On Tuesday 15 July 2008 14:24:30 John covici wrote: > on Tuesday 07/15/2008 Tilghman Lesher([EMAIL PROTECTED]) > wrote > > > On Tuesday 15 July 2008 13:32:12 Artie Gold wrote: > > > Does anyone know of a replacement for meetme that provides native G729 > > > support? The transcoding back and forth from/to 711 is eating too much > > > processor for what we're doing... > > > > Buy a hardware transcoder board. There is simply no way to mix > > compressed audio like that without decompressing first. > > > > And by the way, it's decompressing to signed linear 16-bit audio, not > > ulaw. Even mixing of ulaw requires a decompress to signed linear. > > OK, I guess I need to show my ignorance -- what is the difference > between ulaw and signed linear?
ulaw is a compression algorithm which compresses the 16-bit 8000Hz signed linear (slin) format down to 8-bits per sample. So while signed linear consumes 128kbps, ulaw only consumes 64kbps. Ulaw is actually a fairly simple coding algorithm, and it compresses from and decompresses to slin with a 1-to-many lookup table between the values. So it's pretty fast, as implemented. A more technical explanation can be found on Wikipedia, if you are so inclined: http://en.wikipedia.org/wiki/Μ-law_algorithm -- Tilghman _______________________________________________ -- Bandwidth and Colocation Provided by http://www.api-digital.com -- AstriCon 2008 - September 22 - 25 Phoenix, Arizona Register Now: http://www.astricon.net asterisk-users mailing list To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
