Roll-up Captioning vs. Pop-on Captioning: Which is better?
With roll-up captioning, entire lines of text roll in a continuous, upward motion. Most often, only two to three lines of text will appear at a time, with each new line bumping the text upward to replace the top line. This type of captioning is not synchronized to the video, and is most suited to live events or pre-recorded presentations with a limited number of speakers.
Pop-on captioning allows a deeper dimension of synchronization to the video, which can be particularly helpful to the hard of hearing. With pop-on captioning, the phrases or sentences spoken by each person are timed, and often positioned, to synchronize with the program and help identify the speaker.