Voice over GPRS?

Mikko J Rauhala mjrauhal at cc.helsinki.fi
Fri Feb 2 17:49:19 CET 2007

On pe, 2007-02-02 at 11:37 -0500, ROB wrote:
> 1kb/s isn't going to get you too much audio.  Try encoding an mp3 at
> 1kb/s to see how audible that would be.  I think you'd be looking at
> something more along the lines of 32-64kb/s to get anything that you
> could understand. 

mp3 isn't designed for that, though even speex's minimum is 2kb/s
(probably you want to use more). Anyway, Robert was talking about 1kB/s,
which is quite fine already.

But the main point that GPRS is not for VOIP really stands; short voice
messages, sure, an ongoing dialogue, no.

Of course, you can make a GSM data call (I presume) and thus reserve
bandwidth from the network; some latency issues would remain, but you
could probably get a reasonable VOIP connection going on that with
low-bandwidth Speex; would likely cost you but perhaps be an affordable
option for intl. calls.

(Also, _this_ is how you can accomplish a proper encrypted phone call
using the GSM network with Neo, if you're into security and don't mind
it costing a bit. Doubleplusgood if you can make a data call from cell
to cell direct without both sides having to initiate their own data
calls; not sure about that, GPRS suffices for my uses so haven't looked
at data call capabilities.)

Mikko J Rauhala <mjrauhal at cc.helsinki.fi>
University of Helsinki

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