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手把手教你實(shí)現(xiàn)微信小視頻iOS代碼實(shí)現(xiàn)

 更新時(shí)間：2016年08月27日 14:36:26   作者：pretty guy  
這篇文章主要手把手教你實(shí)現(xiàn)微信小視頻，iOS代碼實(shí)現(xiàn)微信小視頻功能，具有一定的參考價(jià)值，感興趣的小伙伴們可以參考一下

前段時(shí)間項(xiàng)目要求需要在聊天模塊中加入類似微信的小視頻功能，這邊博客主要是為了總結(jié)遇到的問題和解決方法，希望能夠?qū)τ型瑯有枨蟮呐笥延兴鶐椭?br />

效果預(yù)覽：

 

這里先羅列遇到的主要問題：　　
 1.視頻剪裁  微信的小視頻只是取了攝像頭獲取的一部分畫面
 2.滾動預(yù)覽的卡頓問題  AVPlayer播放視頻在滾動中會出現(xiàn)很卡的問題

接下來讓我們一步步來實(shí)現(xiàn)。
Part 1 實(shí)現(xiàn)視頻錄制
1.錄制類WKMovieRecorder實(shí)現(xiàn)
創(chuàng)建一個(gè)錄制類WKMovieRecorder，負(fù)責(zé)視頻錄制。 

@interface WKMovieRecorder : NSObject

+ (WKMovieRecorder*) sharedRecorder; 
 - (instancetype)initWithMaxDuration:(NSTimeInterval)duration;
 @end

定義回調(diào)block 

/**
 * 錄制結(jié)束
 *
 * @param info   回調(diào)信息
 * @param isCancle YES:取消 NO:正常結(jié)束
 */
typedef void(^FinishRecordingBlock)(NSDictionary *info, WKRecorderFinishedReason finishReason);
/**
 * 焦點(diǎn)改變
 */
typedef void(^FocusAreaDidChanged)();
/**
 * 權(quán)限驗(yàn)證
 *
 * @param success 是否成功
 */
typedef void(^AuthorizationResult)(BOOL success);

@interface WKMovieRecorder : NSObject
//回調(diào)
@property (nonatomic, copy) FinishRecordingBlock finishBlock;//錄制結(jié)束回調(diào)
@property (nonatomic, copy) FocusAreaDidChanged focusAreaDidChangedBlock;
@property (nonatomic, copy) AuthorizationResult authorizationResultBlock;
@end

定義一個(gè)cropSize用于視頻裁剪 
@property (nonatomic, assign) CGSize cropSize;

接下來就是capture的實(shí)現(xiàn)了，這里代碼有點(diǎn)長，懶得看的可以直接看后面的視頻剪裁部分

錄制配置：

@interface WKMovieRecorder ()
<
AVCaptureVideoDataOutputSampleBufferDelegate,
AVCaptureAudioDataOutputSampleBufferDelegate,
WKMovieWriterDelegate
>

{
  AVCaptureSession* _session;
  AVCaptureVideoPreviewLayer* _preview;
  WKMovieWriter* _writer;
  //暫停錄制
  BOOL _isCapturing;
  BOOL _isPaused;
  BOOL _discont;
  int _currentFile;
  CMTime _timeOffset;
  CMTime _lastVideo;
  CMTime _lastAudio;
  
  NSTimeInterval _maxDuration;
}

// Session management.
@property (nonatomic, strong) dispatch_queue_t sessionQueue;
@property (nonatomic, strong) dispatch_queue_t videoDataOutputQueue;
@property (nonatomic, strong) AVCaptureSession *session;
@property (nonatomic, strong) AVCaptureDevice *captureDevice;
@property (nonatomic, strong) AVCaptureDeviceInput *videoDeviceInput;
@property (nonatomic, strong) AVCaptureStillImageOutput *stillImageOutput;
@property (nonatomic, strong) AVCaptureConnection *videoConnection;
@property (nonatomic, strong) AVCaptureConnection *audioConnection;
@property (nonatomic, strong) NSDictionary *videoCompressionSettings;
@property (nonatomic, strong) NSDictionary *audioCompressionSettings;
@property (nonatomic, strong) AVAssetWriterInputPixelBufferAdaptor *adaptor;
@property (nonatomic, strong) AVCaptureVideoDataOutput *videoDataOutput;


