pammixinterlace - Man Page

• Merge each row in an image with its two neighbours: pammixinterlace path/to/image.ppm > path/to/output.ppm
• Use the specified filtering mechanism: pammixinterlace -filter linear|fir|ffmpeg path/to/image.ppm > path/to/output.ppm
• Turn on adaptive filtering mode, i.e., only modify pixels that are obviously part of a comb pattern: pammixinterlace -adaptive path/to/image.ppm > path/to/output.ppm

tldr.sh

pammixinterlace

[-filter={linear, fir, ffmpeg}]

[-adaptive]

[infile]

This program is part of Netpbm(1).

pammixinterlace is meant to operate on an image which is the interlacing of two images, where raster rows 0, 2, 4, etc. are from one image and rows 1, 3, 5, etc. are from another.  (See below for why you might expect to encounter such an image).

pammixinterlace makes each row of the output a mixture of the corresponding row of the input and its two neighbors.  It uses half of the main row and a quarter each of the two neighbor rows.

This can be useful if the image is a video capture from an interlaced video source.  In that case, each row shows the subject 1/60 second before or after the two rows that surround it.  If the subject is moving, this can detract from the quality of the image.

In video data streams, you often find each frame contains only half the rows of the image -- the odd half or the even half.  The displayer of the stream displays the rows in their proper positions on a CRT as they come in.  When you display the rows in this order, the CRT has less flicker because a particular area of the screen gets refreshed twice as often.  In the process of capturing such a stream, computers often generate the interlaced image of the type that pammixinterlace works with.  But this interlaced image, when displayed on a CRT, does not look the same as if a displayer were rendering the stream directly on a CRT as it arrived, because of the timing of when the various pixels get drawn and subsequently fade. That's why you need something like pammixinterlace.

You may prefer the effect of simply extracting one of two images. You can do that with pamdeinterlace.

In addition to the options common to all programs based on libnetpbm (most notably -quiet, see Common Options ), pammixinterlace recognizes the following command line options:

-filter={linear,fir,ffmpeg}

This option chooses between one of the three filtering mechanisms. linear is a linear-blend formula.  fir is a size-5 FIR low-pass filter, and ffmpeg is a formula pulled from the documentation of the program ffmpeg .

The default is fir.

-adaptive

This option turns on "adaptive" filtering mode.  In this mode pammixinterlace modifies only pixels that are obviously part of a "comb" pattern.

pamdeinterlace(1), pam(1) pnm(1)

This manual page was generated by the Netpbm tool 'makeman' from HTML source.  The master documentation is at

http://netpbm.sourceforge.net/doc/pammixinterlace.html

pamdeinterlace(1).