Anyone know about video over a network? MPEG-4 compression?

[kranky]

If you are taking video at 640x480 with MPEG-4 compression, and 10% of the picture changes from frame to frame, is only that 10% difference transmitted over the network? And that is a better choice than MJPEG compression, right?

I'm trying to figure out if what I want to do will not suck up too much network capacity, but it appears the compression has more to do with the answer than simply calculating bits/frame x frames/second. Just looking for some guidance if anyone is familiar with it.

 

[jiggahertz]

I'm not familiar with MPEG-4, but in general MPEG works by transmitting a motion field and the resulting motion compensated error. Each of these are then coded. So it depends on the entropy of these 2 fields. I'm not sure how accurate a "X% of the picture changes is". Additionally, there are a bunch of other parameters that can be tweaked (MQUANT), that will change your compression ratio.

 

[jiggahertz]

Also, you're not just transmitting the changes. Anchor frames (I think they're called B-frames) are transmitted to avoid error propagation.

 

[kranky]

Thanks, jiggahertz.

I'm going to use a network camera to look at a control panel. The only thing that would change in the picture is some lights going on or off and that would mean only a small number of pixels would change from frame to frame. I'm hoping that with MPEG-4, I could get a high frames/second without a lot of bandwidth being needed.