[asterisk-dev] iLBC packet loss concealment (was: code-cleanup concerns)

[Tzafrir Cohen]

On Sun, Apr 16, 2006 at 10:22:55AM -0700, John Todd wrote:
> [continuing top-threading madness ;-]
> 
> I agree with everything said thus far in this thread, and I 
> especially agree with Steve's assertions that 4khz is an artificial 
> and sub-standard limit to set for ourselves when we have so much more 
> to work with.  Let me throw a few actual questions to the group, so 
> we can stop being theoretical and try to improve our "product":
> 
> Statements:
>  1) I have heard rumors (not from anyone at Skype) that the iLBC 
> codec used by Skype actually _does_ sound better than normal iLBC 
> even at higher bitrates, due to some clever manipulation of dynamic 
> range.  Can anyone confirm or deny this?  This might suggest how PSTN 
> calls sound "better" even though it's still only G.711 on the PSTN 
> side.
> 
>  2) I've often had problems with Skype's voice quality, so I won't 
> give them the perfect scores that everyone else is attributing to 
> them.  However: Kudos for them for throwing out the old rules.
> 

3. Several people have issues with the license of iLBC. For that reason
it is currently being removed from Debian.

> 
> Questions:
> 
>  1) Does the iLBC codec code in Asterisk perform Packet Loss 
> Concealment (PLC)?  If so, is it being done in the most optimal way? 
> Is it just in IAX2 or in SIP as well?  (there was an answer on this 
> by Zoa, but it still isn't clear.)
> 
>  2) Are the higher bitrate patches I've seen scurrying around the SVN 
> branch mailing list currently in TRUNK or still in "experimental test 
> phase"?  (see oej's "test-this-branch", and bug #5084, which really 
> just seems to support G.722 passthrough, and is not a codec 
> implementation)
> 
>  3) Is this all a moot point until more end devices support iLBC and 
> better PLC? (Hint: I don't think so, since I'd love to terminate all 
> my LD minutes to an Asterisk server with high-bitrate, 
> loss-concealing iLBC instead of just using G.711 like I do today. 
> Bitrates are not my problem; sound quality is my problem, but if I 
> get better than 64kbps for better sound quality then that's a bonus.)

4-6. Basically The above questions, with s/iLBC/speex/ .

-- 
Tzafrir Cohen      sip:tzafrir at local.xorcom.com
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