Speex quality evaluation

These data and scripts are intended to reproduce the experiment for speex quality estimation in lossless environment and comparing given results with other codecs.

Test environment

Originally this test has been performed under GNU/Linux environment with Ubuntu 9.04. In order to successfully reproduce the experiment, one have to install these additional packages and utilities:

• python 2.4 or above (already installed on most Linux systems)
• GNU Make utility (make package)
• gnuplot plotting program (gnuplot package)
• SoX audio manipulation utility (sox package)
• Gnuplot.py, a python interface to the gnuplot plotting program (python-gnuplot package)
• PESQ test utility from ITU-T official site (has no package, not open-source)
• network-emulator tool and pjsip media framework (both open-sources but have no packages)
• Intell IPP codecs
• git revision control system (git-core package)

PESQ utility installation

PESQ utility sources can be downloaded from corresponding ITU-T page. The compilaton result (one binary file) must be placed into the one of the $PATH directories. File must be named pesq.

pjsip, IPP and network-emulator installation

Just before installing network-emulator, the pjproject framework must be downloaded and compiled from its official site

Intel Integrated Performance Primitives are required to get speech quality estimation results for G.723.1, G.729 and some other commercial codecs. An IPP installation HOWTO is available from the PJSIP site.

One should download and install network emulator. Compiling instructions can be found in the README short manual. Binary named emulator must be moved to the $PATH.

experiment launching

If everything goes right, it's possible to perform an experiment. To do this it's enought to type make with one of the prerequisites: <codec_id> or just codecs. The codec_id is nothing but some identifier which defines a bunch of encoder options for emulator utility. These identifiers are listed in Makefile just after "encoding options" line and in the codec variable.

If some of of the codecs (i.e. IPP codecs) has not been compiled, one should comment out or remove corresponding identifiers from codec variable in conf.mk.

It's possible also to investigate the impairments to the speech quality of the codecs connected in tandem, when the next encoder use the output of the previous decoder. Such tandem is defined as the element of the codec variable which looks like a string containing set of codec names concatenated with the use of "__" character sequence. The samples are already defined in the conf.mk.

g726_32__g726_32
g729__g729
g729__g729__g729

etc.

output data

Makefile creates directory structure with experiment results as follow:

|-- input
|   |-- english_female01.pesq
|   |-- english_female01.wav
|   |-- english_female02.pesq
|   |-- english_female02.wav
|   |-- english_female03.pesq
|   |-- english_female03.wav
|   |-- english_female04.pesq
|   |-- english_female04.wav
|    ...
|
|-- output
|   |-- amr_10200
|   |   |-- english_female01.pesq
|   |   |-- english_female01.wav
|   |   |-- english_female02.pesq
|   |   |-- english_female02.wav
|   |  ...
|   |-- speex_2
|   |   |-- english_female01.pesq
|   |   |-- english_female01.wav
|   |   |-- english_female02.pesq
|   |   |-- english_female02.wav
...

First before there are input files which will be prepared from sources. The difference between source and input files is that the last ones have 8kHz sampling rate and adjusted volume (see prepare.sh script for more information).

Then pesq utility compares every input file with itself. This `reference' value is used for the comparison with the pesq values of the degraded speech samples in order to compute the Ie parmeter of the R-factor. The experiments show that the reference pesq has the value 4.549 regardless the input speech sample.

For every input file and every codec identifier the testing tool creates two files:

• degraded .wav-file.
• .pesq file which contains just one floating point number with MOS LQO estimation.

plotting graphics

The plot_data.py utility draws pesq estimation results and stores these ones in the files inside the graphics directory. It's nessesary to type: mkdir graphics before launching this script. As with Makefile above one should comment out values in codec dictionary if corresponding experiment results do not exist.