diff options
Diffstat (limited to 'share/scripts/_amp4.lua')
-rw-r--r-- | share/scripts/_amp4.lua | 79 |
1 files changed, 79 insertions, 0 deletions
diff --git a/share/scripts/_amp4.lua b/share/scripts/_amp4.lua new file mode 100644 index 0000000000..ff4826315d --- /dev/null +++ b/share/scripts/_amp4.lua @@ -0,0 +1,79 @@ +ardour { + ["type"] = "dsp", + name = "Simple Amp IV", + 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 + -- XXX this interpolates dB, resulting in a double-exponential fade XXX + 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 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); -- apply-gain, process in-place + end + n_samples = n_samples - siz + off = off + siz + end +end |