedPresentationTimeStampUs ++;
    return lastDequeuedPresentationTimeStampUs;
}

我从这个例子中得到它 https://github.com/OnlyInAmerica/HWEncoderExperiments/blob/audiotest/HWEncoderExperiments/src/main/java/net/openwatch/hwencoderexperiments/AudioEncodingTest.java为了避免“timestampUs XXX < lastTimestampUs XXX”错误

有人可以帮我解决这个问题吗？

Answer 1

看起来您正在为视频使用系统提供的时间戳，但为音频使用一个简单的计数器。除非以某种方式使用视频时间戳为每一帧的音频播种，并且它只是没有在上面显示。

要使音频和视频同步播放，您需要在预计同时呈现的音频和视频帧上设置相同的呈现时间戳。

另见 related question .