In call volume root modify I have a HTC One m7 international. It has root access. Android lollipop 5.0.2

The in call volume is too low despite being on max volume. 

Which file in the root system should I modify to increase the max volume? What line of code corresponds to this setting? 

Thanks vm
This approach achieves desired functionality by communicating with Android APIs at AIDL level making use of ADB



Run the command:

adb shell service call audio 7 i32 3 i32 0 i32 1


Here, the service call refers to IAudioService. Click here  for more info.


7 is the function named setStreamVolume. It is the 7th in the list of functions in the interface IAudioService. Verify it here. (setStreamVolume takes 3 parameters streamType, index, flag)
i32 is to write the integer INT into the send parcel. (Alternatively we can make use of s16 for UTF-16 string)
3 is streamTypevalue. (Value 1 &rarr; phone, 3 &rarr; speaker, 4 &rarr; alarm, 6 &rarr; bluetooth)
0 is index value and 1 is flag value 


See the source here.