adds some examples of scrolling spctrograms with Makie. Probably with an old version of Makie

examples/waterfall_heatmap.jl

@@ -0,0 +1,67 @@
+using Makie
+using PortAudio
+using DSP
+
+"""
+Slide the values in the given matrix to the right by 1.
+The rightmosts column is discarded and the leftmost column is
+left alone.
+"""
+function shift1!(buf::AbstractMatrix)
+    for col in size(buf,2):-1:2
+        @. buf[:, col] = buf[:, col-1]
+    end
+end
+
+"""
+takes a block of audio, FFT it, and write it to the beginning of the buffer
+"""
+function processbuf!(readbuf, win, dispbuf, fftbuf, fftplan)
+    readbuf .*= win
+    A_mul_B!(fftbuf, fftplan, readbuf)
+    shift1!(dispbuf)
+    @. dispbuf[end:-1:1,1] = log(clamp(abs(fftbuf[1:D]), 0.0001, Inf))
+end
+
+function processblock!(src, buf, win, dispbufs, fftbuf, fftplan)
+    read!(src, buf)
+    for dispbuf in dispbufs
+        processbuf!(buf, win, dispbuf, fftbuf, fftplan)
+    end
+end
+
+N = 1024 # size of audio read
+N2 = N÷2+1 # size of rfft output
+D = 200 # number of bins to display
+M = 200 # amount of history to keep
+src = PortAudioStream(1, 2, blocksize=N)
+buf = Array{Float32}(N) # buffer for reading
+fftplan = plan_rfft(buf; flags=FFTW.EXHAUSTIVE)
+fftbuf = Array{Complex{Float32}}(N2) # destination buf for FFT
+dispbufs = [zeros(Float32, D, M) for i in 1:5, j in 1:5] # STFT bufs
+win = gaussian(N, 0.125)
+
+scene = Scene(resolution=(1000,1000))
+
+#pre-fill the display buffer so we can do a reasonable colormap
+for _ in 1:M
+    processblock!(src, buf, win, dispbufs, fftbuf, fftplan)
+end
+
+heatmaps = map(enumerate(IndexCartesian(), dispbufs)) do ibuf
+    i = ibuf[1]
+    buf = ibuf[2]
+
+    # some function of the 2D index and the value
+    heatmap(buf, offset=(i[2]*size(buf, 2), i[1]*size(buf, 1)))
+end
+
+center!(scene)
+
+while isopen(scene[:screen])
+    processblock!(src, buf, dispbufs, fftbuf, fftplan)
+    for (hm, db) in zip(heatmaps, dispbufs)
+        hm[:heatmap] = db
+    end
+    render_frame(scene)
+end

examples/waterfall_lines.jl

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+using Makie, GeometryTypes
+using PortAudio
+
+N = 1024 # size of audio read
+N2 = N÷2+1 # size of rfft output
+D = 200 # number of bins to display
+M = 100 # number of lines to draw
+S = 0.5 # motion speed of lines
+src = PortAudioStream(1, 2, blocksize=N)
+buf = Array{Float32}(N)
+fftbuf = Array{Complex{Float32}}(N2)
+magbuf = Array{Float32}(N2)
+fftplan = plan_rfft(buf; flags=FFTW.EXHAUSTIVE)
+
+scene = Scene(resolution=(500,500))
+ax = axis(0:0.1:1, 0:0.1:1, 0:0.1:0.5)
+center!(scene)
+
+ls = map(1:M) do _
+    yoffset = to_node(to_value(scene[:time]))
+    offset = lift_node(scene[:time], yoffset) do t, yoff
+        Point3f0(0.0f0, (t-yoff)*S, 0.0f0)
+    end
+    l = lines(linspace(0,1,D), 0.0f0, zeros(Float32, D),
+        offset=offset, color=(:black, 0.1))
+    (yoffset, l)
+end
+
+while isopen(scene[:screen])
+    for (yoffset, line) in ls
+        isopen(scene[:screen]) || break
+        read!(src, buf)
+        A_mul_B!(fftbuf, fftplan, buf)
+        @. magbuf = log(clamp(abs(fftbuf), 0.0001, Inf))/10+0.5
+        line[:z] = magbuf[1:D]
+        push!(yoffset, to_value(scene[:time]))
+    end
+end