Re: Bug#682010: [mumble] Communication failures due to CELT codec library removal

[Chris Knadle <Chris.Knadle@coredump.us>]

On Monday, July 23, 2012 15:43:11, Ron wrote:
> On Mon, Jul 23, 2012 at 02:38:19PM -0400, Chris Knadle wrote:
> > On Monday, July 23, 2012 13:16:55, Ron wrote:
> > > On Mon, Jul 23, 2012 at 03:38:44PM +0100, Ian Jackson wrote:
> > […]
> > 
> > > Maybe that is true for the gamers, but when I asked I didn't get
> > > any confirmation that this was what the problem they saw was - so
> > > I'm guessing a bit here, based mostly on the knowledge of what the
> > > codecs themselves are capable of.
> > > 
> > > I am actually likewise curious to understand this better if that's
> > > not the reason.  It's not surprising celt can sound better, but it
> > > is quite surprising if speex actually sounds Bad.  And for people
> > > just talking, and who pay for their traffic by the MB, or who only
> > > have a low bandwidth pipe, celt may not be the best choice for them
> > > at all anyway.
> > 
> > I seem to recall that the early versions of Mumble that I used defaulted
> > to using Speex.  I seem to remember it sounding sort of like "a so-so
> > cellphone connection", sort of like the person(s) on the other side
> > sounded like they might be slightly underwater.  i.e. "works but not
> > great", whereas CELT sounds very clear [as does Opus].  I can't be
> > positive about this though because I might be mixing this memory up with
> > my memories of other VoIP packages I've used over the years, so I'm
> > likewise curious to hear what Speex sounds like again.
> 
> That's the classic artifact introduced by an echo canceller hunting for
> phase lock, which is exactly what causes it in cell phone connections
> too.  It's not an artifact of the codec itself.
> 
> And unless you really are completely misremembering, really early versions
> of mumble used speex 1.1, which is an inferior codec to what we have today,
> but is still not responsible for introducing that effect.

That all sounds reasonable.  Back then I think I was using many of the default 
settings and as such could have been using echo cancelation.  These days I've 
turned that off because it can sometimes cause echo rather than canceling it.  
Speex 1.1 sounds familiar.

  -- Chris

--
Chris Knadle
Chris.Knadle@coredump.us