//Utilities
@property (nonatomic, strong) NSMutableArray *frames;//存儲錄制幀
@property (nonatomic, assign) CaptureAVSetupResult result;
@property (atomic, readwrite) BOOL isCapturing;
@property (atomic, readwrite) BOOL isPaused;
@property (nonatomic, strong) NSTimer *durationTimer;

@property (nonatomic, assign) WKRecorderFinishedReason finishReason;

@end

實(shí)例化方法： 

+ (WKMovieRecorder *)sharedRecorder
{
  static WKMovieRecorder *recorder;
  static dispatch_once_t onceToken;
  dispatch_once(&onceToken, ^{
    recorder = [[WKMovieRecorder alloc] initWithMaxDuration:CGFLOAT_MAX];
  });
  
  return recorder;
}

- (instancetype)initWithMaxDuration:(NSTimeInterval)duration
{
  if(self = [self init]){
    _maxDuration = duration;
    _duration = 0.f;
  }
  
  return self;
}

- (instancetype)init
{
  self = [super init];
  if (self) {
    _maxDuration = CGFLOAT_MAX;
    _duration = 0.f;
    _sessionQueue = dispatch_queue_create("wukong.movieRecorder.queue", DISPATCH_QUEUE_SERIAL );
    _videoDataOutputQueue = dispatch_queue_create( "wukong.movieRecorder.video", DISPATCH_QUEUE_SERIAL );
    dispatch_set_target_queue( _videoDataOutputQueue, dispatch_get_global_queue( DISPATCH_QUEUE_PRIORITY_HIGH, 0 ) );
  }
  return self;
}

2.初始化設(shè)置
初始化設(shè)置分別為session創(chuàng)建、權(quán)限檢查以及session配置
1）.session創(chuàng)建
self.session = [[AVCaptureSession alloc] init];
self.result = CaptureAVSetupResultSuccess;

2）.權(quán)限檢查

//權(quán)限檢查
    switch ([AVCaptureDevice authorizationStatusForMediaType:AVMediaTypeVideo]) {
      case AVAuthorizationStatusNotDetermined: {
        [AVCaptureDevice requestAccessForMediaType:AVMediaTypeVideo completionHandler:^(BOOL granted) {
          if (granted) {
            self.result = CaptureAVSetupResultSuccess;
          }
        }];
        break;
      }
      case AVAuthorizationStatusAuthorized: {
        
        break;
      }
      default:{
        self.result = CaptureAVSetupResultCameraNotAuthorized;
      }
    }
    
    if ( self.result != CaptureAVSetupResultSuccess) {
      
      if (self.authorizationResultBlock) {
        self.authorizationResultBlock(NO);
      }
      return;
    }
        

3）.session配置
session配置是需要注意的是AVCaptureSession的配置不能在主線程, 需要自行創(chuàng)建串行線程。 
3.1.1 獲取輸入設(shè)備與輸入流

AVCaptureDevice *captureDevice = [[self class] deviceWithMediaType:AVMediaTypeVideo preferringPosition:AVCaptureDevicePositionBack];      
 _captureDevice = captureDevice;
      
 NSError *error = nil;
 _videoDeviceInput = [[AVCaptureDeviceInput alloc] initWithDevice:captureDevice error:&error];
      
 if (!_videoDeviceInput) {
  NSLog(@"未找到設(shè)備");
 }

3.1.2 錄制幀數(shù)設(shè)置
幀數(shù)設(shè)置的主要目的是適配iPhone4，畢竟是應(yīng)該淘汰的機(jī)器了

int frameRate;
      if ( [NSProcessInfo processInfo].processorCount == 1 )
      {
        if ([self.session canSetSessionPreset:AVCaptureSessionPresetLow]) {
          [self.session setSessionPreset:AVCaptureSessionPresetLow];
        }
        frameRate = 10;
      }else{
        if ([self.session canSetSessionPreset:AVCaptureSessionPreset640x480]) {
          [self.session setSessionPreset:AVCaptureSessionPreset640x480];
        }
        frameRate = 30;
      }
      
      CMTime frameDuration = CMTimeMake( 1, frameRate );
      
      if ( [_captureDevice lockForConfiguration:&error] ) {
        _captureDevice.activeVideoMaxFrameDuration = frameDuration;
        _captureDevice.activeVideoMinFrameDuration = frameDuration;
        [_captureDevice unlockForConfiguration];
      }
      else {
        NSLog( @"videoDevice lockForConfiguration returned error %@", error );
      }

