CAOpenGLLayer question (timeInterval)

FROM : John Clayton
DATE : Thu Nov 22 23:57:36 2007

Hello All,

Hope you aint all sick of these... here's another CAOpenGLLayer 
question. In the method:

- (void)drawInCGLContext:(CGLContextObj)glContext
            pixelFormat:(CGLPixelFormatObj)pixelFormat
           forLayerTime:(CFTimeInterval)timeInterval
            displayTime:(const CVTimeStamp *)timeStamp


I implement this and render Quicktime movies via visual contexts... 
all works semi-lovely (I cannot render frames in the past, but thats 
another story), except - sometimes this method is given a timeInterval 
of -1, does anyone know what this means?

Thanks

--
John Clayton