Eu tenho o seguinte script PyObjC:

from Foundation import NSObject
import QTKit
error = None
capture_session = QTKit.QTCaptureSession.alloc().init()
print 'capture_session', capture_session
device = QTKit.QTCaptureDevice.defaultInputDeviceWithMediaType_(QTKit.QTMediaTypeVideo)
print 'device', device, type(device)
success = device.open_(error)
print 'device open success', success, error
if not success:
    raise Exception(error)
capture_device_input = QTKit.QTCaptureDeviceInput.alloc().initWithDevice_(device)
print 'capture_device_input', capture_device_input, capture_device_input.device()
success = capture_session.addInput_error_(capture_device_input, error)
print 'session add input success', success, error
if not success:
    raise Exception(error)
capture_decompressed_video_output = QTKit.QTCaptureDecompressedVideoOutput.alloc().init()
print 'capture_decompressed_video_output', capture_decompressed_video_output
class Delegate(NSObject):
    def captureOutput_didOutputVideoFrame_withSampleBuffer_fromConnection_(self, captureOutput, videoFrame, sampleBuffer, connection):
        print videoFrame, sampleBuffer, connection
delegate = Delegate.alloc().init()
print 'delegate', delegate
capture_decompressed_video_output.setDelegate_(delegate)
print 'output delegate:', capture_decompressed_video_output.delegate()
success = capture_session.addOutput_error_(capture_decompressed_video_output, error)
print 'capture session add output success', success, error
if not success:
    raise Exception(error)
print 'about to run session', capture_session, 'with inputs', capture_session.inputs(), 'and outputs', capture_session.outputs()
capture_session.startRunning()
print 'capture session is running?', capture_session.isRunning()
import time
time.sleep(10)

O programa não reporta erros, mas a luz verde da iSight nunca é ativada e o callback de captura de quadros do delegado nunca é chamado. Aqui está a saída que recebo:

$ python prueba.py 
capture_session <QTCaptureSession: 0x1006c16f0>
device Built-in iSight <objective-c class QTCaptureDALDevice at 0x7fff70366aa8>
device open success (True, None) None
capture_device_input <QTCaptureDeviceInput: 0x1002ae010> Built-in iSight
session add input success (True, None) None
capture_decompressed_video_output <QTCaptureDecompressedVideoOutput: 0x104239f10>
delegate <Delegate: 0x10423af50>
output delegate: <Delegate: 0x10423af50>
capture session add output success (True, None) None
about to run session <QTCaptureSession: 0x1006c16f0> with inputs (
    "<QTCaptureDeviceInput: 0x1002ae010>"
) and outputs (
    "<QTCaptureDecompressedVideoOutput: 0x104239f10>"
)
capture session is running? True

PS: Por favor, não responda Eu deveria tentar o PySight, mas ele não funciona, porque o Xcode não pode compilar o CocoaSequenceGrabber em 64 bits.