Develop Reference

ImageReader.OnImageAvailableListener() not being called when taking a picture

I have a Camera App developed for Android 26 SDK. I have been using it happily with a Motorola G5 and G6 but when I move to a Motorola G7 the app crashes when I press the button to take a picture in my app.
The G7 is running Android 9. I have another Android 9 phone a Samsung S10 plus. The S10 plus does not crash when I press the button for taking a picture.
While debugging I noticed that the G7 doesn't call ImageReader.OnImageAvailableListener while the S10 does. Looking at the code this is where the image is saved for use later on in CameraCaptureSession.CaptureCallback. The callback expects bytes to be populated and crashes when it isn't (I haven't included the stack trace because it's not a little unhelpful but I can if you think you would like to see it).
I can get the G7 to save the image if I run it slowly through debug on 'some' occasions.
So I have a button that calls the function onImageCaptureClick() inside it does a bunch of stuff but one of the things it does is create an ImageReader.OnImageAvailableListener. The OnImageAvailableListener saves the image and populates a variable bytes from the image buffer. This onImageAvailableListener is attached to my reader by using reader.setOnImageAvailableListener(readerListener, null), and this listener is never used. When I get in to the CaptureCallBack the class variable bytes is not populated and the app crashes.
Do you have any idea where I would look to solve this?
protected void onImageCaptureClick() {
if (null == mCameraDevice) {
logger.debug("null == mCameraDevice");
Log.e(TAG, "cameraDevice is null");
return;
}
CameraManager manager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);
try {
CameraCharacteristics characteristics = manager.getCameraCharacteristics(mCameraDevice.getId());
Size[] jpegSizes = null;
if (characteristics != null) {
jpegSizes = characteristics.get(CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP).getOutputSizes(ImageFormat.JPEG);
}
int width = 640;
int height = 480;
if (jpegSizes != null && 0 < jpegSizes.length) {
width = jpegSizes[0].getWidth();
height = jpegSizes[0].getHeight();
}
ImageReader reader = ImageReader.newInstance(width, height, ImageFormat.JPEG, 1);
List < Surface > outputSurfaces = new ArrayList < > (2);
outputSurfaces.add(reader.getSurface());
outputSurfaces.add(new Surface(mTextureView.getSurfaceTexture()));
final CaptureRequest.Builder captureBuilder = mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_STILL_CAPTURE);
captureBuilder.addTarget(reader.getSurface());
if (mFlashMode == FLASH_MODE_OFF) {
captureBuilder.set(CaptureRequest.FLASH_MODE, CaptureRequest.FLASH_MODE_OFF);
logger.debug("FLASH OFF");
}
if (mFlashMode == CONTROL_AE_MODE_ON) {
captureBuilder.set(CaptureRequest.CONTROL_AE_MODE,
CaptureRequest.CONTROL_AE_MODE_ON);
captureBuilder.set(CaptureRequest.FLASH_MODE,
CaptureRequest.FLASH_MODE_TORCH);
logger.debug("FLASH ON");
}
if (mFlashMode == CONTROL_AE_MODE_ON_AUTO_FLASH) {
captureBuilder.set(CaptureRequest.CONTROL_AE_MODE, CaptureRequest.CONTROL_AE_MODE_ON_AUTO_FLASH);
captureBuilder.set(CaptureRequest.FLASH_MODE,
CaptureRequest.FLASH_MODE_OFF);
logger.debug("FLASH AUTO");
}
captureBuilder.set(CaptureRequest.SCALER_CROP_REGION, zoom);
int rotation = getWindowManager().getDefaultDisplay().getRotation();
captureBuilder.set(CaptureRequest.JPEG_ORIENTATION, ORIENTATIONS.get(rotation));
final File file = new File(_pictureUri.getPath());
logger.debug("OnImageCaptureClick: _pictureUri is: " + _pictureUri.getPath());
// ************************************
// this listener is not used on the G7,
// and so the image isn't saved.
// ************************************
ImageReader.OnImageAvailableListener readerListener = new ImageReader.OnImageAvailableListener() {
#Override
public void onImageAvailable(ImageReader reader) {
Image image = null;
try {
image = reader.acquireLatestImage();
ByteBuffer buffer = image.getPlanes()[0].getBuffer();
bytes = new byte[buffer.capacity()];
buffer.get(bytes);
logger.debug("onImageCaptureClick, the filesize to save is: " + bytes.toString());
save();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (image != null) {
image.close();
}
}
}
private void save() throws IOException {
OutputStream output = null;
try {
output = new FileOutputStream(file);
output.write(bytes);
} finally {
if (null != output) {
output.close();
}
}
}
};
// ********************************************************
// the reader sets the listener here but it is never called
// and when I get in to the CaptureCallback the BitmapUtils
// expects bytes to be populated and crashes the app
// ********************************************************
reader.setOnImageAvailableListener(readerListener, null);
final CameraCaptureSession.CaptureCallback captureListener = new CameraCaptureSession.CaptureCallback() {
#Override
public void onCaptureCompleted(#NonNull CameraCaptureSession session, #NonNull CaptureRequest request, #NonNull TotalCaptureResult result) {
super.onCaptureCompleted(session, request, result);
try {
BitmapUtils.addTimeStampAndRotate(_pictureUri, bytes);
Intent intent = new Intent(CameraActivity.this, CameraReviewPhotoActivity.class);
intent.putExtra(MediaStore.EXTRA_OUTPUT, _pictureUri);
startActivityForResult(intent, CameraActivity.kRequest_Code_Approve_Image);
} catch (IOException e) {
e.printStackTrace();
} catch (ImageReadException e) {
e.printStackTrace();
} catch (ImageWriteException e) {
e.printStackTrace();
}
}
};
mCameraDevice.createCaptureSession(outputSurfaces, new CameraCaptureSession.StateCallback() {
#Override
public void onConfigured(CameraCaptureSession session) {
try {
session.capture(captureBuilder.build(), captureListener, null);
} catch (CameraAccessException e) {
e.printStackTrace();
}
}
#Override
public void onConfigureFailed(CameraCaptureSession session) {
Log.w(TAG, "Failed to configure camera");
}
}, null);
} catch (CameraAccessException e) {
e.printStackTrace();
} finally {
takePictureButton.setEnabled(false);
mTextureView.setEnabled(false);
}

