如何在AVFoundation中静音捕获声音？

Question

我想在没有任何声音的情况下使用AVfoundation拍摄图像(是的,我记住,用户选择将实现此功能)

关于堆栈溢出的两个问题提供了最多的信息:

• AVFoundation,如何在captureStillImageAsynchronouslyFromConnection时关闭快门声音？(没有接受并确认答案)

• 在iPhone上静音AVCapture快门声音(AVCaptureVideoDataOutput建议)

这两个答案都指捕获视频帧,我认为这是正确的.问题是AVfoundation库不是很容易掌握,我不能真正掌握它(捕获图像使用AVCaptureStillImageOutput本身对我来说很难).

Answer 1

我发现代码在这里做..

http://www.benjaminloulier.com/articles/ios4-and-direct-access-to-the-camera

重要部分概述..

设置你的会话就像这样

-(void)initialize_and_Start_Session_without_CaptureSound
{
    /*We setup the input*/
    AVCaptureDeviceInput *captureInput = [AVCaptureDeviceInput 
                                          deviceInputWithDevice:[AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo] 
                                          error:nil];
    /*We setupt the output*/
    AVCaptureVideoDataOutput *captureOutput = [[AVCaptureVideoDataOutput alloc] init];
    /*While a frame is processes in -captureOutput:didOutputSampleBuffer:fromConnection: delegate methods no other frames are added in the queue.
     If you don't want this behaviour set the property to NO */
    captureOutput.alwaysDiscardsLateVideoFrames = YES; 
    /*We specify a minimum duration for each frame (play with this settings to avoid having too many frames waiting
     in the queue because it can cause memory issues). It is similar to the inverse of the maximum framerate.
     In this example we set a min frame duration of 1/10 seconds so a maximum framerate of 10fps. We say that
     we are not able to process more than 10 frames per second.*/
    //captureOutput.minFrameDuration = CMTimeMake(1, 10);

    /*We create a serial queue to handle the processing of our frames*/
    dispatch_queue_t queue;
    queue = dispatch_queue_create("cameraQueue", NULL);
    [captureOutput setSampleBufferDelegate:self queue:queue];
    dispatch_release(queue);
    // Set the video output to store frame in BGRA (It is supposed to be faster)
    NSString* key = (NSString*)kCVPixelBufferPixelFormatTypeKey; 
    NSNumber* value = [NSNumber numberWithUnsignedInt:kCVPixelFormatType_32BGRA]; 
    NSDictionary* videoSettings = [NSDictionary dictionaryWithObject:value forKey:key]; 
    [captureOutput setVideoSettings:videoSettings]; 
    /*And we create a capture session*/
    self.session = [[AVCaptureSession alloc] init];
    /*We add input and output*/
    [self.session addInput:captureInput];
    [self.session addOutput:captureOutput];


    /*We start the capture*/
    [self.session startRunning];

}

你将通过以下方法获得相机输出..我制作一个图像并将其添加到我的父视图..你可以根据需要改变它

#pragma mark AVCaptureSession delegate
- (void)captureOutput:(AVCaptureOutput *)captureOutput 
didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer 
       fromConnection:(AVCaptureConnection *)connection 
{ 
    /*We create an autorelease pool because as we are not in the main_queue our code is
     not executed in the main thread. So we have to create an autorelease pool for the thread we are in*/
    if (captureImageNow)
    {

    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

    CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer); 
    /*Lock the image buffer*/
    CVPixelBufferLockBaseAddress(imageBuffer,0); 
    /*Get information about the image*/
    uint8_t *baseAddress = (uint8_t *)CVPixelBufferGetBaseAddress(imageBuffer); 
    size_t bytesPerRow = CVPixelBufferGetBytesPerRow(imageBuffer); 
    size_t width = CVPixelBufferGetWidth(imageBuffer); 
    size_t height = CVPixelBufferGetHeight(imageBuffer);  

    /*Create a CGImageRef from the CVImageBufferRef*/
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB(); 
    CGContextRef newContext = CGBitmapContextCreate(baseAddress, width, height, 8, bytesPerRow, colorSpace, kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst);
    CGImageRef newImage = CGBitmapContextCreateImage(newContext); 

    /*We release some components*/
    CGContextRelease(newContext); 
    CGColorSpaceRelease(colorSpace);

    /*We display the result on the custom layer. All the display stuff must be done in the main thread because
     UIKit is no thread safe, and as we are not in the main thread (remember we didn't use the main_queue)
     we use performSelectorOnMainThread to call our CALayer and tell it to display the CGImage.*/

    /*We display the result on the image view (We need to change the orientation of the image so that the video is displayed correctly).
     Same thing as for the CALayer we are not in the main thread so ...*/
    self.captureImage = [UIImage imageWithCGImage:newImage scale:1.0 orientation:UIImageOrientationRight];

    /*We relase the CGImageRef*/
    CGImageRelease(newImage);


    [self performSelectorOnMainThread:@selector(AddImageToParentView) withObject:nil waitUntilDone:YES];

    /*We unlock the  image buffer*/
    CVPixelBufferUnlockBaseAddress(imageBuffer,0);

    [pool drain];
        captureImageNow = NO;
    }
}