Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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2l02a~
TIME ~ G FOR GENERALIZED ANALYSIS-BY-SYNTHESIS CODING
Field of the I~
The present h~ ion relates generally to speech coding systems and
more s~ifi~ ly to a l~luclion of ba,..l~.; llh ~ uh-,m~,llt~ in analysis-by-s~ n~' '! ~ ~
s speech coding systems.
R~ , . d of the I~
Speech coding systems function to provide cod~. Jld l~ iSe'.l ~lio~c of
speech signals for cc ~ ~- over a channel or network to one or more system
~ce;~ . Each system receiver lbcon~ speech signals from received
l0 cod~.c,ld~. Theamountofcod~ .ldi~ro~ nc~~~ ~i( ~ byasystemina
given time period defines system ' '~. ;.llh and affects the quality of speech
~;p~luced by system l~,ce;.
Designers of speech coding systems often seek to provide high quality '~
speech l~,~ludu.:lion capability using as lit~e ~ .i.lll. as L " '1~ IIù
lS l~u l~ nt~ for high quality speech and low ~ may conflict and ~ fu
present ~, r~ ". ;ag trade-offs in a design process. This nol~ E, speech
coding t. I h ~ u~ S have been de~loped which provide a . ~r ~1' speech quality at
reduced channel halld~.;dlhs. Among these are analysis-~-synthesis speech coding
With analysis-by-~ - speech coding ~,h--i~ s, speech signals are
COdedthrOUgha-.a~erOllll ' ' g~JlU~,edll.~.. A ~ ' ' speechsignalis
synthesized from one or more parameters for co...p~ ;go~- to an original speech signal
tober c' ~ Byvaryingp=,-...~ ffe~.nt~..l1P.:,.dc~n.'~ speech
signals may be -.~ The parameters of the closest - ' ~ s ' '
2s speech signal may then be used to ~pl~iSenl the original speech signal.
Many analysis-l" s.~ Le~;s coders, e.g., most code-excited linear
predicdon (CELP) coders, employ a lDn~ predictor (LTP) to model 1- g t~,llll : ~
Cull~ - - in speech signals. (The term "speech signals" means actual speech or
any of the residual and ~ ~ signals present in analysis-by-sylltlle~;~ coders.)
30 During the sylllllcs;s process, an LTP is COI~ ;ol- ~lly realized either as an all-pole
filter or as an adaptive co~ with gain scaling. As a general matter, long t~
cu..~ r - in speech signals aUow a past l~,COI.,~tl uct~,d speech signal to serve as an
a~ of a culrent speech signal. LTPs work to compare several past speech
signals (which have already been coded) to a current (original) speech signal. By
2~o2o~a
such Cr!llll~AI ;cons, the LTP det rmin~ s which past signal most closely matches the
original signal. A past speech signal is i(l~ntifiq~ by a delay which inrlir~qt~s how
far in the past (from current time) the signal is found. A coder employing an LTP
svb~ f~ a scaled version of the closest ' ~ g past speech signal (i.e., the bestS d~ '') from the current speech signal to yield a signal with reduced long-
term c~ ,lalioll. This signal is then coded, typically with a fixed ~lor~ ;r
codcbook (FSCB). The FSCB index and LTP delay, among other p= ~ t -~ are
Il ~ to a CELP decoder which can recover an estimate of the original speech
from these p~aln~,t~
By mndeling long t~ ll Cullbl - of speech, the quality of -
.~coni,t~ ,t~,d speech at a decoder may be e ~ 9nc~ This e~h~ however, is - ' ~ -~
notachievedwithouta ~ignif- increaseinband..;dlll. Fore li'~ inorderto
model long ~.1ll CUllbl ~ - in speech, conventional CELP coders may transmit 8-
bit delay i.,r,.. ", ~i~m every 5 or 7.5 ms (referred to as a ~Jru,,~c). Such time-
15 varying delay p ~ te-~ require, e.g., between one and two ad~1itinnql Idlobits (kb)
per second of ~ .;.llh. Because ~r~ia~iOnS in LTP delay rnay not be p ~ " Lle
over time (i.e., a se ~ of LTP delay values may be ~ ' - - - in nature), it may
prove difficult to reduce the a1~l;l;n ~ .;dlll lb~uilb~ n~ through im~lu._d
coding of delay ~ -
One ~ uacl- to reducing the extra bandwidth l~ PI~ IS of
analysis-by~ the~is coders ~,a ~ g an LTP might be to transmit LTP delay
values less often and ~e ~ a ' ~' LTP delay values by ~lali~n.
IIo..~ , r -l ' may lead to ~ delay values being used by the LTP
in ~ f, ~ s of the speech signal. For ~ , if the delay is
2s ~ ~ rp~ -1, then the LTP will map past speech signals into the present in a
~_' >~ -1 fashion. As a result, the dil~,.buce between past speech mapped into the
present and the original signal will be larger than it might c,lh~ . ;se be. The FSCB
must then work to undo the effects of this s~boptilllal d~ ,- ~r rather than perform
its normal funcdon of refining ~ rOlul shape. As a result, ~igr'~ audible
30 d;i~t~ni ~ mayresult. -
Summary of the Invention
The present i..~_ntion provides a method and ~p~ --- for Ib 11 ~ g
l; ls.;dill~b4ullb inanalysis-l~ S.~ lcs;scodingsystems. Inr~c~
with the present ill~. . ger~ ~. uli~ed analysis-by-synthesis coding is ~ .idcd
35 through variation of original signals. Original signal variants are referred to às trial . ; ~ .
'';
.. -. ..... .
21020~
original signals. Use of trial original signals in place of or as a ~ rp!~ to the
use of original signals in analysis-by-synthesis coding reduces coding error and bit
rate I~UilG~U~ i. In the context of speech coding, reduced coding error affords less
frequent lln~ .in~ of LTP delay ~ ~( ~ and allows for delay ~ , s'
S with little or no ~1Pgr: ~ in the quality of l~con~llu~,t~,d speech. The u~ ion is
applicable to, among other things, n~,lwol~ ~ for cc, -~ g speech i.,r~ iO,-,
such as, for - . 1 e, wireless (e.g., cellular) and con- ~nUO~ .pkc~r n~,t~
Regarding speech coding, trial original signals are i~ I)r signals
which are p~ ually (e.g., audibly) similar to the actual original signal. The
10 degree of audible ~imil ~ between a trial original signal and the actual original
signal may affect coded bit rate and the quality of speech ~ . d by a receiver
(e.g., the lower the ~ ' ~~" the lower the bit rate and speech quality may be). The
original signal, and hence the trial original signals, may take the form of actual
speech signals or any of the~residual or e-ritP'i-~n signals present in analysis-by- ~ -
15 ",.~hcs;s coders.
In an i11 ~_ e -..hc ' of the present i~ - trial original
signals are ~- - ' as luu~ versions of an original speech signal s~,gr-
Me~&;~llGS of ~imi1 ~~qr (e.g., cross-coll~ ' ) between trial original signals and
cc ~ -U~io~ from an adaptive code~ are evaluated. A trial original signal which
~20 is either the same as one of the trial original signals or a variant of an original or trial
original signal is ~ t~ based on one or more evaluated ...f ~ s of similarity.
an the case of a variant of ~ Iy g ~ trial original signals, the ~lc~ d
trial original signal (i.e., the variant) may c~ ,ond to a time-shift which falls in
between time-shifts which produced ~llG~;ousl~r generated trial original signals.) A ~ -
25 signal ~ ing a coded .. ~ of the original signal is ~ .t d based on
the d~ trial original signal.
:.,. ~ . . ,, :,
Brief Description of the Dra~in~s
Figure 1 presents a c - 1~. - -1 CELP coder.
Figure 2 presents an ill~.~t~ emho~ -lt of the present in.~
Figure 3 presents ~ lo.. i. of samples used in a correlation process
r- g open-loop delay.
Figure 4 presents illustrative time reladonships of delay values for use
with the e.llbc " of Figure 2.
21020~0
Figure S presents an illu~lla~ , embodiment of an adaptive codebook
processor.
Figures 6a-c present illu~lla~ , sample time rçl~tion~hirs for operation
of the adaptive codeboo~ of the c ~ f l-t of Figure 2.
Figure 7 presents an illu~halive e-l-boL,-~ll~ of the time-shift lJIUCeSSOI
of the embodiment of Figure 2.
Figure 8 presents an ir ~_ set of initial con-lition~ for the op~
of the time-shift ~uuCeSSOl of Figure 7. ~ .
Figure 9 presents a flow diagram of the operation of the time-shift
10 plvcessvl of Figure 7.
Figure l0 presents an illU~ dli~r_ segment of original speech used for
g trial original speech signals by time-shifting.
Figure l l presents an ~ _ e-..l~~ 1 of the invention.
Figure 12 presents a finite state machine fl~srnbin~ the operatif~n of a
5 dday ~-as it co-~ time ~ -' Ully between original and time-shifted
slgnals.
Figure 13 presents an illu~hd~ _./~codel for use with the
illu~hdt;~ccoderç...~ ..- 't'i -- ~3inFigure2andinFigure ll.
DetailedDc~_. p'
20 Illustrative Embodiment l' ~.. -e
For clarity of explanatdon, the illustradve ~ ~..hoA ~~ of the present
h~ ion is ~ ' as co...~ -' Çl :- -' blocks (;-~ -J;ug
r.. 1;0~9l blocks labeled as ' l~uce~ The 1~ ;o-~ these blocks l~,~._s~,n~ may - '
be realized through the use of either shared or dcd;~t~ d ha~ v~ g, but not25 limited to, L d~.alG capable of e~ g software. For e~mrle the ~ c of
.,es~uls ~rC~t~ d in Figures S and 7 may be ~, -,.;d~d by a single shared
p~essol. (Use of the term "~lu.,es~" should not be co..shucd to refer eAcl~ ly
to ha..l~ i capable of e ~ c~ g software.)
