[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [HLL] Big bug !?!



Status: RO
Content-Length: 2322
Lines: 46

On Sun, 11 Jan 1998, Volker Ernst wrote:
> 
> To test "real" performance, i sended long patterns of "random" data between
> the two 14.4. The effective end-to-end user-bit-rate (14.4 carrier) was:
> * without V42 10640 Bits/Sec
> * with V42=on 12280 Bits/Sec (more, even though uncompressible data!)
> So there is no chance to get 13000 Bits/Sec over the line :-( this way.

I've always been a big fan of RL test. :-)

> There are different solutions, at least:
> * Stay with 14.4-modems, try using them in sync-mode
Pro: we know that it works. The VP1 uses sync and it sounds better than
many international circuits.
Con: there is no way (correct me if I am wrong) to create a compatible
software emulation using a PC with a standard modem.
My conclusion: sub-optimal given the stated goals of this project.

> * Use something higher than 14.4
Pro: it will work fine inside the EU. Can be done in software.
Con: will not work on transatlantic links. Will not work on links in many
developing countries and other places that might need such a device most.
We in the first world tend to often forget that there is a sizable chunk
of this planet where saying the "wrong" thing can result in a bullet
through the back of your head.
My conclusion: might be good as an optional mode, but bandwidth exeeding
14.4 should not be required.

> * Use different coding algorithm
Pro: allows for use with 14.4 and perhaps even 9600 (GSM data). Allows for
software emulation.
Con: sounds like shit unless we get our hands on a state-of-the-art
vocoder. IMHO, GSM half-rate does not provide sufficient voice quality.
My conclusion: if we can get the CDMA codec, this option might be ideal.
But if we can't, then I honestly don't know which option would be best.

> Thanks for bringing up this alarming point !

Sorry for taking so long to explain this. I have a very demanding daytime
job and am already involved in several freeware projects. I'll try
to give you guys reasonably fast feedback, but that won't always be
possible. I also won't be able to contribute any actual work. Look at me
as an advisor. That's the best I can do at this time. 

-- Lucky Green <shamrock@cypherpunks.to> PGP v5 encrypted email preferred.
   "Tonga? Where the hell is Tonga? They have Cypherpunks there?"