NAME

       y4munsharp - Unsharp filter for YUV4MPEG2 streams

SYNOPSIS

       y4munsharp [options]

DESCRIPTION

       y4munsharp  is  an  implementation  of  the   GIMP  unsharp  filter  for  YUV4MPEG2 streams.  The usual 3
       parameters for unshap mask processing (radius, amount and threshold) are specified on the  command  line.
       By  default  only  the  Y'  (luma) component is processed although processing of the CbCr (chroma) may be
       requested by a commandline option.  Output must be either to a pipe  or  a  file,  leaving  stdout  as  a
       terminal will elicit an error and the program will exit.

OPTIONS

       y4munsharp accepts the following options:

       -v num
            Set verbosity level (0 = quiet, 1 = normal, 2 = debug) (default: 1)

       -h   Print a suage summary and exit

       -L radius,amount,threshold
            Y'  (luma)  unsharp  parameters.   The radius and amount" arguments are floating point numbers.  The
            threshold argument is an integer.  (default: 3.0,0.3,4)  -C  radius,amount,threshold  CbCr  (chroma)
            unsharp  parameters.   The  chroma  is not processed unless this option is given.  Arguments are the
            same type as for the -L option above.  (default: none)

       -N   Filtering can produce output outside the 16 to 240 range for Y' and 16 to 235 for CbCr.  By  default
            values  outside  the  legal  range  are  clipped/cored  (values  over  240 for Y' are set to 240 for
            example).  Using -N the limits 0 and 255 are used instead.

EXAMPLES

       A mild setting:
       y4munsharp -L 2.0,0.3,0

       An aggressive setting:
       y4munsharp -L 5.0,0.5,0

NOTES

       The radius, amount, threshold parameters have the same meaning as the GIMP's unsharp plugin.  This  means
       you  can  use the GIMP on selected frame still images to determine suitable settings for y4munsharp.  The
       key thing to remember is to be subtle - you just barely want to notice the  sharpening  effect.   If  the
       effect is obvious ("jumps out at you") then the parameters are set too aggressively.

       The  chroma  is  not  processed  for  a several reasons:  1) The eye is much more sensitive to changes in
       brightness,  2) the chroma is usually subsampled and doesn't contribute much to the  perceived  sharpness
       of  an  image  -  so  not processing the chroma provides a boost in speed of processing the image, and 3)
       possible artifacting - changes in Y' just make an image brighter/darker but  changes  in  Cb  or  Cr  can
       change   colors and possibly lead to shifts in hue.  Use the -C option to enable processing of the chroma
       planes.

BUGS

       Only the 3 plane YUV4MPEG2 formats are supported.

       Only progressive, top field first or bottom field  first  interlaced  streams  are  handled.   The  mixed
       interlaced stream format is not supported.