Illustratdve e-..hY~ .e-.t~ of the present invention may co--.l~ e digital
30 signal plvcessol (DSP) ~ ;, such as the AT~T DSPl6 or DSP32C, read-only
memory (ROM) for storing software ~ f~ g the ope~tion~ c-~ d below, and
~ndom access memory (RAM) for storing DSP results. Very large scale ~
(VLSI) ~ . c ~ ' - as well as custom VLSI circuitry in c~ - r n
with a general purpose DSP circuit, may also be provided.
2~02~80 ~
Introduction to Conventional CELP ~ -
A conventional analysis-by-~yll~Lvi.is CELP coder is ~lvse.l~vd in
Figure l. A sampled speech signal, s(i), (where i is the sample index) is provided to
a short-term linear prediction filter (STP) 20 of order N, o~ f-d for a current
5 segrnent of speech. Signal x(i ) is an t ~ inn obtained after filtering with the STP:
N
x(i) = s(i) -- ~; an s(i n), (1)
where p= ,...,. ~ . ~ an are provided by linear prediction analy~r lQ Since N isusually about lO samples (for an 8 kHz s~mrling rate), the çYcit~tion signal x(i)
generally retains the long-term ~ - ;r.~ ; Iy of the original signal, s(i). An LTP 30 is
lO provided to remove this ~ . y. ,~
Values for x(i) are usually .i~ t - ...i.-ed on a blockwise basis. Each block
is referred to as a ~,~b.rr~...e. The linear ~,lvlivlion co~rr~ip l~l~> an, are det~ l by
the analy~r lO on aframe-by-frame basis, with aframe having a fixed duration
which is generally an integral multiple of ~Cl~v ~ ~tinnc and usually 20-30 ms
5 in length. Subframe valùes for an are usually l;~Ch -~ Y3 through interpolation.
The LTP, typically ~ r l ' ~ with an adaptive codeboot~ If.S , ~ ~ :
a gain ~(i) and a delay d(i) for use as follows:
- - .~ - .
r(i) = x(i) - ~(i) x(i-d(i)), (2)
where the x(i -d(i)) are samples of a speech signal ;~ - -f~l (or lvcon~llu.;lvd) in
20 earlier subrla~llvs. Thus, the LTP 30 provides the quantity ~(i) x(i -d(i)). Signal
r(i) is the ~ ~ signal lv ~ ~ ~ after ~(i) x(i--d(i)) is subtracted fromx(i).
Signal r(i) is then coded with a FSCB 40. The FSCB 40 yields an index ;...1;~
the codebo~'~ vector and an cssc ~ ~ i scaling factor, ~u(i). Together these qll~ntiti~s
provide an eyrit~tion which most closely matches r(i).
Data l~v~ c~ v of each subframe of speech, namely, LTP
(i) and d(i), and the FSCB index, are co11P~t~d for the integer number
of s -hr., -..~ s equsllinp a frame (typically 2 to 8). Together with the co~ rr.~ :e .l~ an,
this frame of data is c ~ ~ ~ ' to a (~ P decoder where it is used in the
vco.l~Llu.;lion of speech.
- 6- 2 1 0 2 ~ 8 9
.. .....
A CELP decoder p~ . rO. .,.~ the reverse of the coding process ~1ic~lcsed -
above. The FSCB index is received by a FSCB of the receiver (sc--.~ .,es referred -
to as a ~ Le~ ) and the ~coc i-t. ~ vector e(i) (an e~ritP~ion signal) is retrieved
from the co~1r bo( ~ F ' ~ ~ e(i) is used to excite an inverse LTP process (wherein
5 long-term coll~l~ions are ~ .ided) to yield a ~ludnt~ed equivalent of x(i), x(i). A
l~collsll u.,t.,d speech signal, y(i), is obtained by filteAng x(i) with an inverse STP
process (wherein short-term COll~' ~ ~ are provided).
In general, the l~consh~ t~d e ~ -nn X(i) can be interpreted as the
sum of scaled a!ntribu on~ from the adaptive and fixed codebo~JI~. To select thelo vectors from these codeboo~ ~, a pel~ tually relevant error criterion may be used.
This can be done by taking ~1~lLg~ of the spectral masking existing in the humanauditory system. Thus, instead of using the dirf~,lbnCe between the original andecol.stl~ : d speech signals, this error criterion co~ - . the dirr~ ince of
ually weighted signals.
15The p~ iptUa~ igh~;llg of signals ~lf -~ S the ~l ~c present
in speech. In this ~ ~ 'e, the r .. ~ .t~ are ~lf ~ C - ;I~A by an all-pole filter in which
spectral ~le~ ~.. p'~ can be obtained by ~ving the poles inwar~ This is e~lui~.. le.-l -
toreplacingthefilterwith~ 1;cto~ coer~: r.t~i a1, a2. ---, aN,byafilterwith ~ -
rc:r'' ~al, lf2a2, ~-- . l~NaN,where~isape..,~ludlweightingfactor
20 (usually set to a value around 0.8). ~ ~ x
The sampled error signal in the pcl.,~.ally weighted domain, g(i), is: ~
N - ~:
g(i) = x(i) --x(i) + ~ ~nan g(i--n) (3)
n = l
The error criterion of analysis-by-~ ~Pc;c coders is ~( ' - d on a ;" ~ r nP by ; ~ . :
S ~ r ~ basis. For a ,~ ~ r length of L samples, a co.... -.- -1y used c~iterion is:
i+L-I
2~ g(i)2 (4)
where i is the first sample of the subframe. Note that this criterion weighs thee ~ in ~ samples ~ , over the Sl ' ~ ~ the sample x(i +L - l ) affects only
g (i +L - l ), while x(i) affects all samples of g (i) in the present ~--bf, ne
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2102~
The criterion of equation (4) includes the effects of differences iri x(i)
and x( i) prior to î, i.e., prior to the beginning of the present subframe. It is
co~ iclll to define an eY~ it~tion in the present subframe to ~ sellt this zero-input
response of the weighted synthesis filter~
O, i<i~,
q(i) = ~ z(i) -- ~,'Ynan q(i--n), i S i < i+N (S) ~ ~-
n=l
0, i2i+N
where z(i) is the zero-input .r~ e in the present subframe of the ~ ually~
weighted 'a~ llhe~aiS filter when excited withx(i)-x(i) prior to the present subrl~
In the time-domain, the spectral dee~ h~;c by the factor ~results in a
quicker ~ttçnll~tion of the impulse lb;~pOn tb of the all-pole filter. In practice, for a
lo ~o.nplin~ rate of 8 kHz, and y = 0. 8, the impulse l~,~,vllse never has a ~ignifir~nt - - .
part of its energy beyond 20 samples.
Because of its fast decay, the impulse lb;,~nse of the all-pole filter
1/(1 - ~alz~l - ~yNaNz~N)canbea~ byafinite-i.ll~uls~
;,~nse filter. Let ho, hl, ~ ~ ~ ,hR_I denote the impulse lbi,~nse of the latter5 filter. This allows vector notation for the error criterion op~tin~ on the
,p~ually-weighted speech. Because the coders operate on a ;" ~ r ~ by-
a~rbf ~ basis, it is co.. ~ ~nl to define vectors with the length of the subf.. --.. ~ in ::
samples, L. For b , ' 0, for the e - ~ ;t ,t;o ~ signal:
x(i) = [x(i) x(i+l) ~- x(i+L--1)] ~ (6)
20 Further, the spectral-weighting mat~ix H is defined as: ~ ~
:: '
~, .
:, : ;
-8-
21~2~8~ ~
.
ho ~ 0
hl ho
hR _ l hR - 2
ho (7) ;
h
hR-I hR-2
hR--I
- -
Hhas~ nc(L+R-l)xL Thus,thevectorHx(i)~ theentire
responseoftheIIRfilterl/(1 - ~a1z-1 ~ yNaNz~N)tothevectorx(i). With
these -1Pfinition~ an l,r U~ -r 'ly ~ ' ' d criterion is:
x(i) + q(i) --~(i)] HT H [x(i) + q(i) --~(i)'J ( )
With the current ~ of H the error criterion of equation (8) is of the
,' - type (note thatHTH is Toeplitz). If the matnx H is hl ~ ~ to be
square LxL, equation (8) equals ~, (4), which is the more ~ -- cu. ' - e - ~
c tt as used in the original (~ELP. ~ ~ -
0 An m~.~t~ Embodiment for CELP Coding
Figure 2 presents an ill '~_ e-..~ of the present ~ ~ ' - - as
it may be applied to OELP coding. A speech signal in digital form, s(i), is 1 - ~
for coding. Signal s(i) is ~J .;~d to a con~ linear ~ analyzer 100
which produces linear predictive coefficients, an. Signal s(i) is also ~>~o.;dcd to a
15 c~ ~_ -' -llinear~" ~i filter(o~"short-term~ I "(STP)~120,which
operates acc~ll'' g to a process ~ 1 by Eq. (1), and to a con~. ~'- ~' delay i -
~e:' - 140. ~ ~
Delay ~ ' 140 operates to provide an ~ -- rl delay value to the ~ ~ ;
adaptivecct'ebo~ ~esso.150.To~ ' ~delay r ~' validata -~
20 particular sample time, delay e ' 140 pe- r~.. C co~ co~.~;l of a
window of samples of s(i), centered about the particular sample in question, -with
each of a '~ y of ~ O~.D of the same length. The wil~do..D involved in this
COIl~' ~r are i1l ~ in Figure 3.
- ., ~:.
