DGIndex
Although DGIndex's primary use is reading MPEG files, it can also demux audio from the files it reads. This is particularly helpful for files that already have AC-3 audio, as they only need to be demuxed in order to get audio assets.
AviSynth
AviSynth is mainly a video tool, but it also has some powerful audio capabilities. It can even be used to adjust playback speed. It's not necessarily the best tool, for the job, but it's free, does a good job, and can adjust video and audio together to avoid sync issues.AvsP
AvsP is a front end for AviSynth. Unlike visual editors, AviSynth works on a command line and isn't tied to any particular GUI. There are a few programs that offer some features normally associated with visual editors, but since AviSynth is a script driven tool, all these programs are really just fancy script editors. AvsP adds features to help you build AviSynth statements, making it good for beginners. It also adds the ability to use visual controls like sliders to adjust different script variables for advanced users. Those features plus functionality for previewing scripts through a third party program of your choice.ffdshow
The easiest way to read AAC audio, like what our MPEG-4 files have, is with ffdshow. This will allow us to demux the audio to encode to AC-3.Haali Media Splitter
Although MP4 files can store many of the same video and audio streams as AVI files, Windows doesn't come with the necessary components to separate information into streams so they can be read. The Haali Media Splitter gives Windows this ability, allowing ffdshow to decode the audio and video once they've been separated.VirtualDub
While it's better known as an AVI editor and front end for video encoding, VirtualDub has two features that make it valuable for working with audio. It can read AviSynth scripts, meaning if AviSynth can decode it VirtualDub can play it. It also has a feature for saving an audio stream as a Wave file. With AviSynth doing the decoding and VirtualDub saving an uncompressed audio file, we'll end up with a file that can be used as an asset or encoded to AC-3.TMPGEnc AC-3 Plugin
Even though this is really a standalone program, it's sold primarily to be used as a plugin for programs like TMPGEnc DVD Author, or what we'll be using - DVD-Lab Pro. As a result, the GUI isn't very user friendly, and I highly recommend controlling it with other software like we'll be doing here.DVD-Lab Pro
DVD-Lab Pro will be used for a front-end to the AC-3 plugin. You can actually use it without a front-end, but I won't be covering instructions for that since DVD-Lab Pro is also going to be used for authoring.File Names
Up to this point we haven't looked at the names of our various source files. If they had been files we created ourselves there likely would have been some sort of naming convention. Since they originate from different sources some of them have similar names, while others are uniquely named. As I create my DVD assets I try to name them in a more consistent manner so I'll know what the name of a particular file should be before I start looking for it. I also like to name my AviSynth scripts with the same name I'll use for the assets.
For example, the cartoon titled "The Eleventh Hour" has a filename of superman_eleventh_hour.mpeg. Any AviSynth scripts I create for it will be titled "Eleventh Hour.avs" and the video and audio assets will also be named "Eleventh Hour" followed by whatever extension is appropriate.
