 The
ComPacketer ™
Compandent's
ComPacketer is a voice coder which achieves
a breakthrough in quality/bit rate/complexity tradeoff.
Compandent’s novel technology, the ComPacketer
that operates at 2.8 kb/s, produces speech with quality
which exceeds that of ITU-T G.723.1 at 6.3 kb/s,
which is widely used for VoIP. Its performance is demonstrated
in Table 1 below. Using the ComPacketer, only
graceful degradation is introduced in frame erasure
environment, as compared to the higher quality degradation
introduces by the common standards used for VoIP.
Due
to the increasing number of users and services, particularly
in wireless applications, severe limitations are imposed
on the bandwidth available for voice. The use
of Compandent’s low bit-rate technology will allow a
larger number of users, and a wider bandwidth for data,
or for more bandwidth-demanding applications such as
video.
Other
practical comments
1.
The ComPacketer is naturally very suitable for
error concealment applied to packet loss or frame erasure
situations, and may therefore be very suitable for
Voice-over-IP and wireless applications. Its performance
is various Frame Erasure Rates (FER) is demonstrated in
Table 1 below.
2.
The ComPacketer is naturally very suitable for
parametric processing, such as pitch scaling, and slow
or fast playback (time scaling).
ComPacketer
demonstration: (click to play)
Table
1. Demonstration
of the 2.8 kb/s ComPacketer's quality at various
Frame Erasure Rates (FER).
* Note, that the no additional buffering delay was used
at the decoder for error concealment. Future demo will
demonstrates the additional improvement obtained by such
buffering.
Figure
1 illustrates the range of performance advantage
of Compandent’s ComPacketer with respect
to the standard technology used by our competitors in
the fields of secure voice, wireless, VoIP and Public
Switched Telephone Networks (PSTN).
For
example cellular phone uses 8-13 kb/s (kilo bits per
second), standard telephone uses 16-64 kb/s, hence the
ComPacketer's transmission rate is about 1/4
- 1/3 compared to cellular phone, and 1/24 - 1/6 compared
to standard telephone. Even the current standard coders
used for Voice-over-IP and multimedia applications operate
at rates as high as 5.3-6.3 kb/s (G.723.1) to 8 kb/s
(G.729).
Subjective
Tests:
Table
2 and Table 3 summarize the results of subjective tests
conducted to compare the ComPacketer to ITU-T
G723.1 coder. The results indicate that the subjective
quality of the 2.8 kb/s ComPacketer exceeds that
of G.723.1 at 5.3 kb/s, and it is slightly better than
that of G.723.1 at 6.3 kb/s.
| Test |
2.8
kb/s ComPacketer
|
5.3
kb/s G.723.1
|
No
Preference
|
| Female |
40.28%
|
33.33%
|
26.39%
|
| Male |
48.61%
|
24.31%
|
27.08%
|
| Total |
44.44%
|
28.82%
|
26.74%
|
| Table
2. Results of subjective
A/B test for comparison between the 2.8 kb/s ComPacketer
coder to 5.3 kb/s G.723.1. With 95% certainty the
result lies within +/-5.53%. |
| Test |
2.8
kb/s ComPacketer
|
6.3
kb/s G.723.1
|
No
Preference
|
| Female |
38.19%
|
36.81%
|
25.00%
|
| Male |
43.06%
|
31.94%
|
25.00%
|
| Total |
40.63%
|
34.38%
|
25.00%
|
| Table3.
Results of subjective A/B test for comparison between
the 2.8 kb/s ComPacketer coder to 6.3 kb/s G.723.1.
With 95% certainty the result lies within +/-5.59%. |
|
