MediaMuxer有时会导致黑色视频

Question

我正在使用AndroidEncoder生成带有AAC音频的H264视频，该视频既可以通过RTMP网络发送，也可以使用MediaMuxer本地存储在MP4文件中。

广播在RTMP上运行良好，但是在本地保存时，生成的视频有时还可以，有时只是带有声音的黑色帧（或者只是带有某些信息块的第一个部分帧），有时首先播放音频，然后播放视频随机FPS速度。

这是我的Muxer包装器类和MPEG4Writer SDK类显示的输出：

02-28 11:57:38.521 6420-6475/com.myapp.broadcast W/AndroidMuxer: addTrack: Requested adding of track to class AndroidMuxer of type AUDIO
02-28 11:57:38.522 6420-6475/com.myapp.broadcast W/AndroidMuxer: addTrack: Adding track for audio/mp4a-latm
02-28 11:57:38.522 6420-6475/com.myapp.broadcast W/AndroidMuxer: addTrack: Track index to class AndroidMuxer of type AUDIO, track saved for future use!
02-28 11:57:38.621 6420-6470/com.myapp.broadcast W/AndroidMuxer: addTrack: Requested adding of track to class AndroidMuxer of type VIDEO
02-28 11:57:38.621 6420-6470/com.myapp.broadcast W/AndroidMuxer: addTrack: Adding track for video/avc
02-28 11:57:38.621 6420-6470/com.myapp.broadcast W/AndroidMuxer: addTrack: All tracks added, marking Local muxer as ready!
02-28 11:57:38.622 6420-6470/com.myapp.broadcast W/AndroidMuxer: addTrack: Track index to class AndroidMuxer of type VIDEO, track saved for future use!
02-28 11:57:52.050 6420-6420/com.myapp.broadcast I/AndroidMuxer: init: Added audio track widh id 0
02-28 11:57:52.050 6420-6420/com.myapp.broadcast I/AndroidMuxer: init: Added video track widh id 1
02-28 11:57:52.050 6420-6420/com.myapp.broadcast W/AndroidMuxer: init: Muxer was successfully created! Starting to record
02-28 11:57:52.056 6420-6420/com.myapp.broadcast I/MPEG4Writer: limits: 4294967295/0 bytes/us, bit rate: -1 bps and the estimated moov size 3195 bytes
02-28 11:57:52.057 6420-6420/com.myapp.broadcast W/AndroidMuxer: start: Muxer started!
02-28 11:57:52.070 6420-6965/com.myapp.broadcast I/MPEG4Writer: setStartTimestampUs: 0
02-28 11:57:52.070 6420-6965/com.myapp.broadcast I/MPEG4Writer: Earliest track starting time: 0
02-28 11:57:52.083 6420-6966/com.myapp.broadcast I/MPEG4Writer: setStartTimestampUs: 0
02-28 11:58:02.617 6420-6475/com.myapp.broadcast W/AndroidMuxer: writeSampleData: All tracks finished! Calling Stop
02-28 11:58:02.617 6420-6475/com.myapp.broadcast W/AndroidMuxer: stop: Calling stop to the muxer
02-28 11:58:02.617 6420-6475/com.myapp.broadcast D/MPEG4Writer: Audio track stopping
02-28 11:58:02.617 6420-6475/com.myapp.broadcast D/MPEG4Writer: Audio track source stopping
02-28 11:58:02.617 6420-6475/com.myapp.broadcast D/MPEG4Writer: Audio track source stopped
02-28 11:58:02.617 6420-6965/com.myapp.broadcast I/MPEG4Writer: Received total/0-length (452/0) buffers and encoded 452 frames. - Audio
02-28 11:58:02.617 6420-6965/com.myapp.broadcast I/MPEG4Writer: Audio track drift time: 0 us
02-28 11:58:02.617 6420-6475/com.myapp.broadcast D/MPEG4Writer: Audio track stopped
02-28 11:58:02.618 6420-6475/com.myapp.broadcast D/MPEG4Writer: Video track stopping
02-28 11:58:02.618 6420-6475/com.myapp.broadcast D/MPEG4Writer: Video track source stopping
02-28 11:58:02.618 6420-6475/com.myapp.broadcast D/MPEG4Writer: Video track source stopped
02-28 11:58:02.618 6420-6966/com.myapp.broadcast I/MPEG4Writer: Received total/0-length (315/0) buffers and encoded 315 frames. - Video
02-28 11:58:02.618 6420-6475/com.myapp.broadcast D/MPEG4Writer: Video track stopped
02-28 11:58:02.618 6420-6475/com.myapp.broadcast D/MPEG4Writer: Duration from tracks range is [10143021, 10495420] us
02-28 11:58:02.618 6420-6475/com.myapp.broadcast D/MPEG4Writer: Stopping writer thread
02-28 11:58:02.620 6420-6964/com.myapp.broadcast D/MPEG4Writer: 0 chunks are written in the last batch
02-28 11:58:02.620 6420-6475/com.myapp.broadcast D/MPEG4Writer: Writer thread stopped
02-28 11:58:02.621 6420-6475/com.myapp.broadcast I/MPEG4Writer: The mp4 file will not be streamable.
02-28 11:58:02.621 6420-6475/com.myapp.broadcast W/AndroidMuxer: stop: muxer stopped!

