Converting/Decoding a strange audio file

Posted by Problematic on Sat, 09/28/02 - 22:48:14.

Hi there, I am attempting to decipher a "cd" that is played as muzak in a business. The cd consists of 2 files, a file with an .aud extension and a text file that lists all of the songs on the cd in a form of playlist that the cd player uses to make them work. These cds are not normal cds, they have approx. 18 hours of music on them and play in a randomized shuffle form. Upon loading the file into Winamp, I discovered it worked...but as an 18 hour long file. I could slide through and listen to songs here and there, but my question is, how would I go about either dissecting the .aud file and modifying the playlist so I could insert my own songs into it, or creating a usable .aud file out of .wavs that the special cd reader would recognize and play?

-Problematic

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Are you talking about a DVD or something? I will assume not, si

Posted by Macintorque on Sun, 09/29/2002 - 05:45.

First, you need to find out what ".aud" actually means in this case. Since WinAmp can actually play it, that narrows down the possibilities. So, what you need to do, is find a list of file types that WinAmp can read and play. Since the file is 18 hours long, that already leaves out WAVE, AIFF, and Sound Designer files. You ".aud" file has been heavily compressed. Most likely, it's utilizing some form of MPEG. MP3 is a form of MPEG, but only one flavor of many. It could be some sort of MOD music file, but that is unlikely because MOD is more of a sequencer format, and it still isn't too popular. However, .MOD files are capable of compression rates much higher than MP3 or other MPEG formats in terms of raw duration. If the sound quality is really crappy sounding, it could be some kind of A-Law or Mu-Law compression or .AU, or some similar NeXT format.

What I would do is experiment with copies of the .aud file. try renaming it's type to match other likely filetypes. The trouble is, however, that since it's 18 hours long, you are going to have a tough time customizing it to fit your own needs. Most of the time projects like this require converting from a compressed format to a non-compressed format for editing. After that, the results are compressed back to the native format. In your case, you probably have neither the time nor space to decompress an 18-hour long file even if you can find an editor on the planet capable of dealing with such a beast. If this means so much to you, you will need to obtain a file splitter so you can deal with the file in smaller chunks. Still, it will be difficult to do this, because most audio files require a header (first part/top of the file) to play. Your best bet is an editor which can read directly from disk and perform edits without relying too heavily on RAM. This editor needs to be able to open RAW audio files. That way, YOU can tell IT what the format is so you will able to play the different sections after you dice it up into small chunks.

Basically, I am telling you that this project is probably not worth all of the effort. If you really want to create your own .aud file CD, you should just contact the original authors and find out how they did it. If you can't contact them directly, maybe you can find an article online about common muzak CD formats or something. Then you can later obtain your own authoring software to make your own muzak CD.

Trust me, sometimes it's easier to "hack" a human for info than to hack a machine if you're merely searching for legal data. Good luck. This reminds me of a harder version of trying to create your own "QuickTime Musical Instruments" Extension. I was just thinking about that recently. Good luck.