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

rghetta birrachiara at tin.it
Thu Sep 7 19:36:29 CEST 2006


Nico Sabbi and Hartmut Hackmann wrote:
> So MythTV doesn't allow to choose the video format?
Apparently not a non-planar one. I've only found a way to ask for yv12 
or 422p(lanar). But I'll ask on the mythtv mailing list, here is going 
too much off-topic :)
Many, many thanks for you help.

>>> A solution might be to suppress the planar formats on hybrid and duo 
>>> cards.
...
>> 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.
I agree, but imho the current situation is a bit unpleasant because the 
user has no way to know what he can do. I fear that without some help by 
the driver *and* the applications, only a minority of users will get the 
most out of their hybrid cards.
...
> 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.
Is detecting an over-4-DMA-channels situation and returning a specific 
error (perhaps "bandwidth exceeded" or something like that) a viable 
option ?
This way only an illegal combination will be flagged and the application 
  could have a chance to inform the user or revert to a more appropriate 
format.

Greetings and thanks,
Riccardo



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