Maven SLIP audio

Geoff Rehn (EST)
Fri, 25 Nov 1994 09:38:16 -0500


At 4:46 AM 11/25/94 -0800, David Winet wrote:

>I think everyone will be VERY interested to hear if you can run audio
>over a SLIP. Let us know?
>David Winet
>
>On Fri, 25 Nov 1994, Geoff Rehn wrote:

>> ---
>> This weekend, I will be taking home a 28.8 kbps modem to test.
>> One of the things I wish to test is the use of Maven by dialup, using the
>> 16kbps option. I reckon I will get dialup audio going along with CU-SeeMe.
>>
>> If anyone wishes to connect either 1-1 or via our Murdoch University
>> reflector over the weekend, so I can test this Maven audio at 16kbps and
>> low cap CU-SeeMe, please let me know.
>>
>> I will have SLIP access from home.
>>
>> best wishes
>> geoff R.

>From an earlier posting of mine of the other day:

>I haven't had much chance to fully try the (newer) Maven audio with the
>delta-mod encoding, at 16kbps. So far, I haven't managed to get it to work.

>It would seem to me that, if the video were paused, and Maven at 16kbps used,
>an audio link might well be possible at a 28.8kbps modem link.

Well, I can now report that the above does work and quite well at that.

I have tested at this stage a Maven only link using the delta-mod encoding
in Maven 2.0 alpha 18, at 16kbs, over a 28.8kbps link. Very usable audio.
And this was off a reflector - some say that reflected audio is worse than
direct 1-1.

----
>From Charlie Kline's latest Maven README:

>Changes in version 2.0a18:

> Tired of fiddling with frustratingly CPU-intensive DSP algorithms like GSM
>and CELP and trying to cram them onto a 68040, I opened up a digital
>communication textbook and read up on something called Delta Modulation. I've
>implemented a codec for delta-mod, which uses only 16 kilobits per second of
>network bandwidth and doesn't require any fancy floating-point either. This
>may be in reach of SLIP connections, which is what a lot of people have been
>asking for. Quality is somewhat poor; there's a great deal of quantization
>noise in the received audio which sounds like an AM radio station tuned
>slightly off, but the speech is quite intelligible. Comments about this coding
>are welcome.

----

I also tested this morning with just a 14k4 link and I think that is
_almost_ passable as well.

I will be doing a CUSM/Maven test later this weekend but I am confident it
will work, especially if the video is paused.

But, why oh why, the huge variation in the ability of the Macs to handle
both CUSM and Maven audio?

My IIvx at work has no troubles; old Quadra 700 very temperamental; Quadra
605 - receive audio OK, transmit not at all; Quadra AV - no end of hassles.

So, Mac CUSM people, get that copy of Maven 2.0a18 (please don't mail me
and ask where - use an archie search to find your nearest archive: I'm in
Australia!)

I'd love to engage in a Maven audio link up, by dialup.

Geoff R.

---
Geoff Rehn
Academic Services Unit
Murdoch University    Western Australia
rehn@cleo.murdoch.edu.au