Add script to exercise AudioRegion Peak/RMS Normalization

diff --git a/scripts/s_region_gain2.lua b/scripts/s_region_gain2.lua
new file mode 100644 (file)
index 0000000..cec56ca
--- /dev/null
+++ b/scripts/s_region_gain2.lua
@@ -0,0 +1,63 @@
+ardour { ["type"] = "Snippet", name = "Normalize Regions" }
+
+function factory () return function ()
+       -- get Editor GUI Selection
+       -- http://manual.ardour.org/lua-scripting/class_reference/#ArdourUI:Selection
+       local sel = Editor:get_selection ()
+
+       -- prepare undo operation
+       Session:begin_reversible_command ("Lua Normalize")
+       local add_undo = false -- keep track if something has changed
+
+       -- iterate over selected regions
+       -- http://manual.ardour.org/lua-scripting/class_reference/#ArdourUI:RegionSelection
+       for r in sel.regions:regionlist ():iter () do
+               -- test if it's an audio region
+               local ar = r:to_audioregion ();
+               if ar:isnil () then
+                       goto next
+               end
+
+               local peak = ar:maximum_amplitude (nil);
+               local rms  = ar:rms (nil);
+
+               if (peak > 0) then
+                       print ("Region:", r:name (), "peak:", 20 * math.log (peak) / math.log(10), "dBFS")
+                       print ("Region:", r:name (), "rms :", 20 * math.log (rms) / math.log(10), "dBFS")
+               else
+                       print ("Region:", r:name (), " is silent")
+               end
+
+               -- normalize region
+               if (peak > 0) then
+                       -- prepare for undo
+                       r:to_stateful ():clear_changes ()
+                       -- calculate gain.  
+                       local f_rms = rms / 10 ^ (.05 * -18) -- -18dBFS/RMS
+                       local f_peak = peak / 10 ^ (.05 * -1) -- -1dbFS/peak
+                       -- apply gain
+                       if (f_rms > f_peak) then
+                               print ("Region:", r:name (), "RMS  normalized by:", -20 * math.log (f_rms) / math.log(10), "dB")
+                               ar:set_scale_amplitude (1 / f_rms)
+                       else 
+                               print ("Region:", r:name (), "peak normalized by:", -20 * math.log (f_peak) / math.log(10), "dB")
+                               ar:set_scale_amplitude (1 / f_peak)
+                       end
+                       -- save changes (if any) to undo command
+                       if not Session:add_stateful_diff_command (r:to_statefuldestructible ()):empty () then
+                               add_undo = true
+                       end
+               end
+
+               ::next::
+       end
+
+       -- all done. now commit the combined undo operation
+       if add_undo then
+               -- the 'nil' command here means to use all collected diffs
+               Session:commit_reversible_command (nil)
+       else
+               Session:abort_reversible_command ()
+       end
+
+end end