The NHWS: Using A.Pack to make AC-3 Audio
By Eliot Hochberg (eliot@high-mountain.com), April 16, 2003
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Although DVD Studio Pro can use AIFF audio files, there is a better way to create audio for use in a DVD – by using A.Pack to create AC-3 audio. The reason why this is better was explained in the last article, but to reiterate, AC-3 audio provides better compression with little if any reduction in audio quality. In addition, most DVD players can more readily decode AC-3 audio files. All of this adds up to improved DVD performance and more efficient use of disc space.
At first blush, A.Pack audio can appear to be a daunting program. It typically presents the surround sound mode, which has six different audio tracks; but for most projects, you won’t be using these. This article covers what to do in the more common situation of having stereo or mono tracks to put on your DVD.
The first thing to do is to make sure your audio files are in the proper format. Pretty much any format will do, but I typically use AIFF files. You can also use QuickTime files, and I believe WAV files will also function. I haven’t tried MP3s.
The next step is to open the encoding mode pull down menu and select either 1/0 (C) or 2/0 (L/R) (these are the mono and stereo modes, respectively). In a typical surround sound system, there are five or six speakers; two stereo speakers in front, two surround stereo speakers in back, one center speaker usually used for dialog, and sometimes a subwoofer. If you have a stereo file, you should select the 2/0 option. For mono files I also choose stereo, because although most surround systems have a center speaker, some don’t and some folks have DVD systems without surround speakers. Although the systems should decode the mono signal to stereo speakers in these situations, I have found this to be inconsistent in the real world.
Once you have selected your mode, it’s time to select your files. If you have separate left and right files for stereo sound, put the left file in the left speaker, and the right in the right. It isn’t necessary to have separate files though – if you have a single stereo file, simply drag the file onto each speaker. The program will ask which channel to use, defaulting to the appropriate one. For a mono track in stereo mode, use the same track for both channels. If you are doing mono mode, put your mono track in the one speaker shown.
Once you have selected your tracks, it’s time to encode! Click the encode button, and you will be prompted to select a file name and location. Do so, and then wait for the encoding. This usually runs pretty quickly, about 1/10th the length of the footage.
With your audio encoded, you can import it into your DVD. This works the same way as any other audio. Import the audio into DVDSP, then drag it to the track you want it to be used for. Note that it is a good idea to import your main audio track first, then import your other audio tracks. This way your disc will default to your main audio selection without scripting.
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