From the same article, referenced from the Wikipedia page:
"Worse yet, after explaining the echo cancellation to a hostile audience and how it could be done, the same young engineer then had the audacity to suggest that 160 kb/s was too slow, and they really ought to consider a much higher speed, enough for video at perhaps 1.5 Mb/s, much closer to Shannon capacity for a four-mile twisted-pair telephone connection, at least in the toward-customer direction. The laughter was thunderous, and the kid was embarrassed beyond belief (particularly when even his own boss told him to “shut up and sit down”). But that was modern DSL's birth. I know well — that kid was me."
Seems even more precient to have realized video could be sent at 1.5Mbps in 1980. H.120, which operated at that rate, was published in 1984. But I guess DCT-based compression for videotelephones was being researched from around 1975, so I assume 1.5 Mbps must have been demonstrated by that time. Ironically, H.120 doesn't even use DCT but DPCM, which was pretty much obsolete by 1984. That's standards committees for you.
H.120 used that bitrate to be able to send video over a T-1. MPEG-1 used it to be able to encode video on a CD. But even though they're about the same, the bitrate of a CD has nothing to do with the bitrate of a T-1, though it DOES have something vaguely to do with video, since 44.1kHz is the highest sample rate compatible with both NTSC and PAL without requiring more than 3 samples per line, so it's the rate digital audio was recorded at at the time.