iphone - AVAssetImageGenerator cancelAllCGImageGeneration不会取消AllCGImageGeneration

Question

关于AVAssetImageGenerator的信息似乎很少，关于cancelAllCGImageGeneration的信息则更少，所以我希望这不是一个错误。

我正在调用generateCGImagesAsynchronouslyForTimes并成功获取帧，如果我让它处理整个文件，一切都很好。但是当我cancelAllCGImageGeneration ...

...需要一段时间才能取消-很奇怪，但没什么大不了的。

...它继续在每个请求的帧中调用的完成块，结果为AVAssetImageGeneratorCancelled-这似乎是一个奇怪的设计选择，非常不便。

但是主要的问题是，在使用AVAssetImageGeneratorCancelled进行了一系列调用之后，它再次开始使用AVAssetImageGeneratorSucceeded进行调用。有任何想法吗？

(我可以通过在取消时设置一个标志来解决此问题，此后可以忽略图像，但是用户可以重新启动另一个视频的操作，因此逻辑变得混乱。而且我到处都遇到“内存不足”错误)

代码:

AVURLAsset* asset = [AVURLAsset URLAssetWithURL:self.cameraSelection.movieURL options:[NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithBool:YES], AVURLAssetPreferPreciseDurationAndTimingKey, nil]];
NSTimeInterval duration = CMTimeGetSeconds(asset.duration);
float fps = [[asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0].nominalFrameRate;
int frames = duration * fps;

NSMutableArray* requestedTimes = [NSMutableArray array];
for( int i=0; i<frames; i++ )
{
 [requestedTimes addObject:[NSValue valueWithCMTime:CMTimeMake(i, fps)]];
}

assetImageGenerator = [[AVAssetImageGenerator alloc] initWithAsset:asset];
assetImageGenerator.requestedTimeToleranceBefore = kCMTimeZero;
assetImageGenerator.requestedTimeToleranceAfter = kCMTimeZero;
[assetImageGenerator generateCGImagesAsynchronouslyForTimes:requestedTimes completionHandler:^(CMTime requestedTime, CGImageRef image, CMTime actualTime, AVAssetImageGeneratorResult result, NSError *error)
 {
 NSString* resultStr;
 switch (result)
 {
 case AVAssetImageGeneratorSucceeded: resultStr = @"AVAssetImageGeneratorSucceeded"; break;
 case AVAssetImageGeneratorFailed: resultStr = @"AVAssetImageGeneratorFailed"; break;
 case AVAssetImageGeneratorCancelled: resultStr = @"AVAssetImageGeneratorCancelled"; break;
 }
 CFStringRef requestedTimeString = CMTimeCopyDescription(kCFAllocatorDefault, requestedTime);
 CFStringRef actualTimeString = CMTimeCopyDescription(kCFAllocatorDefault, actualTime);
 NSLog(@"%@ requestedTime:%@ actualTime:%@ error:%@", resultStr, (NSString*)requestedTimeString, (NSString*)actualTimeString, error);
 CFRelease(requestedTimeString);
 CFRelease(actualTimeString);
 }];

日志:

