Add crossfade delay, tests and plot cababilities. (#3703)

Author: toots

src/core/sources/blank.ml

@@ -24,26 +24,37 @@ open Mm
 open Source
 
 class blank duration =
-  let ticks = if duration < 0. then -1 else Frame.main_of_seconds duration in
+  let ticks () =
+    let d = duration () in
+    if d < 0. then -1 else Frame.main_of_seconds d
+  in
   object (self)
     inherit source ~name:"blank" ()
 
     (** Remaining time, -1 for infinity. *)
-    val mutable remaining = ticks
+    val mutable remaining = None
+
+    method remaining =
+      match remaining with
+        | Some r -> r
+        | None ->
+            let r = ticks () in
+            remaining <- Some r;
+            r
 
-    method remaining = remaining
     method stype = `Infallible
     method private _is_ready ?frame:_ _ = true
     method self_sync = (`Static, false)
     method! seek x = x
     method seek_source = (self :> Source.source)
-    method abort_track = remaining <- 0
+    method abort_track = remaining <- Some 0
 
     method get_frame ab =
       let position = Frame.position ab in
+      let rem = self#remaining in
       let length =
-        if remaining < 0 then Lazy.force Frame.size - position
-        else min remaining (Lazy.force Frame.size - position)
+        if rem < 0 then Lazy.force Frame.size - position
+        else min rem (Lazy.force Frame.size - position)
       in
       let audio_pos = Frame.audio_of_main position in
       let audio_len = Frame.audio_of_main length in
@@ -73,8 +84,8 @@ class blank duration =
         self#content_type;
 
       Frame.add_break ab (position + length);
-      if Frame.is_partial ab then remaining <- ticks
-      else if remaining > 0 then remaining <- remaining - length
+      if Frame.is_partial ab then remaining <- None
+      else if rem > 0 then remaining <- Some (rem - length)
   end
 
 let blank =
@@ -83,12 +94,12 @@ let blank =
     ~descr:"Produce silence and blank images." ~return_t
     [
       ( "duration",
-        Lang.float_t,
+        Lang.getter_t Lang.float_t,
         Some (Lang.float (-1.)),
         Some
           "Duration of blank tracks in seconds, Negative value means forever."
       );
     ]
     (fun p ->
-      let d = Lang.to_float (List.assoc "duration" p) in
+      let d = Lang.to_float_getter (List.assoc "duration" p) in
       (new blank d :> source))

src/libs/extra/fades.liq

@@ -0,0 +1,77 @@
+# Plot the first crossfade transition. Used for visualizing and testing
+# crossfade transitions.
+# @flag extra
+def cross.plot(~png=null(), ~dir=null(), s) =
+  dir =
+    if
+      null.defined(dir)
+    then
+      null.get(dir)
+    else
+      dir = file.temp_dir("plot")
+      on_cleanup({file.rmdir(dir)})
+      dir
+    end
+
+  old_txt = path.concat(dir, "old.txt")
+  new_txt = path.concat(dir, "new.txt")
+
+  def gnuplot_cmd(filename) =
+    'set term png; set output "#{filename}"; plot "#{new_txt}" using 1:2 with \
+     lines title "new track", "#{old_txt}" using 1:2 with lines title "old \
+     track"'
+  end
+
+  def store_rms(~id, s) =
+    s = rms(duration=settings.frame.duration(), s)
+    t0 = ref(null())
+
+    source.on_frame(
+      s,
+      {
+        let t0 =
+          if
+            null.defined(t0())
+          then
+            null.get(t0())
+          else
+            t0 := source.time(s)
+            null.get(t0())
+          end
+        let v = s.rms()
+        let p = source.time(s) - t0
+        fname = id == "old" ? old_txt : new_txt
+        file.write(append=true, data="#{p}\t#{v}\n", fname)
+      }
+    )
+  end
+
+  plotted = ref(false)
+
+  def transition(old, new) =
+    old = store_rms(id="old", fade.out(old.source))
+    new = store_rms(id="new", fade.in(new.source))
+
+    s = blank(duration=0.1)
+    s =
+      source.on_frame(
+        s,
+        {
+          if
+            null.defined(png) and not plotted()
+          then
+            ignore(
+              process.run(
+                "gnuplot -e #{process.quote(gnuplot_cmd(null.get(png)))}"
+              )
+            )
+          end
+          plotted := true
+        }
+      )
+
+    sequence(merge=true, [add(normalize=false, [new, old]), s])
+  end
+
+  cross(transition, s)
+end