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Re: Bah! How do I change channels?

On Sat, Jun 27, 2009 at 12:25 AM, George Adams<g_adams27@xxxxxxxxxxx> wrote:
> Thanks again to both of you for your help.  I gave the no_poweroff flag a try, but didn't see any difference.  I also tried a "setchannel 3" during the middle of the encoding session, and also saw no change.
> But I think I've found the problem:
>> v4lctl setnorm NTSC; v4lctl setfreqtab us-bcast; v4lctl -v 1 setchannel 3
> vid-open: trying: v4l2-old...
> vid-open: failed: v4l2-old
> vid-open: trying: v4l2...
> v4l2: open
> v4l2: device info:
>  em28xx 0.1.1 / Pinnacle PCTV HD Pro Stick @ usb-0000:00:1a.7-1
> vid-open: ok: v4l2
> freq: reading /usr/share/xawtv/Index.map
> v4l2:   tuner cap:
> v4l2:   tuner rxs:
> v4l2:   tuner cur: MONO
> cmd: "setchannel" "3"
> v4l2: freq: 0.000
> v4l2: close
> What?  freq: 0.000 ?  After finding the ivtv package and compiling its utils, I confirm it with this:
>> v4l2-ctl -F
> Frequency: 0 (0.000000 MHz)
>> ivtv-tune -c 3
> /dev/video0: 61.250 MHz
>> v4l2-ctl -F
> Frequency: 980 (61.250000 MHz)
>> v4lctl setchannel 3
>> v4l2-ctl -F
> Frequency: 0 (0.000000 MHz)
> So mysteriously, it seems like v4lctl is just plain not working.  And ivtv-tune, on the other hand, is working just fine.  After I do that and start Helix Producer, I see channel 3 just like I had hoped.
> (strangely, v4lctl can do other things fine, like change the norm from NTSC to PAL.  It just can't change the channel.)
> So, sorry that it went off in rabbit trails of the device powering down and so forth.  I wonder what happened to my v4lctl program, though?  xawtv itself (running in X) seems to work fine when I tell it to change the channel...
>> Date: Fri, 26 Jun 2009 09:42:06 -0400
>> Subject: Re: Bah! How do I change channels?
>> From: dheitmueller@xxxxxxxxxxxxxx
>> To: awalls@xxxxxxxxx
>> CC: g_adams27@xxxxxxxxxxx; video4linux-list@xxxxxxxxxx; linux-media@xxxxxxxxxxxxxxx
>> On Fri, Jun 26, 2009 at 7:50 AM, Andy Walls wrote:
>>> I use either v4l2-ctl or ivtv-tune
>>> $ ivtv-tune -d /dev/video0 -t us-bcast -c 3
>>> /dev/video0: 61.250 MHz
>>> $ v4l2-ctl -d /dev/video0 -f 61.250
>>> Frequency set to 980 (61.250000 MHz)
>>> Regards,
>>> Andy
>> Hello Andy,
>> I had sent George some email off-list with basically the same
>> commands. I think what might be happening here is the tuner gets
>> powered down when not in use, so I think it might be powered down
>> between the v4l-ctl command and the running of the other application.
>> I have sent him a series of commands to try where he modprobes the
>> xc3028 driver with "no_poweroff=1", and we will see if that starts
>> working.
>> Devin
>> --
>> Devin J. Heitmueller - Kernel Labs
>> http://www.kernellabs.com
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Try 'v4l2-ctl -d /dev/video0 -f 61.250' to tune to broadcast channel 3
per one of Devin's e-mails to you.  I do not know why setchannel is
not working for you.  I use both ivtv-tune v4l2-ctl and both do work
and v4l2-ctl should work in this instance for you.  I always open my
USB TV device via mplayer not specifiying a channel and then use
ivtv-tune executed by a script that is run by an application to tune
channels.  I happened to notice that if I closed mplayer and used
ivtv-tune to tune to another channel and then open my USB TV device,
it would be tuned to that channel.


I too care about the environment.  I am trying to find some extra time
to figure out if my KWorld 330U USB TV devices are actually going into
low power mode or not.  I would say not as they get really hot, so I
unplug them when I am not using them.  I told Devin I would work on
this and I have an accurate analog amp meter, but I got very busy at
work and at home with the kids.  However, I don't believe that the
answer is to disable power management as some of these parts get so
hot that leaving them in a powered state and tuned to a channel will
probably damage the device.  Remember, these are silicon tuners, not
the old discrete tuners that have way more surface area to dissipate


Great job answering questions as usual.  ;-)

Best Regards,

Rob Krakora
Senior Software Engineer
MessageNet Systems
101 East Carmel Dr. Suite 105
Carmel, IN 46032
(317)566-1677 Ext. 206
(317)663-0808 Fax

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