ardour { ["type"] = "dsp", name = "Amplifier", category = "Amplifier", license = "MIT", 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 function dsp_params () return { { ["type"] = "input", name = "Gain", min = -20, max = 20, default = 0, unit="dB"}, } end local lpf = 0.02 -- parameter low-pass filter time-constant local cur_gain = 0 -- current smoothed gain (dB) -- called once when plugin is instantiated function dsp_init (rate) lpf = 780 / rate -- interpolation time constant end function low_pass_filter_param (old, new, limit) if math.abs (old - new) < limit then return new else return old + lpf * (new - old) end end -- 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) local ctrl = CtrlPorts:array() -- get control port array (read/write) 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 32 samples at a time -- and interpolate gain until the current settings match the target values if cur_gain ~= ctrl[1] then changed = true siz = 32 end while n_samples > 0 do if siz > n_samples then siz = n_samples end -- process at most "remaining samples" if changed then -- 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 -- 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); -- 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 pango context globally function render_inline (ctx, w, max_h) 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 = th + 4 -- use text-height with 4px padding if (h > max_h) then h = max_h end -- but at most max-height -- clear background ctx:rectangle (0, 0, w, h) ctx:set_source_rgba (.2, .2, .2, 1.0) ctx:fill () -- center text ctx:set_source_rgba (.8, .8, .8, 1.0) ctx:move_to (.5 * (w - tw), .5 * (h - th)) txt:show_in_cairo_context (ctx) return {w, h} end --]]