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

David George david at thegeorges.us
Wed Nov 24 16:33:08 UTC 2004

On 11/24/2004 11:08 AM, The Cyberwizzard wrote:

> I just checked out the last CVS update looking for a way to get my 
> CX8800 based card to work under mythtv. It looks like we have some 
> improvement as I get a green screen instead of a crash but the old 
> buffer 0 and 1 errors are back.

Which buffer 0 and 1 errors are those?  Please post the error messages.

> Now I know this might something to do with the v4l drivers and I want 
> to force MythTV to use the v4l2 API since that one seems to work fine. 
> (If I understand the source correctly, switching to v4l2 also 
> automatically enables the YUV conversion which is required for this to 
> work).
> 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.

> How do I do this?

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).

> Berend Dekens
> P.S. I switched from the users list to the dev list since every 
> question I asked remained unanswered (prolly because I ask stuff about 
> the internals)

More likely because you are using a cx88 card which a probably very low 
percentage of myth users have.  Most are using Hauppauge PVR cards or 
bttv based cards.  Also cx88 support is very new in Linux and is likely 
not as stable as bttv support.


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