[mythtv] lots of interlacing recently...
myth at dgreaves.com
Mon Aug 9 04:06:18 EDT 2004
Chris Petersen wrote:
>> What does "interlaced" mean?
> basically, every other line belongs to the next frame, which give the
> picture a very jagged appearance if it's not displayed on the intended
I think BM was asking rhetorically :D
I've seen some problems with PAL interlacing too, also through s-video.
All recoverable nicely but not your normal 50fps interlaced video ->
25fps full mpeg frames interlacing. This is more of an offset by one,
25fps film -> 25fps mpeg
I wasn't going to bring it up here but since you did...
Have a look at the ivtv
My first assumption was (is) an ivtv driver bug but it may also be a
If the former then it's ivtv - if the latter then I guess it's a Myth
Here's how I described it:
Lets look at an mpeg frame grabbed by a PVR50
It contains all 576 lines from two consecutively broadcast interlaced
frames (lets call them 1 and 2) Remember this frame I'll call it (I)
Now lets look at the next full frame grabbed 1/25th second later.
It too contains all 576 lines from two consecutively broadcast
interlaced frames (lets call them 3 and 4) Remember this frame too I'll
call it (II) - no pun intended.
Now imagine this is a video (50fps) source.
frames 1,2,3 and 4 all belong to different timepoints. (see diagram 1 on
Jonathan's reference page) There is no way to avoid using deinterlacing
algorithms - tough, live with it (I know, but luckily this *isn't* what
I'm on about)
Now imagine this is a film based source (lets call it 25fps because of
some trickery that broadcasters use.)
Now those 4 frames span either 2 or 3 film frames (call them a,b and c)
[remember we progress 1/50th second between each char.]
or like this:
In the first situation if you have frames 1&2 (ie film frame a) in your
mpeg frame (I) and 2&3 (film frame b) in mpeg frame (II) - a wonderful
reproduction of the original film. This will play back well on a
In the second situation you have frames 1&2 (ie a blend of film frame a
and film frame b) in mpeg frame (I) and frames 2&3 (a blend of film
frames b and c) in mpeg frame (II) - really horrible blurry mpeg that
will always look bad on any progressive scan player - but which will
play back well on a PVR350.
What type of de-interlacing fixes this?
I've heard "reverse telecine" - does one of Myths filters provide this?
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