[mythtv-users] [old] Re: XvMC and libmpeg2 to be dropped in 0.25

Raymond Wagner raymond at wagnerrp.com
Wed Feb 9 14:48:41 UTC 2011


On 2/9/2011 09:35, Gary Buhrmaster wrote:
> On Wed, Feb 9, 2011 at 03:46, Brian J. Murrell<brian at interlinx.bc.ca>  wrote:
> ....
>> I wonder why so many other software projects don't seem to have any
>> problem with this protocol compatibility between various releases and
>> yet myth needs to be sooooo rigid.
> Having (on other software projects) done the programming/testing for
> forward/backward compatibility, I can say that depending on the
> specific details, it can be a *lot* of work to provide such
> compatibility, and to perform the testing of all the edge cases.
> Again, depending on the specific details, you often end up with
> multiple code paths (one for each version case) all of which
> now have to be reviewed for any other change, and tested.  btw,
> all that effort to support multiple versions tends to support only
> a small subset customer base.

Difficulty and time aside, MythTV simply cannot provide backwards 
compatibility at its current state.  With our own server protocol, we 
could spend a lot of code and layer support for old versions to connect 
to.  With the database, the current schema is what you get.  It's 
impossible to have a program magically support some unknown future 
version of the schema, and attempting to write to an unknown schema will 
result in corruption.

As long as clients continue to directly access the database, backwards 
compatibility cannot be done.


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