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我正在开发一个记录多个文件的 iPhone 应用程序，然后我将这些文件合并到一个文件中，最后我将该文件上传到服务器上。我经历过，如果我制作一个 7 mint 的文件，它的大小是 0.85 MB，但是如果我制作两个 3.5 分钟的文件，然后将它们合并到一个文件中，它的大小是 9.75 MB，它的大小非常大并且需要太长时间是时候上传了。请建议我以某种方式处理这个问题。提前感谢`

AVMutableComposition* composition = [[AVMutableComposition alloc] init];
    AVMutableCompositionTrack* audioTrack = [composition addMutableTrackWithMediaType:AVMediaTypeAudio
                                                                     preferredTrackID:kCMPersistentTrackID_Invalid];
    //  kCMPersistentTrackID_Invalid, kCMMediaType_Audio,
    NSArray *searchPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentPath_ = [searchPaths objectAtIndex: 0];
    // RecorderFilePaths contain the path of recorded files
    if ([recordedFilePaths count]>0)
    {
        NSError* error = nil;
        AVURLAsset* masterAsset= nil;
        CMTime time = kCMTimeZero;

        NSURL *tempUrl =[recordedFilePaths objectAtIndex:1];
        time = CMTimeAdd(time, [masterAsset duration]);
        AVURLAsset *Asset = [AVURLAsset URLAssetWithURL:tempUrl options:nil];
        CMTimeRange timeRange  = CMTimeRangeMake(kCMTimeZero, Asset.duration);
        NSArray *ar = [Asset tracksWithMediaType:AVMediaTypeAudio];
        [audioTrack insertTimeRange:timeRange ofTrack:[ar objectAtIndex:0] atTime:kCMTimeZero error:&error];
        //kAudioFormatMPEG4AAC,   AVMediaTypeAudio
        tempUrl = [recordedFilePaths objectAtIndex:0];
        masterAsset = [AVURLAsset URLAssetWithURL:tempUrl options:nil];
        timeRange = CMTimeRangeMake(kCMTimeZero, masterAsset.duration);
        NSArray *tracktypes = [masterAsset tracksWithMediaType:AVMediaTypeAudio];
        [audioTrack insertTimeRange:timeRange ofTrack:[tracktypes objectAtIndex:0] atTime:kCMTimeZero error:&error];

        if (error)
        {
            NSLog(@"%@",error);
            return;
        }

        AVAssetExportSession* exportSession = [AVAssetExportSession
                                               exportSessionWithAsset:composition
                                               presetName:AVAssetExportPresetAppleM4A];
        //  AVAssetExportPresetPassthrough,,AVAssetExportPresetLowQuality
        if (nil == exportSession)
        {            
            return;
        }

        NSString *urlSt = [documentPath_ stringByAppendingPathComponent:[self dateString]];
        NSURL* combined = [[NSURL alloc] initFileURLWithPath:urlSt];

        exportSession.outputURL = combined;
        exportSession.outputFileType = AVFileTypeAppleM4A;
        //  AVFileTypeAIFF , AVFileTypeAIFC, AVFileTypeAIFC,
        [exportSession exportAsynchronouslyWithCompletionHandler:^(void){

            dispatch_async(dispatch_get_main_queue(), ^{
                switch (exportSession.status)
                {
                    case AVAssetExportSessionStatusFailed:
                        NSLog(@"Failed");
                        break;
                    case AVAssetExportSessionStatusCompleted:
                        NSLog(@"Completed");
                        break;
                    case AVAssetExportSessionStatusWaiting:
                        break;
                    default:
                        break;
                }

            });
        }];

        [recordedFilePaths addObject:combined];
}

`

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