Android预览相机返回不完整的数据数组

Question

I'm attempting to do some image processing on images returned by the Android preview camera via onPreviewFrame. This was working fine at sizes up to 1080 by 720, but I attempted to increase resolution to 1920 by 1080. The result is that I end up with incomplete data, and attempting to process every pixel gives an ArrayIndexOutOfBounds exception.

The data of a 1920 by 1080 image has 2073600 pixels, but it appears that the data[] returned by onPreviewFrame is always of size 1382400, regardless of image resolution.

params.setPreviewSize(1920, 1080);

mCamera.setPreviewCallback(new Camera.PreviewCallback() {
        public synchronized void onPreviewFrame(byte[] data, Camera camera) {
            changeMag = 0;
            thisDiff = 0;
            diffPixels = 0;
            try {
                if (currentImage != null) {
                    lastImage = currentImage;
                }
                Log.e("CameraTest", "Incoming data array size is only " + data.length);
}

This logs "Incoming data array size is only 1382400" no matter what preview size I select.

Given that 1920 by 1080 is supposedly a supported size, is there any way to get back that data via onPreviewFrame?

Answer 1

Apparently, 1920x1080 is not supported. If getSupportedPreviewSizes() list does include this resolution, this would not be the first time that a device report is incorrect. For example, Galaxy Nexus claims to support QVGA (320x240) preview, but it cannot deliver such image. setPreviewSize() + setParameters() continue correctly, and even getPreviewSize() reports the expected value. But the preview callback returns an image in size same as the size before setting this resolution.

So, I would expect that you really receive a 1280x720 picture, and can do nothing about it.

Note that it may still be possible to record 1920x1080 video on this device: video recorder may use a special mechanism which involves hardware encoder and often sends the camera data to this encoder without copying it to user space.