[FIX][MOD][GUIDE] AUX Cable + Onboard Mic Fix - Nexus 5 Android Development

I believe I have found a solution to a problem that I have found with the Nexus 5 that I never experienced with my GNex before.
https://productforums.google.com/forum/#!category-topic/nexus/calls-and-voicemail/nexus-5/5G5LXC8XHeI
The above link captures a summary of the problem, but I will restate it here. When plugging headphones or an AUX cable into the phone, the phone seems to utilize standard microphone gain settings (that is - you need to practically hold the phone to your face for the other party to hear you well). I primarily use an AUX cable when I'm in my car and have the phone sitting in my center console or on my lap. When I do this, people cannot hear me. BUT when I enable speakerphone mode, the other party can hear me fine (even without unplugging the AUX cable - though no sound would be going through it). Ah-hah, I believe that this must be a software setting issue and not a hardware issue (even though Google offered to do an RMA).
After some research I came across a system file called mixer_paths.xml which has been used by other devs here (thanks folks!) to improve the performance of the audio OUTPUT of the device (that is increasing the volume we hear on our end). But I had seen no mods fixing the audio input / microphone issues I was having.
I tested my theory today by modifying the mixer_paths.xml file to override the default values under <path name="headset-mic"> and <path name="voice-headset-mic"> to mirror those of <path name="voice-speaker-mic">. Initial testing (a simple phone call to my fiancee) seems to indicate that the receiving party cannot tell the difference between my voice whether speaker is on or off when I have headphones plugged in.
In order to perform this mod/fix you will need to be rooted.
WARNINGS:
Make sure to make a backup of your existing mixer_paths.xml file.
This may cause issues if your headset or AUX cable have their own microphone (I don't have one to test with, so I don't know if it causes issues).
I am not guaranteeing results - I am hoping that this fix works for others and others might be able to test and confirm that this does work. I am not a developer - I am just a somewhat tech savvy guy who was trying to resolve an issue I thought was software related. Hopefully someone who is more savvy will come along and implement these changes into an existing app or program for simplicity!
+ Props to Drummerjed for creating the thread for audio output http://forum.xda-developers.com/showthread.php?t=2532788 which inspired my exploring around for this fix. I hope you don't mind I stole some of your directions for ease of posting.
DIRECTIONS
Before you start modifying you need grant ES File Explorer root access. To do this press the icon in the top left corner then scroll down and select Root Explorer, then select Mount R/W, then select RW for both / and /system.
Open ES File Explorer and navigate to /system/etc and find the file "mixer_paths.xml"
Tap on the file and select ES Note Editor
Press the menu button in the top right corner and select Edit
Find: <path name="headset-mic">
You will see this string just below it:
<path name="adc2" />
<ctl name="ADC2 Volume" value="16" />
<ctl name="DEC5 Volume" value="90" />
Change <path name="adc2" /> to <path name="adc3" />
Change <ctl name="ADC2 Volume" value="16" /> to <ctl name="ADC3 Volume" value="14" />
Change <ctl name="DEC5 Volume" value="90" /> to <ctl name="DEC4 Volume" value="97" />
Find: <path name="voice-headset-mic">
You will see this string just below it:
<path name="adc2" />
<ctl name="ADC2 Volume" value="17" />
<ctl name="DEC5 Volume" value="96" />
Change <path name="adc2" /> to <path name="adc3" />
Change <ctl name="ADC2 Volume" value="17" /> to <ctl name="ADC3 Volume" value="14" />
Change <ctl name="DEC5 Volume" value="96" /> to <ctl name="DEC4 Volume" value="97" />
You will notice we are overwriting the default settings from <path name="voice-speaker-mic"> for both. I found this has worked. This may be more modification than necessary to accomplish the same goal. Please feel free to respond if we can further minimize the amount of changes needed in this file to resolve this issue. I'm happy to make edits and adjustments as needed!

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Thanks! Going to try this later. I have a pair of headphones (mic included) that the same thing happens to. If I plug them in, no one can hear me over the phone. I need to unplug them or enable speaker to work. I honestly thought it was my headphones.

