Various problems with CoreVideo/Image

Hello There,

I did a lot of CoreVideo/Coreimage programming during the last months and found several problems. Before filling bug reports, I'd like to know if I'm doing something wrong or if these bugs are already known.

1) Some DV movies do not work with CoreVideo. I'm working mainly with OpenGL so it mays work in another context. Basically with some movies I receive only a green image, whilst these movies work perfectly in the Quicktime player or when they are decompressed using the old ways (GWorld, etc.).

To reproduce this problem:

Download test2.mov from here:

Simply open it in the LiveVideoMixer (Quartz samples of the developer tools) and you will see only a green rectangle (at least on the hardware I tested).

2) With some codecs (like Photo-JPeg), CoreVideo sends frames only when the movie play back has been started. Changing the movie position does not help. You must at least change the rate once in order to receiving a first frame. It means that you can not display a movie in stop state just after you open it. The solution I found is to start play, waiting for a frame, stop play and set movie time to zero. Then it works as it should.

To reproduce this problem:

Download test1.mov from here:

Another time, simply open it in the LiveVideoMixer (Quartz samples of the developer tools) and you won't have an image until you start play.

3) I'm not sure it is a bug or something I'm missing, but it seems that all the CoreImage effects are done on a green background (at least when you directly apply a CoreImage effects directly on a CV OpenGL buffer). It means that when you do an effect (like a Twirl Vortex) that generate non-opaque value in the alpha-channel, you will have a small green border due to anti-aliasing. I found a solution by rendering the frame to a PBuffer and then sending the PBuffer to the CI effects. It works but it adds an extra rendering pass.

I can provide screenshots if required.

4)  This is not relared to CoreVideo but still is a Quartz related problem. It seems that there is no way to draw to a CGLayer with anti-aliasing turned off. The usual functions like  [[NSGraphicsContext currentContext] setShouldAntialias:NO] simply has not effect at all. Am I missing something ?

5) And a small question: Is it possible to use CoreVideo to do video capture ? It would be very nice to be able to get OpenGL texture through CV buffers directly from a DV camera. Is there anything I'm missing here ? Or do we still have to do it the old way (sequence grabber, etc.) ?

Thank you!

Best regards,

Yves Schmid * GarageCube