[L2Ork-dev] issues on rasbian 9/10

Fri Apr 9 05:00:55 EDT 2021

Ok, I gave that a try now, but unfortunately it didn't help much. :( The
high-pitched noise is gone, so that's an improvement. But the ALSA backend
still only gets a bunch of xruns and then gives up after printing "restart
alsa output; alsa xrun recovery apparently failed" a couple of times in the
terminal, logging "error: audio I/O stuck... closing audio" in the Pd
console.

One thing I noticed in htop is that the nw.js gui spawns quite a few
threads all running at a nice level of -7, while the engine itself runs at
-9. In vanilla you just get the wish gui (a single thread) running at 20,
while the engine runs at -7. So there are some clear differences between
purr-data and vanilla even if the ALSA backend is exactly the same (in that
special build of purr-data I just did). I'm not sure why we run the GUI at
such a high priority; maybe that's part of the problem. Jonathan might be
able to shed some light on this.

As I said before, all these issues go away if you just use an external
sound card, so the dsp *is* part of the equation here. Such a device will
also work with Jack just fine. Even one of those really cheap and small USB
audio adapters that you can get on Amazon for a couple of bucks will do the
trick (I have the one from UGREEN, but the one from Sabrent[1] is also
available on amazon.com and should do the job as well).

[1] https://www.amazon.com/-/de/dp/B00IRVQ0F8

Sorry Marten, I wished I had better news for you. It would still be nice if
you could submit a full bug report on this, so that we can document what we
know about this bug and hopefully fix it some time. But for the time being
my suggestion for you would be to just get one of those little USB audio
thingies and call it a day. ;-)

Best,
Albert

On Fri, Apr 9, 2021 at 2:29 AM Albert Graef <aggraef at gmail.com> wrote:

> Just a quick followup: Comparing the source of our s_audio_alsa.c with
> that of vanilla I do see some substantial differences. In particular, it
> seems that we never backported two of Miller's commits from way back then,
> https://github.com/agraef/pure-data/commit/75819aad and
> https://github.com/agraef/pure-data/commit/de2ba0f6. In particular, the
> former has an entire chunk of sw parameter initializations which is
> completely missing in our code.
>
> What I can do as a quick check is to pull the latest s_audio_alsa.c from
> vanilla into my testing branch and do a test build on my OBS preview
> channel so that we can try it out on the Pi. That way we'll lose Sam
> Thurston's recent MR concerning the error checking code in the module, but
> we can always pull that back in again later if needed (vanilla also has
> some changes there, so Sam's fixes might not be needed any more).
>
> Stay tuned,
> Albert
>
>
>
> On Fri, Apr 9, 2021 at 1:42 AM Albert Graef <aggraef at gmail.com> wrote:
>
>> Hi Marten,
>>
>> I have exactly the same issue on my Raspberry Pi4. Purr works mostly fine
>> even with a cheap USB audio dongle, but not with the built-in soundcard of
>> the Pi. Pd 0.49.0 straight from the Buster repo works fine. So clearly
>> there's a bug lurking in our ALSA support somewhere or we're missing some
>> bit in the backend which makes this work in vanilla.
>>
>> This was discussed on the ml before, and IIRC we've blamed it all on the
>> poor dsp of the Pi. ;-) But this can't be true if it works just fine in
>> vanilla. So we should try again to track this down. It would help if you
>> could submit a bug report at
>> https://git.purrdata.net/jwilkes/purr-data/-/issues, then I'll look into
>> it asap.
>>
>> Thanks,
>> Albert
>>
>>
>> On Thu, Apr 8, 2021 at 4:58 PM Marten Seedorf <marten.seedorf at mailbox.org>
>> wrote:
>>
>>> Hey everyone,
>>>
>>> working on a sound installation with purr-data on the raspberry pi I
>>> encountered some issues that might be worth mentioning.
>>>
>>> I installed the recent rasperry pi os (~ raspbian 10 buster) on a
>>> raspberry pi 3B and installed purr-data from Albert Gräfs repositories on
>>> opensuse.org. The installation went smoothly, but the audio engine
>>> (alsa) didn't work. All I got was a high pitched, distorted noise. I tried
>>> to use jack, but strangely it wasn't able to communicate with the audio
>>> hardware via alsa as well. So it seems that the issue is rather in the OS
>>> than in Purr Data. But: PD Vanilla is working perfectly fine (directly with
>>> alsa, without jack).
>>>
>>> I went back to Raspbian 9 Stretch and installed Purr-Data from the
>>> latest pre-build deb.-package I could find (2.10.1). That worked great.
>>>
>>> I became curious and installed Purr-Data on stretch from the
>>> opensuse-repositories (Raspbian 9) and encountered the same issues as in
>>> buster.
>>>
>>> So in the end, I found a solution that works for me. Still I figure
>>> there could be something wrong with the repositories.
>>>
>>> Best,
>>> Marten
>>> _______________________________________________
>>> L2Ork-dev mailing list
>>> L2Ork-dev at disis.music.vt.edu
>>> https://disis.music.vt.edu/listinfo/l2ork-dev
>>
>>
>>
>> --
>> Dr. Albert Gr"af
>> Computer Music Research Group, JGU Mainz, Germany
>> Email: aggraef at gmail.com, web: https://agraef.github.io/
>>
>
>
> --
> Dr. Albert Gr"af
> Computer Music Research Group, JGU Mainz, Germany
> Email: aggraef at gmail.com, web: https://agraef.github.io/
>

-- 
Dr. Albert Gr"af
Computer Music Research Group, JGU Mainz, Germany
Email: aggraef at gmail.com, web: https://agraef.github.io/
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://disis.music.vt.edu/pipermail/l2ork-dev/attachments/20210409/32a20ef8/attachment.html>