[mythtv] Myth Protocol Command to List Programs

[Michael T. Dean]

On 03/14/2008 11:34 AM, Roger Heflin wrote:
> Michael T. Dean wrote:
>   
>> On 03/14/2008 05:50 AM, Ian Barton wrote:
>>     
>>> I want to be able to get a list of programs from the database for a 
>>> particular channel. Rather than query the database directly, I was 
>>> hoping that there was a Myth Protocol command do it. However, I can't 
>>> seem to find one. Does one exist?
>>>       
>> I was actually just discussing this on IRC with Chris Petersen 
>> (MythWeb/Perl bindings guy) who wanted the same.  I was planning to make 
>> a couple of changes to allow testing whether this would actually work 
>> and scale.  Once I get the modifications done, I'll post the patch so 
>> you can test it, too.

After getting a good start on the patch today, I'm putting this on hold 
for now.  When discussing the patch on IRC, we've begun to consider 
making this information available only through the XML server or through 
the Myth protocol, but not both (though no decisions have been made, 
yet--or, at least, I haven't been informed if they have :).

Since the code to make the information available through XML is already 
available, it's quite likely to "win" if the devs decide to go with a 
single interface.

You can play with the XML stuff using:

wget 
'http://localhost:6544/Myth/GetProgramGuide?StartTime=2008-03-15T12:00:00&EndTime=2008-03-15T14:00:00&NumOfChannels=1&StartChanId=1021&Details=0' 
-O listings.xml

to get a "summary" version or

wget 
'http://localhost:6544/Myth/GetProgramGuide?StartTime=2008-03-15T20:00:00&EndTime=2008-03-15T23:00:00&NumOfChannels=1&StartChanId=1021&Details=1' 
-O listings-detail.xml

to get all program details.

Ian, if you're hoping to get it through the Python bindings, you may 
need to add bindings support for querying/parsing the XML data.

See also contrib/development/MythXMLTest/ (I'm pretty sure in 
0.21-fixes, it's just under the contrib directory) for more details on 
the XML interface.  David Blain (and a few others) has put a /lot/ of 
good stuff in there that's not really being used, yet, though doing so 
would be a /very/ good thing.  Much better than direct DB queries, at 
least.  :)

> Would this interface allow getting details for a single program that you already 
> had some limited amount of information on (say title and subtitle)?
>   

Looks like you can with the XML interface.

> The mvpmc device has limited ram, and has memory issues when attempting to cache 
> all of the details for 500+ recorded programs, so if we could just keep a much 
> smaller amount of details for all of the 500 and then query to fill in the other 
> information as needed for a single program that would solve the memory issue and 
> allow it to deal with large numbers of programs.
>
> We cannot really query all and just take the one we need because the query all 
> really takes too long when you have a large number of programs.
>   

Using GetProgramGuide and specifying a single channel ID and appropriate 
start/end time*** you can limit the info you're dealing with.  And, with 
the "summary" info, you can really cut back on memory usage.  There's also:

wget 
'http://localhost:6544/Myth/GetProgramDetails?StartTime=2008-03-15T20:00:00&ChanId=1021' 
-O program_details.xml

if you want to start with the summary and then fill in details on an 
as-needed basis.

Now, whether XML parsing will work sufficiently fast for the mvpmc is a 
whole different question.  I'll leave it to you to figure that one out.

Mike

***I just posted a ticket (#4956 - 
http://svn.mythtv.org/trac/ticket/4956 ) with a patch that modifies 
GetProgramGuide to return any show that overlaps the StartTime and 
EndTime.  For example, Lost was on from 21:00 to 22:02.  Before the 
patch, a query for ProgramGuide with between 21:00 and 22:00 would not 
return info for Lost.  With the patch, the info would be returned.  And, 
before the patch, a query with StartTime = EndTime would return 
nothing.  After the patch, a query with StartTime = EndTime = 
2008-03-13T21:00:00 would give 2 episodes of Lost--the previous week's 
episode that ended at 21:00 and the current week's episode that starts 
at 21:00.  Therefore, the patch gives all the info you might need and 
allows you to trim, rather than giving most of the information and 
making you continue querying to get the rest.