[MEncoder-users] new doom9 codec comparission (also questions for Doom9)

Corey Hickey bugfood-ml at fatooh.org
Fri Dec 2 01:40:18 CET 2005

Well, I finally went and rented The Matrix and started messing around.
For now I'm concentrating only on mpeg4 -- I'll deal with the exciting
part (snow) later. Also, if someone else can provide a nice windows
binary, I'd appreciate it; I have little experience in that regard and
probably couldn't do as well as many others on this list.

I have several questions and things to comment on.

First, the questions for Doom9.

1. The test is using the original Matrix, right? Not one of the sequels?

2. Encoding the audio using Lame 3.96.1 gives me 127632KB which is
rather different from the 157455KB listed in the 2003 codec comparison.
This is probably due to my Lame being newer and/or the way liba52
downmixed the 5.1 audio when I extracted it from the DVD. When you
perform the test, are you going to use our Lame encoding method or your
own? If you are going to use our methods for the whole process, then
I'll shoot for a final filesize of 716800KB and provide the commands for
each step. If you are going to use your own tools, then can you give me
a target video bitrate to shoot for? You can then mux the
mencoder-created video with your own audio and the filesize should end
up being correct.

3. Are the cropping and scaling parameters going to be the same as in
the 2003 codec comparison?

4. The 2003 comparison used a bicubic scaler; the 2004 comparison used
lanczos. What method are you going to use this time?

5. How soon do you want to get results from us?

Next, questions for mplayer people.

1. I don't know much about postprocessing. On the encoding I'm doing
right now, pp=ac looks a little less blocky than pp=fa. Does anyone have
a good recommendation?

2. As I mentioned before, can someone please provide a Windows binary?

3. I seem to recall that multithreaded encoding incurs a slight penalty
to quality (or, at least, psnr). Do any particular lavcopts make
multithreaded encoding better or worse? If not, I'm just going to find
the best options I can with only one thread and, as a final step, test
threads=2 to make sure nothing blows up.

Last, some comments.

Right now I'm testing the following command:
for i in 1 2 ; do
  time mencoder ~/dumpstream/matrix.vob -aid 128 -oac copy \
-vf crop=718:356:0:60,scale=640:272 -ovc lavc -lavcopts \
cbp:precmp=2:cmp=2:subcmp=2:predia=2:dia=2:preme=2:vme=5:v4mv \
-ofps 24000/1001

I encoded the audio separately with Lame. I'll mux it back in later --
right now I want to isolate video encoding performance. The cropping and
scaling parameters are from the 2003 codec comparison. Bitrate is from
2003 as well; I might have to refine it slightly based on the response I
get from Doom9.

With the above command, I'm getting about 36 fps on an Athlon64 3400+
overclocked to 2544 MHz. That seems like a reasonable framerate and is
about mid-range among the framerates listed in the 2004 codec comparison
on an Athlon64 3500+ (the movie in that test was The Matrix Revolutions,
but it should be similar).

I will investigate qns=2; if it looks much better I might recommend it,
depending on the fps hit. I may recommend turbo for the first pass, if
it doesn't look worse.


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