We should implement handling of CUE points in the standard library, either by calling some external programs or by hacking into liq. This feature has been requested many times, see for example below.

From the ML:

I use liquidsoap 0.9.x and I need to manually apply so-called cue
points (the place where fade out or fade in begins). This data will be
set manually by users of my system and will be pushed to liquidsoap
via metadata in the annotate interface.

In other words: I just want to mix my songs in previously manually
specified points.

I know how to write transition function, but how can I "strip"
specified amount of seconds from the beginning or the end of my song?
Is there any way to do that?

Answer from David:

Liquidsoap has no such facility. However, some people have solved that
problem before by writing a script that cuts a file as wanted, using
corresponding tools for mp3 and ogg formats. Then they could hook up
that script using protocols. I don't remember who it was but we met
them in Berlin. I thought that they gave the script to Romain, but I
might be wrong since he didn't mention it.

It wouldn't be a good solution to have a cut operator because that
would be done after decoding the file. Hence it would be very
inefficient. Unless you cut a very small portion at the beginning of
the file. Regarding the end of file, precision would be an issue
unless we buffer in advance.

Now that I think of it, small cue-in points may be implemented using a
transition that sets the volume to 0 on the new track for a while...
If it sounds like it could be enough for your particular need, and if
you feel like hacking in liquidsoap, it could be something to try.