Add script to exercise AudioRegion Peak/RMS Normalization

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