On 2017-08-10 01:34, Jerry Powell wrote:
I am trying to remove the silence from script generated mp3's but not
ALL
silence (otherwise it all gets crammed up) can someone break this
command
down to me? Please i have read the man page and i just cant wrap my
mind
around it...I've searched and searched google just cant get it
The file has a slight buzz to it
silence -l 1 0.1 1% -1 2.0 5%
I am guessing, as I have never used this effect.
But, the manual says the form of the command is
silence [−l] above-periods [duration threshold[d|%]
[below-periods duration threshold[d|%]]
so first:
- you HAVE specified the optional -l
which affects how 'below-periods' works
- then: above-periods [duration threshold[d|%] is: 1 0.1 1%
and: below-periods duration threshold[d|%] is: -1 2.0 5%
Starting with the 'above-periods' part: 1 0.1 1%
that means above-periods is 1
duration is 0.1
threshold is 1%
So sox will scan from the start of the audio file looking just once (as
above-periods is 1) for an audio signal that is sufficiently more loud
than
'silence' to decide that that's the start of the sound you want.
The 'louder than totally silent' audio will have to be more than
(duration)
0.1 in length to be regarded as significant. But... 0.1 what? The
manual
says that
duration is a time specification with the peculiarity that a bare
number is interpreted as a sample count, not as a number of seconds.
For specifying seconds, either use the t suffix (as in ‘2t’) or
specify minutes, too (as in ‘0:02’).
I imagine you did not mean 0.1 samples. I expect you probably meant
this
value to be 0.1t (for a tenth of a second), or something else?
That 'louder than silent' concept also needs to be defined - how much
louder?
Your 1% means 1% of the loudest that the sound can get (I think it's
not
entirely clear if sox examines the whole audio file first to find out
what its
maximum actual loudness is, or whether it simply means the loudest
signal that
could theoretically be stored in the file).
You also specified: below-periods duration threshold[d|%] is: -1
2.0 5%
so below-periods is -1
duration is 2.0
threshold is 5%
AND the original -l switch was specified.
The same comments as above apply to your duration (probably you meant
2t) and
threshold.
Because your below-periods value is -1 (ie negative) this means you
want sox to
look for periods of 'silence' in the middle of the file. I /think/ but
am not
certain that here it would look for only one such period (because your
-1 is
numerically 1 once it is made positive).
Because you specified the initial -l switch, periods of 'silence'
found in the
middle of the file do not get totally removed. Instead they are shrunk
so that
any that is longer than the duration value you provided would be
replaced by a
shorter bits of 'silence' (of that duration) - or putting it another
way, the
first small part of the 'silence' is kept and the rest thrown away. If
you'd
coded duration properly it might do what you want.
Remember, I'm only guessing!
--
Jeremy Nicoll - my opinions are my own
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