[linux-dvb] Re: Linux DVB API 4 Q's

[Johannes Stezenbach <js@convergence.de>]

Rob.McConnell@Zarlink.Com wrote:
> 
> 1. Open up an fd on the demux device and use the DVB_DMX_ADD_PID_FILTER
> ioctl passing in the PIDs of the video,audio and subtitle streams of BBC1.
> Immediately the PID filters will be activated and start filtering data to
> the h/w buffers.  In this instance, the DVB_DMX_SET_PID_FILTER ioctl isn't
> used, but we should still have it to cater for individual streams on
> individual fds. Right?

DVB_DMX_SET_PID_FILTER will always have to be used for setting
output_format. But see my other Mail.

> 3. The user decides that BBC2 is not worth recording now, but insanely
> decides to record BBC3.

Unbelievable what British users are up to ;-)

> Q: What about BBC2 data left in the circular buffer after the
> DVB_DMX_DEL_PID_FILTER is issued?  We can't flush the global circular
> buffer otherwise we lose the data relevant to BBC1.  Should the
> DVB_DMX_DEL_PID_FILTER then wait until all the data in the buffer is
> consumed before actually stopping/removing the filter?

No. If you have a single threaded program there would be no way to
consume the data if DEL would wait (unless it is consumed inside
the driver).

> Right, I have spoken with our app developers and they don't seem to have
> any issues regarding this one-for-all setup and run ioctl
> (DVB_DMX_ADD_PID_FILTER).  However, for some strange reason some of our
> customers do setup filters without running and then issue the START ioctl.
> They claim they get faster channel changes, but I can't comment on this as
> I haven't seen their s/w.

I doubt this will make a noticable difference. Frontend handling and
video/audio PID caching are much more important.

> I don't mind which way we go as long as the requirements are met - which I
> believe they are.

Good.

Can you have a look at the filter flags and tell me if your requirements
are met there, too?


Regards,
Johannes


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