K4Guitune is a program to tune a musical instrument using your computer and its microphone or line-in input. The pitch detection algorithm is based on finding the first peak in the autocorrelation of the input signal.
It's a port to KDE4 of K3Guitune.
The compilation from source requires the following libraries:
Checkout the latest stable release from the SVN repository
$ svn co svn://svn.gna.org/svn/qpitch/branches/k4guitune k4guitune
and then start the CMake-based build process
$ cd k4guitune $ mkdir build && cd build $ cmake .. $ make $ sudo make install $ k4guitune
The estimated pitch is displayed on a bar (1). The detected pitch is shown by two triangles (2), showing whether the estimated pitch is lower or higher than the correct one. When they are both shown, as in the current example, the note is perfectly in tune (error < 2.5 cents).
Detailed information about the pitch detection are shown on the left: the estimated frequency (3) is shown above and the estimated pitch (4) is shown below. The program doesn't require to select the note to tune manually, but it will be found automatically.
The waveform of the input signal is plotted over a time scale of 20 milliseconds (5). The autocorrelation of the signal is displayed (6), with a red bar showing the estimated frequency (7).
The tuner uses the default OSS audio device. The desired recording source and the signal recording levels can be adjusted using a sound mixer.