The API makes no guarantee about the order of onCaptureCompleted and OnImageAvailableListener. They may arrive in arbitrary order, depending on the device, capture settings, the load on the device, or even the particular OS build you have.
Please don't make any assumptions about it.
Instead, if you need both callbacks to fire before you process something, then wait for both to happen before you move forward. For example, check if the other callback has fired in each callback, and if so, call the method to do the processing.

I think I have found the solution to this.
I have the following phones:
Samsung S10 Plus
Motorola G7
Motorola G6
My app works on the S10 and the G6.
The S10 and G6 both call the OnImageAvailableListener function before the onCaptureCompleted callback. The G7 however calls them both the other way around onCaptureCompleted then OnImageAvailableListener.
According to https://proandroiddev.com/understanding-camera2-api-from-callbacks-part-1-5d348de65950 the correct way is onCaptureCompleted then OnImageAvailableListener.
In my code I am assuming that OnImageAvailableListener has saved the image and then OnCaptureCompleted tries to manipulate it, which causes the crash.
Looking at the INFO_SUPPORTED_HARDWARE_LEVEL of each device I have the following levels of support from none level 0 to uber level 3.
Samsung S10 Plus reports device level support level 1
Motorola G7 reports device level support level 3
Motorola G6 reports device level support level 2
My assumption at this point is that the events fire in a different order when you support the android-camera2 API at Level 3 compared to other levels.
Hope this helps