并不是说虽然本地保存的视频不好，但相同素材的实时流（来自相同的编码过程）还是可以的，所以问题必须出在混音器本身（或更准确地说，是我处理它的方式） ）。

这是我的Muxer包装器（受bigflake的mediacodec示例启发）：

import android.media.MediaCodec;
import android.media.MediaFormat;
import android.media.MediaMuxer;
import android.util.Log;

import java.io.IOException;
import java.nio.ByteBuffer;

/**
 * @hide
 */
public class AndroidMuxer extends Muxer {
    private static final String TAG = "AndroidMuxer";
    private static final boolean VERBOSE = false;

    private MediaMuxer mMuxer;
    private boolean mStarted = false;
    private boolean mStopped = false;
    private boolean mReadyToStart;
    private MediaFormat mVideoTrackFormat;
    private MediaFormat mAudioTrackFormat;

    private long mStartTimeUs = 0;
    @Override
    public void reset() {
        Log.w(TAG, "reset: Reset is called on LOCAL MUXER!");

            mStarted = false;
            mReadyToStart = false;
            mNumTracks = 0;
            mNumTracksFinished = 0;
            Log.w(TAG, "reset: Reset worked on the Muxer");

    }

    /**
     * This will only initialize the fields, we only want the real muxer to be initialized
     * when we go live.
     * @param outputFile outputPath of the file
     * @param format Format of the muxer (will always be MPEG4 TBH)
     */
    public AndroidMuxer(String outputFile, FORMAT format) {
        super(outputFile, format);
        mStarted = false;
    }

    @Override
    public void init() {
        if(!mReadyToStart) {
            return;
        }

        if(mStarted){
            Log.i(TAG, "init: Muxer already created! Skipping!");
            return;
        }


        try {
            switch (mFormat) {
                case MPEG4:
                    mMuxer = new MediaMuxer(mOutputPath, MediaMuxer.OutputFormat.MUXER_OUTPUT_MPEG_4);
                    int audioTrack = mMuxer.addTrack(mAudioTrackFormat);
                    Log.i(TAG, "init: Added audio track widh id " + audioTrack);
                    mAudioTrackIndex = audioTrack;

                    int videoTrack = mMuxer.addTrack(mVideoTrackFormat);
                    Log.i(TAG, "init: Added video track widh id " + videoTrack);
                    mVideoTrackIndex = videoTrack;
                    Log.w(TAG, "init: Muxer was successfully created! Starting to record");
                    start();
                    break;
                default:
                    throw new IllegalArgumentException("Unrecognized format!");
            }
        } catch (IOException e) {
            throw new RuntimeException("MediaMuxer creation failed", e);
        }
    }

    public static AndroidMuxer create(String outputFile, FORMAT format) {
        return new AndroidMuxer(outputFile, format);
    }

    @Override
    public int addTrack(MediaFormat trackFormat, AndroidEncoder.TrackType trackType) {
        Log.w(TAG, "addTrack: Requested adding of track to class " + getClass().getSimpleName() + " of type " + trackType);
        //Super method just keeps track of amount of tracks added
        super.addTrack(trackFormat, trackType);
        Log.w(TAG, "addTrack: Adding track for " + trackFormat.getString(MediaFormat.KEY_MIME));
        if (mStarted)
            throw new RuntimeException("format changed twice");

        //What we do is store the media info for later use once the muxer is created.
        //This is done to prevent file creation until the event goes live.

