CoreVideo Display Link Callback function
CoreVideo Display Link Callback function
- Subject: CoreVideo Display Link Callback function
- From: "San Saeteurn" <email@hidden>
- Date: Fri, 19 Jan 2007 13:44:57 -0800
Hi,
I am trying to build an OpenGL Texture image using CoreVideo. I initialize
the Display Link Thread as Follows:
//Initializing the Display Link and Display Link Callback
CVReturn error = kCVReturnSuccess;
CGDirectDisplayID displayID = CGMainDisplayID();
error = CVDisplayLinkCreateWithDisplay(displayID, &displayLink);
if(error)
{
NSLog(@"DisplayLink created with error:%d", error);
displayLink = NULL;
return;
}
error = CVDisplayLinkSetOutputCallback(displayLink,
(CVDisplayLinkOutputCallback)myCVDisplayLinkDisplayCallback, self);
if(error)
{
NSLog(@"Setting Output Callback error:%d", error);
displayLink = NULL;
return;
}
error = CVDisplayLinkStart(displayLink);
if(error)
{
NSLog(@"Starting display link thread error: %d", error);
return;
}
This occurs in the wakeup function of one of my OpenGL Object Classes.
The callback in implemented as follows:
//Callback Funtions
//The Output Callback Funtion
CVReturn myCVDisplayLinkDisplayCallback(CVDisplayLinkRef displayLink,
const CVTimeStamp *syncTimeStamp,
CVOptionFlags flagsIn,
void *displayLinkContext)
{
if(displayLinkContext == NULL)
NSLog(@"The Passed in Display Link Context is NULL: %@",
displayLinkContext);
return [(GLObjectMovie *)displayLinkContext displayFrame:syncTimeStamp];
}
The function - (void)displayFrame:(const CVTimeStamp *)timeStamp.
The problem:
The parameter in the callback function "void *displayLinkContext" is NULL.
How do I set it to be the active instance of GLObject? In the
initialization of the thread:
error = CVDisplayLinkSetOutputCallback(displayLink,
(CVDisplayLinkOutputCallback)myCVDisplayLinkDisplayCallback, self);
if(error)
{
NSLog(@"Setting Output Callback error:%d", error);
displayLink = NULL;
return;
}
I set the last parameter (void *userData), I set self (meaning the current
active GLObjectMovie instance). This is called from inside the class
instance itself so it isn't NULL.
Any ideas?
-San Saeteurn
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