[AudioI] Faster / Earlier loading? ALSA Mixer - 15 seconds VS 30 seconds

[Matt]

On 31/8/20 11:27 pm, chris rosneau via People wrote:
> Hello all!
>
> I have had success!
> I installed this on my Pi 3.
> Once I opened amixer from the console, and selected device 0 from the 
> F menu, then I selected line in, and unmuted it. BOOM! it works! (and 
> very well!)
>

Nice ! Great project idea, putting a speaker inside a guitar to enhance 
the sound in different ways. What a concept!


> -- So. here is my Question.
>
> Is it possible to have the audio enabled earlier? Before I installed 
> the Zero audio injector, a USB sound card starts working around 1/2 
> way through the boot. Same result with the on board sound. Using this 
> Zero Audio Injector, it isn't active until around 3 seconds after the 
> Os is fully loaded (console login).
>
> Load comparison 1: 15~20 seconds
> A USB sound card would turn on and MODEP would be processing effects 
> 1/2 way through the boot. The boot would continue for the next 15~20 
> seconds. This makes the project appear to be fully booted at 15 
> seconds. Being headless the only indication that the system is 
> working, is that you can hear the effects ;-). Clearly MODEP is 
> running at 15 seconds and just needs the sound card to respond to 
> function.
>
When you look at dmesg output, what is the kernel time point at which 
the audio driver reports itself loading ?


> Load comparison 2: 30~35 seconds
> With Zero Audio Injector installed, it doesn't process audio until a 
> few seconds after the login is reached. I imagine this is because the 
> ALSA mixer settings are applied at that point? that's my guess.
>
>
When you look at dmesg output, what is the kernel time point at which 
the audio driver reports itself loading ? There will probably be a few 
steps here ... I would imagine that first the audio injector overlay 
must load, which triggers the audio drivers to load (eventually). Part 
of loading the audio drivers is to load the codec driver.

There must be a few different checkpoints to loading and starting the 
audio subsystem. First overlay loading, then driver loading. Alsamixer 
setup. Finally user space application startup.

Typically with USB audio, there is no codec driver to be loaded, just 
the USB UAC driver.

For Rasbian, which is based on Debian, you may want to add to your 
research pages relating to Debian, like this one :

https://wiki.debian.org/BootProcessSpeedup



>
> Now that I have asked my question :-) some of you might ask.. why? who 
> cares? lol.
> Here is my story:
>
> My build: Pi 3+ running Patchbox OS (raspian) with the module loaded 
> "MODEP" effects emulator.
> I am placing the pi inside an acoutistc guitar with 2 contact / 
> vibration speakers installed in the body. (this makes any effects 
> sound like they are coming from the actual guitar. sounds really weird 
> and cool. its my cheap DIY version of that "ToneWood amp" that just 
> came out. Don't tell my wife I have spent as much as the real thing. 
> DIY sometimes costs more initially as you get tools and test parts!!! LOL.
>
> Parts used:
> Pi 3+ (mounted on battery pack internally)
> Zero Audio Injector.
> 5 watt stereo amp (super small PCB)
> AA battery pack (body mounted)
> 2 x voltage regulators. (5.5v for the Pi, 7v for the amp)
> 2 x contact / vibration speaker (glued inside the body)
> Clip on sound hole magnetic pickup
> 2 potentiometers, one for output volume, one for balance.
> VU / Batt level indictor (cheap ebay DIY VU that can be used for batt 
> level instead)
> Momentary button, (I want to wire this as a "sudo shutdown now" button.)
>
> Software:
> Patchbox OS (raspian flavor made for audio processing)
> Module: MODEP (drag and drop pedals / effects via any http browser.)
>
> (P.S, what I would kill for, is making the OS, or part of the OS "read 
> only", so just turning it off without a shutdown won't corrupt the SD. 
> I have seen this done on a few similar projects, but I don't know what 
> parts of this particular project "need" writable access.)
>
> Thank you for reading this!
> Let me know any tips or advice you have.
>
> ~Chris
>
>
>
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