如何在 Snow Leopard 中使用 Python 捕获 iSight 帧？

Question

我有以下 PyObjC 脚本：

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)

程序没有报告任何错误，但 iSight 的绿灯从未被激活，并且委托的帧捕获回调从未被调用。这是我得到的输出：

$ 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：请不要回答我应该尝试 PySight，我有但它不会工作，因为 Xcode 无法在 64 位编译 CocoaSequenceGrabber。

Answer 1

您的问题是您没有事件循环。如果你想把它作为一个独立的脚本来做，你必须弄清楚如何创建一个。 PyObjC XCode 模板会自动为您设置：

from PyObjCTools import AppHelper
AppHelper.runEventLoop()

但是，尝试将其插入脚本顶部会显示 AppHelper（可能是 NSApplicationMain）中的某些内容需要一个 plist 文件来从中提取主类。您可以通过创建setup.py 文件并使用py2app 来获得它，类似于PyObjc talk 中的这个示例：

from distutils.core import setup
import py2app
plist = dict(
    NSPrincipalClass='SillyBalls',
)
setup(
    plugin=['SillyBalls.py'],
    data_files=['English.lproj'],
    options=dict(py2app=dict(
        extension='.saver',
        plist=plist,
    )),
)

Answer 2

您应该尝试一下来自 Andrew Straw 的 motmot's camiface 库。它也适用于火线相机，但也适用于 isight，这是您正在寻找的。​​p>

来自教程：

import motmot.cam_iface.cam_iface_ctypes as cam_iface
import numpy as np

mode_num = 0
device_num = 0
num_buffers = 32

cam = cam_iface.Camera(device_num,num_buffers,mode_num)
cam.start_camera()
frame = np.asarray(cam.grab_next_frame_blocking())
print 'grabbed frame with shape %s'%(frame.shape,)