0 votes


I'm using Zoiper 1.23 on Android. No matter the settings I use for making a call, the outbound (Receiving) audio is very low. The other end describes it as 'sounds like you're in a tunnel'

I have tried every setup and configuratoin possible including,  using SIP, changing to IAX, going through my PBX, or just registering directly to the provider (Voip.ms). I have tried toggling automatic gain control, to no affect. When I am internal, directly connected via IAX to the PBX internal IP, and do an echo test, I have confirmed the audio is unacceptably quiet. I have tested this again, outside the network, using sip connection, and then tested the echo test at Voip.MS, to the same effect. On every channel, trunk, protocol, and network, this issue is repeatable. THE TX AUDIO IS TOO LOW. 

Where can I change TX Gain in zoiper; or better yet, can you guys fix the audio transmission volume level please. 

in Android by (130 points)

2 Answers

0 votes

The auto gain control should automatically adjust the volume to be exactly as is expected by the PSTN. You should not be adjusting the gain levels manually as it can lead to distortions.

What phone model is this on ?

Are you able to make a packet capture, including RTP with auto gain enabled that you can send us ? 

by (11.5k points)

Phone model is Samsung Galaxy S4. 

No RTP, because I'm using IAX2 trunking, not SIP. 

iax2 is fine too, i hope we can extract it :)

Pcap of test call - http://we.tl/2OiGzKcbHJ

thanks, can you clarify if this was made with AGC enabled or disabled ?

What version of android are you running ? Is it stock firmware or a custom rom ?

Can you confirm this is on android 5 ?


Could you please let us know the exact model of your Samsung S4?

Is it GT-I9500 or GT-I9505 or some other?

Thank you in advance!

Galaxy S4 SCH-I535 running CyanogenMod 11-20150426 Nightly-d2lte 

Android V 4.4.4

pcap is with AGC enabled. 

Please try with the stock firmware if you can, the cyanogen firmware is known to have serious audio problems because they change the buffer sizes.

Hello I just found this thread as I have the same problem with my new Galaxy S3 Mini (GT-I8200N) with the default firmware when using Zoiper 1.23 the TX audio is really low. When I make a GSM call or use the audio recorder I have the feeling that the AGC is fixing the problem but in Zoiper the TX audio remains low. Is there any way I can enable AGC in Zoiper?

Okay, I tested with stock android 4.4

The audio through Zoiper on the stock android was louder than CyanogenMod, but was still quieter by far, than a normal phone conversation would be. This was with ACG enabled. 

However, due to this information I think it is a CyanogeMod issue, and not a Zoiper issue. 

I'm experiencing the same issue, low mic volume. I'm using version 1.27 on Xiaomi 4c, with MIUI 7 (Android 5.1.1). 

Any recommended fix?

0 votes

I finally found a fix for my LineageOS 14 (basically the new name of CyanogenMod), so I decided to leave an answer here for future readers.

Using a build.prop editor (from the Play Store) I changed:




This solution is also suggested here: https://forum.xda-developers.com/lg-g3/help/fix-fix-voip-calling-lollipop-roms-t2980294

You need to reboot the device after applying the fix.

by (140 points)
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