Automatically detects the boundary between silence and the start of an audio track.
Also, detects audio fade out, and notates a liquidsoap playlist accordingly, with both cue points.
Tracks with quiet but lengthy significant endings, e.g. Queen's "Bohemian Rhapsody" are accommodated.
Detection is based on a certain level of Loudness Units (LU) below the track's measured integrated loudness, according to EBU R.128 calculations. This is no mere "meter reader".
Also annotates the same playlist with accurately measured track durations.
Also measures EBU R.128 volume of track, for use with ReplayGain within liquidsoap. Also optionally converts file to a mezzanine format, simplifying replay, while embedding useful metadata within the mezzanine file and creating a unique filename.
Also examines full directories of audio, creating audio fingerprints of each track, then searches for near-identical tracks.
Also presents this database of near-identical tracks to a user through a web-browser, with pertinent data about all, to permit near-automatic sifting. Browser will highlight all occurrences of selected track to help prevent accidental deletions. Will later automatically output list of files to be deleted.
The fine multimedia automation software liquidsoap, which is the backbone of several user-friendly radio production operations, allows crossfading between sources.
However, it does not automatically fire the next item in a playlist based on a detected end of track; it instead relies on human interaction in writing a cue-point (or the end of a file) to point out where that end might be.
There is a "smart" crossfade operator that looks at how tracks end and begin, to attempt to decide how to blend two tracks together, but it does not detect exactly when to do it.
This Python3 script parses a playlist, uses the EBU R.128 loudness measurement algorithm to determine the last point in an audio file where the loudness falls below a set level (e.g. the song's fade-out, or its end), and supplies metadata that liquidsoap can use to fire the next item in a playlist.
It is currently in test, but works. Run the command with '-h' to get help, or read the source.
The two lines in a Liquidsoap script that do the magic are as follows. I've left lots of buffer room, and do not fade the audio at all, instead allowing the detection of audio levels to allow the track's own fade-out and start levels to do the job.
The files contained in this repository permit a complete, mixed, radio station with high-quality, controlled, audio output suitable for onward distribution.
There are also example files for a crontab and 'expect' scripts to insert hourly, up-to-date news bulletins into the stream.
myplaylist = cue_cut(playlist(length=60.0, "[YOURPLAYLIST]"))
myplaylist = crossfade(fade_out=0.01, fade_in=0.01, conservative=true, myplaylist)
I have altered the liquidsoap script to sample audio at 32,000Hz. This is one of the specificied HE-AACv2 sample rates, and allows better quality audio in stereo at the lowest bit-rates e.g. 32kbit/s.