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understanding joint stereo

Discussion in 'Audio' started by windin, Aug 29, 2004.

  1. windin

    windin Member

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    I am rather new to the concept of joint stereo (only just found out what it probably means). As I understand it, the data that is different between the two channels is put into a side channel while the (usually much larger) information that is common to left and right channels goes into a "main" channel. Proponents of joint stereo say that in compression, this makes a higher absolute error on the side channel, but a lower proportionate error than with stereo compression, because the data size is much less. They then say the absolute and proportionate error with the common track information is much less than with stereo, because far more resources are devoted to it, so it follows that unless left and right channels are completely dissimilar, joint stereo must give a closer approximation of the original file, and with a smaller file size than stereo when decompressed into left and right channels again

    The main difference I can personally tend to hear in joint stereo compared to stereo is not in the stereo separation but in a less bass orientated equalisation. There is also some greater transparency, which may partly be as a result of lighter bass. Of course this could be merely the implementation of joint stereo in the editors I use.

    My point in writing this is that the joint stereo proponents suggest the Lame MP3 encoder should always be used to compress with joint stereo, not stereo. Other lossy formats which might seem better than MP3 (AAC , MPC ...) don't seem to offer joint stereo options in the encoders I have come across. Is joint stereo yesterday's issue now?




     
  2. djscoop

    djscoop Active member

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    i'm not sure about other audio formats, but joint stereo is pretty much the norm for mp3s. if you use stereo, there is more compression because a seperate right and left channel is created, whereas j.s. takes the frequencies that appear on both channels and make it one, so it only has to compress on channel instead of two for every frequency. a much bigger issue is using VBR mode, to allow maximum compression and the least loss of quality possible. if you are converting cds to mp3s just use this guide using eac and lame...it makes the best sounding mp3s i've heard yet.

    http://www.afterdawn.com/guides/archive/mydeneaclame.cfm
     
  3. windin

    windin Member

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    Thanks for the link which I will look at. However having compared VBR to CBR I really prefer CBR. I like classical and a little very soft rock and so seem to sense the loss of detail with VBR in the quiet music which nominally you *might* think needs less resources applied to it.
     

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