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

[Ralph Metzler <rjkm@metzlerbros.de>]

Rob.McConnell@Zarlink.Com writes:
 > I beg to differ on this.  If you have a look at dvb_demux.c there is the
 > function "dvb_dmx_swfilter_section_feed" that gets called when we have some
 > section data available from the h/w.  In this function we have a pointer to
 > a "dvb_demux_filter" that is set from "dvb_demux_feed->filter".  Now each
 > "dvb_demux_filter" has a "next" field that points to another
 > "dvb_demux_filter".  So we have a feed that can have multiple
 > "dvb_demux_filters" attached to it.  The function then calls
 > "dvb_dmx_swfilter_sectionfilter" for each available "dvb_demux_filter"
 > attached to the feed.  This called function then parses the data returned
 > by the h/w for each section filter attached to the feed to check whether a

Yes, you can add several section filters to a section feed. But these
are internal data structures which take into consideration that
most hardware has no completely separate section filters but that they
all have to be associated with a PID filter (or some call them PID feed)
and you can only have one of those per PID. 
So, separate higher (user) level section filters internally have to 
share one feed.

 > match has been found.  You can attach multiple section filters to a single
 > fd by calling "DMX_SET_FILTER" multiple times on the already opened fd.

No, the filter will be stopped at the start of a DMX_SET_FILTER call
and this removes the old section filter from the feed.
An implementation of the new API will just keep a table of filters for
each file descriptor instead.


Ralph


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