[mythtv] Experimental HDTV Recording patch updated

Doug Larrick doug at ties.org
Sun Aug 1 15:01:56 EDT 2004

Daniel Thor Kristjansson wrote:
> I've begun cleaning it up for eventual inclusion in MythTV. It's not
> ready yet. But I would love it if some people gave it a test.

I'll take a look when I get some time.  I'm glad to see you doing this.

> The other ATSC tables are parsed only if we have the MasterGuideTable. I
> haven't done anything to try to parse the Cable Virtual Channel Table,
> the Region Rating Table, System Time Table, or the directed channel
> change tables. 

One minor nit (without having looked at your code): we need to parse the 
STT in order to determine the offset between "GPS time" (which ATSC 
uses) and GMT; right now it's on the order of 12 seconds (GPS time 
doesn't use leap seconds).  Otherwise any guide data read from PSIP will 
be off by this amount.

> Other than cleanup, what I want to do before trying to get this into
> MythTV is to actually parse out the subtitles and send them to the
> screen. I might also want to cache some information so "tuning" to a
> channel in LiveTV mode can be quicker. Right now we have to wait for a
> PAT before we even wait for a PMT, and then we need to wait for a PMT
> before we wait for a GOP in the video stream, all before we begin
> sending data to the ringbuffer. It is a lot of waiting we mostly don't
> have to do.

Subtitles would be nice to see.

I also think it would be cool to update the program guide data from PSIP 
in a few cases:
1. when guide data is completely absent for a channel (i.e. not using 
2. when more info (e.g. episode description) is present in PSIP than in 
Zap2it's data
3. When PSIP claims that a show will begin earlier / end later than the 
data we already have.  This adjustment could allow Myth to automatically 
extend a delayed recording (such as shows delayed after a sporting event).

Unfortunately, the PSIP data I've seen is generally not as high-quality 
as Zap2it's data, but that will change over time.

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