Doom9's Forum - View Single Post

Didée · 31st March 2011, 13:37

@hydra - did you see my comment about colorizing a B/W picture, then printing it to a B/W printer? That was not a mere joke. That was an analogy.

For purposes of downscaling,

Code:

xdest = 720
ydest = 576 # or 480
Spline36resize(xdest,last.height)
Bob(newheight=ydest).SelectEvery(4,0,3).Weave()

does a pretty fair job. Anything more exhaustive will yield only marginal improvement.

For the (very rare) case of interlaced upscaling, like 576i -> 1080i, it's a completely different story.

Main point#1 is that an interlaced source has 50% of data missing (not considering lowpassing). QTGMC is a sophisticated method to interpolate those missing 50% as good as possible.
At the moment you do re-interlacing, you are throwing away 50% of the data again. Poof!

Main point #2 is the kind of de-interlacing used during playback of an interlaced stream. Most realtime deinterlacers are using rather "simple" methods, and therefore can't cope well with "sharp" interlaced sources. That's why lowpassing usually is done before re-interlacing. This makes the job for the deinterlacer much more easy, so even the most simple ones can deliver an acceptable result.

31st March 2011, 13:37	#558 \| Link
Didée Registered User Join Date: Apr 2002 Location: Germany Posts: 5,391	@hydra - did you see my comment about colorizing a B/W picture, then printing it to a B/W printer? That was not a mere joke. That was an analogy. For purposes of downscaling, Code: xdest = 720 ydest = 576 # or 480 Spline36resize(xdest,last.height) Bob(newheight=ydest).SelectEvery(4,0,3).Weave() does a pretty fair job. Anything more exhaustive will yield only marginal improvement. For the (very rare) case of interlaced upscaling, like 576i -> 1080i, it's a completely different story. Main point#1 is that an interlaced source has 50% of data missing (not considering lowpassing). QTGMC is a sophisticated method to interpolate those missing 50% as good as possible. At the moment you do re-interlacing, you are throwing away 50% of the data again. Poof! Main point #2 is the kind of de-interlacing used during playback of an interlaced stream. Most realtime deinterlacers are using rather "simple" methods, and therefore can't cope well with "sharp" interlaced sources. That's why lowpassing usually is done before re-interlacing. This makes the job for the deinterlacer much more easy, so even the most simple ones can deliver an acceptable result. __________________ - We´re at the beginning of the end of mankind´s childhood - My little flickr gallery. (Yes indeed, I do have hobbies other than digital video!)