2013-07-01 12:23:54.815 ImprovEyes [9114:1903] AVAssetImageGenerator成功请求时间:{0/60 = 0.000}实际时间:{0/600 = 0.000}错误:(空)
2013-07-01 12:23:54.864 ImprovEyes [9114:1903] AVAssetImageGenerator成功请求时间:{1/60 = 0.017}实际时间:{10/600 = 0.017}错误:(空)
2013-07-01 12:23:54.894 ImprovEyes [9114:1903] AVAssetImageGenerator成功请求的时间:{2/60 = 0.033} ActualTime:{20/600 = 0.033}错误:(空)
2013-07-01 12:23:54.950 ImprovEyes [9114:1903] AVAssetImageGenerator成功请求时间:{3/60 = 0.050}实际时间:{30/600 = 0.050}错误:(空)
2013-07-01 12:23:54.964 ImprovEyes [9114:1903] AVAssetImageGenerator成功请求时间:{4/60 = 0.067}实际时间:{40/600 = 0.067}错误:(空)
***在这里取消***
2013-07-01 12:23:56.137 ImprovEyes [9114:1903] AVAssetImageGenerator成功请求时间:{53/60 = 0.883}实际时间:{530/600 = 0.883}错误:(空)
2013-07-01 12:23:56.138 ImprovEyes [9114:907] assetImageGenerator cancelAllCGImageGeneration
2013-07-01 12:23:56.210 ImprovEyes [9114:1903] AVAssetImageGenerator成功请求时间:{54/60 = 0.900}实际时间:{540/600 = 0.900}错误:(空)
2013-07-01 12:23:56.230 ImprovEyes [9114:1903] AVAssetImageGenerator成功请求时间:{55/60 = 0.917}实际时间:{550/600 = 0.917}错误:(空)
***继续接收图像然后停止***
2013-07-01 12:23:57.019 ImprovEyes [9114:1903] AVAssetImageGenerator成功请求时间:{90/60 = 1.500} ActualTime:{900/600 = 1.500}错误:(空)
2013-07-01 12:23:57.036 ImprovEyes [9114:1903] AVAssetImageGenerator成功请求时间:{91/60 = 1.517}实际时间:{910/600 = 1.517}错误:(空)
2013-07-01 12:23:57.046 ImprovEyes [9114:1903] AVAssetImageGeneratorCancelled requestedTime:{92/60 = 1.533} actualTime:{INVALID} error:(null)
2013-07-01 12:23:57.056 ImprovEyes [9114:1903] AVAssetImageGeneratorCancelled requestedTime:{93/60 = 1.550} ActualTime:{INVALID} error:(null)
***图像再次到货! ***
2013-07-01 12:24:01.234 ImprovEyes [9114:1903] AVAssetImageGeneratorCancelled requestedTime:{538/60 = 8.967} ActualTime:{INVALID} error:(null)
2013-07-01 12:24:01.241 ImprovEyes [9114:1903] AVAssetImageGeneratorCancelled requestedTime:{539/60 = 8.983} ActualTime:{INVALID} error:(null)
2013-07-01 12:24:01.249 ImprovEyes [9114:1903] AVAssetImageGeneratorCancelled requestedTime:{540/60 = 9.000} actualTime:{INVALID} error:(null)
2013-07-01 12:24:01.259 ImprovEyes [9114:1903] AVAssetImageGenerator成功请求时间:{541/60 = 9.017} ActualTime:{5410/600 = 9.017}错误:(空)
2013-07-01 12:24:01.270 ImprovEyes [9114:1903] AVAssetImageGenerator成功请求时间:{542/60 = 9.033} ActualTime:{5420/600 = 9.033}错误:(空)
2013-07-01 12:24:01.279 ImprovEyes [9114:1903] AVAssetImageGenerator成功请求时间:{543/60 = 9.050}实际时间:{5430/600 = 9.050}错误:(空)
...

Answer 1

我遇到了同样的问题，因为它们已经在队列中，所以它仍然处理一些问题。

尝试这样的事情:

__block BOOL hasErrors = NO;

AVAssetImageGeneratorCompletionHandler handler = ^(CMTime requestedTime, CGImageRef im, CMTime actualTime, AVAssetImageGeneratorResult result, NSError *error) {
    if (!hasErrors) {

        DDLogVerbose(@"ACTUAL GENERATION TIME %f", CMTimeGetSeconds(actualTime));

        if (result != AVAssetImageGeneratorSucceeded) {
            DDLogError(@"Failed to generate thumb: %@", error.localizedDescription);
            hasErrors = YES;
            [generator cancelAllCGImageGeneration];
            finishBlock(images, YES);
        } else {
            [images addObject:[UIImage imageWithCGImage:im]];

            if (CMTIME_COMPARE_INLINE(requestedTime, ==, ((NSValue *) timeIntervals.lastObject).CMTimeValue)) {
                DDLogVerbose(@"Movie composition thumb generation complete");
                finishBlock(images, NO);
            }
        }
    }
};