[mythtv] [mythtv-commits] Ticket #10072: [PATCH] freemheg: Support bitmap backgrounds used by BBC/Freesat

[David Matthews]

On 04/10/2011 12:16, Lawrence Rust wrote:
> On Tue, 2011-10-04 at 10:31 +0100, David Matthews wrote:
>> On 03/10/2011 16:21, Lawrence Rust wrote:
>>> On Mon, 2011-10-03 at 12:36 +0100, David Matthews wrote:
>>>
>>>> I did enquire
>>>> about this when Freesat first appeared but it seemed it was being kept
>>>> under wraps.  Anything that was implemented was just what I could guess.
>>>
>>>> Currently I can't actually test this and the other patches because I'm
>>>> limited to terrestrial at the moment but I'll definitely test them out
>>>> once I get my satellite dish back.
>>>
>>> I'm not sure how applicable these changes would be to FreeView.  I would
>>> have thought that the BBC would want an equivalent service for both.
>>> But as I live in France I've not been able to try FreeView.
>>>
>>
>> The MHEG profile for Freeview (1.06) has been available for a long time
>> (see http://www.dtg.org.uk/publications/books_mheg.html)
>
> I came across that doc first of all but it has little detail about the
> BBC's implementation, which is vital, and has nothing on Interaction
> Channel and other recent changes.  The ETSI ES 202 184 V2.2.1 (2011-03)
> doc is much more useful and applicable to both FreeView and FreeSat.

As far as I'm aware the Interaction Channel is only applicable to 
FreeSat.  MHEG on Freeview only contains what is defined in the 1.06 
profile.  It's possible that they created a new profile for Freeview HD 
and that additional features are present in MHEG on the HD multiplex but 
I haven't heard anything about that.

>>   so I was
>> assuming that the FreeSat profile would similarly be available.  I did
>> enquire on the BBC backstage mailing list and got a reply (
>> http://www.mail-archive.com/backstage@lists.bbc.co.uk/msg07628.html )
>> that suggested there was some chance it might appear eventually.  The
>> BBC have released an open source Java application that supports the
>> Freesat profile ( http://sourceforge.net/projects/mhegplus ) and at
>> least seems to list the resident programs in the profile.  It might be
>> possible to use that at least as a check on the implementation.
>
> I honestly don't think that using some unknown person(s) interpretation
> of a 'secret' specification is good guidance.  Pragmatically the
> simplest solution is the best - just handle the currently used
> extensions.  Worry about further changes if/when they occur.

Obviously the best source of information would be the documentation. 
MHEGplus isn't "some unknown person(s)"; it was an internal BBC project 
that they open-sourced ( 
http://www.bbc.co.uk/blogs/bbcinternet/2010/08/open_source_release_of_mheg_to.html 
) so it was presumably written with access to the documentation.  In the 
absence of access to the documentation it may be a useful second-best. 
Implementation based on observation can only go so far. 
GetEngineSupport strings are a particular problem; it's very difficult 
to guess what to return for a particular feature request.

It would be good to have freemheg implement everything that appears on 
FreeSat.  What you've done already, especially with the Interaction 
Channel code, has filled the major gap.  I'm looking forward to trying 
it when I get my access to satellite back.

David