3.1.3 視頻輸出設(shè)置
視頻輸出設(shè)置需要注意的問題是：要設(shè)置videoConnection的方向，這樣才能保證設(shè)備旋轉(zhuǎn)時(shí)的顯示正常。 

 //Video
      if ([self.session canAddInput:_videoDeviceInput]) {
        
        [self.session addInput:_videoDeviceInput];
        self.videoDeviceInput = _videoDeviceInput;
        [self.session removeOutput:_videoDataOutput];
        
        AVCaptureVideoDataOutput *videoOutput = [[AVCaptureVideoDataOutput alloc] init];
        _videoDataOutput = videoOutput;
        videoOutput.videoSettings = @{ (id)kCVPixelBufferPixelFormatTypeKey : @(kCVPixelFormatType_32BGRA) };
        
        [videoOutput setSampleBufferDelegate:self queue:_videoDataOutputQueue];
        
        videoOutput.alwaysDiscardsLateVideoFrames = NO;
        
        if ( [_session canAddOutput:videoOutput] ) {
          [_session addOutput:videoOutput];
          
          [_captureDevice addObserver:self forKeyPath:@"adjustingFocus" options:NSKeyValueObservingOptionNew context:FocusAreaChangedContext];
          
          _videoConnection = [videoOutput connectionWithMediaType:AVMediaTypeVideo];
          
          if(_videoConnection.isVideoStabilizationSupported){
            _videoConnection.preferredVideoStabilizationMode = AVCaptureVideoStabilizationModeAuto;
          }

          
          UIInterfaceOrientation statusBarOrientation = [UIApplication sharedApplication].statusBarOrientation;
          AVCaptureVideoOrientation initialVideoOrientation = AVCaptureVideoOrientationPortrait;
          if ( statusBarOrientation != UIInterfaceOrientationUnknown ) {
            initialVideoOrientation = (AVCaptureVideoOrientation)statusBarOrientation;
          }
          
          _videoConnection.videoOrientation = initialVideoOrientation;
        }

      }
      else{
        NSLog(@"無法添加視頻輸入到會話");
      }

3.1.4 音頻設(shè)置 
需要注意的是為了不丟幀，需要把音頻輸出的回調(diào)隊(duì)列放在串行隊(duì)列中 

//audio
      AVCaptureDevice *audioDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeAudio];
      AVCaptureDeviceInput *audioDeviceInput = [AVCaptureDeviceInput deviceInputWithDevice:audioDevice error:&error];
      
      
      if ( ! audioDeviceInput ) {
        NSLog( @"Could not create audio device input: %@", error );
      }
      
      if ( [self.session canAddInput:audioDeviceInput] ) {
        [self.session addInput:audioDeviceInput];
        
      }
      else {
        NSLog( @"Could not add audio device input to the session" );
      }
      
      AVCaptureAudioDataOutput *audioOut = [[AVCaptureAudioDataOutput alloc] init];
      // Put audio on its own queue to ensure that our video processing doesn't cause us to drop audio
      dispatch_queue_t audioCaptureQueue = dispatch_queue_create( "wukong.movieRecorder.audio", DISPATCH_QUEUE_SERIAL );
      [audioOut setSampleBufferDelegate:self queue:audioCaptureQueue];
      
      if ( [self.session canAddOutput:audioOut] ) {
        [self.session addOutput:audioOut];
      }
      _audioConnection = [audioOut connectionWithMediaType:AVMediaTypeAudio];

還需要注意一個(gè)問題就是對于session的配置代碼應(yīng)該是這樣的 
[self.session beginConfiguration];

...配置代碼

[self.session commitConfiguration];

