Shift6mq audio distortion

regiq

Original poster
Beta Tester
13 März 2023
2
Hello Forum!

I'm a new Shift6mq user. I've been testing it extensively for some time now using ShiftOS Light versions 3.9L and 4.0L-beta. I didn't use it with the standard G version, but with both of the L versions I can confirm the effect mentioned here.

When listening to audio in a quiet environment there's a distortion heard in the quiet audio passages (a good example: Brian Eno - Neroli), not unlike a quantization noise in low bit depth playback. It's the same when playing back a local media file or a stream on a browser, using headphones out or the internal speaker. I can't hear it when using Apple USB-C to headphone jack adapter, but it has a lot lower volume so it just might be masked. I don't have bluetooth headphones to check it - my bluetooth speaker seems fine, but it introduces noise of it's own.
It sounds like software volume control (system mixer) working in low bit depth introducing quantizaton noise, but - based on my previous experience - likely reason is android audio effects processing after the volume control. An aggressive and unneeded noise gate maybe?

I've had the same problem on my old Xperia with Lineage OS 14 (also Qualcomm chip). Since the device was rooted I could apply a dirty fix based on trial and error, maybe this could hint the direction to a proper software fix:
- at first I've edited audio_policy.conf so that all streams were set to 24 bits bit depth;
- I've added ro.config.media_vol_steps=21 line to build.prop file;
- and in the end I've disabled the audio_effects.conf file.
The last action fixed the low volume noise problem, but it probably brakes some useful audio processing. The problem might have been solvable by tweaking mixer_paths.xml but it was too much for me. I find android audio framework overly complicated.
I hope it might be a hint for developers to find a true solution - if the problem has the same nature on the Shift6mq. I think there shouldn't be any nonadjustable additional processing like noise gate, dynamic compression or equalizer in the media playback path (contrary to the voice path) - and it seems there is.

I've searched the forum for similar issues (with an automatic translator on hand ;)) and found two threads, unfortunately without much forum attention.

I'm looking forward for a fix in one of the future updates, hopefully in ShiftOS 3 line. Right now the audio and screen quality (PenTile AMOLED?) are two letdowns in otherwise very good smartphone, with great modding capabilities, made with such important ideals in mind.
 
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