[mythtv] PCHDTV + DVB Integration / DTVRecorder RingBuffer Reversion Request

Doug Larrick doug at ties.org
Mon Jan 3 09:11:12 EST 2005

Taylor Jacob wrote:

Let me just state up front that I think merging more of DVB and pcHDTV 
support is a good goal.  I think we're suffering from a lack of 
communication and information, not any desire to undermine these plans.

> The concept behind my dvb patchset is to create a database heiarachy that is
> representative of ANY digital television / radio service.. The database used by
> the PCHDTV is not anything like this, and has resulted in code like the DD
> Virtual Channel Number patches that I don't feel are a proper way to go about
> things.. Recording of multiple channels running on the same mux is quite
> difficult down the road with a database that is built around analog tv.. This
> also complicates getting guide data over the air which for ATSC will be
> mandated in 6 months when the broadcast flag kicks in since that is where it is
> present at..  This DD patch also renumbers all of the channel numbers for the
> Air2PC card if you attempt to use it with DD currently which is not necessary
> either..

Where do you get the impression that PSIP guide data in the US will 
suddenly be accurate and persistent across the board once Broadcast Flag 
goes active?  Broadcast Flag is in PSIP, yes, but is a very small part 
of it.  Some stations don't implement the EIT/ETT text tables at all; 
still others implement canned data, which consists of 3-hour shows 
entitled "HD Programming."  One of my channels, last I checked, was 
broadcasting PSIP from 3 months ago.  None of this is going to magically 
change come July.

Also, DataDirect goes out (roughly) 2 weeks; the PSIP guide data that 
I've seen covers a much shorter period (typically 12 hours to 2 days). 
DataDirect also provides much more useful information, precategorized 
for our use: original air date, episode number, separate program and 
episode titles, genre, etc.  PSIP guide data provides none of this, or 
if it does it will require parsing that will vary from station to 
station and program to program.  I think at least optional use of 
DataDirect is here to stay.  I agree it would be nice to be able to have 
a Myth system that's not connected to the Internet, but for ATSC, that's 
not practical at this point.

> Secondly the PCHDTV card ought to use the database structure that I have setup
> for the linux-dvb cards which works properly with ATSC as well as DVB in
> harmony.. 

This would be nice, but IMHO is unlikely to occur before your changes 
are in CVS.  I for one am unwilling to do further development based on 
something that's not in CVS, as my development time is generally limited 
to a few hours a week, and I don't want to spend it doing patch management.

I was also unwilling to wait any longer to do the work I recently did 
around getting freqid and minor channel numbers from DataDirect.  I 
expect a fair number of people have gotten pcHDTV cards for xmas, and 
anything we can do to make setup easier for them (like not requiring 
hand-edits of the channel database) translates to less load on the 
mythtv-users list.

> I also have a service table updating class that constantly monitors
> all of the SI (DVB) or PSIP (ATSC) tables and keeps all the tuning information
> up to date..  This also helps reduce the number of "bad channel hangs" that are
> common to both the DVB codebase and HDTV codebase..

...which is also a good place to grab PSIP guide data and use it to 
supplement what's already present.  Sounds nice.  But short of reading 
your patches, how am I to have known of its existence?  When working on 
changes of large magnitude in the past, I have posted design proposals 
to this list and gotten good feedback; this also serves to keep other 
developers up to date, helping to prevent trodden toes. MythTV-dev is 
low volume (at least compared to -users); no reason to be shy about 
posting to it.

> I feel right now the two groups (PCHDTV and DVB) are going in seperate
> directions.. We need to be more organized if we are going to integrate this
> code properly.. I know it is more difficult to deal with the dvb-patch since it
> is not in myth-cvs now but if any of you PCHDTV developers would like read
> access to the cvs that houses the dvb-patch please let me know and I will be
> glad to provide this to you so we can move twoard integration..

As I stated above, I honestly think that integration needs to take place 
in the main MythTV CVS library.  Otherwise it becomes difficult for me 
to make unrelated progress and submit coherent, tested patches to main 
CVS.  I'd recommend breaking off separable, non-intrusive pieces and 
getting those integrated first.  Then get the cool new stuff accepted, 
with pointers for how we pcHDTV people can utilize it.

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