-- - ~
21 0208~
Figure 3 presents the demarcations for frames (F) and c- ngtitnent
subL~llcs (SF) of samples of signal s(i) (actual sarnple values of s(i) have been
omitted for clarity). Shown are three frames, Fn_ 1 (the past frame), Fn (the current
frame, and Fn+l (the next frame). Each of these frames CrJ~ S 160 sarnples of
5 signal s(i).
The location of frame bou~ n~ ;- s is provided by time shift P1~CSSO~
200 rlicr~csed below. Time shift plucessol 200 provides a sample location dp 1 'ine the end of a ~br.~ ~e of original speech signal, s(i). Delay s 140
simply keeps track of the sul)fiOAlle b ~u ' - s of original speech to know when a ~-
10 frame bluu~ is reached (such a frame b u ~ ~ is at an integral multiple of
S ~ r bo-~ s). Because delay ~ . 140 operates on a frame of speech
prior to the ~1~ of the time shift ~lV/ee~ r 200 on the same frame of speech, ~~
delay s 140 must predict the position of future frame b " ' - - It does
this by adding a fixed number of samples equal to a frame length (e.g., 160 samples)
15 to the last frame b ~u ' ~ provided by the time shift lll~essol 200.
Assume delay c ,~ 140 is to d~,t,. -...;~f a value for delay, M, valid
at the b,ou.. ~l between the culrent and next frames of s(i), M(FBn+ 1). To do this, ~ ~ ;
f~i' ' 140 stores in its memory a window of 160 signal samples s~l~undillg this
~ ~u ' ~ (e 140 must wait to receive samples of signal s(i) valid in the next
20 frame). This window of samples is denoted as window A. Next, ~ 140
p. . r .. ",c a correlation co~ ;f~ with samples of s(i) in window B 1 -- the first of
140 other ~.;nd(,.. of s(i). Window B 1 is a window of 160 samples begi~ ng 20 -
samples earlier than the b ~" " of window A and ending 20 samples earlier than
the end of window A. A CClllb' - value ~ccc- ' with window B 1 is stored in
25 memory. The co~ if ~ ~ process is repeated with window B2, a l60 sample
window beE~ e one sample earlier in time than window B 1. Correladon
cc ..~ iOI~c are p- ~ fi,~...f d for each of the next 138 windows, each window distinct
from the one before by one sample.
As shown in Figure 3, s~ ~ 140 must have enough memory to store
30 what is e~ n i~lly two frames of signal samples. If D is the largest delay value
allowed, then the memory should extend D samples prior to the beg ~ ~ g of
window A. When D = 160, in order to compute an ~ ~ ' delay valid at FBn+ 1.
s - 140 must store samples of s(i) from the be~innine of the third ;~ub~ f,,
SF2, of frame Fn_l to the end of the second ~..hr.n.~.., SFl, of frame Fn+l . Delay,
35 M, is flf ~ Pd by e - 140 based on the B window of samples having the
greatest correlation with the samples of window A. That is, delay is equal to the
- lo-
2~02~8~
number of samples that the most correlated B window is shifted in time from
window A.
The delay e~ r)r 140 (1r~ r s a frame boundary delay estim~te~
M, once per frame. Delay e~ u~ 140 further ~ t~ ...i..~s a delay value, m, valid at
s a fixed number of samples into each subfi~m~ te.g., 10 samples), by conventional
linear intelpolation of delay values valid at frame boun~1Arif s For this puIpose, the
delay value required at 10 samples into the next frame is set equal to the delay value
at the frame boundary.
The timing A~oci~ted with the delay values provided by delay e,~ o.
10 140 is illuslrated in Figure 4. As shown in the Figure, delay values valid at the
frameboi ~ -- s~uluu~ldingframenareM(FBn)andM(FBn+l). Delayvalues
valid at a fixed number ûf samples past each ~ ~brl nl ~ bOundaly (SB) within frame n
are;,,,l;~ as mn(k),k= 0,1,2,3. Thesevaluesof mn (k)ared~ h~ F.d by
interpolation as ~iccllcce~ above. Delay values m n (k) are provided to the adaptive
15 codebook proce~ûl 150. As will be .l;c. ~sed below, the adaptive codebook
ucessor 150 uses this dday i.,rO....~ n to provide an adaptive codf~o
contrihlltir~n to the time shift ~l~)Cc'SSOl 200.
The Adaptive r~rb~
The adapdve codf ~lr p~u~esso~ 150 provides an estimate of a current
20 ~rl_llc of speech (to be coded) to the tdme shift ~JlUCC~';)l 200 based on delay
~ - ' s. mn (k), from the delay e~ 140 and past recoll~Ll uctcd speech signals ~:
from the CELP process. The adaptive codeb~~ lucessol 150 operates by using
delay values, m,A, (k), to flf ~ r. a delay pointer, d(i), to past recon ,l. u-,t~,d speech
signals stored in the memory of plu~ssol 150. Selected past speech samples, x(i),
25 are then provided to pluce:~s~l 200 as an esdmate of the current ~ubr.,.-.., of speech
to be coded. For each s-~ -..f of original speech to be coded, adaptive co~leboo~
uce~ 150 provides a cc - ~-,,~,o~ g subframe of speech samples plus a fixed
number of extra samples which extend into the next s~'l~aLue~ Illustradvely, this
fixed number of extra samples equals 10.
Figure S presents an illu~h.. ~_ ~' ~ ~ of the adapdve co~
pl~,ss~l 150. There~l ~ cc..~ s~ cessùl 155 andRAM l57. E~uce~,~,o
155 receives past lCCo~ u~,tcd speech signals, x(i), and stores them in RAM 157
for use in Cf.. l~ current and next ~ JLallle speech samples. ~ucei,~ol 155 alsoreceives delay values, mn (k), from delay e,~ lu~ 140 which are used in the
35 co...l,.,~ ;on of such sample values. ~ucesiof 155 provides such cs...l...~cd sample
.. . ~ . . . .. . .
.. .
-- . - . . - :
.
-11 -
2~02~8~
values, x(i), to dme shift ~luccssol 200 for use in the generation of trial original
signals.
Each sample of speech provided to the time shift ~ ,eSSOl 200 is
c1etc. ",innd as follows. First, a delay pointer, d(i), valid for the sample in quesdon ~ -
5 (that is, the sample to be provided to the dme shift processor 200) is ~,t~ f'd by
u,CSSOl 155. This is done by interpoladng between a pair of delay values, mn(k)
(provided by delay e 140), which surround the sample in q~upsti~n The
interpoladon ~ used by ~IvCC,SSOI 155 to provide the delay pc~intors~ d(i), is
convendonal linear int~ olali(,n of the provided delay values, mn (k). Next,
10 pluCe,SSOl 155 uses the delay pointer, d(i) (valid for the sample in quesdon), as a
pointer ba,~ d in time to an earlier speech sample which is to be used in the
current frame as the value of the sample in quPstif~n Such earlier sarnples are stored
in RAM 157. In general, the delay pointer, d(i), wirl not point exactly to a past
sample. Instead, d (i) will likely point sol.l~ ; between cnn~ ;ve past
15 samples. Under such ci-c~ r~s, plvcessol 155 ih~ Olal~,s past samples to
~1~ t - ...;..~ a past sample value valid at the moment in time to which the delay pointer
refers. The int~ t~h~ e used by ~.~ ces~o. 155 to d~ e past sample
values is convendonal b n~llimitP~l ~olaiion, such as that llescribed by Rabinerand Schafer, Digital F).~ces~.ng of Speech Signals, pp. 2~31 (1978). The ~
~olalion filter realized by ~ CeSSO~ 155 illustratively employs 20 taps on either ~ -
side of the past sample closest to the dme i~ by the delay value.
Figures 6a-c ill t~ the process by which the adaptive co-leboo~
plu~ SOl 150 selects past samples for use in a current (and next) ,~ f . ..~.~ For
clarity of yl~ 1;o~-, Figures 6a-c assurne that a co...l.ut~ value of d(i) points
25 exacdy to a past sample value, rather to a point in between past sample values. Also,
it will be assumed without loss of generality that the delay values are shorter than the ~-
hv rl ~ length.
As shown in Figure 6a, the samples to be provided to time shift
plu~,eSSOl 200 include samples in a current subLa.lle~ and a fixed number of samples
30 in the next subframe. ~u~,essol 155 receives a delay value for the current S~mCurr~ from the delay ~ ' X 140 and has stored in its memory 157 a delay value
for the previous S. br. ~ mp,e~. To ~e~ ;nf the value of each sample, x(i), of
the current ~.lbL located prior to the point at which mCur~ is valid, ~lvcesi,~l 155
d~ t~ ...;nes a delay pointer, d(i), valid at the sample time i of the sample in ~ P~ti(~n
35 This is done by linear inte.~olalion to the point in time when the sample is valid
using delay mcurr. and the last delay value received from estim~tr~r 140, mpr,~,,. After
- 2102~8~
this delay pointer, d(i), has been cl~ tc. ~ F11, p-ocessol 155 comp~ltes by
b~nfllimi~d interpolation of samples in its memory 157 the sample value valid at a
point in time which is d(i) samples prior to the sample in q~estif~n~ i.e., x(i - d(i)). .,
This sample value is then inserted into a memory location reserved for the current
S ~ubr~ f samplein4l - <-n
In the example of Figure 6, the ~ul~ÇIalllv length is longer than the delay
values. The process by which a given sample in the current ~U~r.,- ..f is ,1. ~ Ill;llf~
is based on ~1. t ....;..i.~g a delay pointer and looking bac~. d in time for a sample
value to use as the given sample value. Thus, ~ O of lc~,o~ lu._tvd speech may
10 be essenli~lly repeated using t- ~limitP~ tv.~lalio n within the current ;.~lbrl.tllle.
