我想在Mac OS X上镜像从网络摄像头接收到的视频。我想避免在收到视频缓冲区后做手动翻转/变换。所以,我想要设置AVCaptureSession
,使得在captureOutput
方法AVCaptureVideoDataOutputSampleBufferDelegate
中接收到的视频缓冲区被AVFoundation本身镜像。我不想使用预览图层。AVFoundation - 如何从网络摄像头镜像视频 - Mac OS X
在设置videoMirrored
属性之前,在iMac(10.8.5)上,为了镜像视频,已成功测试了AVCaptureConnection isVideoMirroringSupported
。但是,在captureOutput
代表中收到的视频缓冲区不是镜像的。
注意:iOS上的视频镜像成功,当我按照this SO回答。但它在mac os x上没有帮助。
使用的代码如下。错误检查被忽略了这篇文章。
//create session
_session = [[AVCaptureSession alloc] init];
//get capture device
_device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
//create sesion input
NSError * error;
_sessionInput = [AVCaptureDeviceInput deviceInputWithDevice:_device error:&error];
//create session output
_sessionOutput = [[AVCaptureVideoDataOutput alloc] init];
[_sessionOutput setAlwaysDiscardsLateVideoFrames:YES];
[[_sessionOutput connectionWithMediaType:AVMediaTypeVideo] setEnabled:YES];
NSDictionary *videoSettings = [NSDictionary dictionaryWithObject: [NSNumber numberWithUnsignedInt:kCVPixelFormatType_32BGRA] forKey:(id)kCVPixelBufferPixelFormatTypeKey];
[_sessionOutput setVideoSettings:videoSettings];
//serial queue to process video frames
dispatch_queue_t videoOutputQueue = dispatch_queue_create("deviceeraQueue", DISPATCH_QUEUE_SERIAL);
[_sessionOutput setSampleBufferDelegate:self queue:videoOutputQueue];
//begin session configuration
[_session beginConfiguration ];
//input and output for session
if([_session canAddInput:_sessionInput]) {
[_session addInput:_sessionInput];
}
if([_session canAddOutput:_sessionOutput]) {
[_session addOutput:_sessionOutput];
}
//set video mirroring
AVCaptureConnection* avConnection = [_sessionOutput connectionWithMediaType:AVMediaTypeVideo];
if([avConnection isVideoMirroringSupported]) {
avConnection.videoMirrored = YES;
NSLog(@"Video mirroring Support: YES"); // this line is printed
} else {
NSLog(@"Video mirroring Support: NO");
}
//set session preset
[_session setSessionPreset:AVCaptureSessionPreset640x480];
[ _session commitConfiguration ];
...........
...........
- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection
{
.........
//sampleBuffer is not mirrored video
........
不太重要1 - 尽管C++,我也试着研究OpenCV的VideoCapture实现方式来镜像视频。但是,OpenCV不会镜像来自Mac的视频(使用翻转)。左边是libVlc/V4L。
不太重要2 - 在this 2010 wwdc苹果演示文稿(3Mb pdf)的幻灯片73中,提到setVideoOrientation
在'AVCaptureVideoDataOutput`连接上不受支持。但在2013年,Apple docs已更新并支持此方法。
谢谢。但有问题,我曾提到过不愿意使用预览图层(在第1段中) – Kiran
OSX不尊重videoMirrored属性,可能是一个错误。使用预览图层是我发现达到效果的唯一方式。 – tansk1