hello, i know almost everyone got tired of this discussion. but i'm still a bit confused. can some one explain stereo and joint-stereo in a simple manner? and does anyone know a pragram that could tell the real MODE(stereo or joint-stereo) of an MP3? another silly newbie question.

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regular (discrete) stereo:

both channels are independent of each other, but share a common bit-reservoir (so if one channel uses 56 of a possible 128kbps, the other channel can get 72)


dual mono (not often seen):

independent channels, and bitrate is split 50/50. pretty much the same as 2 different files muxed together.


MS joint stereo:

Middle/Side stereo. 2 full bandwidth channels, one consisting of left+right and the other left-right. this gives a sum and a difference. it is useful because most music has a very simple stereo image, so large bitrate savings can be made in the difference channel and put into the sum channel (which is mono).

this is a reversible process, so if the encoder is good you wont "lose" anything (in fact, lame -aps gives a better difference signal than a lot of Dolby Digital audio, but that's probably due to the implementations rather than the tech).


IS joint stereo:

Intensity Stereo. this is a little complicated. basically it gives a mono and a limited bandwidth "intensity" stream that "pushes" the mono signal around. think of twiddling the balance knob on your stereo extremely fast. this isn't implemented in LAME, but is in FhG codecs (the sole reason they perform better at lower bitrates IMHO). i don't really know the ins and outs of IS stereo, but a similar effect can be found in FM stereo, so for reference you could listen to some of that.



as far as determining what file is encoded which way, usually "file properties" in Winamp or Foobar2000 will give you whatever the file header says. it gets complicated identifying with LAME because it actually switches between MS (joint) and LR (discrete stereo) on a block level rather than a file level. if lame decides the block will sound good enough in MS, it will encode it that way. when it detects unacceptable differences in MS mode it will encode the block in LR.

http://www.hydrogenaudio.org/forums/index....hl=joint+stereo

The search is your friend.

As far as a program to see what mode the file is encoded in, I can't remember if EncSpot does that or not. I don't have that prog on this computer right now.

EDIT: Looks like MugFunky beat me to it...

Joint stereo at the wiki

Programs:
http://www.hydrogenaudio.org/forums/index....ndpost&p=189385