Ultralite AVB

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agoode
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Re: Ultralite AVB

Postby agoode » Sun Aug 12, 2018 10:02 pm

To answer my own question, it is very easy to trigger this with ctrl-Z (then fg) on whatever is playing. Doing it several times leads to different interesting results.
Adam Goode

Drumfix
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Re: Ultralite AVB

Postby Drumfix » Mon Aug 13, 2018 6:16 am

Reconfiguration means that snd_usb_pcm_prepare from sound/usb/pcm.c is called. aplay does this, if it detects an xrun.
Can you add a log messge at the start of that function and watch if it is called when the glitch is happening?

rofer
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Re: Ultralite AVB

Postby rofer » Tue Aug 14, 2018 12:04 am

Unfortunately that doesn't seem to be it. I see a single reconfigure when I start aplay, then despite usually moving channels twice in a minute I don't see any reconfigures happening then.

Edit: That's not to say reconfigures don't trigger this (I'm not sure how to force one), just that something else must be doing it as well.

agoode
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Re: Ultralite AVB

Postby agoode » Tue Aug 14, 2018 3:32 am

I am pretty sure this device is extremely sensitive to interruptions in the USB stream.

The device works perfectly on my old Mac, and my guess is that the Mac kernel is very careful to always send a valid stream.

Also, Windows users have similar problems with similar devices:
http://www.motunation.com/forum/viewtop ... 14&t=63375

They mention the X99 chipset, which I do have in my computer.

I am still working on some ideas, but I think it is going to come down to some kernel work to ensure the device is always getting a valid stream.
Adam Goode

Drumfix
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Re: Ultralite AVB

Postby Drumfix » Tue Aug 14, 2018 6:36 am

Guess its time for you guys to load the usbmon module and use wireshark to capture the USB stream from/to the device and check if something special is happening when the glitch occurs. I'm currently in for a new >=16 channel interface (Motu 16A, Behringer XR18 or Presonus Studiolive 24R). I tend towards the Motu, but like that issue be fixed beforehand even though i might hook it up through ethernet (AVB) instead of USB.

Musinux
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Re: Ultralite AVB

Postby Musinux » Tue Aug 14, 2018 8:36 am

Drumfix wrote: I tend towards the Motu, but like that issue be fixed beforehand even though i might hook it up through ethernet (AVB) instead of USB.


I thought about this as well. Reading through motunation, there seem to be hickups even with the motu avb switch (450€)...
There are cheap AVB certified PCIe cards by now (needs low timing specs) for about 25€.

There are more problems with this interface which are not alsa or usb specific (i.e. the "crack" when switching sample rate in the web interface or the inability to automatically switch sample rate with spdif-in), which wouldn't be solved with just avb (which could have other timing issues under alsa as well!).

agoode
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Re: Ultralite AVB

Postby agoode » Wed Aug 15, 2018 12:39 am

I've been looking at quite a lot of usbmon captures. Nothing seems to be wrong from Linux. The device simply does not work properly if the USB stream is interrupted at all. I've never seen such a sensitive device. The MOTU 8A works perfectly here, even when I force drops.

I found some forum posts that show this happening under Windows over 2 years ago, with audio recordings that sound the same as what I can reproduce:
http://www.motunation.com/forum/viewtop ... 14&t=61286

Why does the Mac not have problems? I am guessing (but have not yet inspected a USB capture) that the Mac has a very robust USB audio stack that does not drop packets, even under load. Both Windows and Linux will do this more regularly.

Essentially, the Ultralite AVB cannot recover from a buffer underrun over USB.

I am going to look into a few more ideas on Linux, but I think that is the fact of the matter. We'd have to do a significant reworking of Linux to make this device work reliably, unless there is some trick the Mac is doing that I've not seen yet.
Adam Goode

Musinux
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Re: Ultralite AVB

Postby Musinux » Wed Aug 15, 2018 11:38 am

agoode wrote:I've been looking at quite a lot of usbmon captures.


Did you try with the latest, even more sensible firmware version?

agoode
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Re: Ultralite AVB

Postby agoode » Thu Aug 16, 2018 6:16 pm

Yes, sadly my firmware is completely up to date.
Adam Goode

Drumfix
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Re: Ultralite AVB

Postby Drumfix » Fri Aug 17, 2018 5:45 am

Musinux wrote:There are cheap AVB certified PCIe cards by now (needs low timing specs) for about 25€.

Over here the cheapest i210 based card is 35-40€.

As long as the device is directly connected to the computer with no switch in between even a non-avb capable NIC should work.
This certainly requires writing a trivial userspace AVB driver first.

Musinux
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Re: Ultralite AVB

Postby Musinux » Fri Aug 17, 2018 11:17 am

Drumfix wrote:Over here the cheapest i210 based card is 35-40€.

As long as the device is directly connected to the computer with no switch in between even a non-avb capable NIC should work.
This certainly requires writing a trivial userspace AVB driver first.


The hades-canyon NUCs seem to have i210 chips as well.

I think this should "work", but take you the ability to control the interface within your normal (w)lan via http (on other machines, without fiddling).
With a rock-solid interface, I'd give that a try, but with the ultralite, I'd experiment with an avb compatible card for sure.

agoode wrote:Yes, sadly my firmware is completely up to date.

Sorry for being not as accurate with my question. You did your captures only with the new version?
Last edited by Musinux on Sat Aug 18, 2018 12:54 pm, edited 1 time in total.

supereb
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Re: Ultralite AVB

Postby supereb » Sat Aug 18, 2018 12:32 am

Hi everyone, first post here. I've read and re-read this thread several times. Just got a MOTU 8pre-ES (same firmware as the 828es) and I'm experiencing the same problem with channel position randomly shifting in increments of 8 whether the initial or latest firmware is installed. LTC did not change anything for me. I do get the occasional xrun, but I can go through a few channel shifts without incrementing the xrun counter.

EDIT: I forgot to mention, when playing music through a daw on input channels 3/4, I’m not having any problem with channel shifting on the input side. It’s only the playback from the daw moving between 1/2, 9/10, 17/18.

supereb
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Re: Ultralite AVB

Postby supereb » Sun Aug 19, 2018 1:19 pm

Those of you who have Ultralite AVBS's. madmaxmiller on the Harrison Mixbus forum is successfully using an Ultralite AVB using firmware version 1.3.2+520 on AVLinux 2018 using jack 2.

Unfortunately version 1.3.2 is not available for the 8pre-ES, only the 828es even though they share the three most recent firmware versions available.

Musinux
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Re: Ultralite AVB

Postby Musinux » Sun Aug 19, 2018 5:09 pm

supereb wrote:Unfortunately version 1.3.2 is not available for the 8pre-ES, only the 828es even though they share the three most recent firmware versions available.


It does work "successfully" ;) (for a certain time...) for most of us here.

1.3.2 or 1.3.4 (but the newest 2 versions) don't make a difference regarding the major problems.

Drumfix
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Re: Ultralite AVB

Postby Drumfix » Sun Aug 19, 2018 6:28 pm

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