Up: SGI movie Frequently Asked Questions (FAQ)
Next: -33- I want to write a program which can create a JPEG- compressed movie file compatible with the Cosmo Compress board, SGI's hardware JPEG accelerator. How do I do this?
Previous: -31- How do I write a program to read and write compressed data to a movie file?
Subject: -32- I want to write a program which creates a JPEG-
compressed movie file, but I need to control the
compression quality. How do I do this with the Movie
Library?
Date: Fri May 3 11:05:05 PDT 1996
As of IRIX 6.2, there are additional parameters that you can pass
in to mvAddTrack to control the compression quality:
DM_IMAGE_QUALITY_SPATIAL, DM_IMAGE_QUALITY_TEMPORAL, DM_IMAGE_BITRATE.
Note that not all codecs support all of these parameters.
JPEG in particular, supports only the SPATIAL setting.
(Certain Apple codecs support both TEMPORAL and SPATIAL quality
settings; CinePak also supports the BITRATE setting.)
Additionally, you can do the compression yourself (as could be
done prior to IRIX 6.2): create a movie file with all the appropriate
image track parameters (see above), But instead of simply writing
frames to the movie and letting the Movie Library automatically
compress the frames for you, you handle the compression yourself.
To do the compression yourself, you open a Compression Library JPEG
compressor, set the quality factor, and use it to compress each
frame. Then you write the *compressed* data to the movie file
(see above for instructions on how to do this).
The tools (dmconvert/makemovie/movieconvert) support these settings
in Digital Media Tools 5.5 (see the first question in this FAQ) and
IRIX 6.2.
Up: SGI movie Frequently Asked Questions (FAQ)
Next: -33- I want to write a program which can create a JPEG- compressed movie file compatible with the Cosmo Compress board, SGI's hardware JPEG accelerator. How do I do this?
Previous: -31- How do I write a program to read and write compressed data to a movie file?