Subject: RE: [Sipping] RE: draft-stein-great-00.txt

From: Jean-Marc Valin <[email-masked]>
Date: Sat, 08 Oct 2005 14:38:41 +1000

(disclaimer for those who don't know: I'm the author of Speex)

> Sounds like a good idea to me.
> And we should design it from day one for the modern Internet
> environment.

Both Speex and iLBC (as far as I know) *are* designed from day one for
the Internet.

> The G-series codecs put 90% effort into low rate, and 10% into low
> delay.

Untrue. Many G.* codecs are into low bit-delay, G.729 is 10 ms and G.728
is < 1ms.

> It is critical for them to be CBR, and there is no attention to packet
> loss, etc. 

I think CBR (or at least having a max bit-rate) *is* important for VoIP.
As for packet loss, I wouldn't say the G.* don't pay attention to it at
all, but of course the focus is more on bit corruption.

> Only the IETF has the motivation to design a codec for:
> 1) no 4kHz (or 8kHz) limitation 

Speex already does wideband, which is already much better than
narrowband. Yet, I'm still trying to convince people to use wideband
instead of narrowband (even those already using Speex).

> 2) high perceptual quality (not "toll quality")

Try Speex at quality >= 8.

> 3) not necessarily CBR

Why not? While Speex supports VBR, I don't think it's really useful in
VoIP unless you have a large number of connections for the "law of the
average" to apply.

> 4) low delay

Current standard is around 20-30 ms, which is fine for many uses. Of
course lower would be nice, but the overhead becomes important. With 20
ms frames, you pay almost 16 kbps just for the overhead of IP/UDP/RTP.

> 5) resilient to bursty packet loss

If by bursty, you mean 5-10 lost packets in a row, I'm sorry, but
there's just *nothing* that can really be done about it (unless you are
willing to really screw up latency). For more "conventional" (random,
10-20%) loss, then I think Speex and iLBC already do a good job.

	Jean-Marc

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---

From: Dean Willis <[email-masked]>
Date: Mon, 10 Oct 2005 12:30:16 -0500

Ok, Yakov. It looks like you caught the interest of a few people.

I'd suggest you talk to Jon and Allison about organizing a BOF for  
codec work.

And make a new mailing list for said BOF, if approved, and when you  
get that list available, let us know about it here. In  the meantime,  
we're WAY off scope for SIPPING. Feel free to keep talking, but  
please reduce the cc-list to just the active participants (and drop  
off SIPPING).

And if you do have SIP-specific stuff to talk about here, please  
start a new thread. This one is bogged down.

Thanks, everybody.

--
Dean Willis
SIPPING co-chair.