1

我正在尝试使用 AVFoundation 在我的应用程序中实现视频捕获。我在 viewDidLoad 下有以下代码：

session = [[AVCaptureSession alloc] init];
movieFileOutput = [[AVCaptureMovieFileOutput alloc] init];
videoInputDevice = [[AVCaptureDeviceInput alloc] init];
AVCaptureDevice *videoDevice = [self frontFacingCameraIfAvailable];

if (videoDevice)
{
    NSError *error;

    videoInputDevice = [AVCaptureDeviceInput deviceInputWithDevice:videoDevice error:&error];

    if (!error)
    {
        if ([session canAddInput:videoInputDevice])
            [session addInput:videoInputDevice];
        else 
            NSLog (@"Couldn't add input.");
    }

}


AVCaptureDevice *audioCaptureDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeAudio];
NSError *audioError = nil;
AVCaptureDeviceInput *audioInput = [AVCaptureDeviceInput deviceInputWithDevice:audioCaptureDevice error:&audioError];

if (audioInput)
{
    [session addInput:audioInput];
}

movieFileOutput = [[AVCaptureMovieFileOutput alloc] init];

Float64 TotalSeconds = 35;          //Total seconds
int32_t preferredTimeScale = 30;    //Frames per second
CMTime maxDuration = CMTimeMakeWithSeconds(TotalSeconds, preferredTimeScale);   
movieFileOutput.maxRecordedDuration = maxDuration;

movieFileOutput.minFreeDiskSpaceLimit = 1024 * 1024;                        

if ([session canAddOutput:movieFileOutput])
    [session addOutput:movieFileOutput];

[session setSessionPreset:AVCaptureSessionPresetMedium];
if ([session canSetSessionPreset:AVCaptureSessionPreset640x480])        //Check size based configs are supported before setting them
    [session setSessionPreset:AVCaptureSessionPreset640x480];

[self cameraSetOutputProperties];


[session startRunning];

此代码在用于启动捕获的按钮的实现中，除其他外：

NSString *outputPath = [[NSString alloc] initWithFormat:@"%@%@", NSTemporaryDirectory(), @"output.mov"];
NSURL *outputURL = [[NSURL alloc] initFileURLWithPath:outputPath];
NSFileManager *fileManager = [NSFileManager defaultManager];
if ([fileManager fileExistsAtPath:outputPath])
{
    NSError *error;
    if ([fileManager removeItemAtPath:outputPath error:&error] == NO)
    {
        //Error - handle if requried
    }
}
[outputPath release];
//Start recording
[movieFileOutput startRecordingToOutputFileURL:outputURL recordingDelegate:self];
[outputURL release];

当我尝试在设备上运行它时，当我尝试加载所有这些都应该发生的视图时它会崩溃。Xcode 给了我一个“线程 1：EXC_BAD_ACCESS (code=1, address=0x4) 在：

AVFoundation`-[AVCaptureDeviceInput _setDevice:]:
(stuff)
0x3793f608:  ldr    r0, [r1, r0]

错误在最后一行给出。我认为这与某处的 AVCaptureDeviceInput 有关，但我对它可能是什么一无所知。有谁知道我在这里缺少什么？谢谢。

编辑：摆弄断点后，我发现崩溃发生在这一行：

AVCaptureDevice *videoDevice = [self frontFacingCameraIfAvailable];

那么与该方法有关吗？这是我的实现文件，也许那里有问题。

NSArray *videoDevices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];
AVCaptureDevice *captureDevice = nil;
for (AVCaptureDevice *device in videoDevices)
{
    if (device.position == AVCaptureDevicePositionFront)
    {
        captureDevice = device;
        break;
    }
}

//  couldn't find one on the front, so just get the default video device.
if ( ! captureDevice)
{
    captureDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
}

return captureDevice;

编辑2：可能是我正在使用

AVCaptureDevice *videoDevice = [self frontFacingCameraIfAvailable];

并且“自我”以某种方式向其中扔了扳手？我知道在创建 CALayer 时可以这样做

CALayer *aLayer = [CALayer layer];

但我不知道与此等效的 AVCaptureDevice（如果有的话）。我不确定它还能是什么，总而言之，我的代码看起来不错，我尝试过清理项目、重新启动 Xcode、重新启动计算机等。

4

2 回答 2

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我很确定问题在于您正在模拟器上运行程序。模拟器无法使用这些资源。

于 2012-06-26T19:00:51.070 回答
0

设法解决了这个问题（也许）。

添加

@property (nonatomic, retain) AVCaptureDeviceInput *videoInputDevice;

到接口，在实现中合成，并使用这些方法获得前置摄像头：

- (AVCaptureDevice *) cameraWithPosition:(AVCaptureDevicePosition) position
{
NSArray *devices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];
for (AVCaptureDevice *device in devices) {
    if ([device position] == position) {
        return device;
    }
}
return nil;
}

-(AVCaptureDevice *)frontFacingCamera
{
return [self cameraWithPosition:AVCaptureDevicePositionFront];

然后分配给它

videoInputDevice = [AVCaptureDeviceInput deviceInputWithDevice:[self frontFacingCamera] error:&error];

不能 100% 确定它是否有效，因为现在它无法保存，但它不再崩溃了。当我确定它是否有效时，会回来更新它。

于 2012-06-28T18:05:09.683 回答