[linux-dvb] Re: API changes (was: C/A routing Question)

[Holger Waechtler <holger@convergence.de>]

Ralph Metzler wrote:
> Hi,
>
> Florian Schirmer writes:
>  > >Yes, this should be the responsibility of the demux. 
>  > >Just add capability ioctls there. The frontend could be rather dumb. 
>  > >Syncing to TS boundaries, etc. can also be handled by the demux. It 
>  > >will have to do that anyway for budget cards which deliver unaligned 
>  > >data (e.g. Bt878/fusion cards). Demux hardware usually does it by itself.
>  > 
>  > In the latest Fusion code i've pushed all the sync handling down to the
>  > (soft) demux. It needs some tweaks here and there but it basically works.
>  >  
>  > >> I.e. open("/dev/.../dvrN"), then DMX_DVR_SET_PIDS(int num, int16_t
>  > pids[])?
>
> Would a PID bitmap as parameter also make sense if many PIDs are used?
> On the other hand, the PID number usually probably will not be that 
> high and one can use 0x2000 for the whole TS again.
Sounds good and makes sense to me. Beside this it's pretty trivial to 
implement, we wanted to add a PID lookup bitmap anyway...



>  > >Yes. This should make recording all PIDs of one service very easy. A
>  > software 
>  > >filter implementation should also be simple. Now this kind of filter even
>  > seems 
>  > >to fit perfectly to some hardware 
>  > >as Rob McConnell described in his mail. 
>  > 
>  > IMHO the dvr is comletely useless. Instead of adding more and more features
>  > to it we should remove it. At the same time we have to change the demux API
>  > to allow more than one pid filter per fd. If it is possible to route more
>  > than one pid into the same buffer you will basically get the functions the
>  > dvr device provides. If we do it carefully we're able to extend the API
>  > without loosing compatibility. 
> Yes, let's throw the dvr device out.
ok. We still need a precise API proposal.


>  > I dont know alot about hw that provides dvr units. But the hw/driver should
>  > be able to deal with that internally without forcing the user to know about
>  > wether it has dvr support or not. If there is any reason why the hw or sw
>  > requires a dvr device please elaborate why. Thx!
>
> As long as the dvr units are connected to one of the other demux
> channels (same input) this should be fine.
>
> One should also consider if the driver should be able to tell the
> application what it can do in hardware and with direct DMA and what
> has to be emulated and copied in software. 
> Especially on hardware with low power CPUs (low MHz ARM/MIPS) this
> could make big differences.
yes, and especially this hardware has usually a very flexible and 
powerful DMA controller, we should use it as much as possible...

Holger



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