Android USB camera 录视频笔记

https://github.com/saki4510t/UVCCamera

Web usb camera 开源项目
java 流程分析

以USB test8为例   MainActivity
    case R.id.capture_button  --> mCameraHandler.startRecording() --> thread.handleStartRecording();-->
handleStartRecording()...

AbstractUVCCameraHandler.java
public void handleStartRecording() {
            if (DEBUG) Log.v(TAG_THREAD, "handleStartRecording:");
            try {
                if ((mUVCCamera == null) || (mMuxer != null)) return;
                final MediaMuxerWrapper muxer = new MediaMuxerWrapper(".mp4");  // if you record audio only, ".m4a" is also OK.
                MediaVideoBufferEncoder videoEncoder = null;
                Log.e(TAG, "chaolong handleStartRecording: mEncoderType = " + mEncoderType);
                switch (mEncoderType) { //mEncoder = 1
                case 1: // for video capturing using MediaVideoEncoder
                    new MediaVideoEncoder(muxer, getWidth(), getHeight(), mMediaEncoderListener);
                    break;
                case 2: // for video capturing using MediaVideoBufferEncoder
                    videoEncoder = new MediaVideoBufferEncoder(muxer, getWidth(), getHeight(), mMediaEncoderListener);
                    break;
                // case 0:  // for video capturing using MediaSurfaceEncoder
                default:
                    new MediaSurfaceEncoder(muxer, getWidth(), getHeight(), mMediaEncoderListener);
                    break;
                }
                muxer.prepare();
                muxer.startRecording(); 开始存储
                           ....
}
存储方式在 MainActivity 初始化时，指定了1；
mCameraHandler = UVCCameraHandler.createHandler(this, mUVCCameraView,
            USE_SURFACE_ENCODER ? 0 : 1, PREVIEW_WIDTH, PREVIEW_HEIGHT, PREVIEW_MODE);





所以继续分析 new MediaVideoEncoder(muxer, getWidth(), getHeight(), mMediaEncoderListener);

MediaEncoder 回调函数,在MediaVideoEncoder 构造函数传到基类中

AbstractUVCCameraHandler.java
private final MediaEncoder.MediaEncoderListener mMediaEncoderListener = new MediaEncoder.MediaEncoderListener() {
            @Override
            public void onPrepared(final MediaEncoder encoder) {
                if (DEBUG) Log.v(TAG, "onPrepared:encoder=" + encoder);
                mIsRecording = true;
                if (encoder instanceof MediaVideoEncoder)
                try {
                    mWeakCameraView.get().setVideoEncoder((MediaVideoEncoder)encoder);
                } catch (final Exception e) {
                    Log.e(TAG, "onPrepared:", e);
                }
                if (encoder instanceof MediaSurfaceEncoder)
                try {
                    mWeakCameraView.get().setVideoEncoder((MediaSurfaceEncoder)encoder);
                    mUVCCamera.startCapture(((MediaSurfaceEncoder)encoder).getInputSurface());
                } catch (final Exception e) {
                    Log.e(TAG, "onPrepared:", e);
                }
            }

            @Override
            public void onStopped(final MediaEncoder encoder) { 
//                  。。。音频略过
            通过打印log 查看 ，这里只实例化了MediaVideoEncoder
}


public MediaVideoEncoder(final MediaMuxerWrapper muxer, final int width, final int height, final MediaEncoderListener listener) {
        super(muxer, listener); 
        if (DEBUG) Log.i(TAG, "MediaVideoEncoder: ");
        mRenderHandler = RenderHandler.createHandler(TAG);
        mWidth = width;
        mHeight = height;
    }

super(muxer, listener);  将接口赋值到MediaEncoder 

muxer.startRecording(); 开始存储

MediaMuxerWrapper.java 
private MediaEncoder mVideoEncoder, mAudioEncoder;
    public void startRecording() {
        if (mVideoEncoder != null)
            mVideoEncoder.startRecording();
        if (mAudioEncoder != null)
            mAudioEncoder.startRecording();
    }

mVideoEncoder在哪里赋值呢？
void addEncoder(final MediaEncoder encoder) {
        if (encoder instanceof MediaVideoEncoder) {
            if (mVideoEncoder != null)
                throw new IllegalArgumentException("Video encoder already added.");
            mVideoEncoder = encoder;
                         ...
}
addEncode 会传送MediaEncoder基类对象到MediaMuxerWrapper里面
在哪传的呢?
在MediaEncoder 构造函数里面，
 public MediaEncoder(final MediaMuxerWrapper muxer, final MediaEncoderListener listener) {
                ...
        muxer.addEncoder(this);
                ....

存储最终会调用到  MediaEncoder.java
void startRecording() {
    if (DEBUG) Log.v(TAG, "startRecording");
        synchronized (mSync) {
            mIsCapturing = true;
            mRequestStop = false;
            mSync.notifyAll();
        }
    }
为什么这里会有mSync.notifyAll();
因为MediaEncoder构造函数  构造完时会等待
public MediaEncoder(final MediaMuxerWrapper muxer, final MediaEncoderListener listener) {
              ....
        synchronized (mSync) {
            try {
                mSync.wait();  //等待
            } catch (final InterruptedException e) {
            }
              ......
}

@Override
    public void run() {
//      android.os.Process.setThreadPriority(android.os.Process.THREAD_PRIORITY_URGENT_AUDIO);
        synchronized (mSync) {
            mRequestStop = false;
            mRequestDrain = 0;
            mSync.notify();
        }
        final boolean isRunning = true;
        boolean localRequestStop;
        boolean localRequestDrain;
        while (isRunning) {
            synchronized (mSync) {
                localRequestStop = mRequestStop;
                localRequestDrain = (mRequestDrain > 0);
                if (localRequestDrain)
                    mRequestDrain--;
            }
            if (localRequestStop) {
                drain();
                // request stop recording
                signalEndOfInputStream();
                // process output data again for EOS signale
                drain();
                // release all related objects
                release();
                break;
            }
          ..........

signalEndOfInputStream();会保存
protected void encode(final byte[] buffer, final int length, final long presentationTimeUs) {
        //if (DEBUG) Log.v(TAG, "encode:buffer=" + buffer);
        if (!mIsCapturing) return;
        int ix = 0, sz;
        final ByteBuffer[] inputBuffers = mMediaCodec.getInputBuffers();
        while (mIsCapturing && ix < length) {
            final int inputBufferIndex = mMediaCodec.dequeueInputBuffer(TIMEOUT_USEC);
            if (inputBufferIndex >= 0) {
                final ByteBuffer inputBuffer = inputBuffers[inputBufferIndex];
                inputBuffer.clear();
                sz = inputBuffer.remaining();
                sz = (ix + sz < length) ? sz : length - ix;
                if (sz > 0 && (buffer != null)) {
                    inputBuffer.put(buffer, ix, sz);
                }
                ix += sz;
//              if (DEBUG) Log.v(TAG, "encode:queueInputBuffer");
                if (length <= 0) {
                    .....
}