音视频

Android Media 实战二：音视频的录制(二)

Posted by alonealice on 2020-11-01

预览

在页面中添加SurfaceView，同时添加SurfaceHolder.Callback：

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mSurfaceView = (SurfaceView) findViewById(R.id.surface_view);
mSurfaceHolder = mSurfaceView.getHolder();
mSurfaceHolder.addCallback(mSurfaceCallback);

在SurfaceHolder.Callback中的surfaceCreated方法中初始化相机，并开始预览：

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mSurfaceCallback = new SurfaceHolder.Callback() {
    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        boolean suc = true;
        if (mCamera == null) {
            suc = initCamera();
        }
        if (suc) {
            startPreview();
        }
    }


    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {

    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {

    }
};
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private boolean initCamera() {
    int num = Camera.getNumberOfCameras();
    if (num <= 0) {
        return false;
    }
    boolean open = true;
    try {
        mCamera = Camera.open(0);
        mCamera.setPreviewCallback(mPreviewCallback);
        mParameters = mCamera.getParameters();
        mParameters.setRotation(90);
        mParameters.setPreviewFormat(ImageFormat.NV21); // 设置NV21预览格式
        List<Camera.Size> list = mCamera.getParameters().getSupportedPreviewSizes();
        if (list != null && !list.isEmpty()) {
            Camera.Size size = getClosestSupportedSize(list, 720, 1080);
            mParameters.setPreviewSize(size.width, size.height);//预览带下
            mCamera.setParameters(mParameters);
            mCamera.setDisplayOrientation(90);//预览方向
            return true;
        }
    } catch (Exception e) {

    }
    return false;
}

相机开启预览：

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mCamera.setPreviewDisplay(mSurfaceHolder);
mCamera.startPreview();//开始预览

视频数据保存

在相机初始化中添加PreviewCallback，每次预览画面更新时会回调onPreviewFrame方法：

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mPreviewCallback = (bytes, camera) -> {
    if (mIsRecording) {
        Frame frame = new Frame();
        frame.mData = bytes;
        frame.mTime = System.nanoTime() / 1000;
        if (frame.mTime - mPreviewImgTime > 1000 * 1000) {
            mPreviewImgTime = frame.mTime;
        }
        //将预览的nv21数据传递给编码器
        mVideoEncoder.addFrame(bytes);
    }
};
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private void startRecord() {
    mMuxer = new MMuxer(getSaveVideoPath());
    mVideoEncoder = new VideoEncoder2(mMuxer);
    mVideoEncoder.prepare();
    mVideoEncoder.start();
    mIsRecording = true;
}

将onPreviewFrame回调的data，传到VideoEncoder进行编码保存。

VideoEncoder

VideoEncoder的prepare方法会初始化MediaCodecInfo和MediaFormat，同时设置相应的帧率码率，并创建MediaCodec。

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public void prepare() {
    MediaCodecInfo codecInfo = selectCodec(MIME_TYPE);
    if (codecInfo == null) {
        return;
    }
    mColorFormat = MediaCodecInfo.CodecCapabilities.COLOR_FormatYUV420SemiPlanar;//NV12数据格式
    checkColorFormat(codecInfo, MIME_TYPE);
    Log.i(TAG, "colorformat=" + mColorFormat);
    MediaFormat mediaFormat = MediaFormat.createVideoFormat(MIME_TYPE, 720, 1080);
    mediaFormat.setInteger(MediaFormat.KEY_BIT_RATE, BIT_RATE);
    mediaFormat.setInteger(MediaFormat.KEY_FRAME_RATE, FRAME_RATE);
    mediaFormat.setInteger(MediaFormat.KEY_COLOR_FORMAT, mColorFormat);
    try {
        mMediaCodec = MediaCodec.createByCodecName(codecInfo.getName());
    } catch (Exception e) {
        Log.i(TAG, e + "");
    }
    try {
        if (!mIsAllKeyFrame) {
            mediaFormat.setInteger(MediaFormat.KEY_I_FRAME_INTERVAL, 1);  //单位是 秒
        } else {
            mediaFormat.setInteger(MediaFormat.KEY_I_FRAME_INTERVAL, 0);//设置为0
        }
        mMediaCodec.configure(mediaFormat, null, null, MediaCodec.CONFIGURE_FLAG_ENCODE);
        Log.i(TAG, "success configure-----------");
    } catch (Exception e) {
        Log.v(TAG, "config failed " + e);
        try {
            mediaFormat.setInteger(MediaFormat.KEY_I_FRAME_INTERVAL, 1);  //单位是 秒
            mMediaCodec.configure(mediaFormat, null, null, MediaCodec.CONFIGURE_FLAG_ENCODE);
            Log.i(TAG, "config second success");
        } catch (Exception e1) {
            Log.i(TAG, "config second failed " + e1);
        }
    }

    try {
        mMediaCodec.start();
    } catch (Exception e) {
        Log.i(TAG, "start error--" + e);
    }
    mTrackIndex = -1;
}

videoEncoder实现runnable接口。在start方法中会启动线程：

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public void start() {
    mIsRecording = true;
    new Thread(this).start();
}

