[linux-dvb] Re: C/A routing Question

[Rob.McConnell@Zarlink.Com]

Hi again,

For point 4, the h/w that I am using does allow the capability to discard
all packets until the PUSI flag is found in a TS header (after which all TS
packets are matched).  This feature just reduces the amount of packets to
handle/copy/parse etc.   For h/w that didn't implement it, it would
probably be best to implement it in kernel space.  In this way, a user
space process that opened up a fd for a filter on a SI table would get back
the complete 1024 or 4096 bytes of the section table without having to
worry about any additional parsing.

As for point 5, filtering on TS priorities is an option that the Canal +
spec requires, but I haven't seen anyone (broadcaster) use it yet.  If
anyone has, then please let me know ;-)

That's all 4 now,

Rob ;-)



                                                                                                                                
                      Johannes                                                                                                  
                      Stezenbach               To:       Rob.McConnell@zarlink.com                                              
                      <js@convergence.d        cc:       linux-dvb@linuxtv.org                                                  
                      e>                       Subject:  Re: [linux-dvb] Re: C/A routing Question                               
                                                                                                                                
                      26-Feb-2003 02:06                                                                                         
                      PM                                                                                                        
                                                                                                                                
                                                                                                                                




On Tue, Feb 25, 2003 at 01:50:41PM +0000, Rob.McConnell@Zarlink.Com wrote:
>
> I was also having a look at the filter specs and I think we should have
> more flexibility for setting other criteria such as the following:
>
>       1) Whether to allow full TS packet or just payload through.

That's the funtionality of the current PES filter (DMX_OUT_TAP)
(which doesn't guarantee packet alignment for read() calls).

>       2) Whether to allow duplicate TS packets or to discard them.
>       3) Whether to allow or discard TS packets with error flag set.

That's rather special purpose, but worth supporting.

>       4) Whether to match TS packets with the payload unit start
indicator
> set (after which all packets would be matched).

That's too easy to do in userspace (or, in the future, in the DMA-to-hdd
handler). Just throw away the first few TS packets.

>       5) Whether to match on TS packet priorities.

What's that? Or, rather, what is the transport_priority field
used for in real-life applications?

>       6) Whether to allow/disallow TS packets with adaptation field
> through.

That's maybe worth supporting.

> I suppose we could add these options to the "flag" field in the filter
> structs if we wanted to or just have some other IOCTLs to setup the
policy.
> What do you think?

IMHO a "flags" field in (the now mis-named) struct dmx_pes_filter_params
would be fine.


Regards,
Johannes







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