Aspect ratio for VCD/SVCD/DVD

There are four aspect ratios defined for the mpeg standard
  1. 1:1
  2. 4:3
  3. 16:9
  4. 2.21:1
If you want to create a VCD/SVCD/DVD and the aspect ratio of the source video is not one of the four values permitted, you need to change the aspect ratio of the source video otherwise the encoded video will be distorted.
There are two ways to change the aspect ratio of a movie: pad or crop.
Imagine your source video is 576x288 (aspect ratio 2:1) and you want to create a 16/9 NTSC DVD (720x480).
If you are padding the video you have to add 36 horizontal black lines (576x324 aspect 16:9) and scale to 720x480.
If you are cropping the video you have to cut 64 vertical lines (512x288 aspect 16:9) and scale to 720x480.
If you pad the video, all the original video will be visible on the screen, but part of the screen will be black.
If you crop the video, the complete screen will be used for the video, but you will loose the borders of the original video.
In encode2mpeg add:
-mpegfixaspect pad
if you intend to pad the source video, or add
-mpegfixaspect crop
if you intend to crop the source video.

Image rotation

In order to rotate the image of the final mpeg stream add the option 
-rotate 0-3
to the command line. The different values of the argument do the following:
0 rotate clockwise and flip
1 rotate clockwise
2 rotate counterclockwise
3 rotate counterclockwise and flip
this option will set automatically -mpegfixaspect pad because the aspect ratio of a rotated image usually changes (4/3 -> 3/4). You can specify crop adding -mpegfixaspect crop. The option -rotate works only in Avi Mode and Mpeg Mode.

TV overscan zone

On a TV, 5-10% of the edges of the image are not visible. If your movie has some items close to the borders (subtitles, etc.), probably you will not see them on a TV. The option 
-overscan n
will shrink the encoded image of n%. A value between 5 and 10 will let you see on a TV the complete video image. This option will set -mpegfixaspect pad.
It is also possible the give a negative argument to -overscan. The effect is a magnification of the video image (the content close to the borders will be removed). In this case the option -mpegfixaspect crop will be set.

Top