yuvdenoise(1)
NAME
yuvdenoise - Motion-Compensating-YUV4MPEG-frame-denoiser
SYNOPSIS
yuvdenoise [options] </dev/stdin >/dev/stdout
DESCRIPTION
yuvdenoise can be used to remove noise from movie images
in an YUV4MPEG2 stream. This is usefull to reduce the
bitrate needed to encode your captured movies for VCD and
SVCD creation.
OPTIONS
yuvdenoise accepts the following options:
- -v Verbose
- You will get some statistical information on the
input video-stream as mean-SAD so far and the
average SAD of the last image. Additionaly you
will have a translation of these values on a sin
gle Pixel (Noiselevel). - -r Maximum Search Radius
By adding this option you may limit the search
radius. Search radius may internally be reduced by
the algorithm depending on the quality of the cen
ter match.- yuvdenoise -r 16
- This sets the maximum search radius to 16 pixels.
- -I Deinterlace Only
This turns off the denoiser completly. Only the
deinterlacer (if needed) and the black-border-code
remain functional. This gives a great speed-boost
if you don't want to denoise but only to turn bor
ders black and/or to deinterlace.- -B B&W Mode
This is usefull if your material is (our should
be) B&W only. This flag does turn color-MC and all
Chroma off. This should help the encoder to save a
few bits when such material is used. Especially if
your recording does come from an old videotape or
a bad TV-transmission.- -? Display Help
Displays a brief description of the available
options.- -b Border Setting.
If you allready know parts of the image are and
remain black all over the complete sequence of
images, you may use something like this:- yuvdenoise -b 16,16,704,560
- This will set all the pixels in the image outside
that search window to absolute pure black. The
area outside the search window will not go into
the motion compensation algorithm and therefor you
might have a speed gain in processing the movie. - Sometimes it may be usefull to have relative coor
dinates like this: - yuvdenoise -b 16,16,-16,-16
- Provided there is a PAL-frame with 720x576 pixels
both options will turn the same area into black.
HOW IT WORKS
Yuvdenoise works by temporal lowpass filtering. To avoid
motion-blur it transforms the previous image with a
motion-compensation as close as possible to the present
frame. This motion-compensation is performed on 4x4 pixel
blocks. The result is wightened and a block of the trans
formed previous frame is (depending on a matching coeffi
cient) either taken in full, blended with the present
image-block or discarded if the match is to bad.
This procedure implies that the motion-compensation is
very exact. If a video-encoder misses a transformed block
it's not that bad, it only encodes a difference block
there. If the denoiser fails to find a good matching
block, the only solution is to exchange the found block
with the original frame block. Therefor a great amount of
time is spent to find good matches. This is the main rea
son why the denoiser does not run at full framerate at CIF
resolution as you might have wished.
TYPICAL USAGE AND TIPS
As it is self-adapting to the noise-situation found in the
stream you normaly just can go without any options set:
lav2yuv my-video.avi | yuvdenoise | mpeg2enc -t 1 -o myvideo.m1v
However, to obtain the best possible result, you should
take care of the following:
1. Grab at the maximum possible resolution (PAL 768x576
pixels). Even do this if you just want to create a 352x288
pixel movie as downscaling reduces noise, too (and at no
cost to image-quality and/or sharpness in that case).
2. First denoise, then scale! There are some rare situa
tions where the denoiser itself may introduce artefacts
(blocks, etc...). The perceptibilty of these artefacts is
reduced by this processing order.
3. If your movie contains black borders use the -b option
to turn them into real black. This helps the encoder a
lot.
4. You can greatly improve the recorded quality if you use
correct cables. Only use HF-in (the antenna-cable ...) if
you really can't connect your VCR/Camcorder by other means
(Composite, S-Video or best SCART-RGB).
5. If your movie is B&W only, then try the -B switch.
Having that sayed, I normaly use a command-line like this
one:
lav2yuv movie.avi | yuvdenoise -b 8,64,-8,-64 | yuvscaler
-O SIZE_352x288 | mpeg2enc -f 1 -o movie.m1v
Have a lot of fun! ;-)
AUTHOR
This man page was written by Stefan Fendt <stefan@lion
fish.ping.de>.
FURTHER INFOS
If you have questions, remarks, problems or you just want
to contact the developers, the main mailing list for the
MJPEG-tools is:
mjpeg-users@lists.sourceforge.net
For more info, see our website at
http://mjpeg.sourceforge.net/