[Speex-dev] Comparison

Jean-Marc Valin Jean-Marc.Valin at USherbrooke.ca
Thu Jun 9 21:49:50 PDT 2005

> I am asking this because it is believed that Skype is using some iLBC and
> iSAC since GlobalIPSound listed Skype as a partner.

I think (from what I've heard) that's what Skype uses. I have no idea
how iSac sounds because it's proprietary and I've never used Skype. 


> Thanks,
> Joe
> -----Original Message-----
> From: Jean-Marc Valin [mailto:Jean-Marc.Valin at USherbrooke.ca] 
> Sent: Friday, June 10, 2005 12:24 PM
> To: joe_anny at yahoo.com.sg
> Cc: speex-dev at xiph.org
> Subject: Re: [Speex-dev] Comparison
> Hi,
> First, you can see a comparison of the codec features at
> http://www.speex.org/comparison.html
> As for quality/bitrate, the first thing is that Speex supports a lot
> more settings (from 4 to 42 kbps) and does wideband (16 kHz sampling),
> which iLBC doesn't do. I've only tested iLBC once, but I've found that
> Speex has a better quality for the same bit-rate (or lower bit-rate for
> the same quality). This is mainly due to the fact that iLBC is designed
> to encode frames independently (more on this below). Even from their
> site, you see that even at 13.3 or 15 kbps (they don't specify which),
> they have the same quality as G.729A at 8 kbps. 
> Now, their point is that since each frame is independent, the codec is
> more robust to packet losses which is good for VoIP. However, in my
> opinion (and that of others) is that the price in terms of bit-rate is
> too high and you might as well just add redundancy by transmitting some
> packets more than once (as proposed in
> http://www.icassp2004.com/Papers/viewpapers.asp?papernum=3280 ). For
> instance, if it goes to 20% packet loss, then transmitting 8 kbps Speex
> packets twice (4% effective loss) will be much better than iLBC at 15
> kbps.
> Regarding CPU utilization, I have no idea what iLBC requires. For a PC I
> don't think it actually matters and for embedded systems, then you have
> to pay for a fixed-point iLBC license (Speex includes the fixed-point in
> the same code).
> 	Jean-Marc
> P.S. Of course you can say I'm biased since I'm the author of Speex, but
> since you posted to speex-dev, you probably expected that anyway.
> Le vendredi 10 juin 2005 à 09:35 +0800, Joe T a écrit :
> > Hi,
> > 
> > Is there any comparison made between Speex and iLBC free codec? 
> > How would they compare in terms of quality, bitrate and CPU
> > utilization?
> > 
> > Thanks, 
> > Joe
> > 
> > _______________________________________________
> > Speex-dev mailing list
> > Speex-dev at xiph.org
> > http://lists.xiph.org/mailman/listinfo/speex-dev
Jean-Marc Valin <Jean-Marc.Valin at USherbrooke.ca>
Université de Sherbrooke

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