[linux-dvb] a strange EIT Section

Johannes Stezenbach js at linuxtv.org
Tue Jun 21 15:24:56 CEST 2005


Patrick Boettcher wrote:
> On Tue, 21 Jun 2005, Felix Domke wrote:
> >Patrick Boettcher wrote:
> >>>So the section should IMHO never appeared into userspace. Sure it's
> >>>right to be prepared for invalid sections (and drop them), but in this
> >>>case, I suspect a driver/hardware bug.
> >>>Does the hardware use hardware section filtering?
> >>No, this section was received using a budget Card (AirStar2). Parsing
> >>was done by the linux dvb demuxer.
> >>I received a lot of valid (parsable) sections before. This faulty
> >>section (and others) I got, when the signal went through a normal
> >>loss/regain process.
> >Of course there's always the 1:16 possibility to skip a multiple of 16
> >packets on that pid, so the CC will give a failse match.
> 
> I see.
> 
> >Does it happen all the time after a signal regain or only very few times?
> 
> No. It happens rarely, but I can force it, by "playing around" with the 
> antenna.
> 
> What would be your suggestion? A harder syntax check in the program 
> (correct table_id for this PID, section_syntax_indicator == 1) or 
> anything else?

IMHO the software demux should throw away the complete section when
it sees a TS packet with the error indicator set, and then
wait for a good TS packet with PUSI set.

Johannes




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