订阅了您的专栏，问题：获取到NV21格式的frame后如何转成byte[]数组。

public static void readVideo2Bitmap(String uri) throws IOException, InterruptedException {
        FFmpegFrameGrabber grabber = FFmpegFrameGrabber.createDefault(uri);
        grabber.setImageWidth(1280);
        grabber.setImageHeight(720);
        grabber.setPixelFormat(avutil.AV_PIX_FMT_NV21); // 设置像素格式
        grabber.start();
        saveAsNV21(grabber); // 调用下列函数
        grabber.stop();
        grabber.close();
    }

private static void saveAsNV21(FFmpegFrameGrabber grabber) throws IOException, InterruptedException {
        while (Constant.readVideo2BitmapFlag) {
            Frame frame = grabber.grab();
            
            // 这里怎么将frame转换成byte[]数组？

            if (RtspActivity.rgbCameraHelper != null) {
                RtspActivity.rgbCameraHelper.onPreviewFrame(nv21);
            }
            Log.i("djtest", "saveAsBitmaps: nv21长度=" + nv21.length);

            Thread.sleep(40);
        }
    }

            Frame frame = ff.grabFrame();
            AndroidFrameConverter androidFrameConverter = new AndroidFrameConverter();
            Bitmap bitmap = androidFrameConverter.convert(frame);
            ByteArrayOutputStream stream = new ByteArrayOutputStream();
            bitmap.compress(Bitmap.CompressFormat.JPEG, 100, stream);
            byte[] imageInByte = stream.toByteArray();

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