Subject: Re: PSQM (P.861), PSQM+, PAMS

From: [email-masked]
Date: Mon, 3 Jul 2000 14:11:08 +0100

Forgive me for joining this discussion, but as the developer of PAMS and
co-developer of PESQ (P.862) I hope I can comment.  I don't normally read
this list, so please cc me in on any further discussions on this thread
([email-masked]).

Beware of using PSQM or MNB straight from P.861.  These algorithms don't
include time alignment, and PSQM does not include level alignment.  Neither
PSQM nor MNB take account of filtering that may occur in many
systems/networks.  For these reasons they are very inaccurate in many
testing applications.

To fix these problems a much more capable algorithm, PESQ (perceptual
evaluation of speech quality) is expected to become a new ITU recommendation
P.862 some time early in 2001, at which point P.861 will be withdrawn.  PESQ
is the result of a long competition and collaboration in the ITU, and has
been found to perform well at predicting subjective quality in a very wide
range of applications.  It is also much better than PSQM and MNB, even for
working with speech codecs that have none of the time and level alignment or
filtering issues.

Like PESQ, PAMS includes time and level alignment and (from release 3)
ability to deal with filtering, and is suitable for use with a wide range of
telephony codecs and networks.  PAMS has been commercially available since
1998 and is now in wide use in areas such as VoIP testing.

Unfortunately, as P.862 is only a draft ITU recommendation, PESQ is not yet
publicly available.  The source code is available to ITU members only, and
even then under a restrictive license.  So for PESQ I am afraid that you
will have to wait some months to obtain the first commercial
implementations, likely to be available for purchase in Q4 of this year, or
until about February 2001 before you can buy the ITU recommendation
(assuming it is approved), which will have C source code attached.

If you can't wait this long, I can only suggest that you buy PAMS from one
of the companies listed on my website:
http://www.labs.bt.com/people/rixa/pams/ .  For references on PAMS and PESQ,
see my paper list: http://www.labs.bt.com/people/rixa/awr_cv.htm#papers -
e-mail me if you would like a copy of any of these papers.

Regards,

Antony

Antony Rix         [email-masked]
B54/86, Adastral Park, Ipswich IP5 3RE, UK
Tel. +44 (01473) 644 339
http://www.labs.bt.com/people/rixa/