Simplify the logic in HiAndLowPass filter
And beef up comments for readers using the filter as an example.
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@ -4,7 +4,7 @@ ardour {
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category = "Filter",
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license = "GPLv2",
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author = "Ardour Team",
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description = [[High Low Pass filter with up to 48dB / octave]]
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description = [[An Ardour High and Low Pass Filter with de-zipped controls, written in Lua]]
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}
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function dsp_ioconfig ()
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@ -85,6 +85,12 @@ function dsp_configure (ins, outs)
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lp[c] = {}
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-- initialize filters
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-- http://manual.ardour.org/lua-scripting/class_reference/#ARDOUR:DSP:Biquad
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-- A different Biquad is needed for each pass and channel because they
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-- remember the last two samples seen during the last call of Biquad:run().
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-- For continuity these have to come from the previous audio chunk of the
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-- same channel and pass and would be clobbered if the same Biquad was
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-- called several times by cycle.
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for k = 1,4 do
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hp[c][k] = ARDOUR.DSP.Biquad (tbl['samplerate'])
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lp[c][k] = ARDOUR.DSP.Biquad (tbl['samplerate'])
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@ -160,59 +166,58 @@ function dsp_run (ins, outs, n_samples)
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-- process all channels
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for c = 1, #ins do
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-- High Pass
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local xfade = cur[1] - ho
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-- prepare scratch memory
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ARDOUR.DSP.copy_vector (mem:to_float (off), ins[c]:offset (off), siz)
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-- initialize output
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if cur[1] == 0 then
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-- high pass is disabled, just copy data.
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ARDOUR.DSP.copy_vector (outs[c]:offset (off), mem:to_float (off), siz)
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else
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-- clear output, The filter mixes into the output buffer
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ARDOUR.DSP.memset (outs[c]:offset (off), 0, siz)
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end
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-- high pass
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-- allways run all filters so that we can interplate as needed.
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for k = 1,4 do
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if xfade > 0 and k == ho + 1 then
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ARDOUR.DSP.mix_buffers_with_gain (outs[c]:offset (off), mem:to_float (off), siz, 1 - xfade)
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end
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-- run at least |ho| biquads...
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for k = 1,ho do
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hp[c][k]:run (mem:to_float (off), siz)
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end
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ARDOUR.DSP.copy_vector (outs[c]:offset (off), mem:to_float (off), siz)
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if k == ho and xfade == 0 then
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ARDOUR.DSP.copy_vector (outs[c]:offset (off), mem:to_float (off), siz)
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elseif k == ho + 1 then
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ARDOUR.DSP.mix_buffers_with_gain (outs[c]:offset (off), mem:to_float (off), siz, xfade)
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end
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-- mix the output of |ho| biquads (with weight |1-xfade|)
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-- with the output of |ho+1| biquads (with weight |xfade|)
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if xfade > 0 then
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ARDOUR.DSP.apply_gain_to_buffer (outs[c]:offset (off), siz, 1 - xfade)
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hp[c][ho+1]:run (mem:to_float (off), siz)
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ARDOUR.DSP.mix_buffers_with_gain (outs[c]:offset (off), mem:to_float (off), siz, 1 - xfade)
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ho = ho + 1 -- to avoid running another time the biguad |ho+1|
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end
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-- low pass
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-- run remaining biquads because they need to have the correct state
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-- in case they start affecting the next chunck of output
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-- TODO: only run the ones that have a chance to run next cycle
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for k = ho+1,4 do
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hp[c][k]:run (mem:to_float (off), siz)
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end
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-- Low Pass
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xfade = cur[4] - lo
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-- copy output of high-pass into "processing memory"
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-- prepare scratch memory (from high pass output)
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ARDOUR.DSP.copy_vector (mem:to_float (off), outs[c]:offset (off), siz)
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if cur[4] > 0 then
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-- Clear output, Low-pass mixes interpolated data into output.
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-- (Except if the filter is disabled (0) in which case we just keep the output.)
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ARDOUR.DSP.memset (outs[c]:offset (off), 0, siz)
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-- run at least |lo| biquads...
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for k = 1,lo do
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lp[c][k]:run (mem:to_float (off), siz)
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end
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ARDOUR.DSP.copy_vector (outs[c]:offset (off), mem:to_float (off), siz)
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-- mix the output of |lo| biquads (with weight |1-xfade|)
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-- with the output of |lo+1| biquads (with weight |xfade|)
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if xfade > 0 then
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ARDOUR.DSP.apply_gain_to_buffer (outs[c]:offset (off), siz, 1 - xfade)
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lp[c][lo+1]:run (mem:to_float (off), siz)
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ARDOUR.DSP.mix_buffers_with_gain (outs[c]:offset (off), mem:to_float (off), siz, 1 - xfade)
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lo = lo + 1 -- to avoid running another time the biguad |lo+1|
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end
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for k = 1,4 do
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if xfade > 0 and k == lo + 1 then
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ARDOUR.DSP.mix_buffers_with_gain (outs[c]:offset (off), mem:to_float (off), siz, 1 - xfade)
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end
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-- again, run remaining biquads
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for k = lo+1,4 do
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lp[c][k]:run (mem:to_float (off), siz)
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if k == lo and xfade == 0 then
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ARDOUR.DSP.copy_vector (outs[c]:offset (off), mem:to_float (off), siz)
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elseif k == lo + 1 then
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ARDOUR.DSP.mix_buffers_with_gain (outs[c]:offset (off), mem:to_float (off), siz, xfade)
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end
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end
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end
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