[mythtv-users] HD deinterlacing

[Jon Boehm]

Ryan Steffes wrote:
> On 10/1/07, Tom Dexter <digitalaudiorock at gmail.com> wrote:
>> On 10/1/07, Phil Vid <phil.vid at gmail.com> wrote:
>>> Using bob, it feels like the video is slightly sped up at times. When
>>> there is no motion, it seems fine but then when a scene change occurs
>>> it seems like things speed up slightly even though the audio sounds
>>> fine.
>> I've been using bob for quite some time with my RP CRT TV.  Since my X
>> is outputting 1080i doing so required the unsupported change described
>> here:
>>
>> http://www.gossamer-threads.com/lists/mythtv/users/285404#285404
>>
>> Only recently I started noticing the slight speed-up of video like
>> you're describing, though it seemed in my case to be specific to NBC
>> HD broadcasts.  Just as you describe, the video would speed up
>> temporarily without disturbing the audio.  In some cases it would
>> happen when jumping forward or back, as though the specific keyframe
>> it was starting from made a difference.  I never used to see this at
>> all and it doesn't occur with other deinterlacing methods.  However,
>> it appears that I've found a way to correct it.  Today I had an NBC
>> recording where I could reproduce this issue.  I tried adding "+hsync
>> +vsync" to the end of my mode line and now I have no problems with
>> this using bob.
>>
> 
> Did your recording show the correct length?  I've noticed a problem
> that I haven't started to track down where recordings (again,
> predominantly NBCHD, which is why I asked) have periodic burst of
> faster motion.  The length of the show itself shows as being shorter
> than it should be, though.  For example, an hour long show may show as
> being 53 minutes long and when watching it, there's occasional bursts
> of slightly sped up video.  It's not particularly annoying to me, so I
> haven't really started figuring out what's going on; I watch most
> shows at 1:1.15 anyway.
> 

Thought I would chime in here.  I have noticed this behavior.  However 
mine is not with NBCHD it is with CBS_HD prime time.  The program length 
is usually 5 to 7 min shorter than reality.  ( As an aside, Lettermen 
later in the evening doesn't have this problem.)  Usually the visual 
artifacts shows up when returning from a commercial break.  I've noticed 
that turning off Opengl vsync fixes the slowdown/speedup problem.  In 
addition, I've noticed that BOB is not keeping up with these problem 
recordings.  I see the interlacing artifacts during rapid motion 
possibly in relation to a scene change.  I can tell BOB is working since 
I can see the vertical hopping on occasion, but it just not keeping up.

I wonder if Comcast or the local affiliate are messing with the CBS 
stream, or if my HDHomeRun is having problems with the QAM steam.

Jon