[mythtv-users] HD deinterlacing
mythtv.org at sethdaniel.org
Mon Oct 1 18:57:55 UTC 2007
On Mon, Oct 01, 2007 at 11:48:15AM -0700, Jon Boehm wrote:
> 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.
Apparently some stations (notably CBS and NBC here in the States)
broadcast commercials at a different encoding. This fools Mythtv into
displaying the wrong run time. I think this also affects the speedups
you are seeing (and I am also seeing...typically directly after a
commercial break (at least in my case)).
seth / @sethdaniel.org
I either want less decadence or more chance to participate in it.
More information about the mythtv-users