[mythtv-users] Interlaced playback problems

Mark Murray marklmurray at gmail.com
Sat Aug 25 23:37:41 UTC 2007

On 8/25/07, Chris Weiland <hobbiticus at gmail.com> wrote:
> I have 2 problems:
> 1) When I play some programs, interlace detection will flip on and off
> frequently, as often as once every 2-5 frames.  If I run the frontend with
> playback verbosity, it keeps alternating that it is detecting short strings
> of interlaced/progressive frames.  This is easily fixable by setting the
> video scan to interlaced as opposed to "detect", but it's still annoying to
> do it since it's happening so often.  Could this be a problem with the
> stream?  It only seems to happen on recordings from my cable box that is
> connected via firewire.
> 2) Bob deinterlacing is not quite working.  It's like the picture is jumping
> up and down by a pixel or two on each frame.  It is very noticeable in HD
> and even more so in SD.  I also get a lot of these lines when running with
> playback verbosity (on the order of one per second):
> NVP: Video is 3.0885 frames behind audio (too slow), dropping frame to catch
> up.
> I also get:
> 'video_output' mean = '33251.45', std. dev. = '13619.02', fps = '30.06'
> Also, my CPU is not maxed out - it jumps around between 40-60%.  This
> happens when I set the video scan to detect or force it to interlaced.
> I'm running mythtv 20.2, checked out from svn just last night, but this
> problem has been around since I installed mythtv on a dedicated machine - I
> was able to use bob deinterlacing perfectly when I was trying it out.
> Any suggestions?

I don't have any suggestions, but I thought your post was a good
opportunity to talk about a similar issue I'm having - it may be the
same, or at least a related issue.

I notice Myth not respecting my Bob setting on all recordings I make
with my Avermedia A180 DVB card of the QAM256 channels off my cable

There was some discussion of this a while back on a ticket (not really
the place for discussion) about this and it seemed that a theory was
that something in the stream coming from the cable company was
'tricking' myth into thinking the signal was already de-interlaced, so
it was turning off de-interlacing where it didn't think it was needed.

The fact that you're seeing the problem with the stream off your
firewire would seem to indicate that it's a similar problem, although
for me, it seems that de-interlacing isn't working at all for my DVB
recording of Comcast's sream.

There was some indication in the afore-mentioned discussion on the
ticket that this issue had been fixed in SVN (I'm using -fixes, too),
but I'm none too confident that the person who said that was really
referring to the actual problem that was being discussed - then he
closed the ticket.

More information about the mythtv-users mailing list