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

[Rob.McConnell@Zarlink.Com]

>Rob.McConnell@Zarlink.Com writes:
> > How should we treat the DVB_DMX_START and DVB_DMX_STOP ioctls for an fd
> > that has many PID filters associated with it?  Should these ioctls
START
> > and STOP all filters attached to the fd simultaneously, or would it be
> > better to single out specific filters to START and STOP.  The advantage
of
> > allowing this independent control could be for recording multiple PES
to a
> > hdd for example.  If the user is recording BBC1 and BBC2 to a hdd for
> > example, and then decides to stop recording BBC2 and record BBC3
instead,
> > then we wouldn't want to have any break in the recording of BBC1.  We
could
> > issue a DVB_DMX_STOP ioctl on the filters associated with BBC2 (by
their
> > PID value), remove the filters using the DVB_DMX_DEL_FILTER ioctl and
then
> > add new ones using DVB_DMX_ADD_FILTER with the flag set to
> > DVB_DMX_IMMEDIATE_START or using the DVB_DMX_START ioctl on the
specific
> > pid value associated with the fd.
> >
> > So both DVB_DMX_START and DVB_DMX_STOP ioctls in this case would have
to
> > have a handle to the filter required.  In this case, why not specify
the
> > pid value as in the proposition for the ADD/DEL ioctl above?
> >
> > Any thoughts?

> For the ADD/DEL ioctl I agree. For the application you are
> describing using one fd for each channel might make more sense. This
> way, you setup the PIDs for each channel on separate fds and can
> start/stop them all at once. You will also already get the packets for
> each channel in separate buffers (or do you want them in one big TS?).

One big TS should be an option for h/w that does a DMA from a single
circular buffer in memory to a HDD or to another bit of h/w to preprocess
the data.  Also, if someone wanted to follow the MPEG-2 systems spec and
create a TS from its parent TS (albeit timings would be a bit off), then
this could be a useful stab at doing it.

Rob : )






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