Re: [Savonet-users] switch to the beginning of a playlist

[David B. <dav...@gm...>]

Hi Alexandru,

2012/4/24 Alexandru Matei <ale...@gm...>:
> I still get empty source ids if I use the code below.

In fact, what happens is that your transition is not called at all,
right? At least that's what I observed in my tests: I had forgotten
that transitions are not used for track sensitive switches. Indeed,
they don't make sense in that case, the track from source a is already
finished.

Therefore I will propose a simpler solution, which has the
disadvantage of requiring more coding skills. So I'll provide you with
the code (copying verbatim the script that worked for me, and should
be easy to adapt). The idea is to keep in a reference (memory cell)
the id of the previous source, update it using on_track, and reload
when it changes.

small1 = playlist(id="small1","~/media/audio/jazz")
small2 = playlist(id="small2","~/media/audio/misc")

def reload_transition(a,b)
  log("a is #{source.id(a)}, b is #{source.id(b)}")
  b
end

playlists = switch([({0m-44m},small1),
                    ({36m-50m},small2)])

def reload_on_change(s)
  last_seen = ref("")
  def handler(m)
    id = m["source"]
    old_id = !last_seen
    if old_id != id then
      last_seen := id
      if old_id != "" then
        log("Reloading #{old_id}...")
        list.iter(log,server.execute("#{old_id}.reload"))
      end
    end
  end
  on_track(handler,s)
end

playlists = reload_on_change(playlists)

output.icecast(%vorbis,mount="test.ogg",fallible=true,playlists)

> Anyway, I followed your advice and managed to make the transition function.
> I would have never tried to make a function with three parameters for a
> transition because in the doc I read:
> transitions ([(source('a),source('a))->source('a)] – defaults to []):
> Transition functions, padded with fun (x,y) -> y functions.
> I think the documentation needs to be improved.

Well, we may document more the language and type system, but there's
nothing we can do about (source('a),source('a))->source('a):
transitions have to take only two arguments and return a source. The
fact that you can create a function with two arguments from one with
three arguments doesn't change this. To make an analogy, type int
contains 0, 1, 2, etc. but also 1+1...

Cheers,

David

PS:

> This was my mistake. To be sure that nothing bad happens because one source
> is mono and another one stereo I added audio_to_stereo to all my playlists.
> small_playlist = audio_to_stereo(id="small_stereo",
> playlist("..../small.txt")) -> Wrong.

Sounds like a good fix. Why did you write "Wrong"?