前言:前一段时间产品新需求,说是要做微信的小时频功能.
功能需求:360x640 or 640x360的分辨率,大小在2MB 之内的 MP4格式
短视频 demo 地址
思路:使用 AVFoundtion框架提供的 AVCaptureSession进行录制,
大致如下:
摄像头,麦克风(input)->AVCapture Session->AVCaptureVideoDataOutpu(仅视频数据,无音频数据)t,AVCaptureAudioDataOutput(音频数据),AVCaptureStillImageOutput(照片),AVCaptureMovieFileOutput(有视频,也有音频)->AVAssetWriter封装视频和音频格式，写入磁盘，完成录制

关系图.jpg

1.AVCaptureDeviceInput(输入设备):包括摄像头(前置,后置),麦克风,负责采集视频和音频数据
2.AVCaptureVideoDataOutpu:输出视频数据,仅仅只是视频,没有声音,可以对视频格式和参数进行自定义封装和添加滤镜处理
3.AVCaptureAudioDataOutput:输出音频数据,可以对格式和参数进行自定义封装
4.AVCaptureStillImageOutput:照片数据,用户获取静态图像(拍照)
5.AVCaptureMovieFileOutput:输出完整视频(包括音频),优点:录制简单,缺点:可定制性差,短视频不适用(体积太大)
6.AVCapture Session:用于处理输入与输出之间的数据流
7.AVCaptureVideoPreviewLayer:摄像头实时预览 layer, 可以预览摄像头采集的实时视频信息
8.AVAssetWriter:封装音视频格式，写入磁盘

代码示例:

1.录制：

- (AVCaptureSession *)recordSession {
    if (_recordSession == nil) {
        _recordSession = [[AVCaptureSession alloc] init];
        _recordSession.sessionPreset = AVCaptureSessionPresetHigh;
        //添加后置摄像头的输出
        if ([_recordSession canAddInput:self.backCameraInput]) {
            [_recordSession addInput:self.backCameraInput];
        }
        //添加后置麦克风的输出
        if ([_recordSession canAddInput:self.audioMicInput]) {
            [_recordSession addInput:self.audioMicInput];
        }
        //添加视频输出
        if ([_recordSession canAddOutput:self.videoOutput]) {
            [_recordSession addOutput:self.videoOutput];
            _cx = VIDEO_WIDTH;
            _cy = VIDEO_HEIGHT;
        }
        //添加音频输出
        if ([_recordSession canAddOutput:self.audioOutput]) {
            [_recordSession addOutput:self.audioOutput];
        }
        // 静态图像输出
        if ([_recordSession canAddOutput:self.stillImageOutput]) {
            [_recordSession addOutput:self.stillImageOutput];
        }
        //设置视频录制的方向
        self.videoConnection.videoOrientation = AVCaptureVideoOrientationPortrait;
    }
    return _recordSession;
}

//后置摄像头输入
- (AVCaptureDeviceInput *)backCameraInput {
    if (_backCameraInput == nil) {
        NSError *error;
        _backCameraInput = [[AVCaptureDeviceInput alloc] initWithDevice:[self backCamara] error:&error];
        if (error) {
            NSLog(@"获取后置摄像头失败~");
        }
    }
    return _backCameraInput;
}

//前置摄像头输入
- (AVCaptureDeviceInput *)frontCameraInput {
    if (_frontCameraInput == nil) {
        NSError *error;
        _frontCameraInput = [[AVCaptureDeviceInput alloc] initWithDevice:[self frontCamara] error:&error];
        if (error) {
            NSLog(@"获取前置摄像头失败~");
        }
    }
    return _frontCameraInput;
}

//麦克风输入
- (AVCaptureDeviceInput *)audioMicInput {
    if (_audioMicInput == nil) {
        AVCaptureDevice *mic = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeAudio];
        NSError *error;
        _audioMicInput = [AVCaptureDeviceInput deviceInputWithDevice:mic error:&error];
        if (error) {
            NSLog(@"获取麦克风失败~");
        }
    }
    return _audioMicInput;
}