由于篇幅問題，后面的錄制代碼我就挑重點(diǎn)的講了。
3.2  視頻存儲
現(xiàn)在我們需要在AVCaptureVideoDataOutputSampleBufferDelegate與AVCaptureAudioDataOutputSampleBufferDelegate的回調(diào)中，將音頻和視頻寫入沙盒。在這個(gè)過程中需要注意的，在啟動session后獲取到的第一幀黑色的，需要放棄。
3.2.1 創(chuàng)建WKMovieWriter類來封裝視頻存儲操作
WKMovieWriter的主要作用是利用AVAssetWriter拿到CMSampleBufferRef，剪裁后再寫入到沙盒中。
這是剪裁配置的代碼，AVAssetWriter會根據(jù)cropSize來剪裁視頻，這里需要注意的一個(gè)問題是cropSize的width必須是320的整數(shù)倍，不然的話剪裁出來的視頻右側(cè)會出現(xiàn)一條綠色的線

　NSDictionary *videoSettings;
  if (_cropSize.height == 0 || _cropSize.width == 0) {
    
    _cropSize = [UIScreen mainScreen].bounds.size;
    
  }
  
  videoSettings = [NSDictionary dictionaryWithObjectsAndKeys:
           AVVideoCodecH264, AVVideoCodecKey,
           [NSNumber numberWithInt:_cropSize.width], AVVideoWidthKey,
           [NSNumber numberWithInt:_cropSize.height], AVVideoHeightKey,
           AVVideoScalingModeResizeAspectFill,AVVideoScalingModeKey,
           nil];

至此，視頻錄制就完成了。
接下來需要解決的預(yù)覽的問題了 

Part 2 卡頓問題解決
1.1 gif圖生成 
通過查資料發(fā)現(xiàn)了這篇blog 介紹說微信團(tuán)隊(duì)解決預(yù)覽卡頓的問題使用的是播放圖片gif，但是博客中的示例代碼有問題，通過CoreAnimation來播放圖片導(dǎo)致內(nèi)存暴漲而crash。但是，還是給了我一些靈感，因?yàn)橹绊?xiàng)目的啟動頁用到了gif圖片的播放，所以我就想能不能把視頻轉(zhuǎn)成圖片，然后再轉(zhuǎn)成gif圖進(jìn)行播放，這樣不就解決了問題了嗎。于是我開始google功夫不負(fù)有心人找到了，圖片數(shù)組轉(zhuǎn)gif圖片的方法。

gif圖轉(zhuǎn)換代碼 

static void makeAnimatedGif(NSArray *images, NSURL *gifURL, NSTimeInterval duration) {
  NSTimeInterval perSecond = duration /images.count;
  
  NSDictionary *fileProperties = @{
                   (__bridge id)kCGImagePropertyGIFDictionary: @{
                       (__bridge id)kCGImagePropertyGIFLoopCount: @0, // 0 means loop forever
                       }
                   };
  
  NSDictionary *frameProperties = @{
                   (__bridge id)kCGImagePropertyGIFDictionary: @{
                       (__bridge id)kCGImagePropertyGIFDelayTime: @(perSecond), // a float (not double!) in seconds, rounded to centiseconds in the GIF data
                       }
                   };
  
  CGImageDestinationRef destination = CGImageDestinationCreateWithURL((__bridge CFURLRef)gifURL, kUTTypeGIF, images.count, NULL);
  CGImageDestinationSetProperties(destination, (__bridge CFDictionaryRef)fileProperties);
  
  for (UIImage *image in images) {
    @autoreleasepool {
      
      CGImageDestinationAddImage(destination, image.CGImage, (__bridge CFDictionaryRef)frameProperties);
    }
  }
  
  if (!CGImageDestinationFinalize(destination)) {
    NSLog(@"failed to finalize image destination");
  }else{
    
    
  }
  CFRelease(destination);
}

轉(zhuǎn)換是轉(zhuǎn)換成功了，但是出現(xiàn)了新的問題，使用ImageIO生成gif圖片時(shí)會導(dǎo)致內(nèi)存暴漲，瞬間漲到100M以上，如果多個(gè)gif圖同時(shí)生成的話一樣會crash掉，為了解決這個(gè)問題需要用一個(gè)串行隊(duì)列來進(jìn)行g(shù)if圖的生成　　 

1.2 視頻轉(zhuǎn)換為UIImages
主要是通過AVAssetReader、AVAssetTrack、AVAssetReaderTrackOutput 來進(jìn)行轉(zhuǎn)換 

//轉(zhuǎn)成UIImage
- (void)convertVideoUIImagesWithURL:(NSURL *)url finishBlock:(void (^)(id images, NSTimeInterval duration))finishBlock
{
    AVAsset *asset = [AVAsset assetWithURL:url];
    NSError *error = nil;
    self.reader = [[AVAssetReader alloc] initWithAsset:asset error:&error];
    
