Reference Files For Voice Quality Testing And Echo Measurements - OPTICOM OPERA - V 3.5 User Manual

C H A P T E R 6 :
weakness of PSQM by extending the algorithm with a time alignment algorithm
that can handle varying delays as they show up on packet oriented networks.
This solution will, nevertheless, never be the ideal solution for measurements
on such networks, if the implementation needs to conform to the P.861
recommendation.
Due to the widely extended demand for measurement algorithms suitable for
packet oriented transmission in real networks, the ITU started developing a new
recommendation with a widely extended scope. The outcome was
recommendation P.862 (PESQ) [ITUT862][BEER02a][BEER02b], which is in
place now since 2000. Although the basic structure of PESQ is very similar to
PSQM, many details in all parts of the algorithm have been improved. The two
major advances are PESQ including a very good time alignment algorithm that
can handle varying delays and that the final result is a MOS score. For PSQM
the function which mapped the PSQM score to the MOS scale was proprietary
and so frequently leading to totally different results between two
implementations. The following chapter explains PSQM in more detail. PSQM
is chosen here as an example for all modern perception based measurement
methods. Both algorithms will be explained in even more details in the
according chapters where their implementation and usage are described.
6.2 Reference Files for Voice Quality
Testing and Echo Measurements
OPERA Systems are delivered with a complete set of Test files. All WAVE files
are stored in the folder c:\programme\opera\wavefiles. Besides the reference
files used for performing life tests, there is a pair of reference and test file for
each algorithm which are used for demonstrating file based measurements.
These files are called AlgorithmRef.wav and AlgorithmTest.wav, where
Algorithm must be replaced by PSQM, PESQ or Echo. These files must not be
used as reference files for real measurements. For this purpose the files
according to the following table are supplied.
Filename
DefaultRefFileEnglish.wav
DefaultRefFileEnglish-a.wav
DefaultRefFile.wav
DefaultRefFileGerman.wav
DefaultRefFileGerman-a.wav
T E L E P H O N Y B A N D
T E S T I N G
118
V O I C E Q U A L I T Y
Description
English language, male and female
speaker, mu-law.
English language, male and female
speaker, a-law.
Same as DefaultRefFileEnglish.wav
German language, male and female
speaker, mu-law.
German language, male and female
speaker, a-law.