Open Standard For Recording Compressed Voice?

john napiorkowski asks: "I do a lot of voice recording and have been using realaudio, which distributes 'free beer' tools for the job. However, I am greatly concerned by this reliance on such a proprietary tool; is there an open standard, free software replacement available? I have tried MP3, but it doesn't sound remotely as good as realaudio for voice recording at very high compression levels. Fifteen minutes of voice compressed with realaudio is under a meg and sounds almost exactly like the original, while MP3 sounds very poor to get the file that size."

Comments

Right - and why Vorbis probably won't work.

[Andy Dodd]

Yeah. For one thing, all of the information in speech is encoded within a 4 kHz bandwidth, while music is a 22 kHz bandwidth. In addition, there are many differences between the nature of voice signals and music signals.

If you're ONLY dealing with speech, it's much easier to get a good compression ratio than if you have to deal with music, and I'm not just talking about the bandwidth differences.

I wouldn't bother with Vorbis - it was designed for music, so it won't work for voice signals as well as codecs designed for voice.

I would look at codecs like the aforementioned GSM or G.whatever (G.711 is one speech codec, can't remember the others. I'd go to http://www.openh323.org/ for some more information on speech codecs among other things.

Note that G.whatever (and I think GSM) too, are at least somewhat encumbered by patents, but the licensing terms are relatively friendly from what I gather. And they are most definately standardized. (The only speech codec in wide use that I can think of off the top of my head is Qualcomm's PureVoice codec, used quite heavily in CDMA cell phones.)