Add a Lua script snippet processing region data from the editor

diff --git a/scripts/s_region_gain.lua b/scripts/s_region_gain.lua
new file mode 100644 (file)
index 0000000..dec9899
--- /dev/null
+++ b/scripts/s_region_gain.lua
@@ -0,0 +1,81 @@
+ardour { ["type"] = "Snippet", name = "Set Region Gain" }
+
+function factory () return function ()
+       -- get Editor GUI Selection
+       -- http://manual.ardour.org/lua-scripting/class_reference/#ArdourUI:Selection
+       local sel = Editor:get_selection ()
+
+       -- allocate a buffer (float* in C)
+       -- http://manual.ardour.org/lua-scripting/class_reference/#ARDOUR:DSP:DspShm
+       local cmem = ARDOUR.DSP.DspShm (8192)
+
+       -- prepare undo operation
+       Session:begin_reversible_command ("Lua Region Gain")
+       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
+               if r:to_audioregion ():isnil () then
+                       goto next
+               end
+
+               -- to read the Region data, we use the Readable interface of the Region
+               -- http://manual.ardour.org/lua-scripting/class_reference/#ARDOUR:Readable
+               local rd = r:to_readable ()
+
+               local n_samples = rd:readable_length ()
+               local n_channels = rd:n_channels ()
+
+               local peak = 0 -- the audio peak to be calculated
+
+               -- iterate over all channels in Audio Region
+               for c = 0, n_channels do
+                       repeat
+                               local pos = 0
+                               -- read at most 8K samples of channel 'c'
+                               local s = rd:read (cmem:to_float (0), pos, 8192, c)
+                               pos = pos + s
+                               -- access the raw audio data
+                               -- http://manual.ardour.org/lua-scripting/class_reference/#C:FloatArray
+                               local d = cmem:to_float (0):array()
+                               -- iterate over the audio sample data
+                               for i = 0, s do
+                                       if math.abs (d[i]) > peak then
+                                               peak = math.abs (d[i])
+                                       end
+                               end
+                       until pos < n_samples
+               end
+
+               if (peak > 0) then
+                       print ("Region:", r:name (), "peak:", 20 * math.log (peak) / 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 ()
+                       -- apply gain
+                       r:to_audioregion (): set_scale_amplitude (1 / peak)
+                       -- 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