相机预览编解码相关问题

1. 从onPreviewFrame获得的数据是YUV格式黑白的，如何转换为彩色？

private PreviewCallback mPreviewCallback = new PreviewCallback() {

        @Override
        public void onPreviewFrame(byte[] data, Camera camera) {
            if (MediaCodecManager.frame != null) {
                System.arraycopy(data, 0, MediaCodecManager.frame, 0, data.length);
            }
            mCamera.addCallbackBuffer(data);
        }
    };

在编码器里：

mediaCodec.setCallback(new MediaCodec.Callback() {

            @Override
            public void onInputBufferAvailable(MediaCodec codec, int index) {
                NV21toI420SemiPlanar(frame, mFrameData, mPreviewWidth, mPreviewHeight);
                ByteBuffer byteBuffer = codec.getInputBuffer(index);
                byteBuffer.put(mFrameData);
                codec.queueInputBuffer(index, 0, mFrameData.length, 1, BUFFER_FLAG_CODEC_CONFIG);
            }

            @Override
            public void onOutputBufferAvailable(MediaCodec codec, int index,
                    MediaCodec.BufferInfo info) {
                if (index > -1) {
                    ByteBuffer outputBuffer = codec.getOutputBuffer(index);
                    byte[] bb = new byte[info.size];
                    outputBuffer.get(bb);
                    try {
                        fileOutputStream.write(bb);
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                    try {
                        mOutputQueue.put(bb);
                    } catch (InterruptedException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                    codec.releaseOutputBuffer(index, false);
                }
            }

            @Override
            public void onError(MediaCodec codec, MediaCodec.CodecException e) {
                codec.reset();
            }

            @Override
            public void onOutputFormatChanged(MediaCodec codec, MediaFormat format) {
            }
        });

在调用queueInputBuffer给数据之前，调用了函数NV21toI420SemiPlanar进行了颜色转换，这样出来的就是彩色的：

protected void NV21toI420SemiPlanar(byte[] nv21bytes, byte[] i420bytes, int width, int height) {
        final int iSize = width * height;
        System.arraycopy(nv21bytes, 0, i420bytes, 0, iSize);

        for (int iIndex = 0; iIndex < iSize / 2; iIndex += 2) {
            i420bytes[iSize + iIndex / 2 + iSize / 4] = nv21bytes[iSize + iIndex]; // U
            i420bytes[iSize + iIndex / 2] = nv21bytes[iSize + iIndex + 1]; // V
        }
    }