So, for c , 1 , in Figure 6b, a given sample, x(i), takes its value from a previously
dei ~ - ~ sample which plv~cdrvs it in time by a delay d(i), i.e., x(i - d(i)). This
delay is d~ t .. : -f.d as fle~ l above, except the delay values which are ' . ,~
interpolated are the delays from the current ~"br . -..- mC~rr, and the next svbfr~mP
15 m"~, since these delays - --.u ~ samplex(i). R~ ,, signal s~,gm. ..l~ with
constant gain when the delay is shorter than the ~ ~ r length is what
di~ g ~ ' - - the adaptive co~ JlU~ el~v from LTP Slter ng ~Iu~,el~s. -
As shown in Figure 6c, the extra samples in the next ~ubrl~ullv are
f~ in the same fashion as those in Figure 6b. In this case, samples from the
20 current ~ r ~ are used to provide values for samples in the next s ~br ...--~In pracdce, the above~esr"held P1OCC1~JIC of the adapdve c~lebQ~
.lucvssol 150 may be realized by first c~ ;..g all delay pointer values, d(i) for
all sample dmes of the current and portion of the next ~-~br.~..f in ~_ t~nn Then,
for each sample drne, i, of the present or next ,.~bf. .~ ~.f needing a sample value, d(i) ~ -
25 is used as a lefv.vnce to a past dme, i - d(i), at which a sample is "located." In - -
general, there will not be a sample located at dme i -d(i). Therefore, ~ d
~ ~-' - of samples suIrounding time i -d(i) wi~l be required. Once the
~- ~1 d ~ 1-- is ~ .r~ g~ g a sample value at i -d(i), that
sample value is assigned to time i. This process may be repeated in a IvCu,~;~v
30 process for each sarnple in the present or next, l.r.. ... as needed.
Once the adaptdve co~ plv~v550~ 150 has dvt~ . ~ samples for s
use in the current ~ r ~ ~ and a fixed pordon of the next ~ r I , those samples
are plo~idvd to the time shift plUCvi;.~ 200 for use as a basis for ~ - g a
shifted original signal for use in a OELP coding process. The samples lnu.i~vd to
35 the time shift pl~vSSO~ are referred to as the adap~ive codebook con~ribution to the
analysis-by-s~ I.esis process of CELP coding.
- 13- ~
2~ ~2~8~
It should be understood that an all-pole filter may be used in place of the
adaptive codebook re~li7~tinn of an LTP. Ilo.. v~vl, the adaptive codebook
re~li7~ n is particularly well suited to ~;n-~lio~lC where, as illllctrAtPd here, delay
values are generally less than the length of a ~ubf. This is because an adaptiveS codcbook re~li7~tion does not require a d~,t~ .f-d value of LTP gain (here,
codebook gain) simply to provide an LTP contribution in the current ~bf ~ "r This
gain may be clf t~v ...;.-~d later. Unlike the case of the adaptive codf boo~ an all-pole
filter re~li7~tinn of an LTP rPquires the solution of a nonlinP - e, - to obtain a
value for the filter gain when delay is less than s.l~r.,~.,f~ Iength.
10 The Time-Shift P~ wx
The time shift pluCf ssoI 200 dvtv~ ihlf s how to shift s~;J..f - ~ of an
original speech signal such that it may be coded (by an analysis-by-~ the;.;s coding
process, such as ~ELP) with less error than if the original signal was always used for
coding To dme-shift an original speech signal, the dme shift l,lu~s~l 200 first ~ - ''
5 i~lr ~I;fir s within the original speech signal a local ~--~ --- of original speech
signalenergy. Intheillu~hdti~_v-..l~~ d~,s~-;h~lbelow,pl~essoI200selects
a plurality of o.v.1~ g se~ of the original speech signal, each of which ~ -
includes the ide--l;r~D~ local ~ ------ signal energy. P~U~eSSOl 200 c ~ vs eachselected segrnent with a segrnent of the adaptive codcbook cn~ ,I;n~ lu.;dvd by ~:
20 theadaptivecodebook~lucvss~ lS0). lhisc~....pn~;cn~ismadeto~e~-....;.~ the
original speech signal segment which most closely matches the segment of the
adaptive co~l~f ~r ~ bu When the segment of the original speech signal -~
which best matches the segment of the adaptive co~l~on~ co~ ut;o - is
dctv, ~ ~ d, this segment of original speech is used in the f~ ~ of a shifted
25 original speech signal for coding by a CELP process.
As shown in Figure 2, the dme shift pluccv~ol 200 receives an original
residual speech signal, x(i), from the STP 120, and prû.idvs a dme shifted residual,
x(i), for use in the CELP coding process. As shown in Figure 7, time shift pluCvSS~
200 illu~t~ ,vly cc~ e5 p~ûcessol 210; conventional buffer ...- ~.o. ;~ s 220, 230,
30 and 240; conv~ ional ROM 250 for the storage of ~I JcessoI 210 programs; and
coQ~_.. tional RAM 260 for the storage of plucessol 210 results. 9
The olJc~dt;oQ of time shift plucessol 200 will be e~ l with
afe~;nce to Figure 8, which presents an illu~ , starting point for pl~lcessor 200 -~
operation on speech signals, and Figure 9, which presents an illu~llalive flow~
35 diagram for the operation of plucessol 210.
. : .
-14- 2l~,f~n~ -
As shown in Figure 8, ploccsOor 200 begins op~,lalion having received a
buffer 220 of lc~o~lshu~tcd speech lc~lcsen~ g the adaptive codebook contlil.ulion
from the adaptive cod~book ~ cei~ul 150. As f1iicur~sed above, this adaptive
codebook co.ltlibulion co.~ ;ce5 samples of past lcconOI.u~,t~,d speech which have
5 been mapped into the current s. ~ r ~ and a fixed portion of the next subrlaule (see
Figure 6 and hccOAi, ~ ~1icc~ inn) by ~lVCf,SoOl 150. This buffer of lccofl~llu~t~d
speech is loaded into RAM 260 for use by IJlvceOO~l 210. A pointer, dp 1, is
,,,~i~,u ;~-f d by plVcf,OOor 210 and stored in RAM 260 to indicate the end of the latest -
~uI,Çl. lle for which both the adaptive codebonL and FSCB co~.l - ;bul ;m~c have been
0 5Ic t~ i, fA The length of such r ~ 5~ sul~f rame_l, is constant and --
in memory, e.g., ROM 250. Based on prior olJc"Atio - of the plU~CooUl 21Q a timeshifted residua1, x(f ), has been created up to a point in time i~ ; fi~ by a pointer
dpm (pointer dpm is always greater than or equal to dp 1). M~lc~ , a portion of the
original residual signal, x(i), ;f~ d; ~g that ~ ~s~ t ~l with the current t Abr. .. , has ; :
15 been received by buffer 230 and stored in RAM 260. ~u-,essol 210 ~ ;- c (in
RAM 260) a value, acc_shift, lc~ SW~Ath~g the sarnple flicpl - - - - (or
~ , '7tPd shift) between the last sample in the shifted residual signal and a
co l~,q-o-~-l;f~g sarnple in the original residual speech signal. (At ~ ' ' 1 --~ - the
above~lf sc ihed status is ,~f~l;fif d to include dpm =dp 1 and acc sh~ft =O).
Given this set of cc - s, thc tirne shift plU~ oS~l 200 operates to ~ ~
~ - a shifted residual signal for the current ~ ~ r ~ (and possibly a portion ~ ~ -
of the next ~ r , ~ p ~ ~ ~- g on the . -) which best matches the
adaptive cf~4bol-~r c~ ~-~''
Figure 9 presents a flow-diagrarn i11~.~h. ~;..g the o~ of the
25 plo ,essol 210 of Figure 7. According to Figure 9, the first task pe- r~....-f~ by
C~SoOI 210 is to ~ ,.".'~r. whether the time shifted residual, x(~), has been
t,~ up to or beyond the end of the current --~br n~~ -- As shown in Figure 8, the
extent to which the tirne shifted residual has been e- ~t~ -~Cl~ iS given by plointer dpm.
The end of the current s ~hr,.~ ..f is i~ ;f ~ by the sum of cuA~rent s Abii ~ pointer
30 dpl andthefixed~' r ~ length,subframe l. If dpm<dpl+subframe lfurther
pl~e;.~:..g is ~ r,.. ~e~l to extend the shifted residual; else, no further shift
pA~ceoo;ng is required for the current ' fi (see step 305).
If further shift pl~e~'..g is required, pr~cessol 210 d ~ t- ~ A5 the
location of ... - Y ;...- .. energy in a segment of the original residual speech signal, x(i)
35 (see steps 310-375). Ordinarily, the location of ...~ .. energy collcO~nd~ to the
location of a pitch-pulse of voiced speech. IIo..c~., this is not nrc~-~ ;1y t~ case.
- " .. ~ . ...
.- . ,
... ~ . .
.
-15- 219208~
Regardless of whether the " ,~ ,~; " ,. .. ,- energy is ~soci ~tf d with a pitch-pulse or some
other signal feature (such as, e.g., energetic noise), the search for the m~ximllm ~
energy location is made so that shifts in the original signal will be made to best align ~ -
an energetically si~nifir~nt feature in the original speech with a ~ignifir~nt feature in
S the adaptive codebook contrih-~fif n
The beginning of the segment of the original residual speech signal to be
searched is defined with respect to a pointer to an original residual speech signal
sample. This sample co,~ onds to the sample ident fif d by pointer dpm in the
shifted residual signal. This residual speech signal sample pointer, dpm', is
0 detc~.l.il~f,d as the sum of sample pointer dpm and the ~cum~ ~i shift between - - -
x(i)andx(i): dpm'=dpm+acc_shift(see step310). The beginnin~ of theinterval
to be searched, flf sign~t~d by the pointer offset, is then colllr_ ~ (see step 315). ~ -
Next, the length of the interval to be searched is defined (see step 320).
