二、采集视频数据

Demo地址 苹果对于音视频的采集已经提供给我们很好的封装:AVFoundation.framework.我们可以使用AVFoundation框架来采集视频数据.

@interface RTAVVideoCaputre ()<AVCaptureVideoDataOutputSampleBufferDelegate>
{
    AVCaptureVideoPreviewLayer * _preViewLayer;

}
@property (nonatomic,strong)AVCaptureSession *session;
@property (nonatomic,strong)RTAVVideoConfiguration *videoConfiguration;
@end
@implementation RTAVVideoCaputre

- (instancetype)initWithVideoConfiguration:(RTAVVideoConfiguration *)configuration
{
    if (self = [super init]) {
        _videoConfiguration = configuration;
        [self addPreVideo];
    }
    return self;
}
#pragma mark - Method
- (void)addPreVideo
{
    AVCaptureVideoPreviewLayer * preViewLayer = [AVCaptureVideoPreviewLayer layerWithSession:self.session];
    preViewLayer.frame = [UIScreen mainScreen].bounds;
    preViewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill;

    _preViewLayer = preViewLayer;

}

#pragma mark - delegate

#pragma mark AVCaptureSessionDelegete
- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection
{
    CVImageBufferRef imageBuffer  = CMSampleBufferGetImageBuffer(sampleBuffer);
    if (imageBuffer != NULL) {
        if ([_delegate respondsToSelector:@selector(captureOutput:pixelBuffer:)]) {
            [_delegate captureOutput:self pixelBuffer:imageBuffer];
        }
    }
}
#pragma mark - setter & getter
- (AVCaptureSession *)session
{
    if (!_session) {
        //4.
        AVCaptureSession * session = [[AVCaptureSession alloc]init];
        session.sessionPreset = _videoConfiguration.avsessionPreset;
        //1.
        AVCaptureDevice * device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];

        NSError * error = nil;
        //2.
        AVCaptureDeviceInput * videoInput = [AVCaptureDeviceInput deviceInputWithDevice:device error:&error];

        //3.
        AVCaptureVideoDataOutput *  videoOutput = [[AVCaptureVideoDataOutput alloc]init];
        dispatch_queue_t videoDataOutputQueue = dispatch_queue_create("VideoDataOutputQueue", DISPATCH_QUEUE_SERIAL);
        [videoOutput setSampleBufferDelegate:self queue:videoDataOutputQueue];

        [videoOutput connectionWithMediaType:AVMediaTypeVideo] ;

        videoOutput.videoSettings = @{(id)kCVPixelBufferPixelFormatTypeKey:@(kCVPixelFormatType_32BGRA)};

        //设置帧率
        if ([device respondsToSelector:@selector(setActiveVideoMaxFrameDuration:)] && [device respondsToSelector:@selector(setActiveVideoMinFrameDuration:)]) {
            NSError * error ;
            [device lockForConfiguration:&error];
            if (nil == error) {
#if defined (__IPHONE_7_0)
                device.activeVideoMaxFrameDuration = CMTimeMake(1, (int32_t)_videoConfiguration.videoFrameRate);
                device.activeVideoMinFrameDuration = CMTimeMake(1, (int32_t)_videoConfiguration.videoFrameRate);
#endif
            }
            [device unlockForConfiguration];
        }else
        {
            for (AVCaptureConnection * connection in videoOutput.connections) {
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wdeprecated-declarations"
                if ([connection respondsToSelector:@selector(setVideoMinFrameDuration:)])
                    connection.videoMinFrameDuration = CMTimeMake(1,  (int32_t)_videoConfiguration.videoMinFrameRate);

                if ([connection respondsToSelector:@selector(setVideoMaxFrameDuration:)])
                    connection.videoMaxFrameDuration = CMTimeMake(1, (int32_t)_videoConfiguration.videoMaxFrameRate);
#pragma clang diagnostic pop
            }
        }



        //5.
        if ([session canAddInput:videoInput]) {
            [session addInput:videoInput];
        }
        if ([session canAddOutput:videoOutput]) {
            [session addOutput:videoOutput];
        }
        _session = session;

    }
    return _session;
}

1.通过获取系统支持有效的设备类型--视频类型;

2.设置作为捕捉视频的输入设备;

3.设置捕捉数据的输出,通过代理方法(7)获取处理未编解码的帧数据sampleBuffer;

4.每一个实时的捕获,全部通过一个session(会话)来开启;

5.将输入设备和输出设备添加到会话中;

6.开启会话捕获.