[pvrusb2] how to change channels using sysfs

[Mike Isely]

On Fri, 5 Mar 2010, Robert Casper wrote:

> Hello,
> 
> My question is about using Sysfs to select an analog cable TV channel.  
> 
> I understand how to write a value to a cur_val file, and have switched
> between television and composite inputs with no problem.
> 
> Writing a number to the ctl_channel control doesn't work for me.  If I
> echo a 3 to select channel three, there's no error message but the value
> remains at 0.
> 
> I see there is ctl_frequency and a frequency table, but I am selecting a
> cable TV channel, not tuning to a broadcast frequency.  Would I have to
> find a frequency number that corresponds to each cable channel?  If so
> how would I do that?

The driver does not implicitly know about mappings between channel 
numbers and frequency assignments.  It can't - there's just too many 
possibilities out there.  If you want to use the frequency table in the 
driver's sysfs interface you have to program it first.  It's documented 
here:

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

Realize that the information programmed there is not persistent.  This 
information is part of the driver's state corresponding to the hardware 
that is plugged in.  In short, this means that (a) if you have multiple 
tuners you'll have to program the driver once for each, and (b) the 
programming will go away the instant the device is unplugged.  I would 
suggest writing a shell script to do the programming.

  -Mike

-- 

Mike Isely
isely @ isely (dot) net
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