Re: Relationship between fps and Kbps

Adrian Winnard (
Tue, 31 Dec 1996 13:59:21 +0000

>>Does anyone know why there can be high Kbps being sent between two people
>>on DC connection yet the fps is prctically nothing? What is the
>>relationship? I know that the fps is the frame grabbing rate and not the
>>send rate but what the heck are you sending at 30Kbps if you are only
>>grabbing 0.1fps? On the other hand I can be grabbing lots of frames and
>>sending low Kbps, or low on both figures.
>>Also I can sometimes be indicating a receive of .1 or .2fps but am getting
>>a complete frame of movement despite the low figures.
>>This is on a connection with someone who is accessing via a T1 connection
>>but both machines are set to the same send and receive of 28Kbps because of
>>my modem limit.
>>The software just doesn't seem to be able to share the bandwidth evenly at
>>all. Sometimes my vid gets through well apparently but then hardly moves
>>for a long while. The vid I receive seems more consistent but still varies
>>a lot.
>In my experience, this is a function of your processor and video speed,
>especially the processor speed. Using the same connection at work on two
>different machines, I have been able to get between 10kbps and 15kbps
>from a particular reflector. One machine is a 486DX/4-80 and the other
>is a Pentium 120. On the 486, I usually see between 0 and 1 fps, but on
>the Pentium, I get 5 to 7 fps. Again, this is the same reflector, the
>same connection, just different machine speeds.
>I've also been told by White Pine that processor speed is the number one
>factor in how fast your video refreshes (ie frames per second).
> Mark

I don't think that processor speed is the whole story because the processor
demand shouldn't be varying so much yet I can be grabbing 13fps for a short
while then 0.0 then 2.1 then 0.1 for a lot of the time. And as I said
before what am I sending at a good rate of Kbps if the frame grabbing is so

FreePPP shows fantastically high Bps rates during Cu-SeeMe sessions with
occasional peaks well over 100,000 despite being on 28k dial up modem, so
there is no shortage of communication going on!

My processor is a 120mhz PPC and grabs 22fps using camcorder or up to 15fps
with QuickCam when "waiting". BTW I am using Cornell free 0.85b1 (PPC).

The machine sending to me (at a better rate) is a slower 68K Mac!