前言
正文
实时的视频流数据采集用AVFoundation框架的AVCaptureSession类
创建AVCaptureSession->设置输入输出对象-> 用AVCaptureConnection连接输入输出->在回调方法中返回视频数据做处理
重要知识点
由于iphone设备的不同型号的前置、后置摄像头所支持的最高分辨率各不相同,所以在设置时,一定进行判断,不然会采集不出数据.
采集、设置
//初始化AVCaptureSession
self.videoSession =[[AVCaptureSession alloc]init];
//开始配置
[self.videoSession beginConfiguration];
//设置分辨率
[self set_capture_present];
//获取视频设备对象
self.videoDevice = [self cameraWithPosition:position];
//初始化视频捕获输入对象
self.VideoInput = [[AVCaptureDeviceInput alloc]initWithDevice:self.videoDevice error:nil];
//初始化视频捕获输出对象
self.VideoOutput = [[AVCaptureVideoDataOutput alloc]init];
// 是否卡顿时丢帧
[self.VideoOutput setAlwaysDiscardsLateVideoFrames:YES];
// 设置像素格式
self.VideoOutput.videoSettings =[NSDictionary dictionaryWithObject:[NSNumber numberWithInt:kCVPixelFormatType_420YpCbCr8BiPlanarFullRange] forKey:(id)kCVPixelBufferPixelFormatTypeKey];
//将输出对象添加到队列、并设置代理
dispatch_queue_t mProcessQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0);
[self.VideoOutput setSampleBufferDelegate:self queue:mProcessQueue];
//输入,输出对象添加到Session
if ([self.videoSession canAddInput:self.VideoInput])
{
[self.videoSession addInput:self.VideoInput];
}
if ([self.videoSession canAddOutput:self.VideoOutput])
{
[self.videoSession addOutput:self.VideoOutput];
}
//创建连接 AVCaptureConnection输入对像和捕获输出对象之间建立连接。
_videoConnection=[self.VideoOutput connectionWithMediaType:AVMediaTypeVideo];
//视频的方向
[_videoConnection setVideoOrientation:AVCaptureVideoOrientationPortrait];
//设置稳定性，判断connection连接对象是否支持视频稳定
if ([_videoConnection isVideoStabilizationSupported]) {
//这个稳定模式最适合连接
_videoConnection.preferredVideoStabilizationMode = AVCaptureVideoStabilizationModeAuto;
}
//缩放裁剪系数
_videoConnection.videoScaleAndCropFactor = _videoConnection.videoMaxScaleAndCropFactor;
[self.videoSession commitConfiguration];
自动适配设备最高分辨率
- (void)set_capture_present
{
if (![self.videoDevice supportsAVCaptureSessionPreset:AVCaptureSessionPreset1920x1080])
{
if (![self.videoDevice supportsAVCaptureSessionPreset:AVCaptureSessionPreset1280x720])
{
if (![self.videoDevice supportsAVCaptureSessionPreset:AVCaptureSessionPresetiFrame960x540])
{
if (![self.videoDevice supportsAVCaptureSessionPreset:AVCaptureSessionPreset640x480])
{
if (![self.videoDevice supportsAVCaptureSessionPreset:AVCaptureSessionPreset352x288])
{
NSLog(@"what the fuck?");
}else
{
self.videoSession.sessionPreset = AVCaptureSessionPreset352x288;
}
}else
{
self.videoSession.sessionPreset = AVCaptureSessionPresetiFrame960x540;
}
}else
{
self.videoSession.sessionPreset = AVCaptureSessionPresetiFrame960x540;
}
}else
{
self.videoSession.sessionPreset = AVCaptureSessionPreset1280x720;
}
}else
{
self.videoSession.sessionPreset = AVCaptureSessionPreset1920x1080;
}
}
回调
//视频采集数据回调
- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection
{
if (connection == self.videoConnection)
{
//判断是否为采集的第一帧数据
if (!self.isComed)
{
//设置一个起始时间戳
self.startTime = [[NSDate date] timeIntervalSince1970]*1000*1000;
self.isComed = 1;
self.timeStamp = 0;
NSUserDefaults * defaults = [NSUserDefaults standardUserDefaults];
[defaults setInteger:self.startTime forKey:@"startTime"];
}
else
{
self.timeStamp = ([[NSDate date] timeIntervalSince1970]*1000*1000-self.startTime)*0.09;
}
把视频数据和时间戳传给代理类
[self.delegate backWithVideobuffer:sampleBuffer andTimeStamp:self.timeStamp];
}
}
