Posted by Jukka Aho on 12/09/06 18:17

Citizen Bob wrote:

> I have an MPEG-2 clip from a VOB that is 11 minutes in duration.
> It is 765 MB in size. The frame size is 720x480 [...] I converted
> it into an AVI/XviD with Auto Gordian Knot [...] It looks just as
> good in VLC on a 20" CRT monitor as the original. [...] The file
> size is about 1/2 the original, which means I can get the same
> content on half the number of DVDs, which is a significant savings
> in DVD disc cost.

Note that if your original material was shot in interlaced format, with
an interlacing video camera (home video is usually like this) you have
just lost half of the temporal resolution. All motion will be twice as
juddery in the XviD file. (Converting interlaced video from 720×480 to
720×400 implies deinterlacing, which typically causes this kind of
effect - unless the frame rate is upped to the field rate in the
conversion, which most people don't even think of doing.)

You probably can't see the difference on a computer screen, though.
Computer video players will usually deinterlace interlaced material on
the fly, anyway, so the playback of your original file is compromised as
well - on a computer screen. But the difference should be obvious if you
make a DVD out of the original material, play it back on a regular tv
set, and compare that to the converted material. The original clip
should have a noticeably smoother, fluider feel to it in any segment
with fast pans or zooms, or lots of action.

--
znark

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