iOS视频捕获实践篇

该demo以ToyCamera命名

常用类、方法、属性已在【iOS视频捕获入门篇】介绍。
@[toc]

1. 视频流

1.1 设备与输入

前面提到我们不能直接设备，而是需要用一个输入对象将设备封装。先来提供一个前置摄像头和一个后置摄像头。（后置摄像头我们只使用一个）

- (AVCaptureDevice *)videoFrontDevice {
    if (!_captureDevice || self.captureDevice.position != AVCaptureDevicePositionFront) {
        AVCaptureDeviceDiscoverySession *session = [AVCaptureDeviceDiscoverySession discoverySessionWithDeviceTypes:@[AVCaptureDeviceTypeBuiltInDualCamera, AVCaptureDeviceTypeBuiltInTelephotoCamera,AVCaptureDeviceTypeBuiltInWideAngleCamera] mediaType:AVMediaTypeVideo position:AVCaptureDevicePositionFront];
        _captureDevice = session.devices.firstObject;
    }
    return _captureDevice;
}


- (AVCaptureDevice *)videoBackDevice {
    if (!_captureDevice || self.captureDevice.position != AVCaptureDevicePositionBack) {
        AVCaptureDeviceDiscoverySession *session = [AVCaptureDeviceDiscoverySession discoverySessionWithDeviceTypes:@[AVCaptureDeviceTypeBuiltInDualCamera, AVCaptureDeviceTypeBuiltInTelephotoCamera,AVCaptureDeviceTypeBuiltInWideAngleCamera] mediaType:AVMediaTypeVideo position:AVCaptureDevicePositionBack];
        _captureDevice = session.devices.firstObject;
    }
    return _captureDevice;
}

通过Input对象来封装设备：

- (void)_addCaptureIntput {
    [self.metadataDevice lockForConfiguration:nil];
    AVCaptureDeviceInput *deviceInput = [[AVCaptureDeviceInput alloc] initWithDevice:self.videoBackDevice error:nil];
    if ([self.captureSession canAddInput:deviceInput]) {
        [self.captureSession addInput:deviceInput];
    }
    [self.metadataDevice unlockForConfiguration];
}

1.2 输出

先实现视频流，定义一个视频流输出：

@property (nonatomic) AVCaptureVideoDataOutput *captureVideoDataOutput;

_captureVideoDataOutput = [[AVCaptureVideoDataOutput alloc] init];
// delegate可以实现 AVCaptureVideoDataOutputSampleBufferDelegate 中的方法来接收视频帧
[self.captureVideoDataOutput setSampleBufferDelegate:self.delegate queue:self.sampleBufferQueue];
self.captureVideoDataOutput.videoSettings = @{(__bridge NSString *)kCVPixelBufferPixelFormatTypeKey : [NSNumber numberWithInt:kCVPixelFormatType_32BGRA]};

1.3 会话

最重要的就是会话。

_captureSession = [[AVCaptureSession alloc] init];
// 开始配置
[self.captureSession beginConfiguration];
// 设置质量
self.captureSession.sessionPreset = AVCaptureSessionPreset1280x720;
// 添加输入
[self.captureDevice lockForConfiguration:nil];
AVCaptureDeviceInput *deviceInput = [[AVCaptureDeviceInput alloc] initWithDevice:self.videoBackDevice error:nil];
if ([self.captureSession canAddInput:deviceInput]) {
     [self.captureSession addInput:deviceInput];
}
[self.captureDevice unlockForConfiguration];
// 添加输出
if ([self.captureSession canAddOutput:self.captureVideoDataOutput]) {
    [self.captureSession addOutput:self.captureVideoDataOutput];
}
[self.captureSession commitConfiguration];

1.4 预览页

前面的准备工作做完之后，就可以添加预览页面，这样才能看到我们捕获的视频。

// 就是一个Layer，返回后添加到合适的View上即可。
- (AVCaptureVideoPreviewLayer *)videoPreviewLayer {
    if (!_videoPreviewLayer) {
        _videoPreviewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:self.captureSession];
        _videoPreviewLayer.videoGravity= AVLayerVideoGravityResizeAspectFill;
        _videoPreviewLayer.connection.videoOrientation = AVCaptureVideoOrientationPortrait;
    }
    return _videoPreviewLayer;
}

