[linux-dvb] Re: V4 Demux Point

[Johannes Stezenbach <js@convergence.de>]

Rob.McConnell@Zarlink.Com wrote:
> Johannes Stezenbach <js@convergence.de> wrote on 07/09/2004 16:30:02:
> > Rob.McConnell@Zarlink.Com wrote:
> > > There seems to be a technical conflict of interest between DTV chips
> that
> > > have a single h/w output buffer per section filter and ones like ours
> that
> > > allow you to attach multiple section filters on a single PID with a
> common
> > > h/w output buffer.  The current V4 API is indeed clean/lean, but we are
> > > particularly worried about the extra processor load especially as we
> are
> > > running demanding applications like MHEG-5 and 8-day EPG on our h/w.
> >
> > Well, we run MHP and 8-day EPG on platforms which have the same
> > archtecture as yours (one hw ringbuffer per PID-filter, sections
> > get tagged to know which section filter they apply to and have to
> > be copied to the fd rindbuffer).
> 
> Would this be Vulcan? ;^)

Nope. (MIPS core)

> > Even for MHP object carousels (DSM-CC)
> > and EPG data the overhead for doing the additional copy seems to
> > be negligible. It would be noticable (but still bearable) for
> > high bandwidth dvb_net MPE. (Yes, there is some load when MHP
> > runs, but it's nearly all userspace, not kernel.)
> 
> What is the lowest spec h/w + arch that you have successfully tried this
> on?  For example, would a RISC arch running only at 50MHz be fine, or would
> you need something > 200MHz with sufficient cache?  Have you tried running
> this on simple h/w that only does PID filtering?
> 
> I don't want to get into a trap where we have the situation where our or
> someone else's s/w cannot run fast enough on our h/w and we need to
> redesign the API and go through the design cycle again.  Do you have any
> figures for cpu loading (e.g. top) or profiling?

I have no hard numbers for you, sorry.
We had demos running on a dbox2 (66Mhz ppc) and ARM Integrator
(IIRC ~60Mz ARM7TDMI, with a full-featured av7110 in a PCI bus slot).
But that was a while ago. Our current platforms have 150..200Mhz.

You could get an old dbox2 and run the V3 API stuff from
tuxbox.org on it, and see if you have performance problems.

Or maybe someone else with a dbox2 could help you out with
some simple benchmarks like running dvb-apps/test/test_section
on some TS/PID along with top?


Johannes