audiowaveform is a C++ command-line application that generates waveform data from either MP3 or WAV format audio files. Waveform data can be used to produce a visual rendering of the audio, similar in appearance to audio editing applications.

Waveform data files are saved in either binary format (.dat) or JSON (.json). Given an input waveform data file, audiowaveform can also render the audio waveform as a PNG image at a given time offset and zoom level.

The waveform data is produced from an input stereo audio signal by first combining the left and right channels to produce a mono signal. The next stage is to compute the minimum and maximum sample values over groups of N input samples (where N is controlled by the --zoom command-line option), such that each N input samples produces one pair of minimum and maxmimum points in the output.

audiowaveform requires cmake 2.8.7 or later, g++ 4.6.3 or later, and Boost 1.46.0 or later.

The software has been developed on Ubuntu 12.04 and Fedora 18. Due to compiler and library version requirements, the software may not build on earlier operating system releases.

libmad is available from the RPM Fusion free repository. Before running the following yum command you should follow the instructions here to add this repository, if you have not already done so.

$ sudo yum install git cmake libmad-devel libsndfile-devel \
  gd-devel boost-devel

$ sudo apt-get install git-core make cmake gcc g++ libmad0-dev libsndfile1-dev \
  libgd2-xpm-dev libboost-filesystem-dev libboost-program-options-dev

Install XCode and Homebrew, then:

$ brew install cmake
$ brew install libmad
$ brew install libsndfile
$ brew install gd
$ brew install boost --with-c++11

$ git clone https://github.com/bbcrd/audiowaveform.git
$ cd audiowaveform

audiowaveform uses googletest and googlemock for unit testing. Following this advice in the googletest FAQ, download the sources and unzip:

$ wget https://googletest.googlecode.com/files/gtest-1.6.0.zip
$ unzip gtest-1.6.0.zip
$ ln -s gtest-1.6.0 gtest

And similarly, for googlemock:

$ wget https://googlemock.googlecode.com/files/gmock-1.6.0.zip
$ unzip gmock-1.6.0.zip
$ ln -s gmock-1.6.0 gmock

$ mkdir build
$ cd build
$ cmake ..
$ make

The default build type is Release. To build in Debug mode add -D CMAKE_BUILD_TYPE=Debug to the cmake command above. If you don't want to compile the unit tests add -D ENABLE_TESTS=0.

To compile with clang instead of g++:

$ cmake -D CMAKE_C_COMPILER=/usr/local/bin/clang -D CMAKE_CXX_COMPILER=/usr/local/bin/clang++ ..

$ make test

To see detailed test output:

$ ./audiowaveform_tests

$ sudo make install

By default this installs the audiowaveform program in /usr/local/bin, and man pages in /usr/local/share/man. To change these locations, add a -D CMAKE_INSTALL_PREFIX=... option when invoking cmake above.

$ audiowaveform --help

audiowaveform accepts the following command-line options:

Generate waveform data from an MP3 file, at 256 samples per point with 8-bit resolution:

$ audiowaveform -i test.mp3 -o test.dat -z 256 -b 8

Generate a 1000x200 pixel PNG image from a waveform data file, at 512 samples per pixel, starting at 5.0 seconds from the start of the audio:

$ audiowaveform -i test.dat -o test.png -z 512 -s 5.0 -w 1000 -h 200

Convert a waveform data file to JSON format:

$ audiowaveform -i test.dat -o test.json

Generate a 1000x200 PNG image directly from a WAV file, at 300 samples per pixel, starting at 60.0 seconds from the start of the audio:

$ audiowaveform -i test.wav -o test.png -z 300 -s 60.0 -w 1000 -h 200

Note: if you want to render multiple images from the same audio file, it's generally preferable to first create a waveform data (.dat) file, and create the images from that, as decoding long MP3 files can take significant time.

Convert MP3 to WAV format audio:

$ audiowaveform -i test.mp3 -o test.wav

This program contains code from the following open-source projects, used under the terms of these projects' respective licenses:

• Audacity
• madlld

See COPYING for details.

If you have a feature request or want to report a bug, we'd be happy to hear from you. Please either raise an issue, or fork the project and send us a pull request.

This software was written by Chris Needham, chris.needham at bbc.co.uk.

Copyright 2013 British Broadcasting Corporation