        if(trackType == AndroidEncoder.TrackType.VIDEO){
            mVideoTrackFormat = trackFormat;
        }
        else if(trackType == AndroidEncoder.TrackType.AUDIO){
            mAudioTrackFormat = trackFormat;
        }



        if (allTracksAdded()) {
            Log.w(TAG, "addTrack: All tracks added, marking Local muxer as ready!");
            markReadyToStart();
        }
        Log.w(TAG, "addTrack: Track index to class " + getClass().getSimpleName() + " of type " + trackType + ", track saved for future use!");
        //Return dummy
        return 1;
    }


    /**
     *
     * Marking the Muxer as ready to be started but not yet!
     *
     */
    private void markReadyToStart() {
        mReadyToStart = true;
    }



    private void start() {
        if(mStarted){
            Log.i(TAG, "start: Skipped start due to muxer already started");
        }
        mStartTimeUs = 0;
        mMuxer.start();
        Log.w(TAG, "start: Muxer started!");
        mStarted = true;
    }

    protected void stop() {
        if(mStarted) {
            Log.w(TAG, "stop: Calling stop to the muxer");
            mMuxer.stop();
            Log.w(TAG, "stop: muxer stopped!");
            mStarted = false;
            mStopped = true;
            mReadyToStart = false;
        }
    }

    @Override
    public void release() {
        super.release();
        if(mStopped) {
            mMuxer.release();
            mStopped = false;
            mStarted = false;
        }
    }

    @Override
    public boolean isStarted() {
        return mStarted;
    }

    @Override
    public void writeSampleData(MediaCodec encoder, int trackIndex, int bufferIndex, ByteBuffer encodedData, MediaCodec.BufferInfo bufferInfo) {
        if(!mStarted) {

            return;
        }

        super.writeSampleData(encoder, trackIndex, bufferIndex, encodedData, bufferInfo);
        if ((bufferInfo.flags & MediaCodec.BUFFER_FLAG_CODEC_CONFIG) != 0) {
            // MediaMuxer gets the codec config info via the addTrack command
            if (VERBOSE) Log.d(TAG, "ignoring BUFFER_FLAG_CODEC_CONFIG");
            return;
        }

        if (bufferInfo.size == 0) {
            if (VERBOSE) Log.d(TAG, "ignoring zero size buffer");
            return;
        }

        if (!mStarted) {
            Log.w(TAG, "writeSampleData called before muxer started. Ignoring packet. Track index: " + trackIndex + " tracks added: " + mNumTracks);
//            encoder.releaseOutputBuffer(bufferIndex, false);
            return;
        }

//        bufferInfo.presentationTimeUs = getNextRelativePts(bufferInfo.presentationTimeUs, trackIndex);


       if(mStartTimeUs == 0) {
              mStartTimeUs = bufferInfo.presentationTimeUs;
             }
        bufferInfo.presentationTimeUs -= mStartTimeUs;
        if(bufferInfo.presentationTimeUs < 0) {
             bufferInfo.presentationTimeUs = 0;
        }
        bufferInfo.presentationTimeUs = getSafePts(bufferInfo.presentationTimeUs, trackIndex);


        mMuxer.writeSampleData(trackIndex, encodedData, bufferInfo);

//        encoder.releaseOutputBuffer(bufferIndex, false);

        if (allTracksFinished()) {
            Log.w(TAG, "writeSampleData: All tracks finished! Calling Stop");
            stop();
        }
    }

    @Override
    public void forceStop() {
        Log.w(TAG, "forceStop: ForceStop called!");
        stop();
    }
}

请注意，RTMP多路复用器和本地多路复用器可能无法同时启动，这就是为什么我存储媒体信息，然后仅在用户请求启动多路复用器时才使用它的原因。

Answer 1

如果本地多路复用器尚未准备好并且您跳过写入数据包，则可以跳过写入关键帧。 不是关键帧的后来的视频帧只有在到达下一个关键帧之前才能被解码（谁知道如果文件以非关键帧开头，视频播放器是否会感到困惑？）。 如果关键帧之间的间隔很长，则可能在合理的时间内根本无法获得关键帧。 （不过，如果您也通过RTMP进行流式处理，则可能会定期创建关键帧。）

我的建议是确保存储在本地多路复用器就绪之前产生的所有数据包，并在就绪后将它们写入本地多路复用器，或者继续跳过数据包，直到到达下一个关键帧为止。