Subject: Re: [linux-audio-dev] Reference amplitudes and LADSPA (again)
From: Paul Davis (pbd_AT_Op.Net)
Date: Sat Feb 02 2002 - 00:33:58 EET
>I think it would be best if Alsa would either generate samples in
>floats or provide means for querying what is the 0 level. In cheap
ALSA can generate float values. Just use the "plug" or "plughw"
interface.
It can't tell you what you the 0dB level is. In the case of an
all-digital h/w interface, there is no definition of 0dB - that's
dependent on wherever D/A conversion happens.
Its a constant challenge in a studio to get the meters on even 3
pieces of equipment to give consistent 0dB readings ...
>So, we should have separate conversion routines for 16 and 24 bits
>inputs/outputs.
such routines exist in many places, including ALSA, Ardour and others
(probable ecasound, and likely glame too).
>But does this have anything to do with LADSPA and the original
>suggestion? Value 1.0 as 0 dB level is used in both cases.
you suggested tying this to code that does i/o with an audio
interface. i was merely pointing out that its not advisable to assume
too much about how that would work.
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