UVC capture card fails to start preview (err = -51) while webcam works fine

[noho501]

Hi,

I'm using CameraHelper to connect UVC, webcam devices work correctly, but when I connect an HDMI → USB capture card, preview fails with the following error:

[UVCPreview.cpp:549:prepare_preview]: could not negotiate with camera: err = -51

class CustomCameraUvcSource : VideoSource() {

    private var cameraHelper: ICameraHelper? = null
    private var surface: Surface? = null
    private var running = false

    override fun start(surfaceTexture: SurfaceTexture) {
        this.surfaceTexture = surfaceTexture
        surface = Surface(surfaceTexture)

        cameraHelper = CameraHelper().apply {
            setStateCallback(stateCallback)
        }
        running = true
    }

    override fun stop() {
        surface?.let { cameraHelper?.removeSurface(it) }
        surface?.release()
        surface = null
        cameraHelper?.release()
        cameraHelper = null
        running = false
    }

    override fun isRunning(): Boolean = running

    override fun getOrientationConfig() =
        OrientationConfig(forced = OrientationForced.LANDSCAPE)

    private val stateCallback = object : ICameraHelper.StateCallback {

        override fun onAttach(device: UsbDevice) {
            cameraHelper?.selectDevice(device)
        }

        override fun onDeviceOpen(device: UsbDevice, isFirstOpen: Boolean) {
            cameraHelper?.openCamera()
        }

        override fun onCameraOpen(device: UsbDevice) {
            val list = cameraHelper?.supportedSizeList ?: return
            list.forEach {
                Log.d("UVC", "size=${it.width}x${it.height}, type=${it.type}")
            }

            val target = list.firstOrNull {
                it.type == UVCCamera.FRAME_FORMAT_YUYV
            } ?: list.first()

            cameraHelper?.previewSize = target

            surface?.let {
                cameraHelper?.addSurface(it, false)
            }

            cameraHelper?.startPreview()
        }

        override fun onCameraClose(device: UsbDevice) {}
        override fun onDeviceClose(device: UsbDevice) {}
        override fun onDetach(device: UsbDevice) {}
        override fun onCancel(device: UsbDevice) {}
    }
}

Below is my current implementation and logs.

Code (StateCallback)

override fun onCameraOpen(device: UsbDevice) {
    surface?.let { cameraHelper?.addSurface(it, false) }

    val allConfigs = cameraHelper?.supportedSizeList ?: emptyList()

    val mjpegConfigs = allConfigs.filter {
        it.type == UVCCamera.UVC_VS_FRAME_MJPEG
    }

    Log.d("UVC", "Supported sizes = $allConfigs")
    Log.d("UVC", "Supported MJPEG sizes = $mjpegConfigs")

    if (mjpegConfigs.isNotEmpty()) {
        // I tried several indices, including low resolutions
        cameraHelper?.previewSize = mjpegConfigs.first()
        Log.d("UVC", "Selected size = ${cameraHelper?.previewSize}")
    }

    cameraHelper?.startPreview()
}

supportedSizeList output

Supported sizes = [
 Size(1920x1080@60,type:7),
 Size(1920x1080@60,type:7),
 Size(1360x768@60,type:7),
 Size(1280x1024@60,type:7),
 Size(1280x960@60,type:7),
 Size(1280x720@60,type:7),
 Size(1024x768@60,type:7),
 Size(800x600@60,type:7),
 Size(720x576@60,type:7),
 Size(720x480@60,type:7),
 Size(640x480@60,type:7)
]

Supported MJPEG sizes = same list above
Selected size = Size(1920x1080@60,type:7)

Failed to set preview

30fps

• setPreviewSize: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.serenegiant.usb.UVCCamera.setPreviewSize(com.serenegiant.usb.Size)' on a null object reference at com.herohan.uvcapp.CameraInternal.setPreviewSize(CameraInternal.java:127)

60fps

• setPreviewSize: java.lang.IllegalArgumentException: Failed to set preview size at com.serenegiant.usb.UVCCamera.setPreviewSize(UVCCamera.java:467)

Thanks for your time.