Is there a difference between "null packet" and "zero-length packet"?

[jb]

USB Audio, MIDI, and Debug Class specs mention null packets:

In any case, the
endpoint is required to support null packets. This bit must be used by the Host software to determine if the
driver should pad all potential short packets (except null packets) with zero bytes to wMaxPacketSize
length before sending them to an OUT endpoint.

but don't define it anywhere that I can see. Is it the same thing as a zero-length packet?

[Jan Axelson]

same thing