#!/usr/bin/python
# https://ccrma.stanford.edu/courses/422/projects/WaveFormat/

import struct
import math
import sys

# frequency in wav file
Freq = int (sys.argv[1])

# track length in seconds
TrackLength = 5

# sample rate: 8000, 44100, etc.
SampleRate = 44100

# number of channels: Mono = 1, Stereo = 2, etc.
NumChannels = 1

# 8 bits = 8, 16 bits = 16, etc.
BitsPerSample = 16

# PCM = 1 (i.e. Linear quantization)
# Values other than 1 indicate some form of compression.
AudioFormat = 1

# number of samples
NumSamples = int (TrackLength * SampleRate)
 
print 'freq: [', Freq, '], Hz', 'samples: [', NumSamples, '], length: [', TrackLength, '] seconds'
 
f = open ('freq-' + str(Freq) + '.wav', 'w')

########################
# headers of wave file
# Please note, that the data is stored in little-endian byte order.
########################

# Chunk ID
# we are makeing RIFF file, so we have to mark the file as a riff file. 
# (4 bytes)
f.write ('RIFF')

# Size of Chunk ID
# This is the size of the entire file in bytes. 
# 36 bytes of header + XXX bytes of content
# (4 bytes)
f.write (struct.pack ('<i', 36 + BitsPerSample/8 * NumSamples * NumChannels))

# Format
# Contains the letters "WAVE"
# (4 bytes)
f.write ('WAVE')

# The "WAVE" format consists of two subchunks: "fmt " and "data":
# The "fmt " subchunk describes the sound data's format:

# Subchunk1ID
# Contains the letters "fmt "
# (4 bytes)
f.write ('fmt ')

# Subchunk1Size
# 16 (bytes) for PCM. This is the size of the rest of the Subchunk which follows this number.
# (4 bytes)
f.write (struct.pack ('<i', 16))

# Audio Format
# (2 bytes)
f.write (struct.pack ('<h', AudioFormat))

# Number of Channels
# (2 bytes)
f.write (struct.pack ('<h', NumChannels))

# Sample Rate
# (4 bytes)
f.write (struct.pack ('<i', SampleRate))

# Byte Rate
# (4 bytes)
# = SampleRate * NumChannels * BitsPerSample / 8
f.write (struct.pack ('<i', SampleRate * NumChannels * BitsPerSample / 8))

# Block Align
# = NumChannels * BitsPerSample
# The number of bytes for one sample including all channels; avg bytes sec
# (2 bytes)
f.write (struct.pack ('<h', NumChannels * BitsPerSample))

# Bits Per Sample
# (2 bytes)
f.write (struct.pack ('<h', BitsPerSample))

# Subchunk2ID
# Contains the letters "data"
# (4 bytes)
f.write ('data')

# Subchunk2Size
# = NumSamples * NumChannels * BitsPerSample / 8
# This is the number of bytes in the data (pure wav, excluding the header). 
# You can also think of this as the size of the read of the subchunk following this number.
# (all the bytes of wav content)
# (4 bytes)
f.write (struct.pack ('<i', NumChannels * NumSamples * BitsPerSample / 8))

# Data
# The actual sound data.
for k in xrange (NumSamples):
    # 2 * k * Pi * Freq / SampleRate
    y = math.sin (2 * math.pi * k * Freq / SampleRate)
    v = struct.pack ('<h', int (y * 0x7fff))
    f.write (v)
 
f.close ()