Echo issue on OM2008.08 solved

Al Johnson openmoko at
Sun Aug 31 15:50:05 CEST 2008

On Saturday 30 August 2008, Yann SLADEK wrote:
> Hi,
> does your patch work with a FreeRunner ?

The patch turns on the echo and noise suppression capabilities in the GSM 
chipset using one of the hidden and NDA's AT commands someone kindly posted 
on the hardware list. I've tested it on my Freerunner under FSO and it works. 
Since GTA01 uses the same chipset I expect it will work there as well. Note 
that the post to the hardware list doesn't have full documentation of the 
functions so we may not be using the best or most reliable method of 
switching this function on, but for me at least it is a big improvement.

> if yes, why are we able to cancel the echo by setting some values under
> gsmhandset.state here :

See my explanation later in the same thread. It sounds like the echo 
suppression in the GSM chipset is using a noise gate and level control 
similar to the one built into the Wolfson audio chip but not used in the 
current alsa state files.

Note that even with the patch if you turn up the earpiece volume and the mic 
gain high enough there will be echo. The mic will pick up enough of the sound 
from the earpiece to fool the system into thinking you are speaking. 

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