[LAU] Cracking sound via USB (ALSA urb.c:480: frame 5 active: -18)

[Ken Restivo]

On Wed, May 25, 2011 at 08:55:48AM +0200, Jeremy Jongepier wrote:
> On 05/25/2011 01:36 AM, Aurélien Leblond wrote:
>>>> * The USB Controller is the dreaded EHCI USB Controller: Intel*>>* Corporation 5 Series/3400 Series Chipset USB2 Enhanced Host Controller*>>* (rev 05)*>>* But the soundcard I'm usins is USB2, not USB 1.*>Hello Aurélien,
>>> Afaik this doesn't matter, both USB2 and USB1 cards have issues when>used with full duplex on this USB controller or this Rate Matching hub>thing. But maybe this needs some digging in old mails/forum threads, I
>>
>>> could be wrong on this.
>>
>>
>> Damn, as far as my research went, I only thought the problem was only
>> when mixing USB1 and USB2 devices on these ports...
>>
>> I actually did some research... I knew these ports had issue with USB1
>> but couldn't find anything about USB2...
>>
>
> http://lists.linuxaudio.org/pipermail/linux-audio-user/2010-June/070353.html
>
> So not mixing USB1 and USB2 devices but mixing a device performing  
> Full-Speed isochronous-out transactions with a device performing  
> asynchronous transactions. I've tested my Edirol UA-25 with this chipset  
> too and no matter what I tried, full duplex wouldn't work. Does your  
> machine have a Rate Matching Hub? If so could this be the device that  
> does asynchronous transactions maybe? Just guessing here. Or is USB2  
> isochronous and USB1 asynchronous?
>

Wait, what?

I've been doing way too much reading of USB specs (and the hub.c, message.c, and musb driver source code) for work lately, and even though I'm definitely suffering from early onset of Alzheimer's, I distinctly remember reading that Isochronous and Bulk endpoints were only allowed at High Speed (480Mbps).

At Full speed (12Mbps), IIRC, you get Interrupt and Control endpoints, and that's pretty much it.

-ken