[One (M8) Android Development] Rescue9:
CyanogenMod is a free, community built, aftermarket firmware distribution of Android 5.0.x (Lollipop), which is designed to increase performance and reliability over stock Android for your device.

#include <std_disclaimer.h>

/*
* Your warranty is now void.
*
* We are not responsible for bricked devices, dead SD cards,
* thermonuclear war, or you getting fired because the alarm app failed. Please
* do some research if you have any concerns about features included in this ROM
* before flashing it! YOU are choosing to make these modifications, and if
* you point the finger at us for messing up your device, we will laugh at you.
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*/

CyanogenMod is based on the Android Open Source Project with extra contributions from many people within the Android community. It can be used without any need to have any Google application installed. You will need to provide your own Google Applications package (gapps). CyanogenMod does still include various hardware-specific code, which is also slowly being open-sourced anyway.

All the source code for CyanogenMod is available in the CyanogenMod Github repo. And if you would like to contribute to CyanogenMod, please visit our Gerrit Code Review. Your changelog is whatever was merged into gerrit.

Now for the more specific stuff. Let me preface this entire thread by saying that I'm very much out on a limb here. I, as well as many others, have noticed that there are some fairly significant audio issues in CM stretching back to early CM11 builds for the M8. The general fix has always been "install v4a, and it'll work just fine". This isn't really a fix imho, it's a band-aid.

As such, I've created two repos: 4.20.x Sprint Stock, and 02/26 CM Unofficial (NOT NIGHTLY). I've uploaded the various parts that I think are going to be relevant in comparing the two code bases in the hopes that this problem can be tracked to its origin and finally fixed. The repos are on github as Stock and CM.

As far as the problems that have been noticed, it's good to remember that not all problems related to audio issues are what we're trying to address here. As an example, this is not a bluetooth thread, so bluetooth connectivity problems aren't going to be addressed even if it relates to phone calls or music playback. This is by no means a complete list and additional items should be listed as noted in posts. Some of the issues I feel that are actually related to audio problems are as such:

Distortion at loud volumes; speakers sound like crap when played loud, but not on stock or gpe

Improper playback channels; speakerphone volume level activating through phone channel rather than media channel

Sound dropouts during calls; caller can be heard but not hear M8 user (common with V4A Lolli installs)

Problem Submission: If you submit a problem to the list in your responses, please tag it as such;

PROBLEM_ITEM: [my problem description here].​

This will allow me to easily search the thread and add additional known issues to the list. If you submit a problem but don't see it in the list, check Post #2 for reasoning as to why the problem wasn't initially added to the list.

Inside the Stock repo is a logcat that I took while performing operations during music playback. Specifically, I started the music playback via Poweramp, opened AudioFx from inside Poweramp, changed the EQ Preset various times,returned to Poweramp, and stopped the music. I'm hoping that starting with the logcat will lead somewhere..... as I mentioned, I'm waayyy out on a limb here.

As for my device, I'm running my own builds of CM12, no cherry-picks, SuperSu, CM kernel w/ no tweaks, NO V4A. Repo sync for this build includes Settings: reorganization merge on Feb 26, 2015 7:35 AM. Anything after is not in the current build, and therefore not in the CM repo.

ALL help is greatly appreciated, unconstructive / disrespectful comments are not. Here's to hoping this goes somewhere.