Android Camera2, take picture continuously

I need to take pictures continuously with Camera2 API. It works fine on high end devices (for instance a Nexus 5X), but on slower ones (for instance a Samsung Galaxy A3), the preview freezes.
The code is a bit long, so I post only the most relevant parts:
Method called to start my preview:
private void startPreview() {
SurfaceTexture texture = mTextureView.getSurfaceTexture();
if(texture != null) {
try {
// We configure the size of default buffer to be the size of camera preview we want.
texture.setDefaultBufferSize(mPreviewSize.getWidth(), mPreviewSize.getHeight());
// This is the output Surface we need to start preview.
Surface surface = new Surface(texture);
// We set up a CaptureRequest.Builder with the output Surface.
mPreviewRequestBuilder = mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
mPreviewRequestBuilder.addTarget(surface);
// Here, we create a CameraCaptureSession for camera preview.
mCameraDevice.createCaptureSession(Arrays.asList(surface, mImageReader.getSurface()), new CameraCaptureSession.StateCallback() {
#Override
public void onConfigured(#NonNull CameraCaptureSession cameraCaptureSession) {
// If the camera is already closed, return:
if (mCameraDevice == null) { return; }
// When the session is ready, we start displaying the preview.
mCaptureSession = cameraCaptureSession;
// Auto focus should be continuous for camera preview.
mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AF_MODE, CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);
mPreviewRequest = mPreviewRequestBuilder.build();
// Start the preview
try { mCaptureSession.setRepeatingRequest(mPreviewRequest, null, mPreviewBackgroundHandler); }
catch (CameraAccessException e) { e.printStackTrace(); }
}
#Override
public void onConfigureFailed(#NonNull CameraCaptureSession cameraCaptureSession) {
Log.e(TAG, "Configure failed");
}
}, null
);
}
catch (CameraAccessException e) { e.printStackTrace(); }
}
}
Method called to take a picture:
private void takePicture() {
try {
CaptureRequest.Builder captureBuilder = mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_STILL_CAPTURE);
captureBuilder.addTarget(mImageReader.getSurface());
mCaptureSession.capture(captureBuilder.build(), null, mCaptureBackgroundHandler);
}
catch (CameraAccessException e) { e.printStackTrace(); }
}
And here is my ImageReader:
private final ImageReader.OnImageAvailableListener mOnImageAvailableListener = new ImageReader.OnImageAvailableListener() {
#Override
public void onImageAvailable(final ImageReader reader) {
mSaveBackgroundHandler.post(new Runnable() {
#Override
public void run() {
// Set the destination file:
File destination = new File(getExternalFilesDir(null), "image_" + mNumberOfImages + ".jpg");
mNumberOfImages++;
// Acquire the latest image:
Image image = reader.acquireLatestImage();
// Save the image:
ByteBuffer buffer = image.getPlanes()[0].getBuffer();
byte[] bytes = new byte[buffer.remaining()];
buffer.get(bytes);
FileOutputStream output = null;
try {
output = new FileOutputStream(destination);
output.write(bytes);
}
catch (IOException e) { e.printStackTrace(); }
finally {
image.close();
if (null != output) {
try { output.close(); }
catch (IOException e) { e.printStackTrace(); }
}
}
// Take a new picture if needed:
if(mIsTakingPictures) {
takePicture();
}
}
});
}
};
I have a button that toggle the mIsTakingPictures boolean, and makes the first takePicture call.
To recap, I'm using 3 threads:
one for the preview
one for the capture
one for the image saving
What can be the cause of this freeze?

It's impossible to avoid framing lost in your preview when you are taking images all time on weak devices. The only way to avoid this is on devices which support TEMPLATE_ZERO_SHUTTER_LAG and using a reprocessableCaptureSession. The documentation about this is pretty horrible and find a way to implement it can be a odyssey. I have this problem a few months ago and finally I found the way to implement it:
How to use a reprocessCaptureRequest with camera2 API
In that answer you can also find some Google CTS test's which also implements ReprocessableCaptureSession and shoot some burst captures with ZSL template.
Finally, you can also use a CaptureBuilder with your preview surface and the image reader surface attached, in that case your preview will continue working all time and also you will save each frame as a new picture. But you will still having the freeze problem.
I also tried implement a burst capture using a handler which dispatch a new capture call each 100 milliseconds, this second option was pretty good in performance and avoiding frame rate lost, but you will not get as many captures per second like the two ImageReader option.
Hope that my answer will help you a bit, API 2 still being a bit complex and there's not so many examples or information about it.

One thing I noticed on low end devices: the preview stops after a capture, even when using camera 1 api, so it has to be restarted manually, thus producing a small preview freeze when capturing a high resolution picture.
But the camera 2 api provides the possibility to get raw image when taking a still capture (that wasn't possible on the devices I have when using camera 1 (Huawei P7, Sony Xperia E5, wiko UFeel)). Using this feature is much faster than capturing a JPEG (maybe due to JPEG compression), so the preview can be restarted earlier, and the preview freeze is shorter. Of course using this solution you'll have to convert the picture from YUV to JPEG in a background task..

