[pvrusb2] Getting error in increasing frequency

[Mike Isely]

On Mon, 15 Oct 2007, Matt Nyerges wrote:

> I noticed this error a few times last year, but not much.  Recently,
> however, I see this error a lot more.  Whenever it happens my program that
> cat's /dev/video0 gets killed when the video0 file gets removed then added
> back.  I wrote something that watches for this and resumes recording, but it
> would be great to find out what is causing this.  Has anyone seen anything
> like this?

Matt:

This sounds a lot like a piece of hardware is drifting out of tolerance.  
The error here is a USB protocol failure.  Everything else you see is a 
cascade from that first error.  The error code -71 is coming from the 
USB core in Linux; it is a result of an error in communicating with the 
USB device.  Generally this can indicate bad cables, a flakey hub (if 
you are using one) or possibly USB devices experiencing some kind of 
power supply issue (glitches, noise, voltage out of spec, etc).

A couple things you can try:

I assume you only have a single device so unfortunately you can't swap 
pvrusb2 parts around.

Try using a different USB port (or even better, controller).  Honestly I 
don't expect that is going to make any difference but it's easy to try 
and if it does make a difference then that's a clue.

Can you run the device under Windows with Hauppauge's drivers?  If so, 
then clearly if the hardware is having trouble then you should also see 
problems there - at which point you should RMA the device.

There's a module option you can set called "tolerance" that will try to 
paste over this sort of problem in the driver.  Basically it will cause 
the driver to ignore -71 errors if they remain at a rate below a set 
threshold.  This is NOT a fix but it is a way to endure the pain a 
little better.  It also is far from perfect because certain cases of 
that error are simply not recoverable.  But it might help.  See here for 
more info on the parameter:

http://www.isely.net/pvrusb2/usage.html#Logging

It is worth emphasizing that if setting the tolerance parameter helps 
you then you very likely have some kind of hardware problem going on 
that you should fix.  Eventually, even with tolerance enabled, you're 
still going to get a -71 error at an inopportune point which will still 
kill control of the device.  (It's also possible that tolerance won't 
help at all, if in fact this is a case where the device is actually 
crashing.)

  -Mike


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