[Linphone-users] [help!][resent] a terrible howling echo when both linphone-android UA is in speaker mode

[Coca]

Dear all,

Sorry for sending this again since I really need some hint!

I noticed in many android phones (we tested it with at least 50+ types of android)

 a terrible howling echo when both linphone-android UA is in speaker mode or in video chat (speaker mode of course). 

This only happen when both of them are in speaker mode.

Any idea how to tube this issue?  

I saw some ec related parameter in linphonerc file but no idea what they means.

ec_tail_len=120

ec_framesize=128

el_type=mic

el_thres=0.03

el_force=100000

el_sustain=400

el_transmit_thres=1.7

ng_floorgain=0.01

Thank you!

Coca