[mythtv-users] Removing laugh tracks from recordings

[Jeff Simpson]

> Just curious, has anyone thought about ways to remove the Laugh Tracks
> from Sitcoms and such?
> Commercials can be flagged, but how about laugh tracks? It is so
> stupid to laugh at silly stuff when they "ask" us to...

Audio & video at any particular time is either commercial or
not-commercial, so once you flag what a commercial is, you can easily
remove it. Laugh "tracks" as they are called are not really tracks in
the finished product. While they are in the studio, they have separate
tracks for each sound source so they can adjust levels and the like,
but once it hits your TV you only have a left track and a right track
(or maybe 5.1 or similar, but none of those 5 are the "laugh" channel.

But I agree with you on wanting to remove the laugh track. Some of the
funniest things on TV and in real life are funny because nobody is
laughing. Watch The Office (BBC or NBC), and you'll see. It's an
office workplace sitcom without a laugh track. The fact that you just
have to sit there in silence after an awkward moment makes it
hysterical. But we americans aren't all ready for that advance british
humor :-P

> There is equipment available that purports to remove vocal tracks
> from music, for "Karaoke applications. I have no idea how well it works.

These "Karaoke applications" operate by removing all the frequencies
around where human voice is, with a notch filter or similar. It makes
the music sound like crap, and typically you can still hear some of it
in the background. Because you are running a frequency filter on the
sound, you also end up with a lot of artifacts and high-pitched noises
(cracks, snaps, other weird stuff).  Also, because you are doing it
digitally, you only have a limited bandwidth to begin with, so any
further filtering and reencoding is only making it worse.

Real karaoke machines / places / DJs have special recordings of music
that just don't have the vocals recorded at all, so that's why they
work. They aren't removing the lyrics, they just have a recording of
the song that only includes the backup music (and why karaoke discs
will say "Song Title, as made popular by Artist Name", since they
can't really put the artists name on a disc that they don't sing on.)

> Theoretically an application of the same technology might at least
> reduce the level of the offending laugh track, it would be harder
> because the content is similar to dialog which you would want to keep.

Yup, exactly. You can identify the frequencies of laughter (which is
quite different from person to person, and in a laugh track they have
a lot of people, so it's probably quite a frequency spread). If you
could remove the laugh tracks, you would probably also end up removing
actual laughter that is supposed to be there. And probably a lot of
actual speach, too, since I don't believe laughter is all that
different in spectrum from speech.

> Probably beyond anything we can economically do right now, but as you
> say today's impossibility might be tomorrow's Blue Light Special at K-
> Mart.

I'd like it if they recorded everything with more tracks. Not just the
directional-tracks like they do now, but individual mic tracks, so we
could do our own mixing in movies and music. It'd be nice to have just
the vocals in a song or remove the background noise on a movie. I
guess that is probably too much for the average home media user. We
already have the ability to select alternate audio tracks and camera
angles....but apart from listening to a movie in spanish or the audio
commentary track, is it ever used?

 - Jeff