>hmm... further, is the Example 6 supposed to be the standard way to convert
>between 4:3 & 16:9 videos?
It's one example of such a method. There are many different possibilities.
>I tried to apply the mechanism to convert a 640x480 @ 4:3 video back to
>720x DVD video, but get a 720x540 one instead of the original 720x576.
>Why the difference? Here is how I calculate:
>
>The 640x480 @ 4:3 video has 60 pixels black border on top and bottom. So I
>"use the -j option to change the size of the input video before the zoom
>is performed. ", as in Example 4. That'll give me 640x360 @ 4:3.
Actually, it gives you 640x360 @ 16:9. -j and -Y change the frame size
without changing the PAR, so the DAR must change.
>The output frame sizes would be
>
> width = 720
> height = (PAR * width ) / DAR = ( 1/1 * 720) / (4/3) = 540
>
>If there is no distortion during the 2 DAR conversion, the result should
>be exactly 720x576. What's wrong here?
Leaving aside the DAR issue, you're using the wrong PAR. As I mentioned
before (and as is also mentioned on the main "aspect ratio" page), DVDs
do not use a PAR of 1:1. In fact, since DVD players adjust their PAR to
match the video's frame size and DAR, there is no need to perform these
calculations at all; you just need to resize the video to the proper DVD
frame size with -Z and use the proper --export_asr code, as in Example 2.
--Andrew Church
[EMAIL PROTECTED]
http://achurch.org/
