[mythtv] Ticket #1822: XvMC: Initial DVD menu not shown

Robin Gilks g8ecj at gilks.org
Sat Jul 1 11:24:29 UTC 2006

> #1822: XvMC: Initial DVD menu not shown
> ----------------------+-----------------------------------------------------
>  Reporter:  skamithi  |        Owner:  danielk
>      Type:  defect    |       Status:  new
>  Priority:  minor     |    Milestone:  0.20
> Component:  mythtv    |      Version:  head
>  Severity:  medium    |   Resolution:
> ----------------------+-----------------------------------------------------
> Comment (by danielk):
>  I'm punting this for now.
>  It appears the problem is that XvMC pause consumes frames, so we try to
>  get the displayed frame rather than the used frame, so we end up with
> the
>  still frame previous to the one we really want. If we try to get a used
>  frame instead, then we consume it show it will just flash on screen and
>  then go away.
>  If I'm right about the problem, there are four ways to go about fixing
>  this:
>   1. Change the avlib decoding so that it redecodes the still frame as if
>  it were a video.
>   2. Implement a pause frame implementation for XvMC which copies the
>  frame. This might be doable by with BLEND_SUBPICTURE compositing, by
>  compositing the frame with a blank OSD, with BACKEND_SUBPICURE I don't
>  know how you would do it.
>   3. Use another decoder to decode still frames, and use the XvImage
>  supported by all XvMC implementations I know of; or simply use X11 paint
>  calls and block XvMC display. This will problably require some
> additional
>  hacking to get OSD to work.
>   4. Implement some special UpdatePauseFrame for still frames which
> avoids
>  consuming frames by some kind of VideoBuffers frame accounting trickery.
>  None of these are very simple. If #2 is possible it is probably the best
>  solution.
>  There is another possible hack, which is to just disable XvMC for DVDs.
> If
>  no one else is interested in fixing this, I can apply that hack as the
>  fix...

As a result of various other fixes in the last 3-4 weeks, the internal DVD
player no longer exits when it hits these 'dodgy' menus but displays and
then skips directly onto the next item. This means that the player is now
*almost* usable for my Star Trek DS9 DVDs - in fact its fine provided I
only want to play them in English (just as well!) since the option to
change lanuage skips part in half a second :-)

The fact that they display at all makes me wonder if the problem hasn't
moved somewhat (or been mostly fixed) and that a complete solution is not
as complex as first appeared.

Not sure why if XvMC blows up due to a size change a fallback to Xv mode
wouldn't work (not that I'd have a clue as to how to implement it). By
running Xine with the same DVDs with lots of debug turned on, it looks
like it re-inits the whole of XvMC for the new size in order to play them.
Perhaps thats the 'right way'. Dunno...

Robin Gilks

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