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Get tags from M4A file
AudioFileID fileID  = nil;
    OSStatus err        = noErr;

    err = AudioFileOpenURL( (CFURLRef) fileURL, kAudioFileReadPermission, 0, &fileID );
    if( err != noErr ) {
        NSLog( @"AudioFileOpenURL failed" );
        return nil;
    }

    UInt32 id3DataSize  = 0;
    char * rawID3Tag    = NULL;

    err = AudioFileGetPropertyInfo( fileID, kAudioFilePropertyID3Tag, &id3DataSize, NULL );
    if( err != noErr ) {
        NSLog( @"AudioFileGetPropertyInfo failed for ID3 tag" );
        return nil;
    }
    //NSLog( @"id3 data size is %d bytes", id3DataSize );

    rawID3Tag = (char *) malloc( id3DataSize );
    if( rawID3Tag == NULL ) {
        NSLog( @"could not allocate %d bytes of memory for ID3 tag", id3DataSize );
        return nil;
    }

    err = AudioFileGetProperty( fileID, kAudioFilePropertyID3Tag, &id3DataSize, rawID3Tag );
    if( err != noErr ) {
        NSLog( @"AudioFileGetProperty failed for ID3 tag" );
        return nil;
    }


    CFDictionaryRef piDict = nil;
    UInt32 piDataSize   = sizeof( piDict );

    err = AudioFileGetProperty( fileID, kAudioFilePropertyInfoDictionary, &piDataSize, &piDict );
    if( err != noErr ) {
        NSLog( @"AudioFileGetProperty failed for property info dictionary" );
        return nil;
    }


    return (NSDictionary*)piDict;