[arm-allstar] codecs

[David McGough]

Hi Dan,

That list (from the CLI command: "show codecs") shows the "official"  
Asterisk id numbers for the listed CODECs, but it doesn't mean that all
those CODECs are installed and available for use.

To see what CODECs are installed, use the "show translation" command, 
where you'll notice that speex, G729, G723 and G722 are not installed.

Also note that when I added iLBC, I hacked the config to utilize 20mS
frames, NOT the standard 30mS frames, as is typically found in Asterisk. 
This hack was required since everything AllStar related uses 20mS frames, 
no exceptions.

The CODEC2 variants that I installed were for 3.2Kbps and 2.4Kbps data 
streams. I'll try to dredge this code up.

At this other end of the spectrum, I expect G722 (not currently installed) 
might warrant some investigation, even though it requires a higher 
sampling rate.

In my experience, most high-speed WiFi links have plenty of bandwidth for
any standard Asterisk CODECs. If you're piggy-backing on someone else's
backbone, your bandwidth requirements won't even hit the RADAR. The
problem, of course, is highly variable latency when those links get
heavily loaded.

On a historical note, my original reason for adding iLBC was due to
testing using 150Kbps, 900mhz data radios intended for SCADA and telemetry
type communications.  iLBC was the only free CODEC with reasonable audio
quality that would work on that link--and still does today.

73, David KB4FXC


On Sun, 7 May 2017, Dan Keizer wrote:

> Thanks guys - appreciate your feedback on your experiences.
> 
> Interesting : g726 would be using about 40Kbps per connection. iLBC would
> use about 15Kbps and G729 about 8Kbps, codec2 would use about 2.4Kbps.
> While our available bandwidth is normally quite good - I'm also looking at
> sites that may have more latency and being in vicinity of some high power
> broadcast stations, ensuring a good remote wifi connection with good RF
> shielding will be important for these.  While the codec2 project aims to
> have decent SSB-like signal quality, it would no where come close to good
> quality FM - but may be of value in some situations.
> 
> The default installed codecs on the hamvoip project are:
>         INT    BINARY        HEX   TYPE       NAME   DESC
> --------------------------------------------------------------------------------
>           1 (1 <<  0)      (0x1)  audio       g723   (G.723.1)
>           2 (1 <<  1)      (0x2)  audio        gsm   (GSM)
>           4 (1 <<  2)      (0x4)  audio       ulaw   (G.711 u-law)
>           8 (1 <<  3)      (0x8)  audio       alaw   (G.711 A-law)
>          16 (1 <<  4)     (0x10)  audio   g726aal2   (G.726 AAL2)
>          32 (1 <<  5)     (0x20)  audio      adpcm   (ADPCM)
>          64 (1 <<  6)     (0x40)  audio       slin   (16 bit Signed Linear
> PCM)
>         128 (1 <<  7)     (0x80)  audio      lpc10   (LPC10)
>         256 (1 <<  8)    (0x100)  audio       g729   (G.729A)
>         512 (1 <<  9)    (0x200)  audio      speex   (SpeeX)
>        1024 (1 << 10)    (0x400)  audio       ilbc   (iLBC)
>        2048 (1 << 11)    (0x800)  audio       g726   (G.726 RFC3551)
>        4096 (1 << 12)   (0x1000)  audio       g722   (G722)
> 
> I think I'll have to give these a try and test them on the RF side as well.
> (I used g729 as a standard for all my prior asterisk configs).  Will do
> some tests, thanks.
> 
> And, just so I know, what's the preferred method on recompilation -
> -downloading asterisk and rebuilding -- assuming compiling fresh from
> source, what's the usual time frame for recompilation on these machines
> these days?  Do you have source that you have used or just the images?
> 
> 73, Dan ve4drk
>