Le 22 Mai 2005 16:58, Roman Haefeli a écrit :
hi marc
Marc Lavallée wrote:
I understand now. Thanks! But midi-dB resolution (1dB) is much too
small;
interpolation is required to smooth volume transitions from the lowest possible value to a certain level of amplification.
what do you mean by 'too small'? our ears hardly hear the difference of 1dB. from that point of view, 127 steps are enough.
In the good old days when MIDI was hot, I remembered hearing the steps when changing the volume rapidly with a MIDI fader. Maybe I was hearing the difference between a few consecutive steps instead of each steps. I was using consumer-grade equipment, the maximum volume was too high, and I don't know if the scale was linear or logarithmic...
With midi-dB, as explained by IOhannes, the useful range is 0-100, the last 27 steps are reserved to apply some amplification. With 127 steps instead of 100, it gives more precision. I agree that a fader with the full resolution of digital audio is useless, and that 127 steps is enough in most situations. I also use a 127 value slider to change the volume in my audio patches. But when modulating the amplitude of an audio signal with some control data, more rapidely than with a volume fader, 127 steps are not enough.
on the other hand, interpolation is needed anyway. it's not only a matter of the stepsize, but also of the time intervalls between different dB-values. depending on what interface (for example: guis in pd) you use, this intervall is too big, so that it's no way to use all steps of the scale.
Changing the volume smoothly with a low resolution fader works, and with good interpolation its perfect, but not too rapidly because the interpolation must measure the time between each steps.
i usuallly use a square scale, which is somehow betweeen logaritmic and linear scale.
Interesting.
what is a good way? i mean, which scale is used by good mixers like neve?
This article concludes that dBm (electrical power), not dB SPL (Sound Pressure Level, used by Miller) is the one used in the sound recording industry: http://www.modernrecordingtechniques.com/about/excerpt.php
I guess it's only a matter of preferences...
-- Marc