[linux-dvb] problems capturing analog and digital at the same time with lifeview trio

Hartmut Hackmann hartmut.hackmann at t-online.de
Thu Sep 7 00:33:06 CEST 2006


Hi, Nico

Nico Sabbi wrote:
> Hartmut Hackmann wrote:
> 
>> So MythTV doesn't allow to choose the video format?
>> A solution might be to suppress the planar formats on hybrid and duo 
>> cards.
>> The mechanism normally is that the application asks the driver which 
>> formats
>> it supports (VIDIOC_G_FMT). We could reduce the list either
>> - with an insmod option
>> - or simply by the fact that the card supports MPEG (DVB) streaming.
>> But this would reduce the capabilities of the card and i don't know 
>> whether
>> there are cases where only planar formats work, either due to the 
>> application
>> or due to the overlay mechanism.
>>
>> Can anybody comment on this?
>>
>> Best regards
>>    Hartmut
> 
> 
> 
> 
> I think that removing some sample formats tout-court is a bad idea, because
> resampling from yuy2 to yv12 for compressing to mpeg* is very likely to 
> reduce
> quality and introduce slowdowns; if it were possible to remove planar 
> formats
> only when a dvb capture is running the situation would be more reasonable;
> anyway, training the user about what he can and should do is is best 
> option IMO.
> 
>    Nico
> 
Yv12 is a planar format. Thats another argument why i originally didn't do
this...
Its not so easy but possible to "block" the planar formats dynamically in
the driver but i am afraid this won't work in practice:
If i had to write a tv application, i would query the device capabilities
in the beginning of the session and assume these to be fixed afterwards.
A compromise might be a combination of the options: block the planar formats
by default but restore the current behaviour with an insmod option.

Anyway, thanks a lot for your comments.

Hartmut



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