A question about QTKit / Capture & QTVisualContext and working/output colorspaces

Subject: A question about QTKit / Capture & QTVisualContext and working/output colorspaces

Date: Sat, 31 Jan 2009 16:10:06 -0500

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Hello.

I am noticing some difference in behavior colorspace wise between two QTVisualContexts I am using, one drawing a QTKit QTMovie, and one using a QTKit QTCaptureVideoPreviewOutput.

Both contexts have their working and output colorspace set to kColorSpaceGenericRGBLinear via:

QTVisualContextSetAttribute(textureContext, kQTVisualContextWorkingColorSpaceKey, CGColorSpaceCreateWithName(kCGColorSpaceGenericRGBLinear));

QTVisualContextSetAttribute(textureContext, kQTVisualContextOutputColorSpaceKey, CGColorSpaceCreateWithName(kCGColorSpaceGenericRGBLinear));

After my QTVisualContext is created.

I am passing in CVOpenGLTextureRefs as input image keys in to Quartz Composer. I would like to minimize any intermediate colorspace conversions in my pipeline, and it seems as though my QTMovie is behaving as expected; I've done some debugging using a private Quartz Composer patch (Image Debugging Info) and it states that my QTMovie's visual context is reporting the proper linear RGB colorspace, but that my QTCaptureVideoPreviewOutput is reporting 601.

Am a incorrect in assuming that a QTCaptureVideoPreviewOutput attached to a QTVisualContext will adhere to the working/output colorspace keys that the visual context has set?

Ive attempted to set those VisualContext attributes before and after attaching my VideoPreviewOutput to my visualcontext, and neither order has worked or changed it to LinearRGB as requested.

So, in short, how do I properly convert a QTCaptureVideoPreviewOutputs colorspace when attached to a QTVisualContext?

Thanks!

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