TTL high input, outcome?
It looks like the video is showing a configuration where the emitter of an NPN transistor is grounded, and the transistor turn on when a positive base voltage is applied.
The TTL book you mentioned is probably talking about an open emitter configuration, with the emitter being the input and the base connected to a positive supply voltage, through a resistor.  In that case, the emitter needs to be grounded (or taken low) in order to turn on the transistor.
This picture from TI's &quot;Designing With Logic&quot; book 1997, shows a typical open-emitter input stage for a TTL device.

EDIT 1 - Let Me Try
Let's focus on Q1.  The base of Q1 is tied to Vcc (+5V in these devices) through R1.  Forget about the collector of Q1 for now.
Think about these two questions:

What happens to Q1 if the emitter is left open?  Is Q1 turned ON or OFF (ignoring secondary affects like leakage)?

With this circuit, how would you turn Q1 ON?  What does the emitter have to be connected to, or what voltage needs to be applied to the emitter in order for Q1 to turn ON - to start to conduct?