Question

我正试图从基于avfoundation的iphone中捕获的mov视频中提取所有帧这是我的代码

-(void)captureOutput:(AVCaptureFileOutput *)captureOutput
didFinishRecordingToOutputFileAtURL:(NSURL *)outputFileURL
fromConnections:(NSArray *)connections`
error:(NSError *)error
{

    NSLog(@"didFinishRecordingToOutputFileAtURL - enter");
    BOOL RecordedSuccessfully = YES;
    if ([error code] != noErr)
    {
        // A problem occurred: Find out if the recording was successful.
        id value = [[error userInfo] objectForKey:AVErrorRecordingSuccessfullyFinishedKey];
        if (value)
        {
            RecordedSuccessfully = [value boolValue];
        }
    }
    if (RecordedSuccessfully)
    {
        //----- RECORDED SUCESSFULLY -----
        NSLog(@"didFinishRecordingToOutputFileAtURL - success");
        ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];

        AVURLAsset *asset = [[[AVURLAsset alloc] initWithURL:outputFileURL
                                                     options:[NSDictionary      dictionaryWithObjectsAndKeys:[NSNumber numberWithBool:YES],     AVURLAssetPreferPreciseDurationAndTimingKey, nil]] autorelease];
        AVAssetImageGenerator *generator = [[[AVAssetImageGenerator alloc]     initWithAsset:asset] autorelease];`
        generator.appliesPreferredTrackTransform = YES; // if I omit this, the frames are rotated 90° (didn't try in landscape)
        AVVideoComposition * composition = [AVVideoComposition videoCompositionWithPropertiesOfAsset:asset];

        // Retrieving the video properties
        NSTimeInterval duration = CMTimeGetSeconds(asset.duration);
        frameDuration = CMTimeGetSeconds(composition.frameDuration);
        CGSize renderSize = composition.renderSize;
        CGFloat totalFrames = round(duration/frameDuration);

        // Selecting each frame we want to extract : all of them.
        NSMutableArray * times = [NSMutableArray     arrayWithCapacity:round(duration/frameDuration)];
        for (int i=0; i<totalFrames; i++) {
            NSValue *time = [NSValue valueWithCMTime:CMTimeMakeWithSeconds(i*frameDuration, composition.frameDuration.timescale)];
            [times addObject:time];
        }

        __block int i = 0;
        AVAssetImageGeneratorCompletionHandler handler = ^(CMTime requestedTime, CGImageRef im, CMTime actualTime, AVAssetImageGeneratorResult result, NSError *error){
            if (result == AVAssetImageGeneratorSucceeded) {

                [arrImgsMain addObject:[UIImage imageWithCGImage:im]];
            }
            else
                NSLog(@"Ouch: %@", error.description);
            i++;
            [self performSelectorOnMainThread:@selector(setProgressValue:) withObject:    [NSNumber numberWithFloat:i/totalFrames] waitUntilDone:NO];
            if(i == totalFrames) {
                [self performSelectorOnMainThread:@selector(performVideoDidFinish)      withObject:nil waitUntilDone:NO];
            }
        };

        // Launching the process...
        generator.requestedTimeToleranceBefore = kCMTimeZero;
        generator.requestedTimeToleranceAfter = kCMTimeZero;
        generator.maximumSize = renderSize;
        [generator generateCGImagesAsynchronouslyForTimes:times completionHandler:handler];

        int count=[arrImgsMain count];
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"No network connection"
                                                        message:[NSString stringWithFormat:@"%d",count]
                                                       delegate:nil
                                              cancelButtonTitle:@"OK"
                                              otherButtonTitles:nil];
        [alert show];
        [alert release];
    }

在检查设备时，此代码崩溃，这些是崩溃日志请帮助

    Exception Type:  EXC_CRASH (SIGABRT)
    Exception Codes: 0x0000000000000000, 0x0000000000000000
    Crashed Thread:  0

    Last Exception Backtrace:
    0   CoreFoundation                  0x3159729e __exceptionPreprocess + 158
    1   libobjc.A.dylib                 0x3923c97a objc_exception_throw + 26
    2   CoreFoundation                  0x3159ae02 -[NSObject(NSObject)      doesNotRecognizeSelector:] + 166
    3   CoreFoundation                  0x3159952c ___forwarding___ + 388
    4   CoreFoundation                  0x314f0f64 _CF_forwarding_prep_0 + 20
    5   Foundation                      0x31eae0f0 __NSThreadPerformPerform + 456
    6   CoreFoundation                  0x3156c67e         __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 10
    7   CoreFoundation                  0x3156bee4 __CFRunLoopDoSources0 + 208
    8   CoreFoundation                  0x3156acb2 __CFRunLoopRun + 642
    9   CoreFoundation                  0x314ddeb8 CFRunLoopRunSpecific + 352
    10  CoreFoundation                  0x314ddd44 CFRunLoopRunInMode + 100
    11  GraphicsServices                0x350a12e6 GSEventRunModal + 70
    12  UIKit                           0x333f32fc UIApplicationMain + 1116
    13  Animated Photo Cards            0x0002359a 0x22000 + 553
    14  libdyld.dylib                   0x39673b1c start + 0

Answer 1

好的，将评论中的一些内容整理到这个答案中：

异常断点对于找出代码抛出的确切行非常有用。
如果您在堆栈帧或doesNotRecognizeSelector中看到unrecognized selector sent to instance，则可能意味着两件事 - 要么您尚未定义特定方法的实现，要么（更常见的情况是非-ARC环境），你的对象已经被释放了。
Zombie Objects有助于追踪过度释放的物体。当打开时，操作系统会将对象保持为僵尸一点点，所以如果有人试图向它发送消息，你可以抓住红手的罪魁祸首。

最后，答案是：你似乎没有VideoDecompiler中的setProgressValue：方法（在上面的代码中应该是self类）。

Answer 2

以下是从视频中获取缩略图的最简单代码，您只需要获取视频的持续时间并运行for循环并将缩略图保存到某个数组：

MPMoviePlayerController *moviePlayer = [[MPMoviePlayerController alloc] initWithContentURL:imageUrl];
        moviePlayer.shouldAutoplay = NO;
        UIImage *thumbnail = [moviePlayer thumbnailImageAtTime:0.0 timeOption:MPMovieTimeOptionNearestKeyFrame];

我从这位开发人员blog

中找到了这个想法

在ios中获取视频中的所有帧

2 个答案: