re: VDig differences

Simon Biggs (
Tue, 6 Dec 1994 03:58:30 -0500

>Dear CUSM fans
>Having made an unsuccessful request for help for people using CUSM with the
>Mac Videovision card, I can only conclude I am (almost) on my own (some
>others indicated they would be interested in answers).
>For info, I also tried CUSM0.60b1 which looks for any VDIG - It found the
>Videovision VDIG but said it "Couldn't digitize".]
>I guess my problem is a specific instance of a generic problem i.e. CUSM
>seems to only support a (very) limited set of VDIGs. Being a naive and
>optimistic non-techy I had believed the Apple PR when they claimed that the
>use of Quicktime would allow the hardware to be abstracted to a level where
>applications could be made hardware independent. (The theory seems to work
>with most other applications.)

I am not an expert on this, and have always used CU-SeeMe with the AV's inbuilt
digitiser. I also am not familiar with how the Videovision VDig is setup.
However, there is one important difference between some VDig's, even those that
support Quicktime. It is true that QT abstracts the hardware so that its
components (the routines that interface QT to the hardware) can control QT
compatable cards. However, that is not the end of it. Some VDig's live in
strange places (in terms of where they are in RAM) and can have an effect on
how RAM is used relative to VRAM. It is possible that CU-SeeMe requires that
application RAM is used for buffering video information. If so, then if the
Videovision VDig is setup to use System Ram to do this then it will not work,
or not work properly. I know this is the case with the Videospigot (although
that will work, but not properly - crashes can abound, etc). Check out the
Videovision VDig to see where it buffers video data. And try to find out what
CU-SeeMe's requirements are in that area. Thay may be the cause of a conflict.

>Now I understand CUSM does some really smart things in order to do what it
>does, but could it not be a little more well behaved? Does anyone know if
>the issue is:
>a) the cost and time to validate support on other cards?
>b) its on the list to be done - just be patient?!
>c) a technical reason why it wouldn't work?
>If it is (a) then I for one would be very happy to help with alpha or beta
>testing. If it is (b) then I'll just shut up or if it is (c) I'll shut up
>and buy a Quickcam (and add to the growing waiting list).
>Advice pls!
>andy mcleod

I guess you have to remember that CU-SeeMe is shareware/freeware (I'm not sure
which) and that therefore you cannot expect it to perform as well as a piece of
commercial software (although in my experience it is better than a lot of
commercial packages). It is up to the kindness of its developers that it is
what it is.

Simon Biggs
little pig productions
54 Heysham Rd
London N15 6HL
44.81.880 1805 (voice/fax)