difference between "constant quality" and "constant quantizer"

[zz2]

Sorry for this n00bish question, but what is the difference between "constant quality" and "constant quantizer" in x264? I have source with many still pictures and I gues constant quality/quantizer would be better because it can really lower the bitrate in still scenes and increase it in high motion ones.

[foxyshadis]

http://forum.doom9.org/showthread.php?p=760285#post760285 The discussion following this should clear it up.

[DarkZell666]

Try this too :

http://forum.doom9.org/showthread.php?t=107687

--cqp is constant quantizer
--crf is constant rate factor (aka constant quality)