IOS 4.1 code detail
Detailed description of work-around for AVCaptureVideoPreviewLayer problem in IOS 4.1
IOS 4.1 seems to contain a critical bug in the AVCaptureVideoPreviewLayer which causes app’s to freeze when an instance of the class is created.
The normal way to use AVCaptureVideoPreviewLayer is as follows:
// Create the session
session = [[AVCaptureSession alloc] init];
// Configure the session to produce lower resolution video frames, if your
// processing algorithm can cope. We’ll specify medium quality for the
// chosen device.
session.sessionPreset = AVCaptureSessionPresetMedium;
// Find a suitable AVCaptureDevice
AVCaptureDevice *device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
// Create a device input with the device and add it to the session.
AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:device
error:&error];
if (!input) {
// Handling the error appropriately.
return ;
}
[session addInput:input];
// Create a VideoDataOutput and add it to the session
AVCaptureVideoDataOutput *output = [[[AVCaptureVideoDataOutput alloc] init] autorelease];
[session addOutput:output];
// Configure your output.
dispatch_queue_t queue = dispatch_queue_create(“myQueue”, NULL);
[output setSampleBufferDelegate:self queue:queue];
dispatch_release(queue);
// Specify the pixel format
output.videoSettings =
[NSDictionary dictionaryWithObject:
[NSNumber numberWithInt:kCVPixelFormatType_32BGRA] forKey:(id)kCVPixelBufferPixelFormatTypeKey];
// We use 10 fps for barcode reading.
output.minFrameDuration = CMTimeMake(1, 10);
// Start the session running to start the flow of data
[session startRunning];
// Create the video capture preview
// APP WILL FREEZE ON THIS NEXT LINE:
AVCaptureVideoPreviewLayer *previewLayer = [AVCaptureVideoPreviewLayer layerWithSession:Session];
previewLayer.frame = aView.bounds; // Assume you want the preview layer to fill the view.
[aView.layer addSublayer:previewLayer];
Any app using the above code on IOS 4.1 will freeze at the line indicated.
The work-around is to delay the assignment of the output device to the session until after the preview layer has been created:
// Create the session
11px/normal Menlo; padding: 0px; margin: 0px;”>session = [[AVCaptureSession alloc] init];
// Configure the session to produce lower resolution video frames, if your
// processing algorithm can cope. We’ll specify medium quality for the
// chosen device.
session.sessionPreset = AVCaptureSessionPresetMedium;
// Find a suitable AVCaptureDevice
AVCaptureDevice *device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
// Create a device input with the device and add it to the session.
AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:device
error:&error];
if (!input) {
// Handling the error appropriately.
return ;
}
[session addInput:input];
// Create the video capture preview
AVCaptureVideoPreviewLayer *previewLayer = [AVCaptureVideoPreviewLayer layerWithSession:Session];
previewLayer.frame = aView.bounds; // Assume you want the preview layer to fill the view.
[aView.layer addSublayer:previewLayer];
// Create a VideoDataOutput and add it to the session
AVCaptureVideoDataOutput *output = [[[AVCaptureVideoDataOutput alloc] init] autorelease];
[session addOutput:output];
// Configure your output.
dispatch_queue_t queue = dispatch_queue_create(“myQueue”, NULL00;”>);
[output setSampleBufferDelegate:self queue:queue];
dispatch_release(queue);
// Specify the pixel format
output.videoSettings =
[NSDictionary dictionaryWithObject:
[NSNumber numberWithInt:kCVPixelFormatType_32BGRA] forKey:(id)kCVPixelBufferPixelFormatTypeKey];
// We use 10 fps for barcode reading.
output.minFrameDuration = CMTimeMake(1, 10);
// Start the session running to start the flow of data
[session startRunning];