The location of.. -~;.... energy in the segment ofx(i)is then
15 fi~ t~ f-d (see step 325). This d~ - - -on is made with use of a L~
window. This window, centered about the ith sample of the original residual speech
signal, defines sarnples of the original residual used in an energy Cfi....l.u~ The
energy at sample locadon i is ~lf ~ ....;..f~ by the sum of the squares of the samples in
the window. The energy at the (i + l)th sample location is fle~ " -An~i in the same
20 fashion, but with the window moved one sample later in time such that the center
window location now contains the (i + l)th sample. Again, the energy is f3e~ - . . .; ..
as the sum of the squares of the sample values in the window. The energy of eachsample location in the segment is ~ in the same fashion. The energy of
sarnples in a current window may be fif t~ ...;. f d as the energy of an ~" past25 window of samples minus the energy of the sarnple shifted out of the window plus
the energy of the sample shifted into the window. The sample location having
a~so~:sb d with it the ...-x;-.. ~. energy di t ...i-~d in this fashion is i~lentified by a
pointer location.
Once the segment of the original residual signal, x(i), has been searched
30 for the sample having the ~~~ ~ -~~ energy in the segn~nt ~Iu-,essol 210 ..
dcl ' ~ if this ... ~ energy sample is one which has been con~;de.~d in the
previous ~ bl., ~ (and thus not a ..~ . of interest). This is done by
fi~e whether location p.~edes dpm' (see step 330).
If location pl~ced~,s dpm', another search is pe~ ~o~ d by ~ Jcess~
35 210. In this case, however, the segment searched begins at a sarnple spe~ifi~d as
offset = location + 0.75delay (see step 335), and is of duration O.5del~y. The ~ : ~
:. '
' ~ ' ';~
-16- 2102~8~ ~
value delay is provided by delay estim ~tor 140 as the delay valid at the beginnin~ of
the current subframe, M(FBn). Since si~nifi~t pitch-pulse energy features in theoriginal residual signal are likely s~al ' by one delay period, the c~ n of a
new offset allows the search to skip ahead (0.75 delay) and likely find a
5 energy feature within a segment of length Q5 dela,v. The sample location of
",~x;"",." energy is ~1. t~ as ~escribed above with lefv~b-lce to step 325 (see
step 345). -
If location does not proceed dpm', then the first pitch-pulse beyond
dpm' has likely been found, and the flow of control jumps to step 350. :
If the location of .. ~;".~,. signal energy ~ ,f~ at either steps 325
or 345 follows dpm' + delay, then it is likely, but not certain, that a pitch-pulse
located sul-3e~ I to dpm' but prior to dpm' + delay has been missed by the
searches ~vlr~ ed to this dme by processor 210 (see step 350). In this case,
another segment of the original residual signal is defined and the locadon of the
15 ",~.;... .. energy therein is ~ If the locadon of ".-,;------.. signal energy
~lf t~ d at either steps 325 or 345 I,lvcedes dpm' + delay, then the flow of
control jumps to step 380.
,~cc.lmjn~ step 350 results in the need to search another segment of the
original residual speech signal, this segment is ~c t' ~--;-~1 to begin at
20 offset = location--1.25delay (see step 355) and extend for length = O.5delay (see
step 360). The locadon of the ~-- -~ ;------- ~ energy is rlf t~ " ,;l ~1 as cle5~ ;1~ above
with lv~c~vnce to step 325, but the sample pointer to this locadon is saved as
location2 (see step 365).
If the location of ...~ --.. energy (location 2) is s.l~sv~luelll to dpm',
25 then location2 i~lf ~ifif s the locadon of the first pitch-pulse beyond dpm', and
location is set equal to lo( ~Ror~ (see steps 370 and 375). If, on the other hand, the
locadon of ...~ ---.. energy is not beyond dpm', then location2 is not the firstpitch-pulse beyond dpm', and location remains set to the value it was ~c~i~P.cl at
either step 325 or 345 (since under such CilC~ : ~ s, pointer location is not
30 o~v~ tvn by the o~ ~,~ of step 365).
At this point, the locadon of the first pitch-pulse (or energy .. ~ . ;.. )
in a segrnent of the o~iginal residual has been found. Now, a segment of the original
residual signal c s ~ g this location will be defined by l,l~v~.~ 210 through the
setting of certain pointers to samples in the signal. These-pointers specify the3s bf,gh~ g (sfstart) and end (sfend) of this segment co~ -g the ~If te- Il-;l~
locan'on. This segment is defined for later use as part of the process of aligning (or
_ - 17 -
2~ 02~80 : ~
shifting) original residual speech to best match an adaptive codebook contribution.
First, default values for the segment pointers are set by ~ cess(,. 210.
Pointer sfstart is set equal to dpm', the sample location co~ )nt~ g to
dpm + acc_shift (see step 380). This value for sfstart collv~,onds to an q~r1itinnql
5 aec~lrmll-q-t~d shift between x(i) and x(i) of zero. That is, use of a section of x(i)
bc~ g at dpm ' ( = sf start) adds nothing to the q.~cum~llqt~.d shift between the
original and shifted residual signals.
Pointer sfend is set to location + extra. The value extra is a constant
stored in memory (e.g., ROM 250) and is equal to a fixed number of samples, e.g.,
10 10 samples. Use of extra g P ~ ~ that the pitch-pulse (or .. -~ .. energy) of ::
original residu. l speech will not fall at the end of the segment of the original residual
being itl~.nfifiPd by these pointers (see step 380).
The default value of pointer sfend may be overwritten under certain ~ '
C~l~ 'e5 If the default value of sfend would mean that the segment of original
5 residual speech would extend ~ fit 'ly beyond the end of the adapdve codeboo~
co- ~ the pointer sfend is set to end at dp l' + subframe_l + extra, where -
subfrarne l is a constant eq~ ~lling the number of samples in a fixed adapdve
CO~f 1~1' Subfi.u~lCv as .l;~ ed above (see steps 385 and 390). -
The value of sfend may be further u.vl~liltv.l if the locadon of the
20 i~ fifi~d pitch-pulse (or major energy) is ~;g~;fi~ ly beyond the end of the
adapdve code~ ~ r ~ Under such CilC ~-cl --~r~ S the segment is deemed to ~ -
end at the end of the adapdve c~i.- bon~ ~ r bou,ld~uy (see steps 395 and 400).
Note that such a ~ of sfend means that the locadon of the pitch-pulse (or
major energy) is later than the end of the seg~n~nt Therefore, the segrnent no longer
25 contains the pitch-pulse.
At this point, the locadon of the i(le~;r~ pitch-pulse (or .. ~;..----..
energy) is checked to determine whether it falls outside a range of samples b~ - ~ g
at sfs~art and ending at sfend - 1 (see steps 405). If so, x(i) may be t- t~ d with
samples obtained with bandlimited int~ ' ~ of x(i) without need for ' eing
30 acc shif t (that is, flow of control may jump to step 480). Olh~,. .. ;~e, shifdng is
pc fo~ d (see step 410-475).
~s~min~ the locatdon of the i~ ; r.,~ pitch-pulse (or major energy) is ~ ~ '
not outside the range defined above, a set (or seg~ nt) of L samples of x(i) (within a
spe( ified range of samples about the segment defined by s fstart and sferu~) which :
3s most closely matches an L-length section of the adaptive codeb~l co~
(which begins at dpm and ends at dpm +L) is ~ t ~ f~l by ~ ,essol 210.
. ... , .. .. , .. . . . .. .. . . ~
21~2~80
This L-length segment of x(i) may comprise those L samples of the
segment of x( i~ defined by sfstart and sfend, but may also co., .~ e samples
(obtained by b infllimi~f d interpolation) of a segment which is shifted with respect to
sfstart and sfend, ~c~ guponhowcloselyagivenL-lengthsegmentofx(i)
5 matches the L-length section of x(i). As predicates to this flf~t~ ion, a limit on
the range of possible sample shifts (see step 410) and a sample length, L, are
cl.,t~ rd (see step 415). The determi- f n of the "ClOSf'flf.~" (i.e., a measure of
similarity) between L-length segl~ t~; of x(i) and the adapdve codebook
f f~ntribntic~n x(i) is made through a cross-correlation process of these signals (see
10 step 425) ~it will be I ~ ~tood that other Illeasulcs of similarity, such as a
dirrc.~ cf or error signal may also be used). The sf,hfActif n of L-length se~...f fll~ of
x(i) for use in a cross-correlation with a segment of x(i) may be adv~ntagf Iy
~lf~sf~ihed with l~,f~..,nce to Figure 10.
Figure 10 presents an illu~llalive segment of original residual speech
15 signal x(i) which was located as dF srnbed plc~iously with l~,f~,l.,nce to steps 310- s
400. The segment begins at sample sfstart and ends at sample sfend. The pitch-
pulse is at sample location, with the distance between samples location and sfend
equal to extra. As ~lice ~ied above, the samples of x(i) falling within the segment
defined by pointers sfstart and sfend c~lc;.~ond to a shift of ~ro. Shifted ~
20 of x(i) are defined with respect to this ~ro shift position. Each shifted segment is of
length L and begins (and ends) a certain positive or negative number of sample
lengths (or fractions of sample lengths) with respect to the ~ro shi~t position.F ~ ed another way, each shifted segment begins at sfstart + shif t and ends at
sfend + shif t. As shown in Figure 10, the range of possible shifts values for shif t
25 is +limit.
