[linux-dvb] Re: [PATCH] Skystar2 pid filters reorganization

[Holger Waechtler <holger@convergence.de>]

Roberto Ragusa wrote:
> On Sat, 29 Nov 2003 05:29:43 +0100
> Holger Waechtler <holger@convergence.de> wrote:
>
>
> > one of the first checks in the swfilter code will discard them. If you 
> > implement a second check in the hardware driver code this means that 
> > every packet gets checked twice which is probably more expensive.
>
> Every accepted packet is tested twice.
> Discarded packets are tested once (and very early).
> So we gain here and loose there.
>
> In relation to "one of the first checks", do you think that the swfilter
> code is fast enough to let us just open_whole_bandwith when we're out of
> hw filters?
sure, why not? All other decoder-less PCI cards wotk reliably the same 
way...

> Consider that the unwanted/wanted ratio can be 5 or 10 in typical
> usage and much higher in particular cases (we have to open
> everything when scan is asking 10 pids).
I'd suggest to implement and activate the PID filters mostly to save PCI 
bus bandwidth, keeping the PCI latency low with many cards in your PC is 
usually a much more serious problem than CPU load caused by the software 
demux.

And in most environments you don't need the entire 38MBit Stream but 
audio, video and some section data streams which sum up to 4-10MBit...

Holger



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