On Fri, Feb 20, 2009 at 5:28 PM, Steve Wart <email@hidden
> Sorry please disregard my previous post. I finally realized that I've been
> going about this all wrong.
> First, the display link is completely unnecessary as I am taking frames from
> the capture device, not from a movie source file. It's coming back null
> because it has nothing to give me. I need to remove all references to the
> display link from my project.
> Second, I've been confused about the fact that my texture is failing to bind
> is because I'm handing it a CVImageBufferRef while the movie capture
> QTVisualContextCopyImageForTime also returns a CVImageBufferRef. Looking
> more closely at the QTKit frame capture example, the image buffer is
> converted into an image as follows
> NSCIImageRep *imageRep = [NSCIImageRep imageRepWithCIImage:[CIImage
> NSImage *image = [[[NSImage alloc] initWithSize:[imageRep size]]
> [image addRepresentation:imageRep];
> Presumably if I just want to create a texture with this, I can use
> CIImage>>imageWithCVImageBuffer: and forget about creating an NSImage. This
> is actually really cool since it will let me process the image with CI
> instead of using the deprecated QuickDraw code I've been puzzling over. I
> need to do some chroma key processing to set the alpha value based on a
> range of HSV values - does anyone have any suggestions about how to do this?
> Please let me know if you have any pointers about managing these buffers
> efficiently. In particular I want to put as much load onto the GPUs as
> possible (we will probably have two when we start shooting) and we have 8
> cores to play with.
> On Thu, Feb 19, 2009 at 8:23 PM, Steve Wart <email@hidden
>> Thanks vade. I set things up using the QTCaptureVideoPreviewOutput and
>> tried to use the display link to obtain the video data, but I'm a bit
>> puzzled about using QTVisualContextCopyImageForTime to grab my image buffer.
>> The problem is that QTVisualContextIsNewImageAvailable returns false and
>> QTVisualContextCopyImageForTime always returns 0. Can you explain how to use
>> a CVTimeStamp to capture live video?
>> The video output callback gives us the image without needing a timecode,
>> but it's still not in a format I can bind a texture to. A colleague gave me
>> some code yesterday evening that uses the QuickTime video digitizer
>> components, but it's also using deprecated QuickDraw functions to process
>> the image prior to making a texture (but I guess it would be no big deal to
>> migrate that).
>> Is this something I need to be using the VD library for?
>> On Wed, Feb 18, 2009 at 5:55 PM, vade <email@hidden
>>> Your best and easiest bet is to use the QTCaptureVideoPreviewOutput
>>> object rather than the DecompressedVideoOutput object, and set up a visual
>>> context via QTOpenGLTextureContextCreate() that is shared with your
>>> applications main OpenGL context, and then use QTCaptureVideoPreviewOutput
>>> to associate to your QTOpenGLTextureContext via its setVisualContext:
>>> method. You can then use QTVisualContextCopyImageForTime and friends to grab
>>> a frame from your VideoPreviewOutput as a CVOpenGLTextureRef in your timer
>>> or CVDisplayLinkCallback function, and pass it to GL nice and easy using the
>>> CVOpenGLTexture functions to get the clean coords, flipped, and texture ID.
>>> Or, well, in theory :)
>>> On Feb 18, 2009, at 7:37 PM, Steve Wart wrote:
>>>> I'm attempting to combine some of the ideas in QTCoreVideo102..202
>>>> series and the Still Motion Capture application in the QTKit Capture
>>>> Programming guide.
>>>> Essentially I want to capture live video from a camera and use it as a
>>>> texture in OpenGL.
>>>> Instead of using a timer to capture the frame from the display link
>>>> callback, I've got a thread that grabs a CVImageBufferRef from the
>>>> QTCaptureDecompressedVideoOutput object 30 times a second. It successfully
>>>> stores this into my delegate, but when I try to turn it into a texture
>>>> CVOpenGLTextureGetTarget() returns a target of 0, causing glBindTexture() to
>>>> fail with GL_INVALID_ENUM.
>>>> Do I need to do some additional processing on the captured image in
>>>> order to use it as an OpenGL texture?
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