Lame encoder question

I was wondering if someone could explain the difference between encoding in ‘joint stereo’ as opposed to ‘stereo’.


I found a textfile about Joint Stereo, hope it helps you.

Stereo Changed to Joint Stereo
My Stereo setting encodes my MP3 file at Joint Stereo.
To create the highest quality MP3 file, the XingMP3 Encoder always uses *Joint Stereo
(*Stereo mode 1) - at bitrates 128 kbps and below. Stereo mode 1 is sometimes known as
Joint Stereo.
AudioCatalyst version 2.0 includes an Advanced options feature that allows you to override
the default Stereo modes at bitrates 128 kbps and above. This “Force Simple Stereo” option
will not always create the highest quality file. Before selecting Force Simple Stereo When
Possible, read the following important information about Stereo modes.
Don’t confuse Joint Stereo (Stereo mode 1) with the Joint Stereo coding used for MPEG
layer 2 encoding - it is not the same. Joint Stereo (Stereo mode 1) encoding for MPEG layer
3 allows the XingMP3 Encoder to use additional methods of encoding, specifically - MS
Stereo (Middle/Side Stereo), and for lower bitrates only, Intensity Stereo, in addition to the
Independent Channel coding used for Stereo mode 0. MS Stereo uses one channel to encode
information that is identical on the left and right channels and the other channel to encode
the differences between the two channels. Intensity Stereo encodes only bits that are
perceived to be important to the stereophonic image. The XingMP3 Encoder uses Intensity
Stereo only in low bitrate files, (96kbps or less) where file size is critical to the user.
In Joint Stereo (Stereo mode 1), the encoder dynamically (frame by frame) chooses the
method of encoding that produces the best quality for each individual frame. Dynamic
encoding improves compression efficiency which results in a higher quality file using less
Stereo mode 0 encodes the left and right channels independently. The total bitrate remains
constant, but the split between the channels can vary. The XingMP3 Encoder uses this
flexibility to improve quality by allocating more bits to the channel with the more dynamic
signal. For MPEG layer 3 encoding, Stereo mode 0 limits the encoder to only one method of
encoding - Independent Channels. Because Stereo mode 0 is limited to one method of
encoding, Joint Stereo (Stereo mode 1) in most cases produces higher quality. In the
exceptions, the Stereo mode 0 quality will be essentially equivalent to Joint Stereo (Stereo
mode 1).

I think it means that you can select the bitrate it’s being made at. :confused:

Thanks for the reply and info even if it is an exercise in logic. What I did gather is that unless I plan on encoding at a low bit rate, I should stay away from ‘joint stereo’.


All this talk of Xing - the worst quality encoder of all time - even the likes of Fraunhoffer / MP3enc are worse than Lame 3.9+.

Checkout and the analysis section.

Lame 3.9+, lqt (a.b.sounds.aac), MP3+, etc are all great.


no Xing here. using AudioCrusher with newest Lame .dll.

sounds good to me…

***** Don’t ever use Xing or the hacked/original fraunhoffer codecs. **************
Use L.A.M.E.

check out this site.

Now back to the matter at hand.

Joint stereo uses the similarity between the left and right channels.

It encodes Middle-side instead of left-right.

What that means is where both left and right channels are identical, JS only encodes the middle channel, and the side channel results in 0 space required. For a bitrate of 160 KB/s, the result is 160KB for the middle channel, and maximum quality is the result.

When encoding stereo, 1/2 of the bandwidth is given to the left, the other halkf to the right, so for the same 160Kb/s the two streams are encoded @80kb for left, 80kb for right, even if they are identical.

Put simply, JSereo gives the best compression/sound quality for normal use.

But Stereo preserves phase information between the two channels, so can be used at extremely high bitrates for UH quality archiving, or if the sound is used for video.
(for video, the direction does matter)


Stereo encoding preserves complete channel separation between the left and right channels during the encoding process. Joint stereo sums the two channels together for the encoding process. Simple as that. There is some pretty good evidence to suggest that using joint stereo degrades the stereo imaging and introduces phase anomalies. I would use stereo wherever possible.

Thanks for the input!