4

There are usually two rectangles over videos before the final video is released. I guess they might be there to help the camera operator.

  • What purpose do they serve?
  • Do they have a specific name?

Here is an example:

enter image description here

2

These are cropping lines. Most DVD creation software will automatically crop a video to the outer box, which is sometimes referred to as the "Image-Safe Area". The inner box (aka the "Title-Safe Area") is used for placement, so your titles and shots aren't running the risk of bleeding beyond the picture frame.

For more info, take a look at Item #4 on this page:

http://www.westcler.org/gh/hammereric/Video%20I/Notes/titles_graphics.htm

  • I've never heard of authoring software actually doing the cropping, and I'm pretty sure that Sony Vegas never did. It's just the CRT overscan would put stuff behind the bezel. The (admittedly few) DVDs that I've authored have all had the entire image on the DVD (visible inside a computer playback window) but then on CRT televisions wouldn't show the whole image. Can you support the assertion about the authoring software actually cropping the image? – Todd Wilcox Jul 10 '16 at 15:11
2

Historically, these "safe areas" were used in TV because as picture tubes get older, they tend to expand the image. Therefore, things on the edge of the picture--outside the "safe area"--would be lost when viewed on an older set. The inner box is a border for text, to make it even safer. Today's screens don't really have that problem, but I have seen some that will crop the image a bit by default.

  • Even when new, different CRT designs would show different amounts of screen area. – Todd Wilcox Jul 10 '16 at 15:06
1

Both the history and the modern revision of the title safe and action safe boxes that can be displayed in most video editing software are authoritatively explained in a document put out by the National Association of Broadcasters (NAB) in 2010 (emphasis mine):

From the early days of film and television, it has been recognized that not all of the information contained in the original image frame will necessarily be presented to the viewer. In television, the principal limitation has been the use of overscan in the viewer‘s receiver.

In 1957, the SMPTE Journal included a paper entitled Television Receiver Picture Area Losses, in which the author, Charles Townsend, describes research conducted at NBC‘s WRCA-TV in an effort to determine the extent of the broadcast image that was actually seen in viewers’ homes. The paper is reproduced in Annex B. Note that the safe area the author suggests is based on the assumption that all elements within the safe area will be viewable on at least 85% of receivers; no attempt is made to ensure viewability on 100% of receivers.

Television broadcast technology and consumer television equipment strangely stayed the same for many (more than 30) years, and then dramatically changed over the course of a decade or so. Now things are very different from the original study, and so the safe areas have had to be updated.

Later on in the document linked above, the current standard for image safe and title safe boxes is summarized:

SMPTE ST 2046-1 defines the Safe Action Area as a rectangle that is 93% of the width and 93% of the height of the Production Aperture (or 720 x 480 in the case of 480-line formats) and concentric with it. The Safe Title Area is defined as a rectangle that is 90% of the width and 90% of the height of the Production Aperture (or 720 x 480 in the case of 480-line formats) and concentric with it.

The EBU (European Broadcasting Union) has specified the exact same safe areas in their most recent document on the subject. The EBU uses the term Frame Raster Edge instead of Production Aperture and Graphics Safe Area instead of Title Safe Area.

Note: SMPTE stands for "Society of Motion Picture and Television Engineers", which is a body that has determined and published specifications for TV and film technology for a very long time.

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