I've got a couple of odd issues using QTKit to feed an image input port on a QCRenderer in an OpenGL context.
Basically, I capture from a live camera using QTKit/QTCaptureSession. When a frame arrives, I get the image using captureOutput:didOutputVideoFrame:withSampleBuffer:fromConnection: and convert to an NSImage. I then set the input port of my QCRenderer to the image, then tell the QCRenderer to render the frame. It works ok, except for two things: 1. Sometimes the video shown on screen lags noticeably behind, like 10 seconds or so behind. It tends to run very slowly for a short time, then speed itself up to catch back up to realtime. Is that something common to QTCaptureSession, or is it my QCRenderer going too slowly and causing a backlog of frames to render? If it's the latter, is there a way to find out if the last frame has finished rendering so I can discard frames? 2. An odd openGL related bug. Sometimes I want to stop capturing, and do post-processing on the current image. To do this, I do a stopRunning on the QTCaptureSession to stop the camera, then set a NSTimer to render at 30fps. To reactivate the camera, I invalidate the timer, then start the capture session. It works sometimes, other times I get a very odd glitch (or a major crash!). It always seems to fail when stopping the camera. My log shows this: 2009-09-22 14:18:27.930 Resolve[512:10b] Camera inactive: starting timer [my message saying that capture has stopped, and the timer is active] 2009-09-22 14:18:27.972 Resolve[512:ce03] *** Message from <QCSprite = 0x0F5C37C0 "Sprite_1">: OpenGL error 0x0502 (invalid operation) 2009-09-22 14:27:19.162 Resolve[313:ce03] *** Message from <QCSprite = 0x0F5C3AA0 "Sprite_1">: Execution failed at time 275318839.161 [plus several more of these] In the window, sometimes the view flashes white for a second or so, and then the view turns upside down and gets stretched a bit vertically (this is extra bad news, because for this application I doubt anyone would notice if the view was upside down and stretched, but it would ruin the results!) The app continues to run with the upside down image - turning the camera on/off more times has no effect on the view, but in the log I see that sometimes works and sometimes it causes errors. Example from log: 2009-09-22 14:27:19.165 Resolve[313:ce03] *** Message from <QCPatch = 0x0F50D1C0 "(null)">: Execution failed at time 275318839.101 [last error - view is now inverted] 2009-09-22 14:27:32.676 Resolve[313:10b] Camera inactive: starting timer [camera stopped, no issue] 2009-09-22 14:27:46.157 Resolve[313:10b] Camera inactive: starting timer [camera stopped, no issue] 2009-09-22 14:27:46.213 Resolve[313:ce03] *** Message from <QCSprite = 0x0F5C3AA0 "Sprite_1">: OpenGL error 0x0504 (stack underflow) [camera stopped, different error this time] 2009-09-22 14:27:46.215 Resolve[313:ce03] *** Message from <QCSprite = 0x0F5C3AA0 "Sprite_1">: Execution failed at time 275318866.213 [several more of these, then the app works again] Sometimes the app will crash. I have a backtrace if it'll help. A couple of times, I've had it totally lock the OS (only the mouse can be moved - the UI it totally unresponsive) and I had to do a hard reboot. Nothing shows up in the console - the last even is my app reporting that the camera has been turned off :( I'm guessing I'm doing it wrong, any pointers? :) Thanks Chris _______________________________________________ Do not post admin requests to the list. They will be ignored. Quartzcomposer-dev mailing list ([email protected]) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/quartzcomposer-dev/archive%40mail-archive.com This email sent to [email protected]
