[mythtv-users] AC3 and/or S/PDIF (again)

[Michael T. Dean]

On 01/20/2006 02:21 PM, William Lewis wrote:
>> >How 'bout simply disabling 'use video as timebase' at run-time when 
>> passing
>> >raw AC3, regardless of what 'use video as timebase' is set to.
>> >
>> >
>> Yeah.  That's what I was trying to say (that's why I compared it to the
>> runtime disabling of AC-3 passthrough with timestretch and why I said,
>> "[if] there's an AC-3 stream").  Guess I should have used that
>> all-important word, "runtime," though.
> I've never posted a patch to this list before, but how does this look, 
> and, if the answer is "Good", then what do I do with it?
Pretty close...  ;)

The diff should be created as a "unified" diff (using the "-u" option 
for diff).  This way, it will contain the names of the modified files as 
well as some "contextual" information that can be used to merge the 
patch even if the line numbers are not exact (i.e. if the version in SVN 
is changed between the time when you create your patch and when it's 
applied).

The easiest way to get a proper unified diff is to use SVN to create it 
for you.  Simply check out (or update to) the current revision of SVN, 
make changes as required, and--from the top-most directory of the 
project (i.e. the "mythtv" directory you checked out), execute:

svn diff > ../mythtv-disable_timebase_for_passthrough.patch

But note that it will create a patch that contains *all* the differences 
between your working copy and the SVN revision of your working copy.  
Therefore, you should either make sure you modify a clean working copy 
or be prepared to edit your diffs (but, please test the diff if you hand 
edit--it's easy to break a diff with a bad edit or to accidentally 
remove important parts of your change, etc.).

That being said, it looks like your patch will unnecessarily disable 
video as timebase in some situations (although, not knowing exactly 
where this change is supposed to be made, I'm not sure).  If 
AC3PassThru/DTSPassThru and UseVideoTimebase are both enabled, 
UseVideoTimebase will always be disabled, but really should only be 
disabled if the audio stream is determined to be AC3 (or DTS)--that way, 
recordings with PCM or MP2/3 audio can still be played back with 
UseVideoTimebase.  And, lastly, we should probably log a message that 
UseVideoTimebase is being disabled because of pass through (at least for 
something like -v playback (is that the proper log level?)).

If you're still interested in working on it, once you get a good unified 
diff, you can post it in a new ticket on Trac ( http://svn.mythtv.org/ 
).  See also http://svn.mythtv.org/trac/wiki/TicketHowTo .  Note, 
though, that it doesn't hurt to post to the lists first if you have 
questions about the implementation of your patch (like you did this 
time).  If your patch is perfect when entered into Trac, it's more 
likely to be applied quickly and it saves the developers time (so they 
can make Myth even better for all of us).  :)

Mike