AVAssetExportSession

gistfile1.m

    AVAsset *asset = [AVAsset assetWithURL:inputURL];

    NSLocale *locale = [[asset availableChapterLocales] lastObject];
    NSArray *keys = [NSArray arrayWithObjects:AVMetadataCommonKeyTitle, nil];
    NSArray *chapters = [asset chapterMetadataGroupsWithTitleLocale:locale containingItemsWithCommonKeys:keys];
    // Yes, we do have chapters ;-) 8... ;-)

    AVAssetExportSession *exportSession = [[AVAssetExportSession alloc] initWithAsset:asset presetName:AVAssetExportPresetAppleM4A];
    exportSession.outputURL = outputURL;
    exportSession.outputFileType = AVFileTypeAppleM4A;

    [exportSession exportAsynchronouslyWithCompletionHandler:^{
        DLogI(exportSession.status); --> 3 (Succeeded) but lost the chapters.
    }];