Posted by Citizen Bob on 12/09/06 16:41

On Fri, 08 Dec 2006 19:05:30 GMT, "T Shadow"
<NoOne@nonono.com.invalid> wrote:

>if you take the MPG2 and convert it to MPG4 you'll get the loss of 2
>compressions but not a significantly smaller file size than the MPG2.

I do not know what you mean by "significantly smaller".

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 and the bit rate is 10
Mbits/sec (10000 Kb/s). I converted it into an AVI/XviD with Auto
Gordian Knot using two-pass conversion at a resolution setting called
1/2 CD, which yields a 350 MB file size.

If I choose the one-pass resolution and set it at 10%, the file size
drops to 358 MB and the resolution is 720x400, 4335 Kb/s. It took 39
minutes on my 2.4 GHz machine. It looks just as good in VLC on a 20"
CRT monitor as the original. The Qf is 0.4 compared to 0.9 for 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.

Next I rendered it in AGK using one-pass with a setting of 30%. MPEG-4
uses a variable bit rate to deal with fast motion, so if there is no
fast motion, two-pass rendering is not really needed - which is most
of the time for ordinary content. I have used one-pass many times ans
have never run into a problem with dropped frames. The file size is 92
MB, the frame size is 720x400 and the bit rate is 884 Kb/s. It took 20
minutes to render and has Qf = 0.1. For a 19" viewscreen 1,000 Kb/s is
considered the minimum. Amazingly it looks just as good as the
original and the 2-pass rendering in VLC on my 20" CRT monitor.

So there you have it - a significant file size reduction from 765 MB
down to 92 MB, almost a factor of 10. And yet the video looks every
bit as good in the highly compressed version as the original.


--

"Yet the legislative being only a fiduciary power to act for certain
ends, there remains still in the people a supreme power to remove or
alter the legislative, when they find the legislative act contrary to
the trust reposed in them....And thus the community perpetually retains
a supreme power of saving themselves from the attempts and designs of
any body, even of their legislators, whenever they shall be so foolish
or so wicked as to lay and carry on designs against the liberties and
properties of the subject."
--John Locke

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