AVCapture捕获和获取帧缓冲在60 fps在iOS 7 [英] AVCapture capturing and getting framebuffer at 60 fps in iOS 7

问题描述

我开发的应用程序需要尽可能多的帧速率捕获帧缓冲区。我已经知道如何强制iphone以60 fps捕获

I'm developping an app which requires capturing framebuffer at as much fps as possible. I've already figured out how to force iphone to capture at 60 fps but

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

方法只被调用15次第二，这意味着iPhone降级捕获输出到15 fps。

method is being called only 15 times a second, which means that iPhone downgrades capture output to 15 fps.

有人遇到这样的问题吗？是否有可能增加捕获帧速率？

Has anybody faced such problem? Is there any possibility to increase capturing frame rate?

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];

我在这里使用 configureCameraForHighestFrameRate =https://developer.apple.com/library/mac/documentation/AVFoundation/Reference/AVCaptureDevice_Class/Reference/Reference.html> https://developer.apple.com/library/mac/documentation/AVFoundation/Reference /AVCaptureDevice_Class/Reference/Reference.html

I took configureCameraForHighestFrameRate method here https://developer.apple.com/library/mac/documentation/AVFoundation/Reference/AVCaptureDevice_Class/Reference/Reference.html

推荐答案

我在iPhone 5和120上获得60帧的样本fps在iPhone 5s上，当在captureOutput中进行实时运动检测时，以及使用AVAssetWriter将帧保存到视频时。

I am getting samples at 60 fps on the iPhone 5 and 120 fps on the iPhone 5s, both when doing real time motion detection in captureOutput and when saving the frames to a video using AVAssetWriter.

您必须将AVCaptureSession设置为格式支持60 fps：

You have to set thew AVCaptureSession to a format that supports 60 fps:

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];
}

另两个注释，如果要使用AVAssetWriter写入文件。不要使用pixelAdaptor，只要在样例中使用[videoWriterInput appendSampleBuffer：sampleBuffer]

Two other comment if you want to write to a file using AVAssetWriter. Don't use the pixelAdaptor, just ad the samples with [videoWriterInput appendSampleBuffer:sampleBuffer]

其次在设置assetwriter时使用[AVAssetWriterInput assetWriterInputWithMediaType：AVMediaTypeVideo outputSettings：videoSettings sourceFormatHint： formatDescription]。 sourceFormatHint在写入速度上有所不同。

Secondly when setting up the assetwriter use [AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeVideo outputSettings:videoSettings sourceFormatHint:formatDescription]. The sourceFormatHint makes a difference in writing speed.

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