爲什麼AVCaptureSession輸出方向錯誤？

Question

因此，我遵循Apple的指示使用AVCaptureSession：http://developer.apple.com/iphone/library/qa/qa2010/qa1702.html來捕捉視頻會話。我面臨的一個問題是，即使相機/ iPhone設備的方向是垂直的（並且AVCaptureVideoPreviewLayer顯示了垂直相機流），輸出圖像似乎仍處於橫向模式。我檢查了示例代碼imageFromSampleBuffer:中imageBuffer的寬度和高度，我分別獲得了640px和480px。有誰知道爲什麼會出現這種情況？

謝謝！

Answer 1

看看頭文件AVCaptureSession.h。定義了一個名爲AVCaptureVideoOrientation的枚舉，該枚舉定義了各種視頻方向。在AVCaptureConnection對象上有一個名爲videoOrientation的屬性，它是AVCaptureVideoOrientation。你應該可以設置這個來改變視頻的方向。你可能想要AVCaptureVideoOrientationLandscapeRight或AVCaptureVideoOrientationLandscapeLeft。

您可以通過查看會話的輸出來找到會話的AVCaptureConnections。輸出具有連接屬性，該連接屬性是該輸出的一組連接。

Answer 2

我對imageFromSampleBuffer做了一個簡單的單行修改來糾正方向問題（請參閱我在「I modified ...」中的代碼中的評論）。希望它能幫助別人，因爲我在這方面花費了太多時間。

// Create a UIImage from sample buffer data 
- (UIImage *) imageFromSampleBuffer:(CMSampleBufferRef) sampleBuffer { 
    // Get a CMSampleBuffer's Core Video image buffer for the media data 
    CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer); 
    // Lock the base address of the pixel buffer 
    CVPixelBufferLockBaseAddress(imageBuffer, 0); 

    // Get the number of bytes per row for the pixel buffer 
    void *baseAddress = CVPixelBufferGetBaseAddress(imageBuffer); 

    // Get the number of bytes per row for the pixel buffer 
    size_t bytesPerRow = CVPixelBufferGetBytesPerRow(imageBuffer); 
    // Get the pixel buffer width and height 
    size_t width = CVPixelBufferGetWidth(imageBuffer); 
    size_t height = CVPixelBufferGetHeight(imageBuffer); 

    // Create a device-dependent RGB color space 
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB(); 

    // Create a bitmap graphics context with the sample buffer data 
    CGContextRef context1 = CGBitmapContextCreate(baseAddress, width, height, 8, 
               bytesPerRow, colorSpace, kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst); 

    // Create a Quartz image from the pixel data in the bitmap graphics context 
    CGImageRef quartzImage = CGBitmapContextCreateImage(context1); 
    // Unlock the pixel buffer 
    CVPixelBufferUnlockBaseAddress(imageBuffer,0); 

    // Free up the context and color space 
    CGContextRelease(context1); 
    CGColorSpaceRelease(colorSpace); 

    // Create an image object from the Quartz image 
    //I modified this line: [UIImage imageWithCGImage:quartzImage]; to the following to correct the orientation: 
    UIImage *image = [UIImage imageWithCGImage:quartzImage scale:1.0 orientation:UIImageOrientationRight]; 

    // Release the Quartz image 
    CGImageRelease(quartzImage); 

    return (image); 
} 

Answer 3

例如：

AVCaptureConnection *captureConnection = <a capture connection>; 
if ([captureConnection isVideoOrientationSupported]) { 
    captureConnection.videoOrientation = AVCaptureVideoOrientationPortrait; 
} 

默認似乎是AVCaptureVideoOrientationLandscapeRight。請參閱QA1744: Setting the orientation of video with AV Foundation。

Answer 4

這是一個正確的順序：

AVCaptureVideoDataOutput *videoCaptureOutput = [[AVCaptureVideoDataOutput alloc] init]; 

if([self.captureSession canAddOutput:self.videoCaptureOutput]){ 
    [self.captureSession addOutput:self.videoCaptureOutput]; 
}else{ 
    NSLog(@"cantAddOutput"); 
} 

// set portrait orientation 
AVCaptureConnection *conn = [self.videoCaptureOutput connectionWithMediaType:AVMediaTypeVideo]; 
[conn setVideoOrientation:AVCaptureVideoOrientationPortrait]; 

Answer 5

定位問題是與前置攝像頭，所以檢查設備類型和產生新的圖像，它肯定會解決的方向問題：

-(void)capture:(void(^)(UIImage *))handler{ 

AVCaptureConnection *videoConnection = nil; 
for (AVCaptureConnection *connection in self.stillImageOutput.connections) 
{ 
    for (AVCaptureInputPort *port in [connection inputPorts]) 
    { 
     if ([[port mediaType] isEqual:AVMediaTypeVideo]) 
     { 
      videoConnection = connection; 
      break; 
     } 
    } 
    if (videoConnection) { break; } 
} 

