Envelope and Instantaneous Phase in Residual Representation
Abstract
Envelope and instantaneous phase of a real signal are two concepts mainly associated with modulation systems. In this paper is shown how envelope and lnstantaneous phase can be applied in coding systems. In particular, the envelope of t he residual provides informatton ahnut pitch ilnd energy of the signal and can be user to properly codify it. A parametric version of the envelope is taken from the residual of a s ignal and this informat ion ls used ln two different coders: an APC corleranda stochastlcally excited coder. In APC coder the residual envelope is used to quantize the prediction error providing step size and dynamlc bU assignment information. In stochastically excitec coders, the input to the synthesls filter is composecl by the product of the parametric envelope of the residual multiplied by an instantaneous phase taken from a codebook of random phases .
Full text
SIGNAL
PROCESSING I
V:
Theo ies and Applica ions
J. L. Lacoume, A. Chehikian,
N.
Ma ín,
and
J.
Malbos (Edi o s)
Else ie Science Publishe s
B.
V.
(No h-Holland)
© EURASIP,
1988
167
ENVELOPE
AND
INSTANTANEOUS
PHASE
IN RESIDUAL REPRESENTATION
A.
Mo eno,
M.A.
Lagu
n
as
Dp o.
Teo ía
de
la
Señal
y
Com
unicaci
ones.
U.P.C.
E.T.S.I.
Telecomunicacion
Apdo .
30.002,
08080
Ba celona,
Spain.
En elope
and
ins an aneous
pha
s e
o
a
eal
s
lgnal
a e
wo
concep s
mainly
asso
c
i.a ed
wl h
modula ion
sys ems.
In
his
pape
is
shown
how
en elope
and
lns an aneous
phase
can
be
applied
in
coding
sys ems.
In
p
a icula
,
he
en elope
o
he
esidual
p o ides
in o ma on
ahnu
pi ch
ilnd
ene gy
o
he
signal
and
can
be
use l
o
p ope ly
codi y
i .
A
pa ame ic
e sion
o
he
en elope
is
aken
om
he
es
ldual
o
a s
ignal
and
his
i.n o ma
ion
ls
used
ln
wo
d
i. e
en
code s:
an
APC
co le
anda
s ochas lcally
exci ed
code
.
In
APC
code
he
esidual
en elope
i.s
used
o
quan
lze
he
p edic
ion
e o
p o iding
s ep
s
ize
and
dynamlc
bU
assignmen
.in o ma ion.
In
s ochas ically
exci ec!
code s,
he
inpu
o
he
syn hesls
il e
is
composecl
by
he
_p oduc
o
he
pa ame ic
en elope
o
he
esidual
mul
ip
li
ed
by
an
ins an aneous
phase
aken
om
a
codebook
o
andom
phases
.
INTRODUCTION
The
cha ac e iza ion
o
he
p edic ion
e o
in
sp
e
ech
coding
is
impo an
o
ge
a
good
syn he
ic
speech
quali y.
In
wa e o m
code s,
as
ADPO!
/1/
,
he
p edic ion
e o
is
quan ized
and
send
o
he
·
ecei e .
In
his
case,
a
p io i
es ima ion
o
he
wa e o m
o
he
p ed
ic
ion
e o
is
use ul
o
quan
ize
i
p o
pe
ly
.
S ochas ically
exci ed
code s
/2/,
by
he
o he
hand,
ep esen s
speec
h
by
means
o
a
ime
a ying
il e
exci ed
by
a
Gaussian
sequence.
A
ime
a ying
il e
is
buil
using
a
sho
delay
il e
which
p o ides
he
onnan s
s
uc u
e
and
a
long
delay
il e ,
(pi ch
il e ),which
p o ides
he
ine
s uc u e
o
he
spec um.
Exci a ion
s e
quence
is
selec ed
om
a
codebook
o
whi e
Gaussian
sequences
by
minimizing
a
pe cep ual
e o
measu emen
.
Long
del
ay
il
e
is
use ul
in
o
iced
egions
bu
du ing
un oiced
egions
has
small
e ec
.
The e o e
i
is
use ul
o
ha e
a
unc ion
which
p ese es
pUch
and
empo al
ene gy
e olu ion
o
he
esidual
in
o de
o
keep
pi ch
in o m
a
ion
in
oiced
egions
and
ene gy
e olu ion
in
all
kind
o
egions.
Some
e o s
ha e
been
made
in
his
sense
a·s
he
sys em
Vec o
Quan ized
Mul ipulse
Code
VQMP
/3/
,
This
code
uses
a
model
whe e
a
sho
delay
il e
i s
exci ed
by
a
signal
This
wo k
has
b
een
pa ially
suppo ed
by
he
CAICYT
g an
2196/84
o
he
Spanish
Go e n-
men .
ob ained
om
a
codebook
o
mul i
pu
lse
like
sequences
,
ha
is
,
only
ew
alues
o
hese
sequences
a e
di e en
o
m
ze o.
Each
sequence
is
mul
i pl
ied
by a
polynomial
weigh ing
un
c ion
whose
coe ici.en s
a e
es ima ed
i n
o de
o
mlnimlze
a
quad a ic
e o
be ween
he
p edic ion
e o
and
he
unc
ion
i sel .
This
unc
ion
is
calcula ed
e e y
5ms
and
discon inui ies
be ween
ames
a ec s
he
qual
i y
o
he
sy
n h
esized
signal.
T
e
en elo
pe
o
he
esidual
s
ignal,
is
an
associa ed
unc ion
which
p ese es
he
a
bo e
men
ioned
ime
e olu
ion
ea u es
o
he
esidual:
pi ch
and
e
ne~gy
.
This
unc ion
possesses
ano he
impo an
ad an age:
he
posi i e
cha ac e
o
he
en elope
allows
o
ob a
in
a
pa
ame
ic
e s
ion
o
he
en
elo
pe,
wi h
a
conside able
da a
educ ion
in
i s
ep esen a
ion.
In
his
pape
l-e
in onna ion
o
he
en elope
is
used
in
wo
di e en
applica ions
in
speech
coding.
Fi s ,
is
p esen ed
how
he
en
el
ope
o
h
e
esidual
can
help
o
quan ize
p ope ly
he
p edic ion
e o
in
an
ADPCM
sys em.
Ene gy
in o ma ion
de i ed
om
he
en elope
a e
used
o
con ol
he
s ep
size
o
he
quan ize
and
o
assign
bi s
dynamically.
Second,
he
en elope
o
he
esidual
is
applied
in
a
low
bi
a e
coding
sys em
whe e
a
ime
a ying
il e
(sho
delay
il e )
is
exci ed
by
a
signal
composed
by
a
pa ame ic
e sion
o
he
en elope
o
he
esidual,
mul
ipl
ied
by
he
cos
ine
o
an
ins an aneous
phase.
lns an aneous
phase
is
chosen
om a
codebook
in
an
analys
is
by
syn
hes
is
loop
in
o
de
o
mi
n
imize
a
pe
cep
ual
we
igh
ing
e o
.