[mythtv] [PATCH] Automatically set freqid for HDTV

Taylor Jacob rtjacob at earthlink.net
Thu Dec 9 15:45:03 UTC 2004


> The ultimate result of parsing the control tables in ATSC (and DVB) is a
> set of video, audio, and other PIDs in the TS stream to process and/or
> pass through to the recording on disk.  This set of PIDs typically
> remains constant for a given channel, and so storing it in the database
> would speed up tuning; if it's wrong, you will find out once the control
> tables do come along.  DVB in Myth already implements PID caching,
> though IIRC the database format is currently being revised.  There's no
> reason why HDTV can't piggyback onto the same PID caching methods once
> they're stabilized (or now, if I'm misremembering).

I actually have removed PID caching in the DVB code, yes some of the times the
pids remain constant, but since the frequency that the PAT and PMT are sent is
very high there is no reason to cache this value.  It junks up the database,
and if a channel has changed or you get different pids than you expect then you
are hosed as well..  I suspect this would be the case where I live actually
since my PBS station 4-1 & 4-3/4-4/4-5 are on the air until 8pm and then 4-1 &
4-2 go on the air until 11:00 and then it swiches back and forth again.  4-2 is
the 1080i content, and 4-3/4/5 is 480i content during the day..

With DVB only the PAT and PMTs are read real time the SDT (Same as your TVCT)
and other tables are all run from cached versions and when an updated version
shows up in the stream the Database is updated to reflect this (much like a
real set top box would do).

You can take a look at the v2.1 patch which is available for download right now
to give you some sort of idea how the database is laid out..

Taylor


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