[self.stillImageOutput captureStillImageAsynchronouslyFromConnection:videoConnection completionHandler: ^(CMSampleBufferRef imageSampleBuffer, NSError *error) { 

    if (imageSampleBuffer != NULL) { 
     NSData *imageData = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageSampleBuffer]; 
     **UIImage *capturedImage = [UIImage imageWithData:imageData]; 
     if (self.captureDevice == [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo][1]) { 
      capturedImage = [[UIImage alloc] initWithCGImage:capturedImage.CGImage scale:1.0f orientation:UIImageOrientationLeftMirrored]; 
     }** 

     handler(capturedImage); 
    } 
}]; 
} 

Answer 6

ÿ 「所有這些都讓這很難。

在DidOutputSampleBuffer中，只需在抓取圖像之前更改方向即可。這是單聲道，但你必須

public class OutputRecorder : AVCaptureVideoDataOutputSampleBufferDelegate {  
     public override void DidOutputSampleBuffer (AVCaptureOutput captureOutput, CMSampleBuffer sampleBuffer, AVCaptureConnection connection) 
     { 
      try { 
       connection.videoOrientation = AVCaptureVideoOrientation.LandscapeLeft; 

在objC它的這種方法

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

Answer 7

如果AVCaptureVideoPreviewLayer方向是正確的，你可以簡單的設置方向在拍照之前。

AVCaptureStillImageOutput *stillImageOutput; 
AVCaptureVideoPreviewLayer *previewLayer; 
NSData *capturedImageData; 

AVCaptureConnection *videoConnection = [stillImageOutput connectionWithMediaType:AVMediaTypeVideo]; 
if ([videoConnection isVideoOrientationSupported]) { 
    [videoConnection setVideoOrientation:previewLayer.connection.videoOrientation]; 
} 
[stillImageOutput captureStillImageAsynchronouslyFromConnection:videoConnection completionHandler:^(CMSampleBufferRef imageSampleBuffer, NSError *error) { 
    CFDictionaryRef exifAttachments = 
      CMGetAttachment(imageSampleBuffer, kCGImagePropertyExifDictionary, NULL); 
    if (exifAttachments) { 
     // Do something with the attachments. 
    } 
    // TODO need to manually add GPS data to the image captured 
    capturedImageData = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageSampleBuffer]; 
    UIImage *image = [UIImage imageWithData:capturedImageData]; 
}]; 

另外，需要注意的是UIImageOrientation和AVCaptureVideoOrientation不同是很重要的。 UIImageOrientationUp指的是風景模式與音量控制向下朝向地面（而不是如果您考慮使用音量控制作爲快門按鈕）。

因此，用電源按鈕指向天空的縱向（AVCaptureVideoOrientationPortrait）實際上是UIImageOrientationLeft。

Answer 8

對於那些需要使用CIImage和緩衝區方向的人是錯誤的，我使用了這種修正。

就這麼簡單。順便說一句，號碼3,1,6,8是從這裏https://developer.apple.com/reference/imageio/kcgimagepropertyorientation

不要問我爲什麼3,1,6,8是正確的組合。我用蠻力法找到它。如果你知道爲什麼讓解釋的意見，請...

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

    // common way to get CIImage 

    CVPixelBufferRef pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer); 

    CFDictionaryRef attachments = CMCopyDictionaryOfAttachments(kCFAllocatorDefault, sampleBuffer, kCMAttachmentMode_ShouldPropagate); 

    CIImage *ciImage = [[CIImage alloc] initWithCVPixelBuffer:pixelBuffer 
                 options:(__bridge NSDictionary *)attachments]; 

    if (attachments) { 
     CFRelease(attachments); 
    } 

    // fixing the orientation of the CIImage 

    UIInterfaceOrientation curOrientation = [[UIApplication sharedApplication] statusBarOrientation]; 

    if (curOrientation == UIInterfaceOrientationLandscapeLeft){ 
     ciImage = [ciImage imageByApplyingOrientation:3]; 
    } else if (curOrientation == UIInterfaceOrientationLandscapeRight){ 
     ciImage = [ciImage imageByApplyingOrientation:1]; 
    } else if (curOrientation == UIInterfaceOrientationPortrait){ 
     ciImage = [ciImage imageByApplyingOrientation:6]; 
    } else if (curOrientation == UIInterfaceOrientationPortraitUpsideDown){ 
     ciImage = [ciImage imageByApplyingOrientation:8]; 
    } 



    // .... 

} 

Answer 9

剛剛嘗試這一點;）

private func startLiveVideo() { 

    let captureSession = AVCaptureSession() 
    captureSession.sessionPreset = .photo 
    let captureDevice = AVCaptureDevice.default(for: .video) 

    let input = try! AVCaptureDeviceInput(device: captureDevice!) 
    let output = AVCaptureVideoDataOutput() 
    captureSession.addInput(input) 
    captureSession.addOutput(output) 

    output.setSampleBufferDelegate(self, queue: DispatchQueue(label: "videoQueue")) 
    output.connection(with: .video)?.videoOrientation = .portrait 

    let previewLayer = AVCaptureVideoPreviewLayer(session: captureSession) 
    previewLayer.frame = view.bounds 
    view.layer.addSublayer(previewLayer) 

    captureSession.startRunning() 
}