So for r~ one possible shift would be shift =--limit. In this
case, the L-length segment of x(i) defined by such a shift would begin at location
sfstart - limit and end at locadon sfend--limit. Similarly, another possible shift
would be shif t = + limit. In this case, the L-length segment of x(i) defined by such
30 a shift would begin at locadon sfstart + limit and end at location sfend + limit. As
iO ~Fd above, +limit specifies a range of possible shifts. Therefore, shif t maytake on values in the range - limitSshif t~+ limit, given a shift step size (i.e., shift
c~;s;on) of sstep. Step size sstep may be set illu ~ha~ y to 0.5 samples. Samplevalues resulting from r -' ~l shifts are dcl ~-,--i-~rd by co~ ,nlio~ imi~l~.d
35 int~ ' 'on A plurality of 2xlimitlsstep ;~ ;lllf ~ of the original residual signal
x(i) may be defined in this way. A~ are L-length se~;. . Ie~ ~I '; between _limit, wherein
2~2080 ~ ~
each segment overlaps its neighbor segm~nt~ and is distinct from its nearest neighbor
se~;.. t~ by sstep sarnples.
The relative sizes of limit and extra have an effect on system
p~v.Ço~ ce For ey~mpl~ as extra is made larger, greater coding delay is ~-
5 hl~lvduccd to the system. As extra is made smaller, coding delay is reduced, but the
probability that shift will take on a value which excludes a pitch-pulse from the L- '
length segment of x(i) in~;lbds~s. This ~Yc~ nn, when it occurs, causes audible -~
di~tul liO.~ in the speech signal. The probability of eYrlncir~n is . ISO incl..ascd as limit
is made larger. To help insure that eYc1n~inn does not occur, the value of limit0 should be less than the value of extra. For ~ r 1 v~ if the value of extra is l0, limit
maybesetto6.
For each such L-length segment of x(i) thus if 1~ntified~ a measure of ~ -
similarity between the segment and an ~length segment of the adaptive codebook
contribution, x(i), is co...l.u~l This co...l..~l - io-- is illu~llati~,~,ly a cross-
5 correladon. The adaptive co~ segment used for each cross-correlation beginsat dpm and ends at dpm +L (see Figure 8). The cross~- lltvlalioll is ~ . r~.. ~d with a ~ -
step size equal to sstep (should sstep equal a non-integer value, co
- of x(i) is ~tv~rulllltvd in advance to provide the ~
sample values for the seE.- .. ~ ~ ~ of x(i) and x(i)). Each cross-cfJllrvià~ion results in a
20 cross-coll~vldlio.- value (i.e., the measure of similarity). All such cross-co... 1 l;o~
form a set of cross-c~ ll.' values se~ d in time by sstep. Each cross-
Cfjll~ ' - - value of the set is . ~ h~vf~lr~ with a shift co. ~ E to the
L-length segment of x(i) used in the c~ u~ of that value.
Once the set of cross~v~jllrvldLioll values is d~ ~. the segment of
25 the original residual signal having the greatest cross-c~nr1qfion with the adaptive
co l~ b~ segment is d ~ with an increased time res~ 1ntif n (see step 450).
m _ ~_ly, this is done by fl~ t,~ g a second order polynomial curve for each
set of three c ~ ~ _ ~_ cross~o- " 1~l;f n values (a set of three values is distinct from
its nearest - - ghbf~nne sets by one value). The middle value of these three cross-
30 COll~ values in a set c~Jl~ ,onds to a shifted original residual signal as~3et~bed above. The set of three cross-correlation values, and thus the ~cs~r ~
pol~ulll.al curve, is i~ ;.';ed by this middle value and its qt~s~x:- 1 shift. For each
such curve, a .. ,-I ;.. and the location of that .. -~c;.. (loc rnCuc) is ~ ;f~rA
(If loc max is outside the range of the three values, the three values and -q-~f~:A~,d
35 curves are Ls.bgdl~d.) The curve having the greatest ...~;... - .. value i~ nlifi~ s the
shift of the original residual signal which ~luduces the best match with the segment
~ .
- 20 -
of the adaptive codebook cont}ibution. 210 ~ O 8 O
The shift of the original residual signal producing the best match is
refined with knowledge of the location of the ...~xi...,.... of the polynomial curve
having the greatest ...~~;...- ... With the location of the mr-ximllm defined with
S respect to the location of the middle of the three cross-correlation values Q~sociotf-d
with the curve (i.e., a value of shif t), shif t may be refined as
shift = shift + sstep * loc max.
At this point, the best shift of the original residual signal has been
fl~ ti . . Ii i~r~l This shift may then be used to extend the shifted residual, x(i) for a
10 duration L. Since this shift is known, the açcumlllOt~d shift between the original
residual signal, x(i), and the shifted residual signal, x(i) may be updated as
acc_shift = acc_shift + shift (see step 475).
With the ~c--m~llQtffl shift updated, the shifted residual signal, x(i), is
eYtPn~Pd to match acc_shif t with use of the segment of the original residual signal
JllG~l~Of~ e to shift. Note that original residual sample values are available only
at original signal sample times. IIo..~ , in fl- ~ e an optimal shift of the
original residual signal, an ~-~ l.li..g has been pGlrc,~ ed prior to co...puli..e
cross-correlations and a value loc_max (which is generally n~-f~ tcg~ . ) has been
(3rl~ fl1 In general this results in a f c nin-eg~n~r sample time relo inn~hip between
20 the shifted residual signal x(i) and the original residual signal x(i) to be used in
~YtPnfling the shifted residual signal. Therefore, brnfllimit~d illLGl~olaLion of the L-
length segment of the original signal is used to provide sample values of the original
signal which are time-aligned with samples of the shifted residual. Once such time-
rligrfnf-nt is ~ rwlllcd, the samples of this time-aligned signal may be CO~f~ A~ h' d
2s with the existing shifted residual signal (see step 480).
Note that flow of control may have jumped to step 480 without ~r ~ ~ g
the r-~ ~1 shift. In this case, a length of L-samples of the original signal is
to provide samples for the shifted residual with the same value of
acc_shift as the previous shifted residual segment
In either case, dpm is updated to reflect the eYt~n~ n of x(i) (see step
490~.
As shown in Figure 9, once dpm is updated, the flow of control returns Y
to step 305. As ~--~ --t;~ above, step 305 ~ 5 whether further p.vcesj;i g is
requi~f~d to extend the shifted residual beyond the end of the current subframe. If so,
35 control flows through the process pl~ t~,d in steps 310490 of Figure 9 again so
that further t1' t~ s:on of the shifted residual may be pc Çollllcd. Steps 310-490 are
.. . .
- - 2 ~ 0 2 ~
repeated as long as the con-l;tion of step 305 is satisfied. Once the shifted residual ~ -
has been eYte,nded up to or beyond the end of the current adaptive codebook
~u~r~ v, the pointer to the end of the adaptive codebook snbfr~mP is updated (see
step 500) and l~lucvssi-~g a~ 1 with time-shifting the original residual ends.
S Once x(i) is fl~ t~ d by time shift lJluCvSSOr 200, a scale factor
is .~ t~ fd by process 210 as follows~
T~ ~ (13)
where x(i) and x(i) are signals of length equal to a slJ~rlalllv~ This scale factor is
mnltirlie,d by x(i) and provided as output from processor 200.
Referring again to Figure 2, x(i) and adaptive codebook estimate "
~(i)x(i) are supplied to circuit loO which subtracts estimate ~(i)x(i) from
mnflified original x(i). The result is eyf~it~tion residual signal r(i) which is supplied
to a fixed storh~clir coclebof ~ search plucessol 170.
Coflf-hon~ search ~luces~ 170 operates cO-I~v ~I;f).. ~lly to fletf m~in~
5 which of the fixed ~ ~x 1.~1;f~ codebon~ vectors, z(i), scaled by a factor"u(i), most ~ - -
closely matches r(i) in a least squares, ~v~;vpludlly weighted sense. The chosenscaled fixed codebook vector, ~(i) z~l"" (i), is added to the scaled adaptive codebook
vector, ~(i) x(i), to yield the best estimate of a current lvco.~ u.;l-vd speech signal,
x(i). This best estim~t~., x(i), is stored by the adaptive code~ processor 150 in its ~ ~
20 memory. ; -
As is the case with co~ ivonal speech coders, adaptive coflebof!~ delay
and scale factor values, ~ and M, a FSCB index, I FC. and gain, ~1 (i), and linear
prediction c~ rr~ t."l~, a", are CO~ IA ~-d across a channel for l-_con ,llu~:lion by
a conventional CELP decodvf~lvce;~,v~ (see Figure 13). This co~ hon is in
25 the form of a signal reflecting these p~ Because of the reduced error (in the
coding process) afforded by op~ ~hion of the illu~ v f ..bo~ -.l of the present
invention, it is possible to transmit adaptive codebook delay i..fo....~;ûn M, once
per frame, rather than once per s-~bf~ .. Subframe values for delay may be
provided at the receiver by . ~ the delay values in a fashion identical to
30 that done by delay ea~ 140 of the ~ -..;lt~ ~.
By l~ ;''v~ adaptive co~ebook delay inf nn~fion M every frame
rather than every subframe, the bandwidth re~luilu.llenb ~ccoci:~ted with delay may
be c;~nifif~nntly reduced.
-22- 2~ 02~
As fliccllcced above with l-,fe ~,nce to step 475 of Figure 9, acc_shift
S~ an a~cum~ ted shift over dme between the original signal, x(i), and the
shifted signal, x(i). In order to prevent an ever in~;lvdSillg asyll~luully between these
signals,thedelaycs~ o. 140canadjustcDmr ~valuesforMoverdme. An
5 adjusL.ll~ process suitable for this purpose carried out by e ~ t.~ 140 is
adv~nt~geo--cly fl-~scnhed with lcr,~vnce to Figure 12.
