A few years ago, I discovered a site called "FreeSound.org" which sounded quite exciting, but turned out to be rather disappointing because the content was released under the Creative Commons "Sampling+" license, which is not a free license. This made all of the content incompatible with use on free software or free culture projects, and was very frustrating, especially given the name. Last month, though, Creative Commons decided to retire the Sampling+ licenses, and FreeSound.org is rolling out a new site with a license chooser that favors the "CC 0" public domain declaration and the "CC By" attribution licenses -- both compatible with free projects. This will be a big help for free-culture multimedia projects.
Home recording is not that hard or expensive to do, and Audacity provides a great tool for recording and editing dialog. I recently got the equipment together to do decent voice recording for our "Lunatics" video project. Total cost was under $150.00 for a condenser USB microphone system, and the sound is a tremendous improvement over my previous attempts. Now our biggest challenge is the room acoustics. So far, we're having a lot of fun recording dialog.
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.
As I was working on a sound track project for a science-fiction film I've been working on, I remembered reading an article in Free Software Magazine, by Gianluca Pignalberi, in which he described filtering using Gimp and a command-line program then called "ARSE" (version 0.1). The program is now called "The Analysis & Resynthesis Sound Spectrograph" ("ARSS", now version 0.2.3). Combined with an image editor of your choice (I also chose Gimp), it also turns out to be a very interesting way to make original sound effects -- by painting the sound spectrum.
Gimp is universally used for image manipulation. However, with a bit of creativity and a couple of tricks, it can also be used as an audio filter! Here is how...