CreateVideoTrackFromCameraAndShowIt.kt

private fun createVideoTrackFromCameraAndShowIt() {
        val videoCapturer: VideoCapturer? = createVideoCapturer()

        //Create a VideoSource instance
        videoCapturer?.let {
            surfaceTextureHelper = SurfaceTextureHelper.create("CaptureThread", rootEglBase!!.eglBaseContext)
            videoSource = factory?.createVideoSource(videoCapturer.isScreencast)
            videoCapturer.initialize(surfaceTextureHelper, this, videoSource?.capturerObserver)
        }
        localVideoTrack = factory?.createVideoTrack("100", videoSource)

        //Create MediaConstraints - Will be useful for specifying video and audio constraints.
        audioConstraints = MediaConstraints()
        videoConstraints = MediaConstraints()

        //create an AudioSource instance
        audioSource = factory?.createAudioSource(audioConstraints)
        localAudioTrack = factory?.createAudioTrack("101", audioSource)
        
        videoCapturer?.startCapture(1024, 720, 30)
        binding?.localGlSurfaceView?.visibility = View.VISIBLE
        
        // And finally, with our VideoRenderer ready, we
        // can add our renderer to the VideoTrack.
        localVideoTrack?.addSink(binding?.localGlSurfaceView)
}

private fun createVideoCapturer(): VideoCapturer? {
        return if (useCamera2()) {
            createCameraCapturer(Camera2Enumerator(this))
        } else {
            createCameraCapturer(Camera1Enumerator(true))
        }
}

private fun createCameraCapturer(enumerator: CameraEnumerator): VideoCapturer? {
        val deviceNames = enumerator.deviceNames
        for (deviceName in deviceNames) {
            if (enumerator.isFrontFacing(deviceName)) {
                val videoCapturer: VideoCapturer? = enumerator.createCapturer(deviceName, null)
                if (videoCapturer != null) {
                    return videoCapturer
                }
            }
        }
        for (deviceName in deviceNames) {
            if (!enumerator.isFrontFacing(deviceName)) {
                val videoCapturer: VideoCapturer? = enumerator.createCapturer(deviceName, null)
                if (videoCapturer != null) {
                    return videoCapturer
                }
            }
        }
        return null
}

private fun useCamera2(): Boolean {
        return Camera2Enumerator.isSupported(this)
}