Overview
On SGI systems, a plugin is available which calls the dmconvert utility
to save data in the QuickTime and SGI movie formats.
Topics
Overview |
Frame rate |
Compression |
Quality |
Bit rate |
Key frame interval |
Directory |
Command line
Related Priism Topics
Image Capture |
3D Model |
Priism
Use the frame rate option for the dmconvert plugin to specify, in frames
per second, the default frame rate of the generated movie.
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If you are generating a QuickTime movie, the available compression schemes
are:
- None
- The generated movie is not compressed.
- Photo (JPEG)
- Compresses each frame of the movie separately with
the standard JPEG lossy compression algorithm. The
quality parameter controls the lossiness of
the compression.
- Motion JPEG A
- Uses a variant of the JPEG scheme adapted for use
with digital video. The
quality parameter controls the lossiness of
the compression.
- Animation (RLE)
- Compresses the movie with a lossless (run-length
encoding) scheme appropriate for sequences of drawings.
- Video (RPZA)
- Compresses the movie with a lossy compression scheme
designed for desktop video. Both the
quality parameter and
key frame interval affect the lossiness of
the compression.
- Compact Video (Cinepak)
- Is like the Video (RPZA) scheme but
decompresses more quickly at the expense of much longer compression times.
For this compression scheme, you can choose to either maintain a
constant image quality (set via the
quality parameter) or a constant amount of data
per image (set via the bit rate parameter). The
key frame interval also affects the
lossiness of the compression.
- Indeo
- Applies Intel's Indeo compression algorithm. Both the
quality parameter and
key frame interval affect the lossiness of
the compression.
If you are generate a SGI format movie, the available compression schemes
are:
- None
- The generated movie is not compressed.
- JPEG
- Compresses each frame of the movie separately with
the standard JPEG lossy compression algorithm. The
quality parameter controls the lossiness of
the compression.
- RLE
- Applies a lossless compression scheme (8-bit run-length encoding).
Best used for a sequence of rendered or drawn still images.
- RLE24
- Is similar to RLE but uses a 24-bit scheme.
- MVC1
- Is a lossy algorithm which typically compresses by a
factor of 5 (generally worse than JPEG does). The
quality parameter controls the lossiness of
the compression.
- MVC2
- Is a lossy algorithm with similar image quality to MVC1 but
much better compression ratios: typical files are compressed by a factor
of 20.
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The quality parameter affects the image quality for lossy compression
schemes. Valid values are in the range of 0.01 to 0.99 where 0.25 is low
quality, 0.5 is normal quality, and 0.75 is high quality. The size of
the compressed file decreases with decreasing quality.
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Some lossy compression schemes allow you to specify a bit rate (the
effectively the amount of data used to represent each frame) in order
to control the lossiness of the algorithm. A higher bit rate gives better
quality but less compression. Valid values of the bit rate range from 100000
(100 kilobits per second) to 4500000 (4.5 megabits per second).
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A larger interval between key frames will give a higher level of
compression and quicker playback than a smaller key frame interval. A
smaller key frame interval is useful if you wish to stop and start the
movie to examine individual frames. Valid key frame intervals are from
1 to 60 frames.
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The directory parameter controls where the dmconvert plugin writes the
temporary image files which it then combines to form the movie. You may need
to adjust the directory parameter if that directory does not have sufficient
space to store the images.
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When Image Capture is run from the command line on an SGI, you can use
-format=qt
as an option to Image Capture to have it generate a QuickTime movie or
-format=sgimv
as an option to Image Capture to have it generate a movie in the SGI format.
To further control the output, you can append any of the following to
the -format option (when appending first insert a comma: i.e.
-format=qt,frate=5,compress=cvid
):
frate=frames_per_second
- Sets the suggested playback rate; frames_per_second can
be any value between 0.25 and 99. When you do not set the playback rate,
the playback rate for the generated movie will be 15 frames per second.
compress=algorithm_name
- Sets the compression algorithm to use. For QuickTime movies, the allowed
values for algorithm_name are none, jpeg, mjpega, anim, video,
cvid, and indeo. For SGI movies, the allowed values for
algorithm_name are none, jpeg, rle, rle24, mvc1, and mvc2.
For more information about each algorithm, consult the
compression topic.
qual=quality
- Sets the quality of the output when the movie is decompressed.
Valid values for quality range from .01 to 0.99 where .01 is
very low quality and 0.99 is very high quality. If you use no compression
or lossless compression, the quality option has no effect. With the
QuickTime compact video compression algorithm, you can either set a
constant image quality using this option or a constant bit rate using the
brate option; if you specify both, the one that appears last takes
precedence. If you do not set the quality (and either do not use the
QuickTime compact video compression or do not specify a bit rate), you
will get output with a constant decompressed image quality of 0.75.
brate=rate
- Sets the desired bit rate for the QuickTime compact video compression
algorithm. Valid values for rate range from 100000 to
4500000; the default value is 1158000. This option has no effect when
used with any of the other QuickTime compression algorithms and will
generate an error if used with the SGI movie format. If you use the
QuickTime compact video algorithm and do not specify this option, the
generated movie will have constant decompressed image quality and will not
have a constant bit rate.
kdist=key_frame_interval
- Sets the key frame interval to use
with the QuickTime animation, video, compact video, or indeo compression
algorithms. This option does not affect any of the other QuickTime
compression algorithms and will generate an error if used with the SGI
movie format. key_frame_interval can be any integer value
between 1 and 60. If you do not set the key frame interval, the generated
movie will use a key frame interval of 5.
dir=directory
- Sets the directory where temporary image files are stored. If you
do not specify where to store the temporary files, they will be placed
in the directory named by the TMPDIR environment variable or, if that
variable is not set, in /var/tmp.
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