{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Reading and Writing Audio Files with ewave\n",
    "\n",
    "[back to overview page](index.ipynb)\n",
    "\n",
    "https://github.com/melizalab/py-ewave\n",
    "\n",
    "Advantages:\n",
    "\n",
    "* \"pure Python\" (plus NumPy!)\n",
    "* floating-point files can be used\n",
    "* WAVEX is supported\n",
    "* files can be read partially\n",
    "* uses [numpy.memmap](http://docs.scipy.org/doc/numpy/reference/generated/numpy.memmap.html)\n",
    "\n",
    "Disadvantages:\n",
    "\n",
    "* no 24-bit PCM\n",
    "* function for rescaling has to be invoked separately (but at least it's available)\n",
    "\n",
    "Installation:\n",
    "\n",
    "    python3 -m pip install ewave"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Reading"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "import ewave"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "with ewave.open('data/test_wav_pcm16.wav') as w:\n",
    "    print(\"samplerate = {0.sampling_rate} Hz, length = {0.nframes} samples, \"\n",
    "          \"channels = {0.nchannels}, dtype = {0.dtype!r}\".format(w))\n",
    "    data = w.read()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "data"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "%matplotlib inline\n",
    "import matplotlib.pyplot as plt\n",
    "import numpy as np"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "plt.plot(data);"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Obviously, the returned samples have the `dtype` `'int16'` (as stored in the file).\n",
    "To be able to do something useful, we'll have to convert it to floating point and normalize it to a range from -1 to 1.\n",
    "Luckily, there is a function especially made for this:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "np.set_printoptions(precision=4)\n",
    "ewave.rescale(data, 'float32')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Note: until version 1.0.4 this was broken, but now it works (see https://github.com/melizalab/py-ewave/issues/4).\n",
    "\n",
    "Files with floating point data can be used, WAVEX is supported:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "with ewave.open('data/test_wav_float32.wav') as w:\n",
    "    data = w.read()\n",
    "    \n",
    "plt.plot(data);"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Looking good!"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "with ewave.open('data/test_wavex_pcm16.wav') as w:\n",
    "    data = w.read()\n",
    "    \n",
    "plt.plot(data);"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "with ewave.open('data/test_wavex_float32.wav') as w:\n",
    "    data = w.read()\n",
    "    \n",
    "plt.plot(data);"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Opening a 24-bit PCM file fails with a not very verbose error message:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "import traceback\n",
    "try:\n",
    "    ewave.open('data/test_wav_pcm24.wav')\n",
    "except:\n",
    "    traceback.print_exc()\n",
    "else:\n",
    "    print(\"It works (unexpectedly)!\")"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Writing"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "# TODO!"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Version Info"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "print(\"ewave:\", ewave.__version__)\n",
    "\n",
    "import numpy, IPython, sys\n",
    "print(\"NumPy: {}; IPython: {}\".format(numpy.__version__, IPython.__version__))\n",
    "\n",
    "print(\"Python interpreter:\")\n",
    "print(sys.version)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<p xmlns:dct=\"http://purl.org/dc/terms/\">\n",
    "  <a rel=\"license\"\n",
    "     href=\"http://creativecommons.org/publicdomain/zero/1.0/\">\n",
    "    <img src=\"http://i.creativecommons.org/p/zero/1.0/88x31.png\" style=\"border-style: none;\" alt=\"CC0\" />\n",
    "  </a>\n",
    "  <br />\n",
    "  To the extent possible under law,\n",
    "  <span rel=\"dct:publisher\" resource=\"[_:publisher]\">the person who associated CC0</span>\n",
    "  with this work has waived all copyright and related or neighboring\n",
    "  rights to this work.\n",
    "</p>"
   ]
  }
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