[Gta04-owner] Replicant: Android Echo Cancellation

Adrien Dorsaz adrien at adorsaz.ch
Sat May 9 21:38:40 CEST 2015

Hi Lukas / gta04-community,

I've begun to read Android HAL documentation and I've seen in the Audio 
topic [0] some notes which can be useful to avoid voice echo :

> hardware/libhardware/include/hardware/audio_effect.h - represents 
> effects that can be applied to audio such as downmixing, echo, or 
> noise suppression.

Just below this comment, Google says us to refer to the Samsung tuna 
device. So I've checked the Cyanogenmod repository for this device and 
I've found their audio_effects.conf file.

Many audio effects are activated there, but I think we'll need the 
"Audio Echo Cancellation" (aec) module to resolve the issue about 
hearing self during voice call. I've noticed the URL of this 
configuration in that file [1]. Just below this configuration, the "ns" 
module can also be interesting (Noise Suppression).

These configuration make a reference to the 'libaudiopreprocessing.so' 
file (in the head of the audio_effects.conf) that I've found in my 
'out/target/product/gta04/obj/lib' build directory. Maybe we'll be able 
to make a similar configuration for the GTA04 ?

We've just one issue : it's to find the good UUID to set for the 
effects (which is used to find the good module). We've only this hint:

> # The uuid is the implementation specific UUID as specified by the 
> effect vendor. This is not the
> # generic effect type UUID.

I hope it has more meaning for someone here ? I have some hope, because 
I've seen in the libaudioprocessing.so files strings with 'AEC' and 
'NS' refering to the module.s
We just need the good UUID "as specified by the effect vendor".

Hope that's help,

[0]: AOSP Audio: https://source.android.com/devices/audio/implement.html
[1]: Audio Echo Cancellation: 
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