[linux-dvb] Re: V4 API Implementation Q's

[Rob.McConnell@Zarlink.Com]

                      Johannes                                                                                                   
                      Stezenbach               To:       linux-dvb@linuxtv.org                                                   
                      <js@convergence.d        cc:                                                                               
                      e>                       Subject:  [linux-dvb] Re: V4 API Implementation Q's                               
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                      13-Apr-2004 02:20                                                                                          
                      PM                                                                                                         
                                                                                                                                 
                                                                                                                                 










> Well, I think if you write a simple zapping application you would
> statically allocate filters for audio, video, pcr, and allocate
> and set filters for PAT, PMT, EIT-p/f. Then for zapping you just
> set some PIDs and stop/start the filters.

A zapping app would indeed setup the A/V/PCR pids and start providing
streams to the decoders.  As for SI/PSI then I don't see the difference
between setting a filter and it starting immediately or setting a filter
and starting/stopping it later.  Yes, PSI/SI filters would have to be
dynamically allocated/set, but why would you want to start/stop them at a
later time rather than just have them start immediately or simply
remove/stop them (close the fd)?

> Linux, however, is a multitasking system, and allocation needs to
> be more dynamic. Especially with MHP which can take over control
> of zapping completely. Linux DVB software should release unneeded
> resources, and must be prepared that setting a filter can fail
> anytime.

I haven't looked at MHP, so do MHP apps make the distinction between
allocation, setting and start/stopping of filters/feeds?

One of the main arguments I have for providing this distinction in the V4
API is to allow compatibility for existing STB API's that have been ported
to Linux.  However, I do understand that this will mean extra complexity in
terms of handling the state of a filter/feed, but this would at least
provide the flexibility that a DVB API should have.

Let me know what you think....

Cheers,

Rob : )




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