在run方法中，会从帧队列中取出一帧输入，同时会间隔一段时间进行循环。

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public void run() {
    int count = 0;
    //轮询线程
    while (true) {
        count++;
        if (mFrameList.size() > 0) {
            Frame frame = mFrameList.remove(0);
            input(frame);
        }
        try {
            Thread.sleep(mLoopInterval);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        if (!mIsRecording) {
            break;
        }
    }
}

addFrame主要是想队列中添加帧数据

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public void addFrame(byte[] data) {
    Frame frame = new Frame();
    frame.mTime = System.nanoTime() / 1000;
    frame.mData = data;
    mFrameList.add(frame);
}

input方法一个是将数据进行转化，同时向MediaCodec的inputBuffers添加数据，然后会调用output方法

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private void input(Frame frame) {
    ByteBuffer[] inputBuffers = mMediaCodec.getInputBuffers();
    int inputBufferIndex = mMediaCodec.dequeueInputBuffer(TIMEOUT_USEC);
    byte[] dst = null;
    if (frame.mData != null) {
        dst = new byte[frame.mData.length];
        //nv21转nv12
        NV21toI420SemiPlanar(frame.mData, dst, 720, 1080);
    }
    if (inputBufferIndex >= 0) {
        ByteBuffer inputBuffer = inputBuffers[inputBufferIndex];
        inputBuffer.clear();
        if (dst != null) {
            inputBuffer.put(dst);
            mMediaCodec.queueInputBuffer(inputBufferIndex, 0, dst.length, frame.mTime, 0);
            output(false);
        } else {
            mMediaCodec.queueInputBuffer(inputBufferIndex, 0, 0, frame.mTime, MediaCodec.BUFFER_FLAG_END_OF_STREAM);
            output(true);
        }
    }
}

output方法主要是向MMuxer添加轨道，同时从MediaCodec获取数据并写入到MMuxer，而MMuxer跟音视频的录制（一）中相同。

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public void output(boolean isEos) {
        String tag = TAG + "-output";
        ByteBuffer[] outputBuffers = null;
        int count = 0;
        int outputIndex = mMediaCodec.dequeueOutputBuffer(mBufferInfo, TIMEOUT_USEC);
        try {
            outputBuffers = mMediaCodec.getOutputBuffers();
            do {
                if (outputIndex == MediaCodec.INFO_TRY_AGAIN_LATER) {
                    Log.i(tag, "output from encoder not available");
                    if (!isEos) {
                        count++;
                        if (count >= 10) {
//                            break;
                        }
                    }
                } else if (outputIndex == MediaCodec.INFO_OUTPUT_BUFFERS_CHANGED) {
                    outputBuffers = mMediaCodec.getOutputBuffers();
                    Log.i(tag, "encoder output buffers changed");
                } else if (outputIndex == MediaCodec.INFO_OUTPUT_FORMAT_CHANGED) {
                    //加入视频轨道编码模式
                    addTrack();
                    Log.i(tag, "encoder output format change");
                } else if (outputIndex < 0) {
                    Log.e(tag, "output buffer wrong " + outputIndex);
                } else {
                    ByteBuffer outputBuffer = outputBuffers[outputIndex];
                    if (outputBuffer == null) {
                        Log.e(tag, "output buffer null");
                        return;
                    }
                    if ((mBufferInfo.flags & MediaCodec.BUFFER_FLAG_CODEC_CONFIG) != 0) {
                        mBufferInfo.size = 0;
                    }
                    Log.d(tag, "buffer size=" + mBufferInfo.size + " pts=" + mBufferInfo.presentationTimeUs);
                    if (mBufferInfo.size != 0) {
                        if (!mMuxer.isVideoTrackAdd()) {
                            addTrack();
                        }
                        if (!mMuxer.isStarted()) {
                            mMuxer.start();
                        }
                        outputBuffer.position(mBufferInfo.offset);
                        outputBuffer.limit(mBufferInfo.offset + mBufferInfo.size);
                        //编码后的数据输出到混合器
                        mMuxer.writeSampleData(mTrackIndex, outputBuffer, mBufferInfo);
                    }
                    mMediaCodec.releaseOutputBuffer(outputIndex, false);
                    if ((mBufferInfo.flags & MediaCodec.BUFFER_FLAG_END_OF_STREAM) != 0) {
                        // when EOS come.
                        mIsRecording = false;
                        stopMuxer();
                        release();
                        break;      // out of while
                    }
                }
                outputIndex = mMediaCodec.dequeueOutputBuffer(mBufferInfo, TIMEOUT_USEC);

            } while (outputIndex >= 0);
        } catch (Exception e) {
        }

    }



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音视频