相信在iOS应用里面很常用的功能之一就是视频录制了,但是往往系统的录制界面不是我们想要的,所以这时候就得自定义视频录制界面了.当然对很多人来讲的，AVFoundation这个库不是很熟.下面就一步步来实现一个自定义界面把！

创建UI以及相机采集工作

NSError *error = nil;
        self.session = [[AVCaptureSession alloc] init];
//可以根据自己的需求来决定预览层的画质
        _session.sessionPreset = AVCaptureSessionPresetLow;
        AVCaptureDevice *frontCamera = nil;
        AVCaptureDevice *backCamera = nil;
        NSArray *cameras = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];
        for (AVCaptureDevice *camera in cameras) {
            if (camera.position == AVCaptureDevicePositionFront) {
                frontCamera = camera;
            } else {
                backCamera = camera;
            }
        }
        if (!backCamera) {
            self.isCameraSupported = NO;
            return;
        } else {
            self.isCameraSupported = YES;
            if ([backCamera hasTorch]) {
                self.isTorchSupported = YES;
            } else {
                self.isTorchSupported = NO;
            }
        }
        if (!frontCamera) {
            self.isFrontCameraSupported = NO;
        } else {
            self.isFrontCameraSupported = YES;
        }
        [backCamera lockForConfiguration:nil];
        if ([backCamera isExposureModeSupported:AVCaptureExposureModeContinuousAutoExposure]) {
            [backCamera setExposureMode:AVCaptureExposureModeContinuousAutoExposure];
        }
        [backCamera unlockForConfiguration];
        // 用device对象创建一个设备对象input，并将其添加到session
        self.videoDeviceInput = [AVCaptureDeviceInput deviceInputWithDevice:backCamera error:&error];
        if (!_videoDeviceInput) {
            return;
        }
        [_session addInput:_videoDeviceInput];
        
        AVCaptureDeviceInput *audioDeviceInput = [AVCaptureDeviceInput deviceInputWithDevice:[AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeAudio] error:nil];
        if (!audioDeviceInput) {
        }
        _output = [[AVCaptureVideoDataOutput alloc] init];
        [_session addOutput:_output];
        

        dispatch_queue_t queue = dispatch_queue_create("myQueue", NULL);
        [_output setSampleBufferDelegate:self queue:queue];
        //这里作者我需要的是480*480的视频  所有先取640x480,后期通过裁剪来获取到480*480的   画质越高处理的速度相对较慢,所以根据自己的需求来定义
        _session.sessionPreset = AVCaptureSessionPreset640x480;
        
        dispatch_async(dispatch_get_main_queue(), ^{
            self.preViewLayer = [AVCaptureVideoPreviewLayer layerWithSession:_session];
            _preViewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill;
            [_session commitConfiguration];
            // 启动session
             [_session startRunning];
            
            self.preViewLayer.frame = CGRectMake(0, 0, MYSCREENWIDTH, MYSCREENWIDTH*4/4);
//preview是一个UIView,用来加载相机的预览层
            [preview.layer addSublayer:self.preViewLayer];
            
        });

获取视频流

#pragma mark 获取视频流

- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection
{
        //在这里你可以获取到视频采集到的视频帧音频帧,具体要做什么操作  旋转啊  裁剪啊 之类的    就可以根据项目需求来决定
}