Sonic is a simple algorithm for speeding up or slowing down speech. However, it's optimized for speed ups of over 2X, unlike previous algorithms for changing speech rate. The Sonic library is a very simple ANSI C library that is designed to easily be integrated into streaming voice applications, like TTS back ends.
The primary motivation behind Sonic is to enable the blind and visually impaired to improve their productivity with open source speech engines, like espeak. Sonic can also be used by the sighted. For example, Sonic can improve the experience of listening to an audio book on an Android phone.
A native Java port of Sonic is in Sonic.java. Main.java is a simple example of how to use Sonic.java. To play with it, you'll need a "talking.wav" file in the current directory, and you'll want to change the speed, pitch or other parameters manually in Main.java, in the main method.
Sonic is Copyright 2010, 2011, Bill Cox, all rights reserved. It is released under the Apache 2.0 license, to promote usage as widely as possible.
Performance test:
I sped up a 751958176 byte wav file with sonic (a 9 hour, 28 minute mono audio file encoded at 16-bit 11.KHz), but with the output writing disabled. The reported time, running Ubuntu 11.04 on my HP Pavilion dm4 laptop was:
real 0m50.839s user 0m47.370s sys 0m0.620s
The Java version is not much slower. It reported:
real 0m52.043s user 0m51.190s sys 0m0.310s
I upgraded the pitch change algorithm to use a 12-point sinc FIR filter for interpolation, rather than linearly interpolating between points. This significantly reduces noise introduced by the pitch change algorithm. It is most noticable in low-sample-rate streams, such as the 11,025 Hz output of the Eloquence TTS engine. The upgrade is in both the C and Java versions.
Author: Bill Cox email: waywardgeek@gmail.com