How do I remove letterboxing from a video file?

Question

Or add? Is the a free program that can do this without losing resolution?

Answer 1

No-one else is trying so I'll take a stab at this.

First of all, you should recognize that many films are shot and intended to be viewed in a widescreen format. Any attempt to reduce this width distorts or removes part of this image and therefore compromises the film.

Letterboxing fill in the top and bottom of a frame to make the picture portion of a widescreen image fit the aspect ratio (ratio of width to height) of a different shaped (usually more square) screen / monitor / TV. Most commonly it is visible when used for widescreen films (2.20:1 > 2.55:1) when they are viewed on a standard TV (4:3), but they will still show up on an HDTV (16:9). Note this is one way of bridging two, in a visual sense, incompatible technologies.

Can it be removed? Well, yes and no.

The easiest way to "remove" it is to show the video via a front projector on a screen that matches the widescreen aspect ratio of the picture portion of the video and use the zoom lens to just fill the screen. The black bars on top and bottom are then allowed to fall outside the top and bottom of the screen and, assuming the surrounding background is dark coloured, they will disappear.

Another way is to blow up the image so the top and bottom of the picture portion fit the top and bottom of the screen. Unfortunately this means that a portion of the picture on the right and left will be lost off to either side of the screen. This is similar to how widescreen films are converted to full screen. The difference is that the editor continually adjusts (or pans) to select the most appropriate portion of the film (rather than simply accepting the centre). This is the basis of "pan and scan" (do a Google search on the term).

Another way is achieve this if using a TV is to use the zoom control to pick an aspect ratio / setting that fills the screen.
Note, however, that this technique means you lose some of the picture, and sometimes (often?) this is part of the image you don't want to lose.

On a TV one or more of the common zoom settings will stretch (or compress) the image more in one direction than another ... resulting in tall skinny people or short squat ones, or in non-linear distortion more visible at the extremes. Personally I find these settings unwatchable, but some prefer them to simply losing part of the image.

The point I'm trying to make is that letterboxing is normal. It is required to match an image filmed in one aspect ratio to a different aspect ratio screen. Given that films /videos are made in a wide range of formats (including 4:3, 5:4, 16:9, 1.85:1, 2.2:1, 2.25:1, 2.40:1, 2.55:1) for any chosen screen aspect ratio bars will be required on either the sides or the top and bottom of all films other than those that match the screen. While most screens are either 4:3 (standard definition TV) or 16:9 (HDTV) unless you are prepared to only watch program material that fits exactly you are going to see letterboxing.

My advice is to accept that directors intend the film to be viewed the way they shot it and simply get used to it.

That said it is more difficult to ignore letterboxing when viewing a widescreen film on a small SDTV. Since the world is moving that way, and prices are tumbling consider purchasing a larger screen HDTV, or a front projector, to achieve a larger image.

Hope this didn't miss the intent of your question.

Answer 2

There are no black stripes in the original to be removed to begin with.

Lets say your original video resolution is 1280x680. Since your HDTV is, say 1280x720, the TV fills all horizontal pixels, but it is left with extra 40 lines, which are shown black.

There is no way to go from 1280x680 to 1280x720 unless you do some cropping and scaling, which means losing some of the original pixels