ios - AVAssetExportSession 进度卡在 ipad 而不是模拟器

Question

这段代码在模拟器上运行良好。但是，当我尝试在我的 iPad 上运行导出时，它总是卡在进度值 0.14583-ish 处。有人可以帮我弄清楚为什么吗？已经坚持了很长一段时间。

这是我的代码:

NSArray *compatiblePresets = [AVAssetExportSession exportPresetsCompatibleWithAsset:composition];
if ([compatiblePresets containsObject:AVAssetExportPresetLowQuality]) {
    AVAssetExportSession *exportSession = [[AVAssetExportSession alloc]
                                           initWithAsset:composition presetName:AVAssetExportPresetLowQuality];


    exportSession.outputURL = [NSURL fileURLWithPath:[[ShowDAO getUserDocumentDir] stringByAppendingString:exportFilename]];
    exportSession.outputFileType = AVFileTypeQuickTimeMovie;

    CMTime start = CMTimeMakeWithSeconds(0, 1);
    CMTime duration = CMTimeMakeWithSeconds(1000, 1);
    CMTimeRange range = CMTimeRangeMake(start, duration);
    exportSession.timeRange = range;

    [exportSession exportAsynchronouslyWithCompletionHandler:^{
        switch ([exportSession status]) {
            case AVAssetExportSessionStatusCompleted:
                NSLog(@"Export Completed");
                break;
            case AVAssetExportSessionStatusFailed:
                NSLog(@"Export failed: %@", [[exportSession error] localizedDescription]);
                break;
            case AVAssetExportSessionStatusCancelled:
                NSLog(@"Export cancelled");
                break;
            default:
                break;
        }


    }];

    while(exportSession.progress != 1.0){
        NSLog(@"loading... : %f",exportSession.progress);
        sleep(1);
    }
    [exportSession release];

}

Answer 1

while(exportSession.progress != 1.0){
    NSLog(@"loading... : %f",exportSession.progress);
    sleep(1);
}

这个 while 循环阻塞了主线程。 NSLog 可能无法正常触发。试试不用 while 循环？