Create wav file from GLSL shader using python3

I've been experimenting with music shader, but it's getting harder to develop with webGL because it doesn't work. So, I made a script to create a wav file from GLSL shader using python. I think it will be easier to adjust detailed settings if python is involved.

Things necessary

Please install pyopengl and pyaudio with pip. If it doesn't work http://www.lfd.uci.edu/~gohlke/pythonlibs/ Downloading the package from here usually works.

This is the script

The explanation here is difficult, so please use it as a library. The sampling rate is set at 48000. If you like the difference, please fix it appropriately.

from OpenGL.GL import *
from OpenGL.WGL import *
from ctypes import *
import numpy
import pyaudio
import wave
import array

def shader2data(duration, src): #Output time, shader music source
    sampleRate = 48000
    numSamples  = duration*sampleRate
    numSamplesC = numSamples*2
    samples = (c_float * numSamplesC)()
    hWnd = windll.user32.CreateWindowExA(0,0xC018,0,0,0,0,0,0,0,0,0,0)
    hDC = windll.user32.GetDC(hWnd)
    pfd = PIXELFORMATDESCRIPTOR(0,1,0,32,0,0,0,0,0,0,0,0,0,0,0,0,0,32,0,0,0,0,0,0,0)
    SetPixelFormat(hDC,ChoosePixelFormat(hDC, pfd), pfd)
    hGLrc = wglCreateContext(hDC)
    wglMakeCurrent(hDC, hGLrc)
    program = glCreateProgram()
    shader = glCreateShader(GL_VERTEX_SHADER)
    glShaderSource(shader, src)
    glCompileShader(shader)
    if glGetShaderiv(shader, GL_COMPILE_STATUS) != GL_TRUE:
      raise RuntimeError(glGetShaderInfoLog(shader).decode())
    glAttachShader(program, shader)
    outs =  cast((c_char_p*1)(b"gain"), POINTER(POINTER(c_char)))
    glTransformFeedbackVaryings(program, 1, outs, GL_INTERLEAVED_ATTRIBS)
    glLinkProgram(program)
    glUseProgram(program)
    vbo = glGenBuffers(1)
    glBindBuffer(GL_ARRAY_BUFFER, vbo)
    glBufferData(GL_ARRAY_BUFFER, sizeof(samples), None, GL_STATIC_DRAW)
    glBindBufferBase(GL_TRANSFORM_FEEDBACK_BUFFER, 0, vbo)
    glUniform1f(glGetUniformLocation(program, "sampleRate"), sampleRate)
    glEnable(GL_RASTERIZER_DISCARD)
    glBeginTransformFeedback(GL_POINTS)
    glDrawArrays(GL_POINTS, 0, numSamples)
    glEndTransformFeedback()
    glDisable(GL_RASTERIZER_DISCARD)
    glGetBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(samples), byref(samples))
    wglMakeCurrent(0, 0);
    wglDeleteContext(hGLrc);
    windll.user32.ReleaseDC(hWnd, hDC);
    windll.user32.PostQuitMessage(0);
    return numpy.frombuffer(samples, dtype=numpy.float32)

def writeWav(filename, data):    
    sampleRate = 48000
    w = wave.Wave_write(filename)
    w.setnchannels(2)
    w.setsampwidth(2)
    w.setframerate(sampleRate)
    w.writeframes(array.array('h', data*32767).tobytes())
    w.close()

def readWav(filename): 
    w = wave.open(filename, 'rb')
    print("params  :", w.getparams())
    print("duration:", w.getnframes() / w.getframerate(), "sec")
    p = pyaudio.PyAudio()
    stream = p.open(format=p.get_format_from_width(w.getsampwidth()),
                channels=w.getnchannels(),
                rate=w.getframerate(),
                output=True)
    stream.write(w.readframes(w.getnframes()))
    stream.close()
    p.terminate()

def playSound(data):    
    sampleRate = 48000
    p = pyaudio.PyAudio()
    stream = p.open(rate=sampleRate, channels=2, format=pyaudio.paFloat32, output=True)
    stream.write(array.array('f', data).tobytes())
    stream.close()
    p.terminate()

Simple rules for writing shader

It uses the same function name and argument name as mainSound (), which is the main function of shadertoy's music shader. So, you can copy and paste the shader toy music shader for this part. Do not change other uniforms, out, main (), etc.

src = """
#version 300 es

out vec2 gain; 
uniform float sampleRate;    

vec2 mainSound( float time )
{
  return vec2(sin(6.2831*440.0*time)); ;
}

void main() {
  float time = float(gl_VertexID) / sampleRate;
  gain =mainSound(time); 
}
"""

This is the source for the shader. If you put this and shader2data (duration, src) with the output time as an argument, sample data will be output. Enter this sample data and file name in writeWav (filename, data) to create a wav file. You can hear the sound with readWav (filename). If you want to output the sound as it is without creating a file, use playSound (data).

data = shader2data(2,src)
filename = "output.wav"
writeWav(filename, data)
readWav(filename)
playSound(data)

I use it like this.

Finally

I don't think there is any demand, but I wrote an article that doubles as a memorandum. I put the ipython file here. https://gist.github.com/gaziya/e5d40b0df1a65510af81b124c4ecf4cc