Clear Image Reader Buffer in CameraX API

Question

I am using CameraX API and its ImageAnalysis to analyze each frame. Processing of frames takes some time and imageReader buffer gets filled resulting in this error -

[ImageReader-256x144f23m4-11920-0](id:2e9000000000,api:4,p:651,c:11920) waitForFreeSlotThenRelock: timeout

How can I clear the Image Reader when it gets filled up and carry on processing frames at the same speed.

Here is my analyze Function

        @SuppressLint("UnsafeOptInUsageError")
        override fun analyze(imageProxy: ImageProxy) {
            val image = imageProxy.image

            if (image != null) {
                val inputImage =
                    InputImage.fromMediaImage(image, imageProxy.imageInfo.rotationDegrees)
                processImage(inputImage, imageProxy)
            }else {
                imageProxy.close()
            }
        }
       

And ProcessImage Function

 @SuppressLint("UnsafeOptInUsageError")
        private fun processImage(image: InputImage, imageProxy: ImageProxy) {
            poseDetector.process(image).addOnSuccessListener { results ->
                posesfromMLKit = getPoseCoordinate(results, imageProxy)
                if (isFullDetectionStarted) {
                    getPoints(posesfromMLKit)
                }
                try {
                    // Convert Image to BitMap
                    val yBuffer = imageProxy.image!!.planes[0].buffer // Y
                    val vuBuffer = imageProxy.image!!.planes[2].buffer // VU

                    val ySize = yBuffer.remaining()
                    val vuSize = vuBuffer.remaining()

                    val nv21 = ByteArray(ySize + vuSize)

                    yBuffer.get(nv21, 0, ySize)
                    vuBuffer.get(nv21, ySize, vuSize)

                    val yuvImage =
                        YuvImage(nv21, ImageFormat.NV21, image!!.width, image!!.height, null)
                    val out = ByteArrayOutputStream()
                    yuvImage.compressToJpeg(Rect(0, 0, yuvImage.width, yuvImage.height), 50, out)
                    val imageBytes = out.toByteArray()
                    base64EncodedFrame = Base64.getEncoder().encodeToString(imageBytes).toString()
                } catch (e: Exception) {
                    imageProxy.close()
                }
                frameratePerSecond++
                imageProxy.close()
            }.addOnFailureListener { e ->
                imageProxy.close()
            }.addOnCompleteListener {
                imageProxy.close()
//                    CoroutineScope(Dispatchers.IO).launch {
//                        delay(100)
//                        imageProxy.close()
//                    }
            }.addOnCanceledListener {
                imageProxy.close()
            }
        }

I tried dropping some frames when processImage function is processing 1 frame. But it resulted in Slow Processing somehow.

but that solved the error, yet it is not a good approach for this project.

Answer 1

The ImageReader queue does not get filled up with the default ImageAnalysis configs. e.g. the STRATEGY_KEEP_ONLY_LATEST mode. With this mode, CameraX keeps dropping incoming frames until the current frame is closed. Could you post your ImageAnalysis configuration?

The resolution is 256x144 which is uncommon for camera. My guess is that it's the queue in MLKit gets filled up.