[mythtv] Internal DVD player incorrectly detects video scan (interlacing)

Matt Doran matt.doran at papercut.biz
Thu May 31 12:46:15 UTC 2007

Matt Doran wrote:
> David Asher wrote:
>> The internal player always starts off in interlaced mode, then follows
>> the flags provided by the video blindly.  It looks like this DVD's
>> video is clearly stating it is progressive scan.  Every frame is
>> saying progressive.  Unfortunately, many DVD's are authored
>> incorrectly.  (See The Secrets of Home Theater website for a VERY
>> involved discussion of the complexities of deinterlacing and how badly
>> DVD's are often authored)
>> My guess is that this is not a very solvable problem in the current
>> state of things.  I would love to learn enough to know how to DETECT
>> mis-flagged video like the Faroujda (sp?) hardware solutions do in
>> higher end DVD players, but I haven't had the time.
I've done some further investigation, and I'm not sure that the DVD is 
at fault.   I've tried playing it in mplayer and xine and both look fine.

I'm starting to think this is a problem with the bob deinterlacing.   If 
I use another deinterlacer (like kernel) I don't get the poor output.  
Could this be some bad interaction between bob and the dvd video?  In 
addition to the ugly playback when bob is enabled, I also see some 
tearing.   But as soon as I override the video scan and set it to 
interlaced, it looks good again.

This evidence seems to suggest that it's not the video scan detection 
that's the problem, but the bob deinterlacer?  I don't have any idea of 
how all the components work together, but could the bob deinterlacer 
still be enabled even though it shouldn't be?? 

Any thoughts?


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