Re: [linux-audio-dev] Reference amplitudes and LADSPA (again)

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Subject: Re: [linux-audio-dev] Reference amplitudes and LADSPA (again)
From: Juhana Sadeharju (kouhia_AT_nic.funet.fi)
Date: Fri Feb 01 2002 - 22:12:52 EET


>>A/D converter should output values in range (-1,1); that is
>>what I have always assumed.
>
>i don't want to be too pedantic, but "A/D converter" is not a very
>useful phrase. nothing that we do in software does A/D or D/A

Ouch, I forgot when you noticed us about this issue a while ago.

>conversion. i think what you mean is that the source that moves data
>to and from an audio interface should clip values to the range -1..+1,

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
16-bit cards the 0 level is the peak value 32767, but in 24-bit
streams the 0 level is not at the maximum values. There is are AES
and EBU standards on this if I remember correctly.

So, we should have separate conversion routines for 16 and 24 bits
inputs/outputs.

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.

Juhana


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