Re: [linux-audio-dev] scaling jackinput to dbSPL

From: Dominique Michel <dominique.michel@email-addr-hidden>
Date: Tue Aug 15 2006 - 21:43:49 EEST

Le Tue, 15 Aug 2006 14:03:34 -0400,
Paul Davis <paul@email-addr-hidden> a écrit :

> > The db inside jack are dbFS with a maximum possible signal of 0 db.
> > Now, both jacqeq and jackmix give you a maximum conrol level at +6dB.
> > It mean at +6dB in those EQ is equal to 0dbFS in jack.
>
> there are no dB units inside of JACK. some JACK applications use dBFS,
> that much is true. however, it is not true that because the allow a gain
> level of +6dB (or any value for that matter) that +6dB in that app
> equals 0dBFS. this is because JACK's floating point sample format allows
> values above 0dBFS, even though when such a value is passed to DAC, it
> will be clipped and caused distortion or worse.
>
> within JACK, 0dBFS corresponds to a sample value of +/1.0, and will
> emerge from the other side of your DAC with the maximum voltage level
> that the DAC can emit. values above 0 dBFS are legal within JACK, but
> should probably never be routed to a physical output port.
>
> --p
>
>
Thank you for this explanation.

Dominique
Received on Wed Aug 16 00:15:04 2006

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