Hi,

I have an idea about joint stereo types and what "ms" and "ss" means, but EncSpot shows me "is" and "mixed" as different possibilities. What are these modes for and why doesn't LAME use them.
Can someone give me a short introduction into these modes?

A similar question about the block-type modes. Why is the "mixed" mode never been used?

Thank

"IS" and "Mixed" are different stereo modes used mainly for low bitrate encodings with the fraunhoffer encoder (well.. I've only seen it in such files anyway). ( <- This is wrong, see next reply of mine )

It's a low quality mode, and not implemented in lame
IS = intensity stereo. I think it works similarly to the coupled stereo modes of Vorbis at low Q's (although I can be wrong).

Mixed is like mono, if i'm not wrong. (Basically, it would mean that it would use a "IS" frame when stereo image is important, and Mixed when it is not).

I suppose this is clear (and accurate!). Correct me if needed.

Check out this thread:
http://www.hydrogenaudio.org/forums/index....=ST&f=16&t=1481

Shortly, Lame and practically every other mp3 encoder don't use mixed blocks because it's difficult to implement properly and the quality gain is somewhat questional.

Thanks for the info. B)

JohnV, I think Mixed stereo mode has nothing to do with mixed blocks.

[Edit : Wooops! I've just realized that the 2nd question didn't have anything to do with stereo modes ]



I've further checked my mp3 collection, and found out that the files that use IS<->Mixed stereo mode are the ones created by Xing (very old), as reported by EncSpot. (winamp and encspot say they are joint stereo files)

I even have a few that I made myself (from vinyl), but I don't remember which program I used to do them.
(too many years ago.. :·P)

Here is a sample (7 secs) of one of such files: http://www.terra.es/personal4/jas00010/fil...%20(sample).zip

RENAME IT TO MP3 ( I think this site didn't allow to store .mp3's there )

This current sample shows that all frames used are "mixed" (again, in encspot) , although the complete song had a few ( 0.3%!!!!! ) of IS frames.

I was wrong as well with the suposition that "mixed" meant mono, so I don't know what's its meaning.

EDIT 2:

I've also found now a file where the TAG's ( id3v1 and id3v2 ) say that it has been made with RealJukebox (1), and it has IS-Mixed mode stereo as well.
This is more like a warning, if anyone uses, or have used realjukebox (v1) to encode files to mp3.