r.out.mpeggrass - Online in the Cloud

PROGRAM:

NAME

r.out.mpeg - Converts raster map series to MPEG movie.

KEYWORDS

raster, export, animation

SYNOPSIS

r.out.mpeg
r.out.mpeg --help
r.out.mpeg [-c] view1=name[,name,...] [view2=name[,name,...]] [view3=name[,name,...]]
[view4=name[,name,...]] output=name [quality=integer] [--overwrite] [--help]
[--verbose] [--quiet] [--ui]

Flags:
-c
Convert on the fly, uses less disk space
Requires r.out.ppm with stdout option

--overwrite
Allow output files to overwrite existing files

--help
Print usage summary

--verbose
Verbose module output

--quiet
Quiet module output

--ui
Force launching GUI dialog

Parameters:
view1=name[,name,...] [required]
Name of input raster map(s) for view no.1

view2=name[,name,...]
Name of input raster map(s) for view no.2

view3=name[,name,...]
Name of input raster map(s) for view no.3

view4=name[,name,...]
Name of input raster map(s) for view no.4

output=name [required]
Name for output file

quality=integer
Quality factor (1 = highest quality, lowest compression)
Options: 1-5
Default: 3

DESCRIPTION

r.out.mpeg is a tool for combining a series of GRASS raster maps into a single MPEG-1
(Motion Pictures Experts Group) format file. MPEG-1 is a "lossy" video compression
format, so the quality of each resulting frame of the animation will be much diminished
from the original raster image. The resulting output file may then be viewed using your
favorite mpeg-format viewing program. MPEG-2 and MPEG-4 provide much better quality
animations.

The user may define up to four "views", or sub-windows, to animate simultaneously. e.g.,
View 1 could be rainfall, View 2 flooded areas, View 3 damage to bridges or levees, View 4
other economic damage, all animated as a time series. A black border 2 pixels wide is
drawn around each view. There is an arbitrary limit of 400 files per view (400 animation
frames). Temporary files are created in the conversion process, so lack of adequate tmp
space could also limit the number of frames you are able to convert.

The environment variable GMPEG_SIZE is checked for a value to use as the dimension, in
pixels, of the longest dimension of the animation image. If GMPEG_SIZE is not set, the
animation size defaults to the rows & columns in the current GRASS region, scaling if
necessary to a default minimum size of 200 and maximum of 500. These size defaults are
overridden when using the -c flag (see below). The resolution of the current GRASS region
is maintained, independent of image size. Playback programs have to decode the compressed
data "on-the-fly", therefore smaller dimensioned animations will provide higher frame
rates and smoother animations.

UNIX - style wild cards may be used with the command line version in place of a raster map
name, but wild cards must be quoted.

A quality value of quality=1 will yield higher quality images, but with less compression
(larger MPEG file size). Compression ratios will vary depending on the number of frames in
the animation, but an MPEG produced using quality=5 will usually be about 60% the size of
the MPEG produced using quality=1.

Example

r.out.mpeg view1="rain[1-9]","rain1[0-2]" view2="temp*"

If the number of files differs for each view, the view with the fewest files will
determine the number of frames in the animation.

With -c flag the module converts "on the fly", uses less disk space by using r.out.ppm
with stdout option to convert frames as needed instead of converting all frames to ppm
before encoding. Only use when encoding a single view. Use of this option also overrides
any size defaults, using the CURRENTLY DEFINED GRASS REGION for the output size. So be
careful to set region to a reasonable size prior to encoding.

KNOWN ISSUES

MPEG images must be 16-pixel aligned for successful compression, so if the rows & columns
of the calculated image size (scaled, with borders added) are not evenly divisible by 16,
a few rows/columns will be cut off the bottom & right sides of the image. The MPEG format
is optimized to recognize image MOTION, so abrupt changes from one frame to another will
cause a "noisy" encoding.

NOTES

This program requires the program mpeg_encode (aka ppmtompeg):

MPEG-1 Video Software Encoder
(Version 1.3; March 14, 1994)

Lawrence A. Rowe, Kevin Gong, Ketan Patel, and Dan Wallach Computer Science Division-EECS,
Univ. of Calif. at Berkeley

Available from Berkeley: http://biowiki.org/BerkeleyMpegEncoder
or as part of the netpbm package (ppmtompeg): http://netpbm.sourceforge.net

Use of the -c flag requires the r.out.ppm GRASS module with the stdout option.

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