Re: More than 64kbps

Marc Lindahl (shark@dti.net)
Thu, 28 Nov 1996 03:31:31 -0500


>o ATM - up to 622.000 Kbps - Perfect Sound and Video Quality.

Actually, ATM is a protocol, like TCP/IP (kinda -- flame anyone?). Popular
transports run it at 25Mbs (desktop), 155Mbs (OC1, could be coax or FDDI
fibert), and 622Mbs (OC3, fiber). But, you could run ATM over another
digital links, like SCSI, Firewire, RS422, whatever. Just wouldn't have
anyone to hook up to!

>o SDSL - 2048 Mbps

Actually you missed a decimal point, it's 2.048Mbs. This is used by the
telcos to run T1 lines over ratty twisted pair. Often, it only achieves
half that rate.

HDSL -- promises 100's of Mb/s over short twisted pair (like 50ft from
house to curb)...

>A broadcast of a screen at 1024x768x16.777.216 and 30 frames per second
>means a minimum of 566.000 Kbps.

Well, calm down! NTSC video is about 480x640/30fps (actually 240x640/60
fields/s). So then you get about 28MB/s max, or 280Mbs. And that's with
no compression! JPEG every frame by 3:1 (you won't even notice!) and you
get less than 100Mbs -- 100-base-T ethernet rates!

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