wtf? it does encode in 'joint stereo'

[Bertone]

i just realized that gordian knot does not use "-m s" to encode the mp3-streams in stereo.

after demuxing a stream out of one movie it read "joint stereo" in winamp.

so, do i have to change the parameters and add "-m s" manually?

[Doom9]

in lame using joint stereo is actually a good idea

[Bertone]

doom9:

oh. hm. i am encoding mp3s for the last 6-7 years, i always thought its about the badest thing you can do to an audio-stream. might be wrong with that.
why? and why in lame?

thanks for answering that fast

[Gabriel_Bouvigne]

Because 6 years ago Lame was not available, and so there was perhaps no high quality joint-stereo implementation available

[Bertone]

Gabriel_Bouvigne:

ok ok. maybe joint stereo is not what i thought it is. possible.
could you explain it to me? or give me a link?

[Gabriel_Bouvigne]

In mp3 joint stereo is any combination of stereo, intensity stereo, middle/side stereo.

In Lame only m/s stereo is implemented, so lame decides for each frame between stereo and m/s stereo only.

What is m/s stereo:

if l and r are similar, then encode m and s instead of l and r.
m = (l+r)/sqrt(2)
s = (l-r)/sqrt(2)

transformation from lr to ms is totally loseless and so reversible.
It is just a way to save a few bits.

What is IS: (not present in lame)
higher part of the spectrum is encoded as mono, and angular position of the signal in stored. This technique always destroy pro logic info.

[Bertone]

Gabriel_Bouvigne:

thanks. i think i got it now.