Re: [Pyobjc-dev] Problem with signature for QTKit Delegate (CVImageBufferRef)

[Ronald O. <ron...@ma...>]

Ulrich,

The CoreVideo bindings in subversion were incorrect until a moment  
ago. I've just checked in an updated version of the Quartz bindings  
(r2166), those fix most of the problems with CoreVideo.

That said, I haven't used the CoreVideo bindings in real code yet and  
there aren't any Python examples using CoreVideo either and this means  
there may be issues left.  Other than creating CVPixel buffers in  
Python code (CVPixelBufferCreate and friends) the bindings should be  
complete though.

To answer your question:

First of all: use "import Quartz" in your module to ensure that the  
CoreVideo bindings are loaded, otherwise
    PyObjC won't load the right framework bindings.

PyObjC should then automaticly deduce the correct signature for the  
delegate method, not doing so would be a bug in the QTKit bindings.

BTW. Which version of PyObjC are you using?

Ronald

On 20 Apr, 2009, at 3:23, Ulrich Eck wrote:

> hi,
>
> i spend a couple of days to find out how to do video capturing using  
> the current pyobc QTKit framework wrappers and run into a problem...
>
> i couldn't find out, how to write the signature for the selector of  
> my delegate for QTCaptureDecompressedVideoOutput
> with the following definition:
>
> - (void)captureOutput:(QTCaptureOutput *)captureOutput  
> didOutputVideoFrame:(CVImageBufferRef)videoFrame
>        withSampleBuffer:(QTSampleBuffer *)sampleBuffer  
> fromConnection:(QTCaptureConnection *)connection
>
> i tried several signature definitions like:
>
> @objc.signature('v@:@{__CVBuffer=*}@@')
> @objc.signature('v@:@{__CVBuffer=@}@@')
> @objc.signature('v@:@^{__CVBuffer=}@@')
> @objc.signature('v@:@@@@')
>
> but they all end up in either a PyObcPointer created warning or a  
> NSCFType for videoStream, which seems not be usable
> at all (can i cast to an CVImageBufferRef somehow ?).
>
> output example without signature:
> PyObjCPointer created: at 0x29f4590 of type {__CVBuffer=}@@
> got frame: <QTCaptureDecompressedVideoOutput: 0x2981ac0>  
> <PyObjCPointer object at 0x25c8b78> <QTSampleBuffer: 0x29f3600>  
> <QTCaptureConnection: 0x2982510 vide 2vuy>
>
> output example for the "@objc.signature('v@:@@@@')" signature:
> got frame: <QTCaptureDecompressedVideoOutput: 0x2982010> <NSCFType:  
> 0x29f7310> <QTSampleBuffer: 0x29f5bf0> <QTCaptureConnection:  
> 0x2982a60 vide 2vuy>
>
> using "@objc.signature('v@:@{__CVBuffer=}@@')" results in an error  
> message:
> <type 'exceptions.RuntimeError'>: Cannot create FFI CIF: 1
>
>
> now i'm lost ... has anyone here on the list an idea how to convice  
> the pyobjc wrapper to pass me a valid object/reference to the
> CVImageBufferRef or what to do with the NSCFType to get to the  
> buffer -- as shown in the example below .. i want to extract the  
> image-data
> from the captured video (possibly as string-buffer reference for  
> further use with numpy+ctypes).
>
> any help is greatly appreciated !!
>
> thanks for your help
>
> cheers Ulrich
>
>
> here is a minimal example of my code (created a simple pyobjc app in  
> xcode and this is the main app-delegate):
> i can also provide the whole example for tests if needed.
>
>
> ############################
> from Foundation import *
> from AppKit import *
> from QTKit import *
>
> k24RGBPixelFormat             = 0x00000018    # 24 bit rgb
> k32ARGBPixelFormat            = 0x00000020    # 32 bit argb    (Mac)
>
> class qtkit_captureAppDelegate(NSObject):
>     def applicationDidFinishLaunching_(self, sender):
>         NSLog("Application did finish launching.")
>
>
>         session = QTCaptureSession.alloc().init()
>
>         device =  
> QTCaptureDevice.defaultInputDeviceWithMediaType_(QTMediaTypeVideo)
>         if device is None:
>             print "failed to open device."
>             return
>
>         device.open_(None)
>
>         input = QTCaptureDeviceInput.alloc().initWithDevice_(device)
>         session.addInput_error_(input, None)
>
>         output = QTCaptureDecompressedVideoOutput.alloc().init()
>
>         settings = dict(kCVPixelBufferWidthKey=640.0,
>                         kCVPixelBufferHeightKey=480.0,
>                          
> kCVPixelBufferPixelFormatTypeKey=k32ARGBPixelFormat,
>                         )
>
>         output.setPixelBufferAttributes_(settings)
>         session.addOutput_error_(output, None)
>
>         class logger(NSObject):
>
>             current_buffer = None
>
>             # Declaration:
>             #- (void)captureOutput:(QTCaptureOutput *)captureOutput  
> didOutputVideoFrame:(CVImageBufferRef)videoFrame
>             #       withSampleBuffer:(QTSampleBuffer *)sampleBuffer  
> fromConnection:(QTCaptureConnection *)connection
>
>             #@objc.signature('v@:@{__CVBuffer=*}@@')
>             #@objc.signature('v@:@{__CVBuffer=@}@@')
>             #@objc.signature('v@:@^{__CVBuffer=}@@')
>             @objc.signature('v@:@@@@')
>             def  
> captureOutput_didOutputVideoFrame_withSampleBuffer_fromConnection_ 
> (self, captureOutput, videoFrame, sampleBuffer, connection):
>                 NSLog("got frame: %s %s %s %s" % (captureOutput,  
> videoFrame, sampleBuffer, connection))
>
>                 # always have only one frame retained
>                 #CVBufferRetain(videoFrame)
>                 #buffer_to_release = self.current_buffer
>                 #self.current_buffer = videoFrame
>                 #if buffer_to_release is not None:
>                 #    CVBufferRelease(buffer_to_release)
>
>                 # convert the CVImageBuffer into an NSImage
>                 #cimg = CIImage.initWithCVImageBuffer_(test)
>                 #rep = NSCIImageRep.initWithCIImage_(cimg)
>                 #nimg = NSImage.alloc().initWithSize_(rep.size())
>                 #nimg.addRepresentation_(rep)
>
>
>         cb = logger.alloc().init()
>         output.setDelegate_(cb)
>         session.startRunning()
>
>         self._data = (session, device, input, output, cb)
>
> ############################
>
> ------------------------------------------------------------------------------
> Stay on top of everything new and different, both inside and
> around Java (TM) technology - register by April 22, and save
> $200 on the JavaOne (SM) conference, June 2-5, 2009, San Francisco.
> 300 plus technical and hands-on sessions. Register today.
> Use priority code J9JMT32. http://p.sf.net/sfu/p_______________________________________________
> Pyobjc-dev mailing list
> Pyo...@li...
> https://lists.sourceforge.net/lists/listinfo/pyobjc-dev