Cut silence (below specified level)

[iSerganov]

Hey community!

Can you please help me to find a way to cut silence in the beginning and in the end of a track?
E.g. if loudness level falls below -45dB cut the beginning (or the end of a track).

I found ffmpeg.filter.silenceremove filter in Liquidsoap documentation. However I am not really sure how can I use it...

Thanks in advance!

[vitoyucepi]

Hi @iSerganov,
You're probably looking for the blank.* function group:

• blank.detect
• blank.eat
• blank.skip
• blank.strip

You may also want to check out the examples in the book.

I should also mention that autocue may provide a better experience.

[iSerganov]

Thanks for info provided, @vitoyucepi!
It looks like autocue is exactly what I need... Could you please point me to a doc or example where I can configure and enable it for cutting silence, (and maybe smart crossfading) purposes?

[gAlleb]

Hi @iSerganov. From this issue #4057 I've got an impression that you have familiarized yourself with autocue

settings.autocue.cue_file.silence := -45.0
About this setting: LU below integrated track loudness for cue-in & cue-out points (silence removal at beginning & end of a track) (default: -42.0)

The above setting is for autocue by MoonBase59.

If we are talking about internal autocue then we have this settings:
settings.autocue.internal.cue_in_threshold - defaults to -34.0
settings.autocue.internal.cue_out_threshold - defaults to -42.0

You can see all settings for internal autocue here -> https://github.com/savonet/liquidsoap/blob/27dda43947cdb39fca16a9fb435dc9f45bee1e4b/src/libs/autocue.liq and for autocue by Moonbase59 here -> https://github.com/Moonbase59/autocue

---

1. Internal autocue will calculate all the fade_* values for you and its setup as easy as:

enable_autocue_metadata()
s = playlist("music.m3u8")
s = amplify(1.,override="liq_amplify", s)
s = crossfade(s)
output(s)

2. Autocue.cue_file won't calculate fade_* values, defaults are: fade_in = 0.1, fade_out = 2.5. Which will default to a more segue-like "crossfading". E.g. :

# Fading/crossing/segueing
def custom_crossfade(old, new) =

        add(normalize=false, [
          fade.in(
            initial_metadata=new.metadata,
            duration=settings.autocue.cue_file.fade_in(),
            new.source
          ),
          fade.out(
            initial_metadata=old.metadata,
            duration=settings.autocue.cue_file.fade_out(),
            old.source
          )
        ])

end

radio = cross(
  duration=settings.autocue.cue_file.fade_out(),
  custom_crossfade,
  radio
)

[iSerganov]

That's absolutely makes sense!

And the option No. 2 is exactly what I was looking for! I need to make fade_in/fade_out values configurable rather than automatically computed.

As to the settings.autocue.cue_file.silence := -45.0, I was looking at it, but it wasn't clear where exactly it detects and cuts silence (end, start or middle of the file), so thanks for clarifying it.

That's a great and super helpful explanation which absolutely answers my question.

Thank you @gAlleb!