In my previous column, I described the success I've had with using VP8 for compressing the video for the Lib-Ray main feature multimedia file. At the end of that process, though, I still have a silent film. We also need to get the audio, and make a decision about the format. WebM calls for Vorbis sound, which probably makes sense for internet downloads, but this is where we part ways -- for my application, bit-perfect audio with FLAC seems to make more sense, at least for the main audio tracks (Vorbis is still in the picture for things like commentaries).
Ogg Vorbis and Ogg FLAC (the Ogg stream version of the Free Lossless Audio Codec) are popular free-licensed and patent-free codecs for handling sound. These are the formats I'll be using in a complex Ogg Theora video file that I am creating as part of my "Lib-Ray" experiment in creating an alternative format for distributing high definition video. In order to do this, I'll need to solve several technical challenges using the FLAC command line tools, Audacity, and VLC, which I'll demonstrate here.
Film soundtracks are usually made available in either "Stereo" or "5.1 Surround" sound, although other possibilities exist. Quite a few of the source sound recordings I've been using are "binaural" recordings, which sound eerily realistic over earphones, but often less impressive when played back on speakers. What does this stuff mean, and how can I use free software tools to make the most of it? This will be an ongoing learning experience, but I want to start with a brief description of these most common technologies, and how they are supported by the file formats we have available to us: Vorbis, FLAC, and WAV.