[AudioI] Octo sound card on Raspberry pi3 B+ aarch64

[Marc Lavallée]

Hi Rafael,

The sound file you sent in your previous message ("[AudioI] Distortion 
in the sound of audio Injector octo") is horrible. Your problem could be 
caused by a mismatch between the analog outputs of the Octo and the 
analog inputs of your amplifier... If you lower the output volume of the 
Octo, does it sound better? What kind of audio file and what software 
are you using? It's difficult to help from email...

My solution was to fix a problem with the inputs (the outputs where 
fine), but it may solve your problem too. Sound on Linux can be affected 
by many things, like too much Desktop activity. Using a low latency 
kernel and tuning the OS can help a lot. Using a realtime kernel for 
ensuring realtime priorities of sound processing can help even more. Of 
course it's easier to fix such problems with some experience of Linux; 
explaining all the steps would be too long, so you can check the links I 
sent, it worked for me...

Marc

P.S. I once visited UNAM and experienced the MUAC Sound Camera. :-)

Le 2023-07-15 à 11 h 19, RAFAEL QUEZADA CRUCES a écrit :
>
> Hello, I also have the problem with the distortion, but in my case 
> this happen when I reproduce some audio file. Do you know, how solve 
> this? I am in a Raspberry Pi 4 with Bullseye
>
>
>> El 13 jul 2023, a las 14:54, Marc Lavallée via People 
>> <people at lists.audioinjector.net> escribió:
>>
>> Here's my solution with an OS based on RaspiOS Bullseye (with kernel 
>> 6.1).
>>
>> A quick way to check if the inputs are saturated by noise:
>>
>> $ arecord -c 6 -f S24_LE -V mono -r 96000 /dev/null
>> Recording WAVE '/dev/null' : Signed 24 bit Little Endian, Rate 96000 
>> Hz, Channels 6
>> ##################################################+| MAX
>>
>> In my case, the result is the same with all combinations of number of 
>> channels, sample resolution, sampling rate, and input levels.
>>
>> Because the Linux images included in the RaspiOS distributions (that 
>> can be installed from apt) are missing the required overlays, I 
>> installed a Linux kernel version 5 made specifically for the RPI: 
>> https://github.com/kdoren/linux/wiki
>>
>> I installed the arm64 PREMPT_RT version because it prefer it for 
>> audio, but it's not required.
>>
>> Then I tuned the OS for audio with help from this script: 
>> https://pypi.org/project/rtcqs/
>>
>> Here's more tuning info, specifically for the RPI: 
>> https://wiki.linuxaudio.org/wiki/raspberrypi
>>
>> The above arecord command will show a VU meter that momentarily go up 
>> to MAX, then it quickly go down to 0%; this is a known issue when 
>> initializing the Octo for recording. When using a sound server like 
>> Jack, the inputs of the Octo are initialized when the server starts, 
>> so that could be a way to avoid spikes when recording from jack.
>>
>> I hope it helps (until the issue is solved for kernel 6).
>>
>> Marc
>>
>>
>> Le 2023-07-12 à 08 h 01, Fabricio de Abreu Bozzi a écrit :
>>> Hi Marc,
>>>
>>> yes, I can try the suggested kernel.
>>>
>>> thanks.
>>> Fabricio
>>>
>>> On Wed, Jul 12, 2023, 08:51 Marc Lavallée via People 
>>> <people at lists.audioinjector.net> wrote:
>>>
>>>     Le 2023-07-12 à 07 h 42, I wrote :
>>>
>>>     > Hi Fabricio,
>>>     >
>>>     > Can you try with an earlier OS using a kernel version 5.10+, for
>>>     > example one based on Debian Buster?
>>>     >
>>>     >
>>>     https://downloads.raspberrypi.org/raspios_armhf/images/raspios_armhf-2021-11-08/
>>>     >
>>>     Oops! The link I sent for the OS based on Bullseye, here's the
>>>     link for
>>>     the OS based on Buster (with kernel 5.10+):
>>>
>>>     https://downloads.raspberrypi.org/raspios_armhf/images/raspios_armhf-2021-05-28/
>>>
>>>     Marc
>>>
>>>     -- 
>>>     People mailing list
>>>     People at lists.audioinjector.net
>>>     https://lists.audioinjector.net/mailman/listinfo/people
>>>
>>
>> -- 
>> People mailing list
>> People at lists.audioinjector.net
>> https://lists.audioinjector.net/mailman/listinfo/people
>
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