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

[Loren Merritt]

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

On Thu, 30 Dec 2004, Tuukka Toivonen wrote:

> x264 gives typically 14% (8-16%) higher bitrate in average than JM at the 
> tested PSNR levels and QP values, making it much worse. On the good side, 
> although I didn't specifically test for speed, x264 was staggering fast. It 
> was capable encoding about 30 fps CIF realtime on my Athlon 2 GHz, whereas JM 
> is hopelessly slow (hundreds of times slower).
>
> Let me know if I made some mistake (not optimal options in x264 or such)
> or if the results just look wrong.

"--subme 5" always helps, usually by around 5%. (Though I usually test on 
D1, not CIF. You might see a different amount of improvement.)
"-A all" usually helps, though it's not guaranteed.

> 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.

--Loren Merritt

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