joint stereo

[Baarryy]

Joint-Stereo, is this mid/side stereo. i do not want to use joint stereo if it is the older version which combines the left and right audio channels at higher frequencies. I am also wondering what exactly dual channel is supposed to be, obviously it is not stereo or there would not be a separate setting.

[Spoon]

Re: joint stereo

There is no problems using Joint Stereo with Lame (assuming that is the format you are talking about), it is mid/side.

[xoas]

Re: joint stereo

The issue about the dual channel setting is described in support documentation for Lame 3.96.1 thusly:

dual channels
In this mode, the 2 channels will be totally indenpendently encoded. Each channel will have exactly half of the bitrate. This mode is designed for applications like dual languages encoding (ex: English in one channel and French in the other). Using this encoding mode for regular stereo files will result in a lower quality encoding.

So it is like the television audio dual channel setting.

In case you are interested, it also discusses some other settings:

* -m s/j/f/d/m stereo mode
Joint-stereo is the default mode for stereo files with VBR when -V is more than 4 or fixed bitrates of 160kbs or less. At higher fixed bitrates or higher VBR settings, the default is stereo.

stereo
In this mode, the encoder makes no use of potentially existing correlations between the two input channels. It can, however, negotiate the bit demand between both channel, i.e. give one channel more bits if the other contains silence or needs less bits because of a lower complexity.

joint stereo
In this mode, the encoder will make use of a correlation between both channels. The signal will be matrixed into a sum ("mid"), computed by L+R, and difference ("side") signal, computed by L-R, and more bits are allocated to the mid channel.
This will effectively increase the bandwidth if the signal does not have too much stereo separation, thus giving a significant gain in encoding quality.

Using mid/side stereo inappropriately can result in audible compression artifacts. To much switching between mid/side and regular stereo can also sound bad. To determine when to switch to mid/side stereo, LAME uses a much more sophisticated algorithm than that described in the ISO documentation, and thus is safe to use in joint stereo mode.

EDIT: You can find the download for these source files here:

http://sourceforge.net/project/showfiles.php?group_id=290

Best wishes,
Bill