小编Diu*_*eus的帖子

我正试图在iPhone 5s上以最高分辨率(AVCaptureSessionPresetPhoto)拍摄多张照片.我尝试使用以下代码:

    dispatch_semaphore_t sync = dispatch_semaphore_create(0);
while( [self isBurstModeEnabled] == YES )
                {
        [stillImageOutput captureStillImageAsynchronouslyFromConnection:videoConnection completionHandler: ^(CMSampleBufferRef imageSampleBuffer, NSError *error)
                             {

                                 if (imageSampleBuffer != NULL)
                                 {
                                     NSData *imageData = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageSampleBuffer];
                                     NSString *videoThumbPath = [NSString
                                                                 stringWithFormat:@"%@/img%d.png",
                                                                 burstFolderPath,
                                                                 index];

                                     [imageData writeToFile:videoThumbPath atomically:YES];
                                     if( 0 == index )
                                     {
                                         [self NSLogPrint:[NSString stringWithFormat:@"Created photo at %@",videoThumbPath]];
                                     }
                                 }
                                 dispatch_semaphore_signal(sync);
                             }];
    dispatch_semaphore_wait(sync, DISPATCH_TIME_FOREVER);
}

使用此代码,我每秒可以获得大约2张照片,无法接近原生相机应用程序的突发模式的性能.我究竟做错了什么？此外,我尝试使用上面的代码没有信号量,但在这种情况下,我有奇怪的行为,一些照片丢失(img0.png img1.png img3.png将存在,但img2.png将丢失).使用第二种方法,性能会更好,但仍然不能与原生应用程序性能相媲美(在我的测试中,相机应用程序每秒会产生大约8.4张照片).

当我使用AVCaptureVideoDataOutput和AVCaptureAudioDataOutput录制音频+视频时,我遇到了延迟问题.有时视频会阻塞几毫秒,有时音频与视频不同步.

我插入了一些日志并观察到我首先在captureOutput回调中获得了大量视频缓冲区,并且在一段时间后我得到了音频缓冲区(有时我根本没有收到音频缓冲区,结果视频没有声音).如果我评论处理视频缓冲区的代码,我会毫无问题地获得音频缓冲区.

这是我正在使用的代码:

-(void)initMovieOutput:(AVCaptureSession *)captureSessionLocal
{   
    AVCaptureVideoDataOutput *dataOutput = [[AVCaptureVideoDataOutput alloc] init];
    self._videoOutput = dataOutput;
    [dataOutput release];

    self._videoOutput.alwaysDiscardsLateVideoFrames = NO;
    self._videoOutput.videoSettings = [NSDictionary dictionaryWithObject: [NSNumber numberWithInt:kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange]
                                                             forKey:(id)kCVPixelBufferPixelFormatTypeKey
                                  ];     
    AVCaptureAudioDataOutput *audioOutput =  [[AVCaptureAudioDataOutput alloc] init];
    self._audioOutput = audioOutput;
    [audioOutput release];

    [captureSessionLocal addOutput:self._videoOutput];
    [captureSessionLocal addOutput:self._audioOutput];


    // Setup the queue
    dispatch_queue_t queue = dispatch_queue_create("MyQueue", NULL);
    [self._videoOutput setSampleBufferDelegate:self queue:queue];
    [self._audioOutput setSampleBufferDelegate:self queue:queue];
    dispatch_release(queue);
}

在这里我设置了作者:

-(BOOL) setupWriter:(NSURL *)videoURL session:(AVCaptureSession *)captureSessionLocal
{
    NSError *error = nil;
    self._videoWriter = [[AVAssetWriter alloc] initWithURL:videoURL fileType:AVFileTypeQuickTimeMovie
                                                         error:&error];
    NSParameterAssert(self._videoWriter);


    // …

我正在使用AVAssetWriter和captureOutput回调来录制视频和音频。问题在于，在大约5％的情况下，我无法从第二个零开始生成缩略图（如果我尝试在视频中走得更远，则没有问题）。我得到的错误是：

错误域= AVFoundationErrorDomain代码= -11832“无法打开” UserInfo = 0x4b31b0 {NSLocalizedFailureReason =无法使用该介质。NSUnderlyingError = 0x4effb0“操作无法完成。（OSStatus错误-12431。）” }

这是我正在使用的代码：

AVURLAsset *asset=[[AVURLAsset alloc] initWithURL:url options:nil];
AVAssetImageGenerator *generator = [[AVAssetImageGenerator alloc] initWithAsset:asset];
generator.appliesPreferredTrackTransform=TRUE;
[asset release];
CMTime thumbTime = CMTimeMakeWithSeconds(0,30);

AVAssetImageGeneratorCompletionHandler handler = ^(CMTime requestedTime, CGImageRef im, CMTime actualTime, AVAssetImageGeneratorResult result, NSError *error)
{
    if (result != AVAssetImageGeneratorSucceeded)
    {
        [self NSLogPrint:[NSString stringWithFormat:@"couldn't generate thumbnail, error:%@", error]];
    }

    UIImage *thumbImg=[[UIImage imageWithCGImage:im] retain];   

    [image setImage:thumbImg];
    [thumbImg release];

    [generator release];
};

CGSize maxSize = CGSizeMake(177, 100);
generator.maximumSize = …

我的代码播放视频文件有问题.每当我以全屏模式播放文件时,播放都不会占用我的所有屏幕.这是相关代码:

     NSURL *url = [NSURL fileURLWithPath:@"Somefile.mov"];
     moviePlayer = [[MPMoviePlayerController alloc] initWithContentURL:url];
    [moviePlayer setControlStyle:MPMovieControlStyleFullscreen];
    [moviePlayer setFullscreen:YES];
    moviePlayer.view.frame = self.switchView.frame;
    [self.switchView addSubview:moviePlayer.view];

    [[NSNotificationCenter defaultCenter] 
    addObserver:self
    selector:@selector(movieFinishedCallback:)                                                 
    name:MPMoviePlayerPlaybackDidFinishNotification
    object:moviePlayer];

    [[NSNotificationCenter defaultCenter] 
     addObserver:self
     selector:@selector(playbackStateDidChange:)                                                 
     name:MPMoviePlayerPlaybackStateDidChangeNotification
     object:moviePlayer];

    [moviePlayer prepareToPlay];
    [moviePlayer play];

这是我得到的输出: