ios取出视频的每一帧图片（关键帧，AVAssetImageGenerator）

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[mImageGenerator generateCGImagesAsynchronouslyForTimes:[NSArray arrayWithObject:[NSValue valueWithCMTime:CMTimeMakeWithSeconds(time, NSEC_PER_SEC)]] completionHandler:  

    ^(CMTime requestedTime, CGImageRef image, CMTime actualTime, AVAssetImageGeneratorResult result, NSError *error)  

    {  

   

        NSLog(@"actual got image at time:%f", CMTimeGetSeconds(actualTime));  

        if (image)  

        {  

            [CATransaction begin];  

            [CATransaction setDisableActions:YES];  

            [layer setContents:(id)image];  

   

            //UIImage *img = [UIImage imageWithCGImage:image];  

            //UIImageWriteToSavedPhotosAlbum(img, self, nil, nil);  

   

            [CATransaction commit];  

        }  

    }];  

   

如何取得第一帧

AVFoundationframework 

 CoreMediaframework

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+ (UIImage*) thumbnailImageForVideo:(NSURL *)videoURL atTime:(NSTimeInterval)time {  

    AVURLAsset *asset = [[[AVURLAsset alloc] initWithURL:videoURL options:nil] autorelease];  

    NSParameterAssert(asset);  

    AVAssetImageGenerator *assetImageGenerator = [[[AVAssetImageGenerator alloc] initWithAsset:asset] autorelease];  

    assetImageGenerator.appliesPreferredTrackTransform = YES;  

    assetImageGenerator.apertureMode = AVAssetImageGeneratorApertureModeEncodedPixels;  

  

    CGImageRef thumbnailImageRef = NULL;  

    CFTimeInterval thumbnailImageTime = time;  

    NSError *thumbnailImageGenerationError = nil;  

    thumbnailImageRef = [assetImageGenerator copyCGImageAtTime:CMTimeMake(thumbnailImageTime, 60) actualTime:NULL error:&thumbnailImageGenerationError];  

  

    if (!thumbnailImageRef)  

        NSLog(@"thumbnailImageGenerationError %@", thumbnailImageGenerationError);  

  

    UIImage *thumbnailImage = thumbnailImageRef ? [[[UIImage alloc] initWithCGImage:thumbnailImageRef] autorelease] : nil;  

  

    return thumbnailImage;