[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 22:39:28 CEST 2006


Hi, Riccardo

rghetta wrote:
> 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.
> 
That's a pity. It whould be nice if you could drive this a bit...

>>>> 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.
> ...
Aggreed
> 
>> 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.
>
This can be detected and would be far better than nothing. But this message
would go into the kernel log. Afaik, there is no way to get this on a display.
Its also dangerous to refuse the streaming. Some applications don't have
timouts and will simpy hang if a DMA streaimg doesn't happen...


> Greetings and thanks,
> Riccardo
> 
Some more thinking necessary?

HArtmut



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