I420ToNV21 YV12toNV21

YUV420P，Y，U，V三个分量都是平面格式，分为I420和YV12。在I420格式（即：YUV）；但YV12则是相反（即：YVU）。
YUV420SP, Y分量平面格式，UV打包格式, 即NV12。 NV12与NV21类似，U 和 V 交错排列,不同在于UV顺序。
I420: YYYYYYYY UU VV    =>YUV420P
YV12: YYYYYYYY VV UU    =>YUV420P
NV12: YYYYYYYY UVUV     =>YUV420SP
NV21: YYYYYYYY VUVU     =>YUV420SP

private void YV12toNV21(final byte[] input, final byte[] output, final int width, final int height) {
        long startMs = System.currentTimeMillis();
        final int frameSize = width * height;
        final int qFrameSize = frameSize / 4;
        final int tempFrameSize = frameSize * 5 / 4;
        
        System.arraycopy(input, 0, output, 0, frameSize); // Y
 
        for (int i = 0; i < qFrameSize; i++) {
            output[frameSize + i * 2] = input[frameSize + i]; // Cb (U)
            output[frameSize + i * 2 + 1] = input[tempFrameSize + i]; // Cr (V)
        }
    }
 

//I420 To NV21
    private void I420ToNV21(final byte[] input, final byte[] output, final int width, final int height) {
        //long startMs = System.currentTimeMillis();
        final int frameSize = width * height;
        final int qFrameSize = frameSize / 4;
        final int tempFrameSize = frameSize * 5 / 4;
        
        System.arraycopy(input, 0, output, 0, frameSize); // Y
 
        for (int i = 0; i < qFrameSize; i++) {
            output[frameSize + i * 2] = input[tempFrameSize + i]; // Cb (U)
            output[frameSize + i * 2 + 1] = input[frameSize + i]; // Cr (V)
        }
    }