What setting to use for Standard Definition...

[xbox360]

Hello I am using the x264.exe, what is the lowest setting I can use for Standard Definition just before the picture quality goes bad ?

I want to maximize the compressability of my encoded video, but still maintaining quality.

Curently I am just using:

--output video.264 --bitrate 1500 --progress --pass 1
--output video.264 --bitrate 1500 --progress --pass 2

[xbox360]

Is this setting's any better ?

--output video.264 --bitrate 1500 --progress --pass 1 --ref 5 --bframes 4 --b-bias 50 --subme 6 --no-chroma-me --me umh
--output video.264 --bitrate 1500 --progress --pass 2 --ref 5 --bframes 4 --b-bias 50 --subme 6 --no-chroma-me --me umh

[audyovydeo]

Is this setting's any better ?

--output video.264 --bitrate 1500 --progress --pass 1 --ref 5 --bframes 4 --b-bias 50 --subme 6 --no-chroma-me --me umh
--output video.264 --bitrate 1500 --progress --pass 2 --ref 5 --bframes 4 --b-bias 50 --subme 6 --no-chroma-me --me umh

You've *gotta* do some more reading on the subject.
Briefly, however, there are 3 things you must be aware of :

1. source picture quality
2. file compression
3. your eyes

in x264, some settings determine how much of the original quality is preserved, others affect how much the file is compressed.
So, to answer your question :

"what is the lowest setting I can use for Standard Definition just before the picture quality goes bad ?"

1. it depends on your eyes
2. it depends on the source.

That is, you can experiment and identify the best settings for a given footage below which your eyes will say "NO". However, these settings will be completely useless on a different source.

Imagine the different compressibility of a hollywood fast-action movie /vs/ a 1970's french nouvelle vague film, with 1.5h of quasi-static people staring into each other's eyes.
Get the idea ?

If you follow other threads you'll see people using anything from crf18 to 24.
My suggestion, inspired by your settings :

--crf [18 to 22 test around a bit] --ref 4 --bframes 4 --subme 6 --me umh

Forget 2-pass unless storage is a problem for you.

cheers
audyovydeo