Re: Simultanous PID!?

["Kearney" <clausen@cosy.sbg.ac.at>]

what about the processing overhead?
How many machine instructions and memory references would it take on a
"typical" modern processor to decide whether this is a TSpacket which should
be deliverd to the next upper layer or simply dropped - i.e. do the saem
thing a hardware interface does?

--cls

----- Original Message -----
From: "Thomas 'Dent' Mirlacher" <dent@cosy.sbg.ac.at>
To: <ip-dvb@erg.abdn.ac.uk>
Sent: Tuesday, April 30, 2002 11:25 AM
Subject: RE: Simultanous PID!?


> On Tue, 30 Apr 2002, Maciocco, Christian wrote:
>
> > That's a limitation of hardware based MPEG-2 TS decoder, usually limited
to
> > 8, 16 or 32 PIDs. Software based decoder such as the one available with
> > Windows XP BDA (Broadcast Data Architecture) where the full MPEG2 TS is
fed
> > out of the tuner to the software decoder there is no PID limit beside
your
> > available memory.
>
> just a remark: there are also capable implementations for other OSes out
there.
>
> filtering itself is not a problem with memory.
>
> quick calculation:
> 2^13 PIDs. - so a lookup table would have 2^13bits, which is 1KB.
> (most current computers have more then that :)
>
> ... also if you have a table with one byte per PID (because you
> want to lookup a specific encapsulation, which you're binding
> to the PIDs, this shouldn't be a problem (8KB))
>
> the only problem you could have with memory is if you have all the
datastreams
> interleaved on all the PIDs (for simplicity assume we're using all the
PIDs
> for network data), also another thing we will not account is the overhead
> for encapsulation (and TS headers)
>
> worst case memory usage for reassembling/decapsulation:
>
> (MTU-184)*2^13 ... around that at least.
>
> and with an MTU of 64K this would lead to 64M if i'm correct. - this
> could well be some problem, but with a smaller MTU=1500, we need 10M
> for reassembling the data. (worst case)
>
> ++Thomas
>
> --
> in some way i do, and in some way i don't.
>