[PD] I2S audio possibilities

[Brian Fay]

Thanks for the info, my experience with USB was pretty similar - had to run
Pd in headless mode (no X), and definitely needed to do a lot of tweaking
before things were satisfying.

The Wolfson sounds like it could be a little bit of work to get running,
but I'm glad to hear that the quality is good. I'll keep an eye on it and
see if they do anything to support the new model of the Pi.

On Wed, Feb 4, 2015 at 11:58 AM, Simon Wise <simonzwise at gmail.com> wrote:

> On 05/02/15 02:34, Brian Fay wrote:
>
>> Simon, have you compared the wolfson to any USB interfaces? I'm curious
>> about how it performs by comparison, using no more than 2 input and 2
>> output channels. I had some success with a USB interface on a Pi using pd
>> and alsa, and got down to somewhere around 15 milliseconds of latency.
>>
>> I couldn't avoid occasional pops and clicks, and if I really pushed the
>> number of effects I was using at once I would get some serious xruns. With
>> the wolfson bypassing USB altogether, is it easier to achieve a low
>> latency?
>>
>
> I have found that you really need to minimise everything to get the Pis
> running smoothly, certainly no X and only what is strictly needed for
> control .. they are not powerful devices but the access you have to GPIOs
> and such, and the ability to program things at a low level means they can
> be made to do some tasks well, and fast. The usb is to be avoided if at all
> possible, I'd like to test the A model (with the single USB-OTG directly
> from the chip) it might be better than going via that usb/ethernet chip,
> the A+ looks really compact as well.
>
> I didn't need low latency, I got the wolfsons hoping for better quality
> analogue I/O, their digital I/O options, the possibility of linking them
> clock-wise and to avoid the endless usb hassles (there are other things I
> need the USB for!) ... they work well for this and I will do some serious
> testing but the audio has been clean and sounding good so far ... and I
> have learnt quite a lot about the various low level interface options.
>
>
>> And since you mentioned an RT kernel, I'm curious - did you patch it
>> yourself, or is there already an image available? Is it stable, or does it
>> randomly freeze?
>>
>
> I didn't patch it myself, I have been using it in a dozen machines which
> now run consistently ... I have been chasing some issue that was causing
> them to crash after a while, replacing a pile of bash scripts and multiple
> calls to some little dbus CL programs with the same thing directly from C
> in a pd external has fixed the issue .. on the non-RT B+ system as well, so
> it probably was not kernel related.
>
>
> here are some notes I've made ... including instructions and links to the
> kernel and files, and sources ... all on my dropbox, and the original link
> I used. They are running notes from a project, so there is a bit of
> extraneous info but download and install instructions are in there:
>
> https://www.dropbox.com/s/1scwpdufk41k4es/04.setupWolfsonAudio.txt
>
>
>
> Simon
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.puredata.info/pipermail/pd-list/attachments/20150204/1923728c/attachment.html>