Affdex Android SDK - Save and use CameraDetector

Mostly I want to know if there is a fundamental conflict that I can't share the same resource with the library, if so, I will need to take a different approach.
My goal is to have low quality video with the detector's meta data saved at the same time, so that I can do some post processing and slicing without much of a delay.
Based on the CameraDetectorDemo - camera detector
I have been initializing a MediaRecorder, but it saves a black screen if I start it before the detector, and it crashes on start (with code -19) if I start it after the detector. The detector is attaching the preview, maybe it is to do with that.
I added some buttons to control these functions:
protected void cameraInit() {
String state = Environment.getExternalStorageState();
if (!Environment.MEDIA_MOUNTED.equals(state)) {
Log.d(LOG_TAG, "Drive not mounted - cannot write video");
return;
}
File file = new File(getExternalFilesDir(Environment.DIRECTORY_MOVIES), "demo.gp3");
Log.d(LOG_TAG, String.format("Camera Initializing. Setting output to: %s", file.getAbsolutePath()));
// Set sources
recorder.setAudioSource(MediaRecorder.AudioSource.MIC);
recorder.setVideoSource(MediaRecorder.VideoSource.CAMERA);
// Set profile
recorder.setProfile(CamcorderProfile.get(CamcorderProfile.QUALITY_LOW));
// Set output profile
recorder.setOutputFile(file.getAbsolutePath());
// Set preview output
recorder.setPreviewDisplay(cameraPreview.getHolder().getSurface());
try {
this.recorder.prepare();
} catch (IOException e) {
Log.e(LOG_TAG, "IO exception on camera Initialization");
e.printStackTrace();
} catch (IllegalStateException e) {
// This is thrown if the previous calls are not called with the
// proper order
Log.e(LOG_TAG, "Failed to initialize things properly :( ");
e.printStackTrace();
}
}
protected void cameraStart() {
Log.d(LOG_TAG, "Camera Start");
this.recorder.start();
}
protected void cameraStop() {
Log.d(LOG_TAG, "Camera Stop");
this.recorder.stop();
}

The Affdex SDK's CameraDetector needs access to the camera to get its preview frames and process them, so that's not going to work if the MediaRecorder has control of the camera.
Probably your best bet is to take preview frames from the camera, feed them to an Affdex FrameDetector for processing, and also save them to a video file via a MediaCodec and MediaMuxer, although I haven't tried that.

HandlerThread blocks UI android

I am working on a modification of Google's Camera2 API example for Android, found here: https://github.com/googlesamples/android-Camera2Basic
I am uploading captured images to Cloudinary, and obviously need to do so in a background thread so the UI isn't blocked.
The problem I'm running into, however, is that the UI actually is blocked when the image is uploaded even though from what I understand, it shouldn't be, because the Handler is created with the Looper from a background thread like so:
private void startBackgroundThread() {
mBackgroundThread = new HandlerThread("CameraBackground");
mBackgroundThread.start();
mBackgroundHandler = new Handler(mBackgroundThread.getLooper());
}
The ImageSaver class, which is responsible for writing the captured image to disk, is as follows:
private static class ImageSaver implements Runnable {
/**
* The JPEG image
*/
private final Image mImage;
/**
* The file we save the image into.
*/
private final File mFile;
public ImageSaver(Image image, File file ) {
mImage = image;
mFile = file;
}
#Override
public void run() {
ByteBuffer buffer = mImage.getPlanes()[0].getBuffer();
byte[] bytes = new byte[buffer.remaining()];
buffer.get(bytes);
FileOutputStream output = null;
try {
output = new FileOutputStream(mFile);
output.write(bytes);
InputStream is = new ByteArrayInputStream(bytes);
Map uploadResult = CloudinaryManager.getInstance().uploader().upload(is, ObjectUtils.asMap(
"api_key", CloudinaryManager.CLOUDINARY_API_KEY,
"api_secret", CloudinaryManager.CLOUDINARY_SECRET_KEY
));
System.out.println("result");
} catch (IOException e) {
e.printStackTrace();
} finally {
mImage.close();
if (null != output) {
try {
output.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
The ImageSaver is added to the Handler here:
private final ImageReader.OnImageAvailableListener mOnImageAvailableListener
= new ImageReader.OnImageAvailableListener() {
#Override
public void onImageAvailable(ImageReader reader) {
mBackgroundHandler.post(new ImageSaver(reader.acquireNextImage(), mFile));
}
};
I would appreciate any help or advice to point me in the right direction.

