AVAssetExportSession无法在ios5中运行

Question

在我的应用程序中,我使用AVAssetExportSession组合两个音频文件,它在早期的ios版本中工作正常.但在ios5设备中它无法正常工作.我得到的是一个错误

AVAssetExportSessionStatusFailed: Error Domain=AVFoundationErrorDomain Code=-11820 "Cannot Complete Export" UserInfo=0x1df1c0 {NSLocalizedRecoverySuggestion=Try exporting again., NSLocalizedDescription=Cannot Complete Export}

我用于导出的代码如下所示

有没有人遇到过同样的问题？请提供宝贵的建议.我迫切需要解决这个问题..

//Export function to export the combined audios as one.
-(void)exportAudioFile:(AVComposition*)combinedComposition
{
    AVAssetExportSession *exportSession = [[AVAssetExportSession alloc] initWithAsset:combinedComposition
                                                                           presetName:AVAssetExportPresetPassthrough];
    NSArray *presets =[AVAssetExportSession exportPresetsCompatibleWithAsset:combinedComposition];
    NSLog(@"presets======%@",presets);
    NSLog (@"can export: %@", exportSession.supportedFileTypes);
    NSArray *dirs = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectoryPath = [dirs objectAtIndex:0];
    exportPath = [documentsDirectoryPath stringByAppendingPathComponent:@"CombinedNew.m4a"];
    [[NSFileManager defaultManager] removeItemAtPath:exportPath error:nil];
    exportURL = [NSURL fileURLWithPath:exportPath];
    exportSession.outputURL = exportURL;
    exportSession.outputFileType = @"com.apple.m4a-audio";
    exportSession.shouldOptimizeForNetworkUse = YES;
    [exportSession exportAsynchronouslyWithCompletionHandler:^{
        NSLog (@"i is in your block, exportin. status is %d",
               exportSession.status);
        switch (exportSession.status) 
        {
            case AVAssetExportSessionStatusFailed: 
            {
                // log error to text view
                NSError *exportError = exportSession.error;
                DEBUG_LOG(@"AVAssetExportSessionStatusFailed: %@", exportError);
                [self enableUI];
                break;
            }
            case AVAssetExportSessionStatusCompleted: 
            {
                DEBUG_LOG(@"AVAssetExportSessionStatusCompleted");
                DEBUG_LOG(@"Completed export");
                exportSuccess = YES;
                if (recorderFilePath) 
                {
                    NSError *finalurlError;
                    [[NSFileManager defaultManager]removeItemAtPath:recorderFilePath  error:&finalurlError];
                    finalurlError = nil;
                    [[NSFileManager defaultManager]copyItemAtPath:[exportURL path] toPath:recorderFilePath error:&finalurlError];
                }
                isExported = YES;
                fileUrl = [NSURL fileURLWithPath:recorderFilePath];  
                [self performSelectorInBackground:@selector(updatePlayerForUrl:) withObject:fileUrl];
                break;
            }
            case AVAssetExportSessionStatusUnknown: 
            {   
                DEBUG_LOG(@"AVAssetExportSessionStatusUnknown");                 
                break;
            }
            case AVAssetExportSessionStatusExporting: 
            { 
                DEBUG_LOG(@"AVAssetExportSessionStatusExporting");                 
                break;
            }
            case AVAssetExportSessionStatusCancelled: 
            { 
                DEBUG_LOG(@"AVAssetExportSessionStatusCancelled");
                break;
            }
            case AVAssetExportSessionStatusWaiting: 
            { 
                DEBUG_LOG(@"AVAssetExportSessionStatusWaiting");                 
                break;
            }
            default: 
            { 
                DEBUG_LOG(@"didn't get export status");                
                break;
            }

        };
    }];
    [exportSession release];
}

Answer 1

我为自己整理了答案,并希望与遇到同样问题的其他人分享.

问题是由于某种原因,AVAssetExportPresetPassthrough在ios5中无法正常工作.用它代替AVAssetExportPresetAppleM4A解决问题.
但现在出口需要更长的时间.