[mythtv-commits] Ticket #5643: Match refreshrate with input framerate to reduce judder.

MythTV mythtv at cvs.mythtv.org
Tue Aug 26 00:51:06 UTC 2008

#5643: Match refreshrate with input framerate to reduce judder.
 Reporter:  henrik.sorensen at gmail.com  |       Owner:  ijr    
     Type:  enhancement                |      Status:  new    
 Priority:  minor                      |   Milestone:  unknown
Component:  mythtv                     |     Version:  unknown
 Severity:  medium                     |     Mlocked:  0      
 Film, PAL and NTSC video material all have different frame rates, ideally
 each should be shown at or a multiple of that frame rate, so each frame is
 shown the intended amount of time, otherwise slight motion judder occur in
 scenes where the camera pans and the like.

 I made a patch against 0.21fixes that extends the custom video mode
 code to automagically attempt to choose a refresh rate based on the video
 frame rate.

 Basically I modified the videoout_xv and base class so they require the
 video fps on initialisation, which nuppelvideoplayer already has at the
 point it inits a videoout instance. (only base and xv videoout classes are
 modified in the patch)

 Then it's mostly a matter of getting the video fps to
 DisplayResScreen::FindBestMatch() which is slightly modified so it also
 accepts multiples of your video fps, say 50hz for 25fps, 60hz for 30fps

 One annoyance I found with auto changing of refresh rates, was that when
 you switch inputs in live tv, it would switch gui to resolution/refresh
 only to switch back to the same resolution and refresh rate on the new

 To work around that I introduced a new setting GuiVidModeRefreshRate in
 the style of the other mode settings. If you set that to the likely TV
 refresh rate (50hz in my case in PAL land), you avoid the switch cycle.
 Read support for GuiVidModeRefreshRate is in the patch, but no gui
 configuration of it.

Ticket URL: <http://svn.mythtv.org/trac/ticket/5643>
MythTV <http://www.mythtv.org/>

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