I believe it's because there is a lock in the background being used by the camera ... Since you acquiring an Image from the ImageReader, I suspect, it is holding a lock until you are done with the resource ... So as a suggestion, I would fill up the byte array inside the onImageAvailable, close the image you acquired, and send the byte array to the AsyncTask to execute saving

I had the same issue and after some investigation and testing, discovered it is not actually freezing the UI, it is freezing the camera preview which on many camera apps give the same impression.
If you take a look at the method unLockFocus() you can see that it sets the camera back to the normal state of preview.
Looking at the point at which this is called you can see it is not until the image has been saved:
.
.
.
CameraCaptureSession.CaptureCallback CaptureCallback
= new CameraCaptureSession.CaptureCallback() {
#Override
public void onCaptureCompleted(#NonNull CameraCaptureSession session,
#NonNull CaptureRequest request,
#NonNull TotalCaptureResult result) {
showToast("Saved: " + mFile);
Log.d(TAG, mFile.toString());
unlockFocus();
}
};
By calling this at an earlier point in the camera save sequence the preview is enabled and the UI appears unlocked again much earlier.
I have experimented and it appears to work if it is called just after acquiring the image and before saving it - I also removed the original call to unLockFocus in the captureCallback. Note that I have not done any proper testing of race conditions etc so I would strongly advise experimenting yourself to make sure your case works (I will update this if I do verify it more):
/**
* This a callback object for the {#link ImageReader}. "onImageAvailable" will be called when a
* still image is ready to be saved.
*/
private final ImageReader.OnImageAvailableListener mOnImageAvailableListener
= new ImageReader.OnImageAvailableListener() {
#Override
public void onImageAvailable(ImageReader reader) {
Log.d(TAG,"onImageAvailable");
//Get the image
Image cameraImage = reader.acquireNextImage();
//Now unlock the focus so the UI does not look locked - note that this is a much earlier point than in the
//original Camera2Basic example from google as the original place was causing the preview to lock during any
//image manipulation and saving.
unlockFocus();
//Save the image file in the background - note check you have permissions granted by user or this will cause an exception.
mBackgroundHandler.post(new ImageSaver(getActivity().getApplicationContext(), cameraImage, outputPicFile);
}
};

