What font is best for full screen closed captions?

Question

I'd like to upload some closed caption audiobooks to YouTube where the video is simply the subtitles for the text being read. [Here's an example].

What design would best suit this purpose?

I'm pretty set on a simple design: single font, plain background, etc.
In particular, what set of the following best suits my purpose?:

1. font face
2. background color
3. font size
4. margin size
5. font color

Answer 1

Since this is screen reading where the text itself changes outside of the control of the user, I would look at the Guidance on Standards for Subtitling:

• Basic Text Display Subtitle legibility studies result in the following requirements:

  • Teletext characters should be displayed in double height and mixed (upper and lower) case.
  • Words within a subtitle should be separated by a single space.
  • (White) text should normally be presented in a black box
  • The standard punctuation of printed English should be used. Punctuation gives valuable clues to syntactic structure and must be carefully displayed in order to be effective.

• Colour

  • The majority of text/background colour combinations are not satisfactory for subtitling, being insufficiently legible. The most legible text colours on a black background are white, yellow, cyan and green. Use of magenta, red and blue should be avoided.

• Formatting

  • A maximum subtitle length of two lines is recommended. Three lines may be used if the subtitler is confident that no important picture information will be obscured.
  • Ideally, each subtitle should also comprise a single complete sentence.

More examples in the linked article.

Answer 2

It's a good idea. Although, I would change two things in the example video you offered:

1. Lower case is more readable.
2. slow the speed to help the reader-listener process since first we tend to verify the resemblance between text and audio and afterwards we try to understand what was saying.