ios - 我想限制AVCapture框架中的视频捕获帧速率

我正在尝试限制我的应用程序的视频捕获帧速率，因为我发现它会影响VoiceOver性能。

目前，它从摄像机捕获帧，然后使用OpenGL例程尽快处理这些帧。我想在拍摄过程中设置特定的帧率。

我期望可以通过使用videoMinFrameDuration或minFrameDuration来做到这一点，但这似乎对性能没有影响。有任何想法吗？

    NSArray *devices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];
for (AVCaptureDevice *device in devices)
{
    if ([device position] == AVCaptureDevicePositionBack)
    {
        backFacingCamera = device;
                    //  SET SOME OTHER PROPERTIES
    }
}


// Create the capture session
captureSession = [[AVCaptureSession alloc] init];

// Add the video input
NSError *error = nil;
videoInput = [[[AVCaptureDeviceInput alloc] initWithDevice:backFacingCamera error:&error] autorelease];

// Add the video frame output
videoOutput = [[AVCaptureVideoDataOutput alloc] init];
[videoOutput setAlwaysDiscardsLateVideoFrames:YES];

[videoOutput setVideoSettings:[NSDictionary dictionaryWithObject:[NSNumber numberWithInt:kCVPixelFormatType_32BGRA] forKey:(id)kCVPixelBufferPixelFormatTypeKey]];
[videoOutput setSampleBufferDelegate:self queue:dispatch_get_main_queue()];



// Start capturing
if([backFacingCamera supportsAVCaptureSessionPreset:AVCaptureSessionPreset1920x1080])
{
    [captureSession setSessionPreset:AVCaptureSessionPreset1920x1080];
    captureDeviceWidth = 1920;
    captureDeviceHeight = 1080;
    #if defined(VA_DEBUG)
    NSLog(@"Video AVCaptureSessionPreset1920x1080");
    #endif
}
else  do some fall back stuff

// If you wish to cap the frame rate to a known value, such as 15 fps, set
// minFrameDuration.
AVCaptureConnection *conn = [videoOutput connectionWithMediaType:AVMediaTypeVideo];
if (conn.supportsVideoMinFrameDuration)
    conn.videoMinFrameDuration = CMTimeMake(1,2);
else
    videoOutput.minFrameDuration = CMTimeMake(1,2);


if ([captureSession canAddInput:videoInput])
    [captureSession addInput:videoInput];


if ([captureSession canAddOutput:videoOutput])
    [captureSession addOutput:videoOutput];

if (![captureSession isRunning])
    [captureSession startRunning];

有任何想法吗？我想念什么吗？这是节流的最佳方法吗？

AVCaptureConnection *conn = [videoOutput connectionWithMediaType:AVMediaTypeVideo];
if (conn.supportsVideoMinFrameDuration)
    conn.videoMinFrameDuration = CMTimeMake(1,2);
else
    videoOutput.minFrameDuration = CMTimeMake(1,2);

最佳答案

迈克·乌尔里希(Mike Ullrich)的答案一直持续到ios7。不幸的是，这两种方法在ios7中已被弃用。您必须在AVCaptureDevice本身上设置activeVideo{Min|Max}FrameDuration。就像是:

int fps                             = 30;  // Change this value
AVCaptureDevice *device             = ...; // Get the active capture device
[device lockForConfiguration:nil];
[device setActiveVideoMinFrameDuration:CMTimeMake(1, fps)];
[device setActiveVideoMaxFrameDuration:CMTimeMake(1, fps)];
[device unlockForConfiguration];

关于ios - 我想限制AVCapture框架中的视频捕获帧速率，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/9497959/