iOS mp3 duration to plist, the plist can then be manually copied to the plist.

gistfile1.m

    NSString *plistFilename = [[NSBundle mainBundle] pathForResource:@"voice_list" ofType:@"plist"];
    NSMutableDictionary *plist = [[NSMutableDictionary alloc] initWithContentsOfFile:plistFilename];
    
    for (NSInteger xt = 1; xt < 13; ++xt) {
        for (NSInteger row = 1; row < 13; ++row) {
        
            NSString *sum = [NSString stringWithFormat:@"mel%ldx%lde%d", (long)row, (long)xt, (row * xt)];
            
            NSMutableDictionary *sumDict = [plist objectForKey:sum];
            
            AVURLAsset* audioAsset = [AVURLAsset URLAssetWithURL:[[NSBundle mainBundle] URLForResource:sum withExtension:@"mp3"] options:nil];
            CMTime audioDuration = audioAsset.duration;
            float audioDurationSeconds = CMTimeGetSeconds(audioDuration);
            
            if (audioDurationSeconds > 0) {
                [sumDict setValue:[NSNumber numberWithFloat:audioDurationSeconds] forKey:@"to_all"];
            
                [sumDict setValue:[NSNumber numberWithFloat:audioDurationSeconds] forKey:@"to_eq"];
                
                
            }
        }
    }
    
    NSArray *documentPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,
                                                                 NSUserDomainMask, YES);
    
    NSString *docsDir = documentPaths[0];
    NSString *filePathInDocsDir = [docsDir stringByAppendingPathComponent:@"voice_list.plist"];
    
    
    if ([plist writeToFile:filePathInDocsDir atomically:YES]) {
        NSLog(@"Successfully finished writing to file");
    } else {
        NSLog(@"failed to write");
    }