[mythtv-users] Dual USB stick problems

Alan Chandler alan at chandlerfamily.org.uk
Wed Sep 6 12:54:07 UTC 2006

After a lot of good work over the last few days I have now got either one of 
my two Freecom usb dvb-t tuners to work correctly, and am proceeding to get 
it working inside Mythtv so that I can have a mythtv-backed on my server.  
With one working, my CPU loading does not seem particularly high. 

However, if I plug the second tuner into a free usb port whilst the first 
tuner is running tzap, this first tuner starts loosing sync. Even if neither 
tuner is doing anything I am getting error messages in dmesg/syslog of -71 
every few seconds, which appears to be errors reported by the usb driver of 
protocol failures. 

I am running on a 1.7Ghz Celeron and the usb 2.0 card is a no name PCI card 
that I recently bought with 4 external and one internal usb sockets.  The 
motherboard also has some (2?) usb (1.0) ports, but these are disabled in 
the bios.  Nevertheless linux, via lspci, reports about 5 usb ports of which 
only one is labeled usb 2.0. 

Given the nature of the problem and with pure speculation, I suspect that my 
processor is struggling with responding to some usb interrupts fast enough - 
given that the CPU loading with the tuner installed still hardly gets above 
a few percent, making it unlikely that it is some general lack of processor 

My questions to this list are 

 - Have people had success with multiple usb dvb-t tuners with processors of 
a similar sort of power to my 1.7Ghz Celeron?
 - Does the quality of the usb card have any effect - could I remove the 
problems by either purchasing a better card, or by putting a hub between the 
tuners and the card?
 - Are there any other steps I could take to either identify the source of 
the problem or (better still) avoid it. 


Alan Chandler
alan at chandlerfamily.org.uk
(via webmail - normally means I am not at my computer)

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