至此其实就有一个可以看的见的视频流了。但是仅仅看到不是我们所希望的，我们需要拍照、录视频等。当然对于使用视频流做追踪、处理是够了。而且使用视频输出的视频帧也可以转为图片从而实现拍照。

2. 拍照

2.1 输出

输入我们可以共用，对于正式的拍照，我们需要使用AVCapturePhotoOutput实现。

_capturePhotoOutput = [[AVCapturePhotoOutput alloc] init];
[self.captureSession addOutput:self.capturePhotoOutput];
NSMutableArray<AVVideoCodecType> *availablePhotoCodecTypes = [NSMutableArray array];
AVCapturePhotoSettings *settings;
for (AVVideoCodecType type in self.capturePhotoOutput.availablePhotoCodecTypes) {
    if ([type isEqualToString:AVVideoCodecTypeJPEG]) {
        settings = [AVCapturePhotoSettings photoSettingsWithFormat:@{AVVideoCodecKey: AVVideoCodecTypeJPEG}];
        [availablePhotoCodecTypes addObject:AVVideoCodecTypeJPEG];
        break;
    }
}
// 这里的原因在【iOS视频捕获入门篇】已介绍
if (settings) {
    [self.capturePhotoOutput setPreparedPhotoSettingsArray:@[settings] completionHandler:^(BOOL prepared, NSError * _Nullable error) {
        if (prepared) {
            
        } else if (error) {
            
        }
    }];
}

2.2 获得照片

通过下面的api获得照片。每次获取照片时，我们都需要传入一个AVCapturePhotoSettings。

// delegate需要实现 AVCapturePhotoCaptureDelegate 协议
[self.capturePhotoOutput capturePhotoWithSettings:[AVCapturePhotoSettings photoSettingsWithFormat:@{AVVideoCodecKey: AVVideoCodecTypeJPEG}] delegate:self.delegate];

// 实现 AVCapturePhotoCaptureDelegate 协议
- (void)captureOutput:(AVCapturePhotoOutput *)output didFinishProcessingPhoto:(AVCapturePhoto *)photo error:(nullable NSError *)error {
    if (!error) {
        NSData *data = [photo fileDataRepresentation];
        UIImage *image = [UIImage imageWithData:data];
      // 保存照片
        [TCUtility saveImage:image];
        }
}

3. 录制视频

这里录制视频没有录制音频，只有视频画面。

录制视频我们需要使用到 AVCaptureMovieFileOutput。其属性和方法在【iOS视频捕获入门篇】已介绍

_captureMovieFileOutput = [[AVCaptureMovieFileOutput alloc] init];

// 简单点，其他参数使用默认的
if ([self.captureSession canAddOutput:self.captureMovieFileOutput]) {
	[self.captureSession addOutput:self.captureMovieFileOutput];
}

我们使用一个方法就可以实现开始录制和停止录制

- (void)captureVideo {
  // 如果是录制中，那么本次调用就是停止录制
    if (self.captureMovieFileOutput.isRecording) {
        [self.captureMovieFileOutput stopRecording];
    }
  // 否则就是开始录制
    NSString *urlString = [NSTemporaryDirectory() stringByAppendingString:[NSString stringWithFormat:@"%.0f.mov", [[NSDate date] timeIntervalSince1970] * 1000]];
    NSURL *url = [NSURL fileURLWithPath:urlString];
  // 代理
    [self.captureMovieFileOutput startRecordingToOutputFileURL:url recordingDelegate:self.delegate];
}
// 实现代理
- (void)captureOutput:(AVCaptureFileOutput *)output didFinishRecordingToOutputFileAtURL:(NSURL *)outputFileURL fromConnections:(NSArray<AVCaptureConnection *> *)connections error:(nullable NSError *)error {
  // 可以将URL存入到相册
    [TCUtility saveVideo:outputFileURL];
}