Sound quality in calls.

[Al Johnson]

On Thursday 18 September 2008, Marco Trevisan (Treviño) wrote:
> Tom Yates wrote:
> > i experimented yesterday with turning on the hardware echo cancellation,
> > and that worked for one call (allowed me to increase Speaker Playback
> > Volume to 117) but then things went back to being very echoey.  so unless
> > i'm willing to have a minicom session at the beginning of every call,
> > that's not usable right now; i'll have to wait until the AT%N0187 is
> > integrated into qtopia's call-handling logic.
>
> So do you think that calling that AT command before of doing/answering a
> call would improve the sound quality?
> If it is, I guess this could be done quite easily in the code... So if I
> find some free time, I'll try it!

It was persistent over 2 calls when I tried it in FSO, but it certainly 
shouldn't do any harm. I used mickeyterm to enable and disable it mid call to 
check that call to call variability wasn't playing a part. It may also be 
worth trying some of the other settings. From the hardware list post:

  "0083" "Short AEC is active"
  "0283" "Long AEC is active"
  "028B" "Long AEC -6 dB is active"
  "0293" "Long AEC -12 dB is active"
  "029B" "Long AEC -18 dB is active"
  "0105" "Noise reduction is active"
  "0125" "Noise reduction -6 dB is active"
  "0145" "Noise reduction -12 dB is active"
  "0165" "Noise reduction -18 dB is active"
  "0187" "Both AEC and Noise reduction are active"
  "0001" "AEC and Noise reduction are unactivated"

These are bitmasked. From LSB upward the usage appears to be:
LSB - always true
AEC (short or long)
NR
-6dB on AEC
-12dB on AEC
-6dB on NR
-12dB on NR
AEC (short or long)
NR
Long AEC

So far AFAIK only 0001 (nothing) and 0187 (short AEC and NR) have been tried. 
What does Long AEC do? Or -XdB for AEC and NR? Do other combinations than 
those listed work? Does 0387 give us Long AEC and NR?