Bug Low performance when using WebCam

On a laptop with RTX 2070 Max Q, The process of grabbing the webcam image takes 10ms.
_JS_WebCamVideo_GrabFrame


I couldn't find a way to set WebCamTexture readable to false.

Code (JavaScript):

1.   function _JS_WebCamVideo_GrabFrame(deviceId, buffer, destWidth, destHeight) {
2.     if (!MediaDevices[deviceId].video) {
3.       console.error("WebCam not initialized.");
4.       return
5.     }
6.     var context = webcam.canvas.getContext("2d");
7.     if (context) {
8.       canvas.width = destWidth;
9.       canvas.height = destHeight;
10.       context.drawImage(MediaDevices[deviceId].video, 0, 0, MediaDevices[deviceId].video.videoWidth, MediaDevices[deviceId].video.videoHeight, 0, 0, destWidth, destHeight);
11.       var imageData = context.getImageData(0, 0, destWidth, destHeight);
12.       writeArrayToMemory(imageData.data, buffer)
13.     } else {
14.       console.log("2d Context is null")
15.     }
16.   }

Looking at the code, I think that if the WebCamTexture readable could be set to false, using an external canvas 2D, getting image data, and writing it to memory, could have been redundant, as drawing the image on a texture on the main context(similar to how VideoPlayer.targetTexture is implemented in WebGL) would be much faster.

 

Is it possible to reuse the context? This may or may not carry a significant overhead.

Also this seems to be polling the camera. Does it support pushing (events)? Since most webcams only deliver 30 fps you may be getting images twice when webgl runs at 60 fps.

 

The performance tab show that getcontext costs almost nothing (I guess the browser cache it).

I guess they can optimize it by polling only once in x frames, based on the camera refresh rate.