AVCapture在iOS 7中捕获并获得60 fps的帧缓冲区

我正在开发一个应用程序,需要尽可能多的fps捕获帧缓冲区.我已经弄清楚如何强制 iphone以60 fps捕获

- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection

方法被称为只有15次,这意味着iPhone降级捕获输出到15 fps.

有没有人面临这样的问题？是否有可能增加捕获帧速率？

更新我的代码：

camera = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
if([camera isTorchModeSupported:AVCapturetorchModeOn]) {
   [camera lockForConfiguration:nil];
   camera.torchMode=AVCapturetorchModeOn;
   [camera unlockForConfiguration];
}
[self configureCameraForHighestFrameRate:camera];

// Create a AVCaptureInput with the camera device
NSError *error=nil;
AVCaptureInput* cameraInput = [[AVCaptureDeviceInput alloc] initWithDevice:camera error:&error];
if (cameraInput == nil) {
   NSLog(@"Error to create camera capture:%@",error);
}

// Set the output
AVCaptureVideoDataOutput* videoOutput = [[AVCaptureVideoDataOutput alloc] init];

// create a queue to run the capture on
dispatch_queue_t captureQueue=dispatch_queue_create("captureQueue",NULL);

// setup our delegate
[videoOutput setSampleBufferDelegate:self queue:captureQueue];

// configure the pixel format
videoOutput.videoSettings = [NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithUnsignedInt:kCVPixelFormatType_32BGRA],(id)kCVPixelBufferPixelFormatTypeKey,nil];

// Add the input and output
[captureSession addInput:cameraInput];
[captureSession addOutput:videoOutput];

我在这里采用了configureCameraForHighestFrameRate方法https://developer.apple.com/library/mac/documentation/AVFoundation/Reference/AVCaptureDevice_Class/Reference/Reference.html

解决方法

我在iPhone 5上获得了60 fps的采样率,在iPhone 5上采用了120 fps,无论是在捕获输出中进行实时运动检测还是使用AVAssetWriter将帧保存到视频中.

您必须将AVCaptureSession设置为支持60 fps的格式：

AVsession = [[AVCaptureSession alloc] init];

AVCaptureDevice *videoDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
AVCaptureDeviceInput *capInput = [AVCaptureDeviceInput deviceInputWithDevice:videoDevice error:&error];
if (capInput) [AVsession addInput:capInput];

for(AVCaptureDeviceFormat *vFormat in [videoDevice formats] ) 
{
    CMFormatDescriptionRef description= vFormat.formatDescription;
    float maxrate=((AVFrameRaterange*)[vFormat.videoSupportedFrameRateranges objectAtIndex:0]).maxFrameRate;

    if(maxrate>59 && CMFormatDescriptionGetMediaSubType(description)==kCVPixelFormatType_420YpCbCr8BiPlanarFullRange)
    {
        if ( YES == [videoDevice lockForConfiguration:NULL] ) 
        {
           videoDevice.activeFormat = vFormat;
           [videoDevice setActiveVideoMinFrameDuration:CMTimeMake(10,600)];
           [videoDevice setActiveVideoMaxFrameDuration:CMTimeMake(10,600)];
           [videoDevice unlockForConfiguration];
           NSLog(@"formats  %@ %@ %@",vFormat.mediaType,vFormat.formatDescription,vFormat.videoSupportedFrameRateranges);
        }
     }
}

prevLayer = [AVCaptureVideoPreviewLayer layerWithSession: AVsession];
prevLayer.videoGravity = AVLayerVideoGravityResizeAspectFill;
[self.view.layer addSublayer: prevLayer];

AVCaptureVideoDataOutput *videoOut = [[AVCaptureVideoDataOutput alloc] init];
dispatch_queue_t videoQueue = dispatch_queue_create("videoQueue",NULL);
[videoOut setSampleBufferDelegate:self queue:videoQueue];

videoOut.videoSettings = @{(id)kCVPixelBufferPixelFormatTypeKey: @(kCVPixelFormatType_32BGRA)};
videoOut.alwaysdiscardsLateVideoFrames=YES;

if (videoOut)
{
    [AVsession addOutput:videoOut];
    videoConnection = [videoOut connectionWithMediaType:AVMediaTypeVideo];
}

如果您想使用AVAssetWriter写入一个文件,另外两个评论.不要使用pixelAdaptor,只需要添加样品

[videoWriterInput appendSampleBuffer:sampleBuffer]

其次,当设置assetwriter使用

[AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeVideo
                                   outputSettings:videoSettings 
                                 sourceFormatHint:formatDescription];

sourceFormatHint在写入速度方面有所不同.