//视频输出
- (AVCaptureVideoDataOutput *)videoOutput {
    if (_videoOutput == nil) {
        _videoOutput = [[AVCaptureVideoDataOutput alloc] init];
        [_videoOutput setSampleBufferDelegate:self queue:self.captureQueue];
        NSDictionary* setcapSettings = [NSDictionary dictionaryWithObjectsAndKeys:
                                        [NSNumber numberWithInt:kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange], kCVPixelBufferPixelFormatTypeKey,
                                        nil];
        _videoOutput.videoSettings = setcapSettings;
    }
    return _videoOutput;
}

//音频输出
- (AVCaptureAudioDataOutput *)audioOutput {
    if (_audioOutput == nil) {
        _audioOutput = [[AVCaptureAudioDataOutput alloc] init];
        [_audioOutput setSampleBufferDelegate:self queue:self.captureQueue];
    }
    return _audioOutput;
}

//静态图像输出
- (AVCaptureStillImageOutput *)stillImageOutput{
    if (_stillImageOutput == nil) {
        _stillImageOutput = [[AVCaptureStillImageOutput alloc]init];
        _stillImageOutput.outputSettings = @{AVVideoCodecKey:AVVideoCodecJPEG};
    }
    return _stillImageOutput;
}
//视频连接
- (AVCaptureConnection *)videoConnection {
    _videoConnection = [self.videoOutput connectionWithMediaType:AVMediaTypeVideo];
    return _videoConnection;
}

//音频连接
- (AVCaptureConnection *)audioConnection {
    if (_audioConnection == nil) {
        _audioConnection = [self.audioOutput connectionWithMediaType:AVMediaTypeAudio];
    }
    return _audioConnection;
}

//捕获到的视频呈现的layer
- (AVCaptureVideoPreviewLayer *)previewLayer {
    if (_previewLayer == nil) {
        //通过AVCaptureSession初始化
        AVCaptureVideoPreviewLayer *preview = [[AVCaptureVideoPreviewLayer alloc] initWithSession:self.recordSession];
        //设置比例为铺满全屏
        preview.videoGravity = AVLayerVideoGravityResizeAspectFill;
        _previewLayer = preview;
    }
    return _previewLayer;
}

//录制的队列
- (dispatch_queue_t)captureQueue {
    if (_captureQueue == nil) {
        _captureQueue = dispatch_queue_create("cn.qiuyouqun.im.wclrecordengine.capture", DISPATCH_QUEUE_SERIAL);
    }
    return _captureQueue;
}

</pre>

2.格式封装和配置参数
<pre>
//初始化视频输入
- (void)initVideoInputHeight:(NSInteger)cy width:(NSInteger)cx {
    //录制视频的一些配置，分辨率，编码方式等等
    NSInteger numPixels = cx * cy;
    //每像素比特
    CGFloat bitsPerPixel = 6.0;
    NSInteger bitsPerSecond = numPixels * bitsPerPixel;
    
    // 码率和帧率设置
    NSDictionary *compressionProperties = @{ AVVideoAverageBitRateKey:@(bitsPerSecond),
                                             AVVideoExpectedSourceFrameRateKey:@(30),
                                             AVVideoMaxKeyFrameIntervalKey:@(30),
                                             AVVideoProfileLevelKey:AVVideoProfileLevelH264BaselineAutoLevel };
    NSDictionary* settings = @{AVVideoCodecKey:AVVideoCodecH264,
                               AVVideoScalingModeKey:AVVideoScalingModeResizeAspectFill,
                               AVVideoWidthKey:@(cx),
                               AVVideoHeightKey:@(cy),
                               AVVideoCompressionPropertiesKey:compressionProperties };
    
    //初始化视频写入类
    _videoInput = [AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeVideo outputSettings:settings];
    _videoInput.transform = [self transformFromCurrentVideoOrientationToOrientation:AVCaptureVideoOrientationPortrait];
    //表明输入是否应该调整其处理为实时数据源的数据
    _videoInput.expectsMediaDataInRealTime = YES;
    //将视频输入源加入
    if ([_writer canAddInput:_videoInput]) {
        [_writer addInput:_videoInput];
    }
}

