sox-users

[SoX-users] SoX man page error in FM broadcast signal example

[Doug L. <dg...@dl...>]

The part of the SoX manual that describes effects includes a long example command for producing a US-style FM
broadcast signal (to find it, search for FM in caps in http://sox.sourceforge.net/sox.html#EFFECTS).

The example includes the effect 

    sinc 8000- 29 100

This is invalid syntax. I wonder if it's an editing mistake from the days of the filter effect?

I'm not sure what this should be, but I'd love to find out.

For reference, the full example effects chain is this (collapsed onto a single line):

    gain -3 sinc 8000- 29 100 mcompand "0.005,0.1 -47,-40,-34,-34,-17,-33" 100 "0.003,0.05 -47,-40,-34,-34,-17,-33" 400 "0.000625,0.0125 -47,-40,-34,-34,-15,-33" 1600 "0.0001,0.025 -47,-40,-34,-34,-31,-31,-0,-30" 6400 "0,0.025 -38,-31,-28,-28,-0,-25" gain 15 highpass 22 highpass 22 sinc -n 255 -b 16 -17500 gain 9


-- 
Doug Lee                 dg...@dl...                http://www.dlee.org
SSB BART Group           dou...@ss...   http://www.ssbbartgroup.com
"Determine that the thing can and shall be done, and then...find
the way." - Abraham Lincoln

Re: [SoX-users] SoX man page error in FM broadcast signal example

[Eric W. <nor...@yh...>]

Doug Lee <dg...@dl...> wrote:
> The example includes the effect 
> 
>     sinc 8000- 29 100
> 
> This is invalid syntax. I wonder if it's an editing mistake from the days of the filter effect?

Seems to be, it was introduced in commit f146ff926 ("filter -> sinc")

> I'm not sure what this should be, but I'd love to find out.

Going into git history (with: git log -p -- src/filter.c),
I could see the old help text for that was:

	low-high [ windowlength [ beta ] ]

For the sinc effect, the required low-high frequency parameter seems
obvious enough (8000-)

And the "-b beta" parameter in sinc probably corresponds to the old
positional "beta" in filter being 100.

I'm not sure what the old "windowlength" parameter corresponds to in
sinc.  We shall wait for robs or somebody else knowledgeable in signal
processing to answer.