On Thu, 2 Nov 2006, [ISO-8859-15] Bernhard Fr?hmesser wrote:
> I have recorded a really old Video from a VHS Tape (recorded about 25
> years ago).
With a tape that old I'm almost positive you'll need to do some
color correction. Maybe PAL tapes age differently than NTSC but
my experience has been that tapes more than a few years old need
correction.
> The video is in really bad condition, and i have been playing around
> with the mjpegtools to improve quality but nothing was really satisfying.
It also appears that the tape was either damaged OR the VHS deck's
heads scratched the tape.
> So far i played around and tested a bit with yuvmedianfilter, yuvdenoise
> y4munsharp.
sharpening is almost never a good idea with poor quality or noisy
video. The sharpening (edge enhancement) emphasizes the noise and
makes the picture look worse than before.
medianfiltering the chroma only, then using yuvdenoise with moderately
high thresholds (-t 6,10,10 and perhaps even add -m 4,8,8) will help
with the noise but there's not a lot to be done about the scratches
or lines.
> I have two pictures from the source online, they are available at:...
> You can see black lines (first picture) and white lines (second ...
> Is it possible to remove or reduce these lines and do an
> overall image improvement for the whole video.
That type of damage is not "noise" so the tools you've been trying
to use will not be effective. Yes, you could blur the lines out of
existence but that would remove almost all the picture detail as well.
You're going to need to go frame by frame with something like
Photoshop (or the GIMP?) and fix the damaged area with a small (just
a couple pixels whide) brush/pencil. I think the 'healing' tool in
Photoshop would work well but the 'clone stamp' could do nicely as
well. Probably want to de-interlace the video first though,
dealing with interlaced data in graphic tools is difficult.
IF the lines are consistently in the same place then it could be
possible to 'automate' the process (I know Photoshop can "record your
actions" and then play them back over a directory of images - maybe
the GIMP can do the same thing?).
But dealing with thousands of still frames is a pain, so a 'video
stream' capability would be preferable.
Are the lines in the same place during the duration of the movie? If
so then it might be possible to write a program to clone pixels from
a (very) nearby location over the scratch/lines. If you're using
FinalCutPro there is a "clone area" plugin available from
http://www.cgm-online.com/eiperle/cgm_screenshots_v3_e.html
scroll down to "CGM clone area"
The other idea is video compositing software - something like Shake
http://www.apple.com/shake/
(which I am told is available for linux - but I do not know if the
price is the same as for OSX)
could probably be programmed to do scratch/line removal.
OR find someone to write a scratch removal filter for mjpegtools :)
Hmmm, there is some software at Inria
http://www-sop.inria.fr/odyssee/research/tschumperle-deriche:02d/appliu/
that might be useful - but it's basially a library that would need
some wrapper code to interface to a Y4M stream.
Cheers,
Steven Schultz
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