    NSTimeInterval duration = CMTimeGetSeconds(asset.duration);
    __weak typeof(self)weakSelf = self;
    dispatch_queue_t backgroundQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0);
    dispatch_async(backgroundQueue, ^{
      __strong typeof(weakSelf) strongSelf = weakSelf;
      NSLog(@"");
      
      
      if (error) {
        NSLog(@"%@", [error localizedDescription]);
        
      }
      
      NSArray *videoTracks = [asset tracksWithMediaType:AVMediaTypeVideo];
      
      AVAssetTrack *videoTrack =[videoTracks firstObject];
      if (!videoTrack) {
        return ;
      }
      int m_pixelFormatType;
      //   視頻播放時(shí)，
      m_pixelFormatType = kCVPixelFormatType_32BGRA;
      // 其他用途，如視頻壓縮
      //  m_pixelFormatType = kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange;
      
      NSMutableDictionary *options = [NSMutableDictionary dictionary];
      [options setObject:@(m_pixelFormatType) forKey:(id)kCVPixelBufferPixelFormatTypeKey];
      AVAssetReaderTrackOutput *videoReaderOutput = [[AVAssetReaderTrackOutput alloc] initWithTrack:videoTrack outputSettings:options];
      
      if ([strongSelf.reader canAddOutput:videoReaderOutput]) {
        
        [strongSelf.reader addOutput:videoReaderOutput];
      }
      [strongSelf.reader startReading];
      
      
      NSMutableArray *images = [NSMutableArray array];
      // 要確保nominalFrameRate>0，之前出現(xiàn)過android拍的0幀視頻
      while ([strongSelf.reader status] == AVAssetReaderStatusReading && videoTrack.nominalFrameRate > 0) {
         @autoreleasepool {
        // 讀取 video sample
        CMSampleBufferRef videoBuffer = [videoReaderOutput copyNextSampleBuffer];
        
        if (!videoBuffer) {
          break;
        }
        
        [images addObject:[WKVideoConverter convertSampleBufferRefToUIImage:videoBuffer]];
        
        CFRelease(videoBuffer);
      }
      
      
     }
      if (finishBlock) {
        dispatch_async(dispatch_get_main_queue(), ^{
          finishBlock(images, duration);
        });
      }
    });
 

}

在這里有一個(gè)值得注意的問題，在視頻轉(zhuǎn)image的過程中，由于轉(zhuǎn)換時(shí)間很短，在短時(shí)間內(nèi)videoBuffer不能夠及時(shí)得到釋放，在多個(gè)視頻同時(shí)轉(zhuǎn)換時(shí)任然會出現(xiàn)內(nèi)存問題，這個(gè)時(shí)候就需要用autoreleasepool來實(shí)現(xiàn)及時(shí)釋放 

@autoreleasepool {
 // 讀取 video sample
 CMSampleBufferRef videoBuffer = [videoReaderOutput copyNextSampleBuffer];
 　　if (!videoBuffer) {
   break;
   }
          
 　　[images addObject:[WKVideoConverter convertSampleBufferRefToUIImage:videoBuffer]];
 　　 CFRelease(videoBuffer); }

至此，微信小視頻的難點(diǎn)(我認(rèn)為的)就解決了，至于其他的實(shí)現(xiàn)代碼請看demo就基本實(shí)現(xiàn)了，demo可以從這里下載。

視頻暫停錄制 http://www.gdcl.co.uk/2013/02/20/iPhone-Pause.html
視頻crop綠邊解決 http://stackoverflow.com/questions/22883525/avassetexportsession-giving-me-a-green-border-on-right-and-bottom-of-output-vide
視頻裁剪：http://stackoverflow.com/questions/15737781/video-capture-with-11-aspect-ratio-in-ios/16910263#16910263
CMSampleBufferRef轉(zhuǎn)image https://developer.apple.com/library/ios/qa/qa1702/_index.html
微信小視頻分析 http://www.jianshu.com/p/3d5ccbde0de1

感謝以上文章的作者

以上就是本文的全部內(nèi)容，希望對大家的學(xué)習(xí)有所幫助，也希望大家多多支持腳本之家。

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