[pvrusb2] documentation ctl_signal_present

Mike Isely isely at isely.net
Thu Mar 22 21:53:05 CDT 2007

On Tue, 20 Mar 2007, marcel wrote:

> Hi Mike,
> Thank you for this great driver! I was especially impressed by the
> sysfs interface, beautiful, simple and very unix.
> I just finished ripping old video-8 tapes for my father via
> composite-in. To automatically detect end or empty tape I was suprised
> to find that ctl_signal_present not only works with the television input
> but also with the composite input. Probably by checking syncing signals.
> So I suggest a document change in doc/controls.txt:
> ctl_signal_present - This is a read only boolean value, reports true
>     when there is a valid signal present for the television input *or
> composite input*.  If
>     any other input is selected this will always be true.
> Just a few gotchas. This only works with your version 20070207 or
> 20070127, not the kernel version 2.6.19/20. In your version this ctl is
> presented as an integer, 0=false, 65535=true; the kernel version(s)
> reports a boolean, true,false.

As part of the work to get the FM radio reception working correctly, I 
(finally) reimplemented the code that pulled status info back from the 
chip-level client drivers.  As part of that I reworked the signal 
status.  Previously I was just reading a binary value but with those 
changes it can now read a signal strength value (provided that the 
underlying driver provides that value).  This is why it changed from a 
boolean to an integer.  However I realize now that I probably missed 
updating the documentation about this control - which is why it is 
described as a boolean but reads as an integer.  An easy update.

I'm also reading that status from a different spot now, which probably 
is why the behavior has changed a bit for the other inputs.

The relevant changes for the above took place after the 2.6.20 kernel 
was frozen (quite a long time ago).  However the 2.6.21 kernel should 
include these changes, and of course as you can see the standalone 
driver already has that change.

> The following is a quick and dirty script for ripping composite video:


Nice script!


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