Figure 12 presents a finite-state machine having states A, B and C. The
state of this machine lvl,r,sen~s an amount of ~5~ I to ~ ~ values for M
to prevent ever hl~,lt,aslng a;~ elllUII~. T f nC between states are based on
10 values for acc shif t provided by time shift plUCf SSOI 200. When the machine is in
state A, the delay value M(FBn+ 1 ) used to flf t~, I..in~ values for delays mn (k) is not
t~d When in state B, the machine adjusts M(FBn+l ) as follows:
M(FB n + I ) = M(FB n + 1) + ~ where o illu;~tlali-vly equals one sample dme. When
in state C, the machine adjusts M(FB n + 1 ) as follows:
15 M(FBn+l ) = M(FBn+l )~~vi~ -
Given an inidal state (A, B, or C), the finite state machine operates by
keeping track of values of acc_shif t. If the value of acc_shif t is such that a;f - - for m ~:l;....:. g between the current state and another state is met, a
- to the other state occurs. For ~ cS--min~ the machine is in state A
20 (an ill..stlali-v inidal state for e 140) and--3ms ~ acc_shif t < 3ms, the
machine would remain in state A and M(FBn+~ ) would not be mf~-.fifif ~1 If the
valueof acc_shift exceeds 3ms, themachineI nn~tO stateCand M(FBn+1)
iS i-~,lC i by one sample time to help offset ~he a~ -clllul~ .f~ by
acc_shif t. If, on the other hand, when in state A acc_shif t becomes less than
2s - 3ms, the machine i ~ - to state B and M(FB n + l ) is d,~,lc ~ by one
sample to help offset the zs~ ,Llu..~. The op~. is sirnilar for states B and C.
An All~ Dlustrative Embodiment
One ~ to the m ~_ embodiment p~ s ~ in Figure 2 is
plC3~ ~ in Figure 11. In this f ~..ho'~ , a trial signal gvnV alûl 610 receives an
30 original digital speech signal, x(i), and gv.~e._ - a plurality of trial original signals,
x(i). The trial oliginal signal g _ 610 co-~ ;.es a lilllv-shirl ~JlUCvS~Of~ similar
to that plCS ~ ' ~1 in Figures 2, 7, and 9, but which does not perform a Cv'llC' '-~n
between a trial original signal fmd an adaptive coflf bo~ conhibuti~n Rather, this
time shift pl~]Cf,;~:~Ol simply provides a plurality of L~length tlial original signals
35 based on a plurality ûf shifts of original speech signal x(i). As fl; c. ~ ~.s~d above with
.,
-23- 210208a
reference to Figure 10, these trial original signals areL-length segments of theoriginal signal dctv.llf~nvd by shifts of step size sstep over a range of +limit with
respect to an L-length segment beginnin~ at sample sfstart and ending at sample
sfend. Because it pvlrf l.lls no cross-correlation between the original residual and
S trial original signals, ~ .. 610 does not select a trial original signal for coding
on its own. Rather it provides the trial original signals, x(i), it gv.lvlUtvs to a
codf,./~ llf~ 620 for p
Codvl/~ tLes; cr 620cfJ~ vs aconventional analysis-by-s~ llf,s;s ~ -
coder, such as the conventional CELP coder p-vsv-ltvd in Figure 1. The sy ' ~
10 (or lvconsLIuvtvd) original signal, x(i), is that shown in Figure 1 as the sum of the
adaptive and fixed codebook output signals, e~i)+~(i)x(i-d(i)) (see circuit 45 of
Figure 1). The coded signal pa~lvtCl~ fl- t- "~inf~d by the analysis ~l~rCf ~;ng of the
CELP coder (from which the ~ l.f ~ signal x(i) is genPr~tf-d) may be saved in
RAM for later use. The output of the coder/synthPsi7P.r 620, x(i), is thus an estimate
1S of the original signal, x(i), based on a given trial original signal, x(i). This estimate
of the original signal is Ihvlvartvr co ~ vl with the trial original signal to -
rl. ~ .. ;nr a measure of the similarity between the e ~ original, x(i), and the
trial original, x(i). This measure similarity is provided to a subtraction circuit 630,
which flf ~ . .n;~f~ s a dirÇvl-v..v-v (or error) signal, E(i), between the two signals. The
20 error signal E(i) is pluvidc~ to the trial signal gfmP~tf r 610 which keeps track of
the error ~CSof ~ ~ with a given trial original signal. Once all trial original signals
have been plvl,f,sse~ in this way, the trial signal g~ o~ may dctr,. ..~;~f which trial
signal, x(i), produced the best measure of similarity (e.g., the smallest error).
Thvlvàrtvl~ ~vnvldtvl 610 may signal the coder/s~ l.f ,;, ,~ 620 to use the saved code
2s F ~llvtvl~ accof~ ed with the trial original signal having the smallest error. These
L ~lvtvl~ may be ~c ~ to a receiver as a coded lv~lvse ~ if ~ ~ of the
original signal,x(i).
It will be undvl~tvod by those of ordinary skill in the art that reference
to signals such as the "original" signal, ''lvcou~llu-;lvd'' signal, etc., may include
30 lefvlvncv to 5e~ thereof. MOlb~ whether a given signal is I r ~ ~ d or not
does not change its ~ ' avtvl as an "original" signal, a "trial original" signal, etc.
Hence, use of the term "samples" with lefvlv.~ce to, e.g., an "original signal" may
include those sarnple values of the signal provided by an ~lrQ~mrlin~ (suchas con~,vntional t dlimitpd hltv.~,ol~ion), those samples which are not the result of
35 urs~mrling, or both.
' '' -24- 2102~8Q
Introduction to Appendix
Attached as an appendix hereto is an illustradve set of software
programs related to the first illu~ ive embodiment ~licrllc~ed above. The software
~)lug~ 5 of this set are written in the "C" plu~ ..h-g lAngllagç An e ~ o 1;..~ .l
S of this invention may be ylu.;dcd by t;Y~ ~-ulh~e these plUol~lS on a general purpose
COI11~J. , for exr---p~e~ the Iris Indigo work stadon ~AA~ h.d by Silicon (~r.~hirc
Inc. Note that ~ubluulil~es '~c~h:nr~ and "Illodilyol;g" cc,..~ ...A generally to
those functions pl~ ~ in Figure 9.
.:: -
... . ~, . . . . . .
~ ' ............................ .. ' ~
- 25 -
:' '
Nov 16 09:07 1992 mod.c Page 1
2~ 02~80 -
~include "macro.h"
/ * ., . . '
* mod - modify residual
void mod( residualm, accshift, d_shift, shiftr, exctation, residual,
dpl, dpm, lpcw, lpcorder, delay, subframel, extra, fcnt)
float *residualm; /* output: modified residual signal */
float *accshift; /* output: shift from mresidual to residual */
float *d_shift; /* output: local shift for all samples */
float shiftr; /* input: ~i shift range */ ' ~
float *exctation; /* input: adaptive codebook excitation */ - .: .
float *residual; /* input: original residual */
~ int dpl; /* input: pointer to output signals */
int *dpm; /* in/out: pointer to end of residualm */ :
float *lpcw; /* input: weigted lpc coefficients */ :~- -:
int lpcorder; /* input: lpc order */ : ..
float delay; /* input: delay */ : -: :
int su~framel; /* input: subframe length */ ~ - .
int extra; /* input: additional exctation constructed */
long fcnt; -
.
void cshiftframe~);
void modifyorig();
float shiftr2;
int sfstart, sfend;
while( *dpm < dpl+subframel){
cshiftframe( &sfstart, &sfend, &shiftr2, *dpm, residual, dpl,
*accshift, shiftr, delay, subframel, extra, fcnt);
modifyorig( residualm, accshift, d_shift, dpm, shiftr2, exctation,
residual, sfstart, sfend);
: ' :
,, ::
,
-( , :. ' ~: ~'::
: ' ~ ' ' :'
:
:: . . . - ' : : ~
- 26 -
Nov _ 19:56 1992 cshiftframe.c Page 1 2 1 ~ 2 0 8 ~
#include "macro.h"
/*
* cshiftframe - find optimal frame shift
*/
void cshiftframe( sfstart, sfend, maxshift2, dpm, residual, dpl, accshift,
maxshift, delay, subframel, extra, fcnt)
int *sfstart; /* output: shift-frame start */
int *sfend; /* output: shift-frame ending */
float *maxshift2; /* output: one-sided shift range */
int dpm; /* output: up to where residualm exists */
float *residual; /* input : original residual signal */
int dpl; /* input : output signal pointer */
float accshift; /* input : shift of output versus input */
float maxshift; /* input : r~Y; shift range */
float delay; /* input : local pitch value */
int subframel; /* input : subframe length */
int extra; /* input : additional excitation beyond current frme */
long fcnt; /* input : frame counter (D~BUG) */
void maxeloc(); /* determine location of max energy */
float maxener;
int offset;
int iacshift;
int length;
int loc, loc2;
if( delay < 0){
iacshift = -accshift + 0.5;
iacshift = -iacshift;
else
iacshift = -accshift + 0.5; -
/* determine first a pitch pulse somewhere near dpm */
length = 1.5 * delay;
offset = dpm + iacshift - 0.25 * delay; : ::
maxeloc( &loc, 6r~Yenerr residual, offset, length, 2);
loc -= iacshift;
printf("cshiftframe: firstloc %d ", loc - dpl); - ~
/* now find the first pitch pulse for sure */ ~-
if( loc < dpm){
offset = loc + iacshift + 0.75 * delay + 0.5;
length = 0.5 * delay;
maxeloc( &loc, r~-Y~n~r~ residual, offset, length, 2);
loc -= iacshift;
printf~" Aloc %dn, loc - dpl);
I
if( loc > dpm+delay)l . . :~
offset = loc + iacshift - 1.25 * delay + 0.5; : :
lenqth = 0~5.* delay;
maxeloc( &loc2, ~r-Y~n~r~ residual, offset, length, 2);
loc2 -= iacshift; '~
if( loc2 >= dpm) loc = loc2;
printf(" Bloc %d", loc - dpl);
- 27 -
.: .
