use const

[ardour.git] / scripts / amp4.lua

diff --git a/scripts/amp4.lua b/scripts/amp4.lua
index a348d166f456c58f23545e366367d3b39806d098..276b4a0af6726f3377ab30fad798b97c5db7ff06 100644 (file)
--- a/scripts/amp4.lua
+++ b/scripts/amp4.lua
@@ -1,17 +1,16 @@
 ardour {
        ["type"]    = "dsp",
-       name        = "Amplifier",
+       name        = "a-Amplifier",
        category    = "Amplifier",
        license     = "MIT",
-       author      = "Robin Gareus",
-       email       = "robin@gareus.org",
-       site        = "http://gareus.org",
-       description = [[ Versatile +/- 20dB multichannel amplifier]]
+       author      = "Ardour Team",
+       description = [[Versatile +/- 20dB multichannel amplifier]]
 }
 
 function dsp_ioconfig ()
        return
        {
+               -- -1, -1 = any number of channels as long as input and output count matches
                { audio_in = -1, audio_out = -1},
        }
 end
@@ -25,7 +24,7 @@ function dsp_params ()
 end
 
 local lpf = 0.02 -- parameter low-pass filter time-constant
-local cur_gain = 0 -- current gain (dB)
+local cur_gain = 0 -- current smoothed gain (dB)
 
 -- called once when plugin is instantiated
 function dsp_init (rate)
@@ -40,22 +39,15 @@ function low_pass_filter_param (old, new, limit)
        end
 end
 
--- use ardour's vectorized functions
---
--- This is as efficient as Ardour doing it itself in C++
--- Lua function overhead is negligible
---
--- this also exemplifies the /simpler/ way of delegating the
--- channel-mapping to ardour.
-
+-- the DSP callback function
+-- "ins" and "outs" are http://manual.ardour.org/lua-scripting/class_reference/#C:FloatArray
 function dsp_run (ins, outs, n_samples)
-       assert (#ins == #outs) -- ensure that we can run in-place (channel count matches)
        local ctrl = CtrlPorts:array() -- get control port array (read/write)
-       local siz = n_samples
-       local off = 0
+       local siz = n_samples -- samples remaining to process
+       local off = 0 -- already processed samples
        local changed = false
 
-       -- if the gain parameter was changed, process at most 64 samples at a time
+       -- if the gain parameter was changed, process at most 32 samples at a time
        -- and interpolate gain until the current settings match the target values
        if cur_gain ~= ctrl[1] then
                changed = true
@@ -63,45 +55,53 @@ function dsp_run (ins, outs, n_samples)
        end
 
        while n_samples > 0 do
-               if siz > n_samples then siz = n_samples end
+               if siz > n_samples then siz = n_samples end -- process at most "remaining samples"
                if changed then
-                       cur_gain = low_pass_filter_param (cur_gain, ctrl[1], 0.05)
+                       -- smooth gain changes above 0.02 dB difference
+                       cur_gain = low_pass_filter_param (cur_gain, ctrl[1], 0.02)
                end
 
                local gain = ARDOUR.DSP.dB_to_coefficient (cur_gain) -- 10 ^ (0.05 * cur_gain)
+
                for c = 1,#ins do -- process all channels
                        -- check if output and input buffers for this channel are identical
                        -- http://manual.ardour.org/lua-scripting/class_reference/#C:FloatArray
-                       if not ins[c]:sameinstance (outs[c]) then
+                       if ins[c] ~= outs[c] then
                                -- http://manual.ardour.org/lua-scripting/class_reference/#ARDOUR:DSP
                                ARDOUR.DSP.copy_vector (outs[c]:offset (off), ins[c]:offset (off), siz)
                        end
-                       ARDOUR.DSP.apply_gain_to_buffer (outs[c]:offset (off), siz, gain); -- process in-place
+                       ARDOUR.DSP.apply_gain_to_buffer (outs[c]:offset (off), siz, gain); -- apply-gain, process in-place
                end
                n_samples = n_samples - siz
                off = off + siz
        end
 
+--[[
        if changed then
                self:queue_draw () -- notify display
        end
+--]]
 end
 
 -------------------------------------------------------------------------------
 --- inline display + text example
 
-local txt = nil -- cache globally
+--[[
+local txt = nil -- cache pango context globally
+
 function render_inline (ctx, w, max_h)
-       local ctrl = CtrlPorts:array ()
+       local ctrl = CtrlPorts:array () -- get control ports
 
        if not txt then
+               -- allocate PangoLayout and set font
+               --http://manual.ardour.org/lua-scripting/class_reference/#Cairo:PangoLayout
                txt = Cairo.PangoLayout (ctx, "Mono 8px")
        end
 
        txt:set_text (string.format ("%+.2f dB", ctrl[1]));
        tw, th = txt:get_pixel_size ()
 
-       local h = math.ceil (th + 4) -- use text-height with 4px padding
+       local h = th + 4 -- use text-height with 4px padding
        if (h > max_h) then h = max_h end -- but at most max-height
 
        -- clear background
@@ -111,8 +111,9 @@ function render_inline (ctx, w, max_h)
 
        -- center text
        ctx:set_source_rgba (.8, .8, .8, 1.0)
-       ctx:move_to ( .5 * (w - tw), .5 * (h - th))
+       ctx:move_to (.5 * (w - tw), .5 * (h - th))
        txt:show_in_cairo_context (ctx)
 
        return {w, h}
 end
+--]]