Is your footage interlaced?
I don’t believe you are suggesting the edges are bad but that the overall image is soft.
If your footage is interlaced, make sure your footage is set to Lower fields first for NTSC and that the rendered is also set this way.
You can also try to to separate fields to none and render no fields as long as your final output is interlaced this should also work.
Now are you using a high quality codec, most people suggest qt animation but tent to use photojpg at about 98 percent.
either way depends on disk space.
good luck