Re: Dolby A example (was Re: Has anyone ever used `echos` or `chorus`?)

Thanks for the fast turnaround on that one!

Your name currently appears in the (slowly) evolving beta of my next Audir =
release, because you permitted me
to include "dlbac" and "dlbad" pseudo-effects in Audir. A direct link to th=
e relevant doc section:
https://www.dlee.org/audir/beta/#short_dlb

Please advise if you want any changes to this.

Also, st^H^Hborrowing from my effect set for direct use in SoX is fine by m=
e, the Audir author. Finally,
please pardon the complete lack of styling; I am blind and designed my webs=
ite primarily for blind people to
get information and resources quickly, so I never bothered with such niceti=
es, though surely I should.

On Wed, Feb 12, 2025 at 05:44:01PM +0100, Martin Guy wrote:
On 12/02/25 16:35, Doug Lee wrote:
> On Tue, Feb 11, 2025 at 07:49:38PM +0100, SoX NG wrote:
> > so I've replaced it with a different example: Dolby A compression and d=
ecompression,
> > which is probably also more useful as I think more people still have ta=
pe recorders than
> > need to compand for FM radio.
> > =

> > https://codeberg.org/sox_ng/sox_ng/issues/408 - The "mcompand" example =
doesn't work
> I do get an error on the final element of the decompress mcompand though:
> =

> ".1,.1 4:-41,-56,-21,-36,-23,-26,-14,-17,-9,-9"
> =

> does not increase monotonically.


Ah, thanks for reporting that.


Dolby does it with 3-20kHz and 9-20kHz companders in parallel,

which mcompand can't do in one invocation.

It was my attempt to make 5dB more to the difference ramped down

to 0db in four steps without using decimals and I got it wrong.

Now it adds from 4dB down to 0dB in 4 steps. Can't stand decimals,

can't hear 1dB difference, in fact can't hear above 9kHz any more, sigh.


# Dolby A compressor
sox_ng in.au dolbyA.au mcompand \
=A0=A0=A0 ".1,.1 4:-56,-46,-36,-26,-26,-20,-17,-15,-9,-9" 80 \
=A0=A0=A0 ".1,.1 4:-56,-46,-36,-26,-26,-20,-17,-15,-9,-9" 3k \
=A0=A0=A0 ".1,.1 4:-56,-46,-36,-26,-26,-20,-17,-15,-9,-9" 9k \
=A0=A0=A0 ".1,.1 4:-56,-42,-36,-23,-26,-18,-17,-14,-9,-9"

# Dolby A decompressor
sox_ng dolbyA.au out.au mcompand \
=A0=A0=A0 ".1,.1 4:-46,-56,-26,-36,-20,-26,-15,-17,-9,-9" 80 \
=A0=A0=A0 ".1,.1 4:-46,-56,-26,-36,-20,-26,-15,-17,-9,-9" 3k \
=A0=A0=A0 ".1,.1 4:-46,-56,-26,-36,-20,-26,-15,-17,-9,-9" 9k \
=A0=A0=A0 ".1,.1 4:-42,-56,-23,-36,-18,-26,-14,-17,-9,-9"


Not like I actually tried running it after the mod or anything.

Just too confident.


Thanks again


=A0=A0=A0 M

-- =

Doug Lee                 [email protected]                http://www.dlee.org
"Characters live to be noticed. People with character notice how
they live." -- Nancy Moser