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audible differences between stereo and mono

2013-03-07
2013-09-14
  • WillyFoobar
    WillyFoobar
    2013-03-07

    Dear Timidity team.
    I use Timidty++-2.14.0

    When I generate a wav-file there
    is an audible difference between mono and stereo output (from PCM wav files)

    I use crazy_frog_-_axel_f.mid, that can be found at
    http://freemidi.org/directory-1079

    I cannot send this midi file directly due to copyright issues.

    timidity crazy_frog_-_axel_f.mid         -OwM -o mono.wav
    timidity crazy_frog_-_axel_f.mid         -OwS -o stereo.wav
    timidity crazy_frog_-_axel_f.mid -Ow -o default.wav

    there is a hearable difference between mono.wav vs. stereo.wav.
    The same difference for default.wav (this is a stereo output)

    The stereo sounds a little bit more smooth and has more reverb.

    Even using  the option -preserve-silence  there is the same difference.
    Even, when I split the two stereo channels into two separate wav files,
    the audible difference does not change.

    Is this a result of the mid notes that uses stereo interaction?
    I did not find any controller events that deal with pan or something similar.

    Does anybody have an idea, where this difference comes from?
    I want to produce the same sound quality in mono compared with stereo.

    Yours,
      WillyFoobar

     
    • SATO Kentaro
      SATO Kentaro
      2013-09-14

      IIRC some of the effects including ones specified in soundfonts are applied only when the output is stereo by design. (Note also that there's panning in soundfont itself, assuming you are using soundfonts.)
      That might have made difference in the case.
      You may have to first output in stereo then mixdown to mono.