//初始化音频输入
- (void)initAudioInputChannels:(int)ch samples:(Float64)rate {
    //音频的一些配置包括音频各种这里为AAC,音频通道、采样率和音频的比特率
    NSDictionary *settings = @{AVEncoderBitRatePerChannelKey:@(28000),
                               AVFormatIDKey:@(kAudioFormatMPEG4AAC),
                               AVNumberOfChannelsKey:@(1),
                               AVSampleRateKey:@(22050) };
    //初始化音频写入类
    _audioInput = [AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeAudio outputSettings:settings];
    //表明输入是否应该调整其处理为实时数据源的数据
    _audioInput.expectsMediaDataInRealTime = YES;
    //将音频输入源加入
    [_writer addInput:_audioInput];
}
</pre>

3.视频方向控制
<pre>
- (CMMotionManager *)motionManager{
    if (!_motionManager) {
        _motionManager = [[CMMotionManager alloc]init];
        _motionManager.deviceMotionUpdateInterval = MOTION_UPDATE_INTERVAL;
    }
    return _motionManager;
}
// 开始
- (void)startDeviceMotionUpdates{
    if (_motionManager.deviceMotionAvailable) {
        [_motionManager startDeviceMotionUpdatesToQueue:[NSOperationQueue currentQueue] withHandler:^(CMDeviceMotion * _Nullable motion, NSError * _Nullable error) {
            [self performSelectorOnMainThread:@selector(handleDeviceMotion:) withObject:motion waitUntilDone:YES];
        }];
    }
}
// 结束
- (void)stopDeviceMotionUpdates{
    [_motionManager stopDeviceMotionUpdates];
}
- (void)handleDeviceMotion:(CMDeviceMotion *)deviceMotion{
    double x = deviceMotion.gravity.x;
    double y = deviceMotion.gravity.y;
    if (fabs(y) >= fabs(x))
    {
        if (y >= 0){
            _deviceOrientation = UIDeviceOrientationPortraitUpsideDown;
            _videoOrientation = AVCaptureVideoOrientationPortraitUpsideDown;
            //NSLog(@"UIDeviceOrientationPortraitUpsideDown--AVCaptureVideoOrientationPortraitUpsideDown");
        }
        else{
            _deviceOrientation = UIDeviceOrientationPortrait;
            _videoOrientation = AVCaptureVideoOrientationPortrait;
            //NSLog(@"UIDeviceOrientationPortrait--AVCaptureVideoOrientationPortrait");
        }
    }
    else{
        if (x >= 0){
            _deviceOrientation = UIDeviceOrientationLandscapeRight;
            _videoOrientation = AVCaptureVideoOrientationLandscapeRight;
            //NSLog(@"UIDeviceOrientationLandscapeRight--AVCaptureVideoOrientationLandscapeRight");
        }
        else{
            _deviceOrientation = UIDeviceOrientationLandscapeLeft;
            _videoOrientation = AVCaptureVideoOrientationLandscapeLeft;
           // NSLog(@"UIDeviceOrientationLandscapeLeft--AVCaptureVideoOrientationLandscapeLeft");
        }
    }
    ;
    if (_delegate && [_delegate respondsToSelector:@selector(motionManagerDeviceOrientation:)]) {
        [_delegate motionManagerDeviceOrientation:_deviceOrientation];
    }
}
// 调整设备取向
- (AVCaptureVideoOrientation)currentVideoOrientation{
    AVCaptureVideoOrientation orientation;
    switch ([SGMotionManager sharedManager].deviceOrientation) {
        case UIDeviceOrientationPortrait:
            orientation = AVCaptureVideoOrientationPortrait;
            break;
        case UIDeviceOrientationLandscapeRight:
            orientation = AVCaptureVideoOrientationLandscapeLeft;
            break;
        case UIDeviceOrientationPortraitUpsideDown:
            orientation = AVCaptureVideoOrientationPortraitUpsideDown;
            break;
        default:
            orientation = AVCaptureVideoOrientationLandscapeRight;
            break;
    }
    return orientation;
}

PS: 以上只是贴出了部分代码片段,完整代码请看 demo