I am new to Camera2 framework and trying to understand the logic of creation of capture sessions.
I need a simple thing - preview and record video. I also want to set the correct orientation hint at the time I start recording the video. But I came to a chicken/egg problem.
Here is my logic:
In order to start recording, I am doing this:
val recordRequest = session.device.createCaptureRequest(CameraDevice.TEMPLATE_RECORD).apply {
// Add the preview and recording surface targets
addTarget(viewFinder.holder.surface)
addTarget(recorder.surface)
}.build()
session.setRepeatingRequest(recordRequest, null, cameraHandler)
recorder.setOrientationHint(it) // NOT allowed after getSurface()!
recorder.prepare() // NOT allowed after getSurface()!
recorder.start()
However, I already called recorder.surface (or getSurface()) when I added targets above. One can think that I can prepare and then add targets, however, the documentation for addTarget() says, that the surface The Surface added must be one of the surfaces included in the most recent call to CameraDevice#createCaptureSession
That leads to an interesting problem. Whenever I open the app, I need to create the capture session to start previewing camera image. However, at the point of creation the createCaptureSession() needs to include all the surfaces that will come in future capture requests. Which means that I also need to include the recording surface, even if I simply open camera without recording yet. How do I get this Surface for recording? Well, the documentation says I can get it from MediaRecorder or I can get it from MediaCodec. I want to get it from MediaRecorder since I want to use CamcorderProfiles. However, as I showed in the above code, once I get the surface from the recorder at the point of session creation - I cannot do any changes there at the point of starting recording, like setting orientation hint.
The official Camera2Video sample app does a trick - it uses createPersistentInputSurface however in their example the camera is fixed, which allows them to allocate enough memory for it and use that surface throughout the app lifecycle.
How can this be solved? Am I misunderstanding the concepts here? How can I create the recorder at a later point, when I start recording, but still have the surface for it created earlier, when I open the camera for preview?
Using a persistent input surface is the right approach. Create a new MediaRecorder once you know the orientation for recording, and set its Surface using the persistent input surface.
That's exactly what the Camera2Video sample does, as well:
// React to user touching the capture button
capture_button.setOnTouchListener { view, event ->
when (event.action) {
MotionEvent.ACTION_DOWN -> lifecycleScope.launch(Dispatchers.IO) {
// Prevents screen rotation during the video recording
requireActivity().requestedOrientation =
ActivityInfo.SCREEN_ORIENTATION_LOCKED
// Start recording repeating requests, which will stop the ongoing preview
// repeating requests without having to explicitly call `session.stopRepeating`
session.setRepeatingRequest(recordRequest, null, cameraHandler)
// Finalizes recorder setup and starts recording
recorder.apply {
// Sets output orientation based on current sensor value at start time
relativeOrientation.value?.let { setOrientationHint(it) }
prepare()
start()
}
and recorder is created with an earlier-created persistent surface:
/** Saves the video recording */
private val recorder: MediaRecorder by lazy { createRecorder(recorderSurface)
}
When you say the camera is fixed, do you mean the app orientation being fixed, or that the sample doesn't support switching front/back cameras? None of that should particularly matter for persistent surfaces; you can create a new one when you switch cameras or change orientations, if you need to.