iOS小视频录制(类似微信)

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：
<pre>

• (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;
  }

</pre>

PS: 以上只是贴出了部分代码片段,完整代码请看 demo