How to get each frame data using camera2 API in Android5.0 in realtime

I am working with camera2Basic now and trying to get each frame data to do some image processing. I am using camera2 API in Android5.0, everything is fine when only doing the camera preview and it is fluid. But the preview stuck when I use the ImageReader.OnImageAvailableListener callback to get each frame data, this cause a bad User Experience.
The following is my related codes:
This is the setup for camera and ImageReader, I set the format of image is YUV_420_888
public<T> Size setUpCameraOutputs(CameraManager cameraManager,Class<T> kClass, int width, int height) {
boolean flagSuccess = true;
try {
for (String cameraId : cameraManager.getCameraIdList()) {
CameraCharacteristics characteristics = cameraManager.getCameraCharacteristics(cameraId);
// choose the front or back camera
if (FLAG_CAMERA.BACK_CAMERA == mChosenCamera &&
CameraCharacteristics.LENS_FACING_BACK != characteristics.get(CameraCharacteristics.LENS_FACING)) {
continue;
}
if (FLAG_CAMERA.FRONT_CAMERA == mChosenCamera &&
CameraCharacteristics.LENS_FACING_FRONT != characteristics.get(CameraCharacteristics.LENS_FACING)) {
continue;
}
StreamConfigurationMap map = characteristics.get(
CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP);
Size largestSize = Collections.max(
Arrays.asList(map.getOutputSizes(ImageFormat.YUV_420_888)),
new CompareSizesByArea());
mImageReader = ImageReader.newInstance(largestSize.getWidth(), largestSize.getHeight(),
ImageFormat.YUV_420_888, 3);
mImageReader.setOnImageAvailableListener(mOnImageAvailableListener, mBackgroundHandler);
...
mCameraId = cameraId;
}
} catch (CameraAccessException e) {
e.printStackTrace();
} catch (NullPointerException e) {
}
......
}
When the camera opened successfully, I Create a CameraCaptureSession for camera preview
private void createCameraPreviewSession() {
if (null == mTexture) {
return;
}
// We configure the size of default buffer to be the size of camera preview we want.
mTexture.setDefaultBufferSize(mPreviewSize.getWidth(), mPreviewSize.getHeight());
// This is the output Surface we need to start preview
Surface surface = new Surface(mTexture);
// We set up a CaptureRequest.Builder with the output Surface.
try {
mPreviewRequestBuilder =
mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
mPreviewRequestBuilder.addTarget(mImageReader.getSurface());
mPreviewRequestBuilder.addTarget(surface);
// We create a CameraCaptureSession for camera preview
mCameraDevice.createCaptureSession(Arrays.asList(surface, mImageReader.getSurface()),
new CameraCaptureSession.StateCallback() {
#Override
public void onConfigured(CameraCaptureSession session) {
if (null == mCameraDevice) {
return;
}
// when the session is ready, we start displaying the preview
mCaptureSession = session;
// Finally, we start displaying the camera preview
mPreviewRequest = mPreviewRequestBuilder.build();
try {
mCaptureSession.setRepeatingRequest(mPreviewRequest,
mCaptureCallback, mBackgroundHandler);
} catch (CameraAccessException e) {
e.printStackTrace();
}
}
#Override
public void onConfigureFailed(CameraCaptureSession session) {
}
}, null);
} catch (CameraAccessException e) {
e.printStackTrace();
}
}
The last is the ImageReader.OnImageAvailableListener callback
private final ImageReader.OnImageAvailableListener mOnImageAvailableListener = new ImageReader.OnImageAvailableListener() {
#Override
public void onImageAvailable(ImageReader reader) {
Log.d(TAG, "The onImageAvailable thread id: " + Thread.currentThread().getId());
Image readImage = reader.acquireLatestImage();
readImage.close();
}
};
Maybe I do the wrong setup but I try several times and it doesn't work. Maybe there is another way to get frame data rather than ImageReader but I don't know.
Anybody knows how to get each frame data in realtime?

I do not believe that Chen is correct. The image format has almost 0 effect on the speed on the devices I have tested. Instead, the problem seems to be with the image size. On an Xperia Z3 Compact with the image format YUV_420_888, I am offered a bunch of different options in the StreamConfigurationMap's getOutputSizes method:
[1600x1200, 1280x720, 960x720, 720x480, 640x480, 480x320, 320x240, 176x144]
For these respective sizes, the maximum fps I get when setting mImageReader.getSurface() as a target for the mPreviewRequestBuilder are:
[13, 18, 25, 28, 30, 30, 30, 30 ]
So one solution is to use a lower resolution to achieve the rate you want. For the curious... note that these timings do not seem to be affected by the line
mPreviewRequestBuilder.addTarget(surface);
...
mCameraDevice.createCaptureSession(Arrays.asList(surface, mImageReader.getSurface()),
I was worried that adding the surface on the screen might be adding overhead, but if I remove that first line and change the second to
mCameraDevice.createCaptureSession(Arrays.asList(mImageReader.getSurface()),
then I see the timings change by less than 1 fps. So it doesn't seem to matter whether you are also displaying the image on the screen.
I think there is simply some overhead in the camera2 API or ImageReader's framework that makes it impossible to get the full rate that the TextureView is clearly getting.
One of the most disappointing things of all is that, if you switch back to the deprecated Camera API, you can easily get 30 fps by setting up a PreviewCallback via the Camera.setPreviewCallbackWithBuffer method. With that method, I am able to get 30fps regardless of the resolution. Specifically, although it does not offer me 1600x1200 directly, it does offer 1920x1080, and even that is 30fps.

I'm trying the same things, I think you may change the Format like
mImageReader = ImageReader.newInstance(largestSize.getWidth(),
largestSize.getHeight(),
ImageFormat.FLEX_RGB_888, 3);
Because using the YUV may cause CPU to compress the data and it may cost some time. RGB can be directly showed on the device. And detect face from image should put in other Thread you must know it.