iOS视频直播之视频采集一（硬编码）

视频采集

主要是通过< AVFoundation >框架进行采集

demo下载地址

• 采集画面，这里必须使用真机，模拟器不支持

  
  
  

• 1.创建会话

    AVCaptureSession *captureSession = [[AVCaptureSession alloc] init];
    captureSession.sessionPreset = AVCaptureSessionPreset1280x720;
    self.captureSession = captureSession;
  

• 2.设置视频的输入

    // 2.1获取输入设备，摄像头,默认为后置
    AVCaptureDevice *videoDevice = [self getVideoDevice:AVCaptureDevicePositionBack];
  
    //2.2创建对应视频输入对象
    AVCaptureDeviceInput *videoDeviceInput = [AVCaptureDeviceInput deviceInputWithDevice:videoDevice error:nil];
  
    //2.3添加到会话中
    // 注意：最好要判断是否能添加输入，会话不能添加空的
    if ([captureSession canAddInput:videoDeviceInput])   {
     [captureSession addInput:videoDeviceInput];
    }
  

• 3.设置视频的输出

    // 3.1获取视频输出设备
    AVCaptureVideoDataOutput *videoOutput = [[AVCaptureVideoDataOutput alloc] init];
    //默认为YES，接收器会立即丢弃接收到的帧，在代理里面，NO的时候，将允许在丢弃之前有更多时间处理旧帧
   // [videoOutput setAlwaysDiscardsLateVideoFrames:NO];
    // 3.2 设置输出代理，捕获视频样品数据
    dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
    [videoOutput setSampleBufferDelegate:self queue:queue];
    if ([captureSession canAddOutput:videoOutput]) {
        [captureSession addOutput:videoOutput];
    }
    
    //3.3 设置视频输出方向
    // 注意：设置方向，必须在videoOutput添加到captureSession之后，否则出错
    AVCaptureConnection *connection = [videoOutput connectionWithMediaType:AVMediaTypeVideo];
    if (connection.isVideoOrientationSupported) {
        [connection setVideoOrientation:AVCaptureVideoOrientationPortrait];
    }

4. 添加视频预览层

AVCaptureVideoPreviewLayer *layer = [AVCaptureVideoPreviewLayer layerWithSession:captureSession];
self.preViewlayer = layer;
[layer setVideoGravity:AVLayerVideoGravityResizeAspect];
layer.frame = preview.bounds;
[preview.layer insertSublayer:layer atIndex:0];

5.开始采集

[captureSession startRunning];

• 获取摄像头方向

//指定摄像头方向，获取摄像头
- (AVCaptureDevice *)getVideoDevice:(AVCaptureDevicePosition)position{
    NSArray *devices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];
    for (AVCaptureDevice *device in devices) {
        if (device.position == position) {
            return device;
        }
    }
    return nil;
}

• 切换摄像头

// 切换采集摄像头
- (void)switchScene:(UIView *)preview{
    // 1.添加动画
    CATransition *rotaionAnim = [[CATransition alloc] init];
    rotaionAnim.type = @"oglFlip";
    rotaionAnim.subtype = @"fromLeft";
    rotaionAnim.duration = 0.5;
    [preview.layer addAnimation:rotaionAnim forKey:nil];
    
    // 2.获取当前镜头
    AVCaptureDevicePosition position = self.videoDeviceInput.device.position == AVCaptureDevicePositionBack ? AVCaptureDevicePositionFront : AVCaptureDevicePositionBack;
    
    // 3.创建新的input对象
    AVCaptureDevice *newDevice = [self getVideoDevice:position];
    AVCaptureDeviceInput *newDeviceInput = [AVCaptureDeviceInput deviceInputWithDevice:newDevice error:nil];
    
    // 4.移除旧输入，添加新输入
    [self.captureSession beginConfiguration];
    [self.captureSession removeInput:self.videoDeviceInput];
    [self.captureSession addInput:newDeviceInput];
    // 此处要重新设置视频输出方向，默认会旋转90度
    self.connection = [_videoOutput connectionWithMediaType:AVMediaTypeVideo];
    if (_connection.isVideoOrientationSupported) {
        [_connection setVideoOrientation:AVCaptureVideoOrientationPortrait];
    }

    [self.captureSession commitConfiguration];
    // 5.保存新输入
    self.videoDeviceInput = newDeviceInput;
}

• 实现代理 -- AVCaptureVideoDataOutputSampleBufferDelegat

- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection{
    NSLog(@"获取到一帧数据");
    // 对获取到的数据进行编码，编码部分在下一篇继续讲
    dispatch_sync(mEncodeQueue, ^{
        [self.encoder encodeFrame:sampleBuffer];
    });
}

• 停止采集

- (void)stopCapturing{
    // 停止扫描
    [self.captureSession stopRunning];
    // 移除预览图层
    [self.preViewlayer removeFromSuperlayer];
    // 将对象置为nil
    self.captureSession = nil;
}

本文采集到的视频并没有进行编码和写入文件，下一篇将会介绍硬编码，使用ios自带的VideoToolbox库。