DivX Fast-Motion

[SuSE]

i've two qustion:
why shouldn't i use fast-motion, although i can get better results and smaller files?
and
is there any method to find out the correct bitrate for example for 1 cd (if you calculate the bitrate as normal the file is much smaller)?

[Schultz]

there is no bitrate calculator for fast-motion codec because of the codec being so unpredictable. As the Low Motion can be somewhat predictable since it generally stays around the bitrate that you set.

[diji1]

Hi SuSE,

1 - I personally dont use the hi-motion codec at all...
but i seem to remember reading somewhere ( can't remember where, sorry ) that the low-motion codec looks
better than hi-motion *regardless* of the amount of motion occurring on-screen at bitrates of 1000 - 1500 and upwards.

So if you consider that the average movie at 1 CD size is say 900, and most of the time in the average movie theres not a lot of motion ( theres exceptions as always ) i think your better off not using it at all, although maybe in some movies it leads to a better balance between quality/filesize...be debateable i think.

I pretty much always do 2cd rips regardless of movie length and i have tested using the hi-motion codec on a movie with lotsa motion the whole way through ( handheld cam the whole way through - yeah, ok, it was pr0n ;) ) - this movie was really hard to compress, i used 1250 bitrate for a 2cd rip..... for this movie use of the hi-motion codec definitly led to a reduction in quality even at this bitrate.

2 - I assume you're not using gknot to encode your movies. I used to use nandub..... man am i glad i changed to gknot :). I'm really impressed with this app. I've only done 4 dvds using it so far, but every time time the final avi has been within 100K of what i entered as the desired file size be... and i've felt that i have been able to make a better choice of resolution as well

Check the guide at doom9 for gknot info :)

Take it easy! :)

[LotionBoy]

Fast Motion gives smaller files for a simple reason. It uses higher Data Reduction Factors than the low motion codec. Which means it always compresses more than the low motion codec and gives smaller files. Honestly, you shouldn't be using either codec for DVD conversion, you should be using something like Nandub or Fairuse that makes use of both codec (or in Nandub's case, kinda makes the two obsolete).

For smaller shorter stuff (like short films and animatics for my work) I use Low motion at 1500 because it looks damn good and for short files it doesn't make too large of a file

To summarize:

Fast Motion is bad because it cannot handle slow detailed scenes in movies.
Low Motion is bad because it makes action scenes too big.

If you are going to use just one codec, use low motion because fast motion will always look worst in the most noticable areas. But use FairUse or Nandub for the best looking stuff

LotionBoy

[pdontthink]

diji1, it is interesting that you always go with 2CDs.
I would be interested to hear why (it's what I do as
well, although there are people who say that if you do
that, why not move to VCD or SVCD format, since you can
also play it on a standalone player).

You might want to respond in a more appropriate thread:

http://forum.doom9.org/showthread.php?s=&threadid=13988

Cheers!

[movmasty]

@SuSE why shouldn't i use fast-motion, although i can get better results and smaller files?
and is there any method to find out the correct bitrate for example for 1 cd (if you calculate the bitrate as normal the file is much smaller)?
1)why shouldn't you use fast-motion?

2)since fast motion has a max "Details Removing Factor" 0f 5,
it cant go beyond a certain file size.
then also if you set a higer bitrate, the codec cant match it.

same thing happens with the low motion, but at a very higher level,
since low motion uses a min drf of 2(rhat is the min drf of mpg4,mpg1 and 2 have also drf 1).
i mean that if you use,e.g.,a bitrate of 5000kb,then raising it at 6000kb, wont produce an higer size.

if you would like to do a fast 1pass encoding,"fast motion style",
but with higer quality and higer size limit,
i suggest you to encode in nandub,
setting min DRF to 4, and max to 8