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RoyJ said:
Thanks! Going to try this later. I have a pair of headphones (mic included) that the same thing happens to. If I plug them in, no one can hear me over the phone. I need to unplug them or enable speaker to work. I honestly thought it was my headphones.
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One thing you might also try is taking a look at your headphones+MIC and seeing how they line up with the above chart. From my understanding, the Nexus 5 uses an OMTP set-up and not a CTIA (aka iPhone compatible) set-up internally. You can buy a converter for a few bucks off of Amazon (made by Sony). So if the software fix I suggested in post 1 doesn't help, you could give that a try.
Good luck!

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people hear me just fine when i plug in aux cable in my car. but this is handy if the problem ever occurs

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I was wondering about those parameters when I was browsing through that file. Was going to play some but never got around to it!
Good job!

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zoomass07 said:
One thing you might also try is taking a look at your headphones+MIC and seeing how they line up with the above chart. From my understanding, the Nexus 5 uses an OMTP set-up and not a CTIA (aka iPhone compatible) set-up internally. You can buy a converter for a few bucks off of Amazon (made by Sony). So if the software fix I suggested in post 1 doesn't help, you could give that a try.
Good luck!
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Click to collapse
How can I test which my headphone is?
Also do you know if the nexus 4 used OMTP or CTIA?
Found a post stating that nexus 4 is ctia so if my mic didn't work for those then they'll probably work on my n5 correct (assuming they're omtp).
Also same post stated that ctia has grey rings and omtp is black or blue rings on the 3.5mm plug, any truth to that as I can't tell if mine is black or grey.
Sent from my Nexus 5 using Tapatalk

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fone_fanatic said:
How can I test which my headphone is?
Also do you know if the nexus 4 used OMTP or CTIA?
Found a post stating that nexus 4 is ctia so if my mic didn't work for those then they'll probably work on my n5 correct (assuming they're omtp).
Also same post stated that ctia has grey rings and omtp is black or blue rings on the 3.5mm plug, any truth to that as I can't tell if mine is black or grey.
Sent from my Nexus 5 using Tapatalk
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It's harder to tell the difference between CTIA and OMTP than it is knowing whether there is a mic or not. I'm not sure about the colorization on the rings. I do know that I've read the N5 is OMTP (not sure how much truth there is to that). You can look into whether your headphones are marketed as "iPhone compatible" it is likely CTIA.

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Anyone try this on voip service? I'm using fongo as my main voice service
Sent from my Nexus 5 using Tapatalk

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detdett said:
Anyone try this on voip service? I'm using fongo as my main voice service
Sent from my Nexus 5 using Tapatalk
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Should still work - what I would do is give it a shot! Make a copy of the file and save it as a backup. Make the changes suggested and test it out.
If it doesn't work for you, revert to the back up and report back to us! I started this thread in hopes we could all work together to help alleviate this issue - because Google hasn't expressed an interest in doing so.

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I've last cataclysm rom. why es file explorer doesn't allow me to save the new xml?

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phantomEVO said:
I've last cataclysm rom. why es file explorer doesn't allow me to save the new xml?
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Worked fine with root explorer

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Great find! I'll be testing these over the course of today!

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Is this consistently working for you all? I had great success at first... But now I'm having the same people who told me I sounded fine reporting the poor sound issues again.

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i've only <path name="headset-mic"> and <path name="voice-speaker-mic"> and not <path name="voice-headset-mic">

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I'm on minimus rom w/ franco kernel. Never had this issue, I leave my aux plugged in from car and when I answer, people can hear me just fine. Sitting about 2-3ft away from phone

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Echo fix?
Hello,
This seems to be the same issue i'm having, but no one mentioned an echo...
When I plug an aux cable into the phone and am in a call, the caller hears a horrible echo. I have to put the phone on speakerphone (obviously bypassing the whole sound system) for them to be able to hear properly.
In my head, i image that if i was user the Speakerphone settings for the mic while connecting the aux cable, then it would work.
Is this what your proposed solution would do?
I'd love to get this fixed. Thanks!