[x264-devel] Re: x264 vs JM 7.5c encoding results

[Tuukka Toivonen]

On Thu, 30 Dec 2004, Loren Merritt wrote:

> Is there any particular reason you're using JM 7.5 as opposed to 9.2?

None good, just that
- I don't think 9.2 has improved much coding quality since the standard
   is anyway fixed now. I suppose they're mainly fixing bugs and adding
   support for some esoteric features like error resilience?
- I had JM 7.5 and the coding results already on my disk; it's so slow
   that doing the tests would take quite a long time.

> "--subme 5" always helps, usually by around 5%. (Though I usually test on D1,

Indeed, it helped greatly, 8-10% with these sequences.
IMO, --subme 5 should be the default.

> not CIF. You might see a different amount of improvement.)

There aren't many standard sequences with higher resolution than CIF,
it would be nice if others could repeat the tests (->standard sequences).

> "-A all" usually helps, though it's not guaranteed.

I used that.

>> P.S. I wonder what are the major reasons for difference between the two 
>> encoders?
> Mostly that JM uses rate/distortion optimization, whereas x264 uses SATD.
> JM also uses a slower motion search.

So x264 doesn't use rate distortion to either mode selection nor the motion
vector estimation? Why not? I don't think that RD-optimization is so slow,
at least for motion estimation. It's just a table lookup and an addition to
the SAD/SATD per one checking point.

I updated the results at
http://www.ee.oulu.fi/~tuukkat/mplayer/tests/x264test/readme.html
included also --subme 5 this time.

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