Aspect ratio for VCD/SVCD/DVD
There are four aspect ratios defined for the mpeg standard
- 1:1
- 4:3
- 16:9
- 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 (NTSC DVD).
If you are cropping the video you have to cut 64 vertical lines
(512x288 aspect 16:9) and scale to 720x480 (NTSC DVD).
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.