Re: Win95 Codec Questions

Jason Williams (streak@ccwf.cc.utexas.edu)
Tue, 30 Jun 1998 17:47:16 -0500 (CDT)


On Tue, 30 Jun 1998, Brian K. Dowtin wrote:
> Questions about Win95 and Video Codecs

Since you're dealing with the Cornell version...keep in mind that the
grayscale codec is the only one that's builtin. Unlike the WP version,
Cornell doesn't use an external codec for grayscale.

> 1. Are all codecs able to compress as well as decompress?

As far as I know, they can.

> 2. If not - how does Win95 know the difference?

There may be certain system calls to let you know if you can compress
and/or decompress. I'm not sure since I haven't done any Windows systems
programming.

> 3. What are the 'n' things that must be done to let Win95 access a codec?
>
> eg. (1) add VIDC.codec=codec.dll to system.ini
> (2) etc..

It may/may not be as simple as that. I played around with that awhile
back. Just adding to the system.ini didn't seem to do it for me. You
have to "register" the codec in the registry (one of those long strings).

The best way I've learned to poke around is to take a look at the way
Paradigm Matrix distributed the MJPEG codec (http://www.pmatrix.com). The
OEMSETUP.INF files are fairly straight forward. I tried uninstalling the
H.263 codec once to try and figure out why the Cornell 1.0 version can't
seem to see H.263 Mac senders using the 3.1.0.31 Mac version. Instead of
reinstalling 3.1.1.016, I decided to play with the OEMSETUP.INF file from
MJPEG. I got it re-installed within a matter of 5-10 minutes.

> 4. What makes a codec 'usable' by Cornell Cu-SeeMe? Unusable by CU-SeeMe?

Here's some excerpts from Steve concerning the codecs:
"Everytime it starts, V32X scans to see if the following codecs are
installed: IV32, IV41, IV50, MJPG, and VX1K. The VX1K codec (H.263) will
not show up in the combobox of V32X's Video tab, as V32X can't currently
send that codec. But, the rest, if installed, should show up there."

"When it starts, V32X tries to open (and then close) each codec it "knows
about" using the VFW API call ICOpen(). A parameter of ICOpen() is the
Four Character Code (FourCC) of the codec being opened."

--
streak@ccwf.cc.utexas.edu    * Jason Williams -- Austin, Tx.  |     |
streak@mail.utexas.edu       * University of Texas at Austin  | ___ |
streak@cs.utexas.edu         * BS Computer Science             \_|_/
*************** http://ccwf.cc.utexas.edu/~streak/ **************|