I found the Recommended encoder setting is --alt-preset standard and so on.
I searched the lame help file, but which do not explain the meaning for "-alt". lame's help file just sugget use --preset standard.
What's the difference between them? And what's the -alt stand for?

There was a point of time where the lame devs refused to accept --alt-preset as the 'standard' to use. That has changed though, now --preset is the same as --alt-preset (although i'm not sure if it's the same for the ABR presets), but since most of us are already used to --alt-preset, it stuck.

If I remember correctly it's ''alternate".

that means the lame version after 3.90.3 the --alt-preset is the same as --preset ?

No from 3.94 onwards (which in release versions means 3.95 onwards).

No. There was a point of time where Dibrom refused to have his presets under the --preset switch because of the existance of other presets with lower quality.


From 3.93 and newer.

And that includes 3.90.3 as it was released later than 3.93.

Actually only the modified 3.90.3 includes the --preset switches for Dibrom's presets. Vanilla 3.90.3 uses the 3.90 lame.exe frontend AFAIK.

dev0

This is correct. I back-ported the synonyms and the 'medium' presets.