No~ 1~-14:56 1992 cshiftframe.c Page 2
2~ 02~8~
*sfstart = dpm;
*sfend = loc + extra;
*maxshift2 = maxshift;
if( *sfend >'dpl + subframel + extra)
*sfend = dpl + subframel + extra; ~ ~.
if( loc >= dpl + subframel + extra/2)
*sfend = dpl + subframel; .
if( loc >= *sfend 11 loc < *sfstart)
*maxshift2 = 0; ~ ~
printf(" loc is: %d\n",loc-dpl); :
/* debugging pictures */
/* " '
{ . :
char titlel[100~;
static float w11200], w2[200];
register int i; ~ :
for( i=0; i<200; i++) wl[i] = 0.0; . :
wl[loc-dpl-l] =50.0;wl[1oc-dpl+l]= 50.0; wl[loc-dpl]=100; . - :
for( i=0; i< subframel+extra; i++) w2[i] = residual[dpl+iacshift+i];
for( i=0; i<*sfstart-dpl; i++) w2[i] = 0.0;
for( i=*sfend-dpl; i<subframel+extra; i++) w2[i] = 0.0;
sprintf(titlel,"shiftrange %5.3f", *maxshift2); -
pictures3( residual+dpl+iacshift, subframel+extra, wl, subframel+extra, .::.
w2, subframel+extra, fcnt, titlel, "considered", "shifted");
':~
: . , ~
' '' ' ' , ~' ;"~ ~,;
' ~ . ' , ''''. - , ~
- 28 -
Nov ~' 09:07 1992 maxeloc.c Page l
21~2~
#include "macro.h"
void maxeloc( maxloc, maxener, signal, dp, length, ewl)
int *maxloc; /* output: location of maximum energy */
float *maxener; /* output: energy at loc */
float *signal; /* input: signal for which energy is to be found*/
int dp; /* input: data pointer into signal */
int length; /* input: window of data */
int ewl; /* input: half length of energy window */
float ener;
register int i;
int tail, front;
ener = 0.0;
front = dp + ewl;
tail = dp - ewl;
for( i=tail; i<=front; i+t)
ener += signal[i] * signal[i];
*maxloc = dp;
*maxener = ener;
for( i=l; i<length; i++){ -
front++;
ener += signal[front] * signal[front] - signal[tail] * signal[tail];
tail++;
if( *maxener < ener){
*maxloc = i + dp; ;- :~
*~ ner = ener; :~
-- 29 --
Nov - ~'12:37 1992 modifyorig.c Page 1 2 ~ 0 2 0 8 0 : ~ ~
~include "macro.h" -~
t* . :~ .
* modifyorig - modify original - ~.
*/ ,
void modif~orig( residualm, accshift, d_shift, dpm, shiftrange, :.
exctation, residual, dpl, sfend)
float *residualm; /* output: modified residual signal */
float *accshift; /* in/out: accumulated shift */
float *d_shift; /* output: local shift value */
int *dpm, /* output: first nonvalid sample of residualm */ ::. :float shiftrange; /* input : one side of shift range */ : :
float *exctation; /* input : excitation waveform */ ~ ~ ;
float *residual; /* input : original residual signal */ : :
int dpl; /* input : window start */ : ~:
int sfend; /* input : window end */ ~ :~
void bl intrp();
void getcrit();
void testi_ubound(); .
int k;
float criterion, best;
float shift;
float optshift;
float locmax;
int leftlimit, rightlimit;
int length; ' : :::.
#define MAXDIM 100 : : -:.~
float critlMAXDIM]; : ~ :-.. :.-
float a, b;
float sstep
length = sfend - dpl; . .~
' ' ' ':. .' '. . . ' ~., ~.' ' :: .:
/* first we upsample by a factor 2 */ . .:~
sstep = 0.5;
rightlimit = shiftrange/sstep + O S;
leftlimit = -rightlimit;
if( leftlimit == rightlimit) rightlimit = leftlimit - 1; :
printf( modifyorig: llim %d rlim %d", leftlimit, rightlimit);
testi_ubound( rightlimit*2+1, MAXDIM, modifyorig.cl");
for(k=leftlimit; k<=rightlimit; k++){ . -~
shift = *accshift + k * sstep; : .
getcrit( crit+k-leftlimit, residual+dpl, exctation+dpl, shift, length);
/* then we interpolate the criterion */
best = 0.0; : .
optshift = *accshift; :. :
for(k=leftlimit+l; k<rightlimit; k++){
shift = *accshift + k * sstep;
a = crit[k-leftlimit+l~ + crit[k-leftlimit-1] - 2.0 * crit[k-leftlimit~
criterion = -2.0;
ift a != 0.0){
b = crit[k-leftlimit~l] - crit[k-leftlimit-1];
locmax = - b / (2.0 * a); . :
if( locmax <- 0.5 && locmax >= -O.S) ~ ~
'~ .
: : :
,,..,~,.
- 30 -
Nov lP-~2:37 1992 modifyorig c Page 2 21020~a
criterion = a * locmax * locmax + b * locmax + 2.0 * crit[k-leftiimit~;
if( criterion > best)(
optshift = shift + sstep * locmax;
best = criterion;
*accshift = optshift;
printf(" optshift %5.2f best %.4e\n", optshift, best);
if( best<=l.0)
for(k=leftlimit+1; k<rightlimit; k++)
printf("k=%d %f\n", k, crit[k-leftlimit]);
for( k=0; k<length; k++)(
bl intrp( residualm+dpl+k, residual+dpl+k, *accshift, 0.9, 8);
d shift[dpl+k] = *accshift;
*dpm = dpl+length;
: '' :::
.. ;'.,.~ ~.
- 31 -
Nav 1~ 09:07 1992 bl_intrp.c Page 1 210208B
#include "macro.h"
/* : :
* bl_intrp - band-limited interpolation
void bl_intrp~ output, input, delay, factor, fl)
float *output; /* output: interpolated output value */
float *input; /* input : array to be interpolated */
float delay; /* input : delay where actual input is */
float factor; /* input : cut-off frequency (relative to fs*/
int fl; /* input : filter length is 2*fl+1 */
/* NOTES
* computes "input" signal value
* at "delay" prior to the array pointer "input" into the "input" array.
*/ : :
register int n;
register float t;
register float *f; ;-
register float argl, arg3; ~-
register float denom;
int offset;
if( delay < 0){
offset = -delay + 0.5, ~ - -~, ;
offset = -offset; - -~ - ~
}
else
offset = delay + 0.5;
t = offset - delay;
f = input - offset; /* center sum around f */
denom = 2.0 / (2.0 * fl + 1.0);
*output = 0.0;
for( n= -fl; n<=fl; n++)l
argl = PI * factor * (t-n);
arg3 = PI * (t-n);
if( argl < l.e-2 && argl > -l e-2)/* just copy */
*output += factor * *(f+n);
else /* sinc function multiplied by hamming window */
*output += factor * (0.54 + 0.46 * cos( arg3 * denom )) *
*(f+n) * sin( argl) / argl;
':
, ...
,
- 32 -
Nov 16 09:07 1992 testbound.c Page 1
,* '' 21020~0
* testi_ubound - test if argument a exceeds int boundary b and print text :
void testi_ubound( a, b, text)
int a; /* input: value to be tested */ - :
int b; /* input: boundary value */
char *text; /* input: program name */
if( a > b){
printf("\n%s-f-value exceeds range %d > %d\n", text, a, b); :.
exit(10);
)
/ * '~: -* testi bound - test if argument a exceeds range bl,b2 and print text
*/ .:
void testi_bound( a, bl, b2, text) -~.
int a; /* input: value to be tested */
int bl,b2; /* input: boundary values */ ~:
char *text; t* input: program name */
if~ a < bl )~
printf("\n%s-f-value exceeds range %d < %d\n", text, a, bl);
exittlO); ..
else if (a > b2 )~
printf~n\n%s-f-value exceeds range %d > %d\n", text, a, b2); ~ ~:.. :
exit(10); ~ :
/*
* testf_bound - test if argument a exceeds range bl,b2 and print text
*/ .:,
void testf_bound( a, bl, b2, text)
float a; t* input: value to be tested */
float bl,b2; /* input: boundary values */
char *text; /* input: program name ~/
, . ..
if( a < bl )~
printf("\n%s-f-value exceeds range %f < %f\n , text, a, bl); :.
exit(10); : :
else if (a > b2 )~
printf("\n%s-f-value exceeds range %f > %f\n", text, a, b2); :. .
exit(10); ~ ........ -
}
,...
* testd_bound - test if argument a exceeds range bl,b2 and print text
void testd_bound( a, bl, b2, text)
double a; /* input: value to be tested */
double bl,b2; /* input: boundary values */
char *text; . /* input: program name */
..
if~ a < bl )~
~.
- 33 -
Nov 16 09:07 1992 testbound.c Page 2 210208~ ~ ~
printf("\n%s-f-value exceeds range %f < %f~n", text, a, bl);
exit(10);
}
else if (a > b2 )~
printf("\n%s-f-value exceeds range %f > %f\n", text, a, .b2);
exit(lO);
' ' ,
,'::: ~"-::: . '' ' ' ~ - ' ': ' . '
- 34 - :
v 16 09:07 1992 getcrit.c Page 1 21020~0
#include "macro h"
/ * :: :
* getcrit - compute error between excitation and shifted residual
*/
void getcrit~ criterion, residual, exctation, shift, length) .
float *criterion; /* output: error criterion */
float *residual; /* input : residual signal */
float *exctation; /* input : reference signal */
float shift; /* input : shift */
int length; /* input : vector length */
void bl_intrp();
float output;
register int i;
*criterion = 0.0; .
for( i=O; i<length; i++)(
bl_intrp( &output, residual+i, shift, 0.9, 8);
*criterion += output * exctation[i];
';~.
