[mythtv] How to make sure v4l2 is being used (compile flag?)

Martin Forssen maf at tkrat.org
Fri Nov 26 22:21:41 UTC 2004

I see the same symptoms.

On 24 Nov, David George wrote:
> Which buffer 0 and 1 errors are those?  Please post the error messages.

2004-11-22 22:02:11.038 Changing from None to WatchingLiveTV
VIDIOCMCAPTUREi0: Invalid argument
VIDIOCMCAPTUREi1: Invalid argument
VIDIOCMCAPTURE0: Invalid argument
VIDIOCMCAPTURE1: Invalid argument
VIDIOCMCAPTURE0: Invalid argument
VIDIOCMCAPTURE1: Invalid argument

and the last two lines repeats ad infinitum.

>> However, after looking through the docs and googling for hours I still 
>> haven't found a way to determine which interface (v4l/v4l2) is being 
>> used and when it uses the old API, force myth to use the new (either 
>> by command flag or recompile).
> The source code is the ultimate docs.  There is no compile flag.  It is 
> not necessary to recompile.

I realized why it is using v4l1. That is hardcoded on line 875 of
libs/libmythtv/NuppelVideoRecorder.cpp. The line was introduced in
version 1.182. If I comment out that line it works a little bit better
for me. I still have very bad picture (may be my antenna) and the
picture freezes every now and then (I will look into that).

> Mythtv queries the capabilities from the capture card driver.  If the 
> driver says it is v4l2, myth uses it.  Which cx88 card do you have?  
> What kernel version?  What v4l version?  This is the kind of stuff that 
> changes daily (or at least weekly).

I have a Leadtek Winfast 2000 XP. I run kernel 2.6.9 but am using the
20041117 snapshot of the video4linux drivers. I am using the CVS version
of mythtv and just updated.


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