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doCPLC.pas
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{
publish with BSD Licence.
Copyright (c) Terry Lao
}
unit doCPLC;
{$MODE Delphi}
interface
uses iLBC_define,C2Delphi_header;
{----------------------------------------------------------------*
* Compute cross correlation and pitch gain for pitch prediction
* of last subframe at given lag.
*---------------------------------------------------------------}
procedure compCorr(
cc:pareal; { (o) cross correlation coefficient }
gc:pareal; { (o) gain }
pm:pareal;
buffer:PAreal; { (i) signal buffer }
lag:integer; { (i) pitch lag }
bLen:integer; { (i) length of buffer }
sRange:integer { (i) correlation search length }
);
procedure doThePLC(
PLCresidual:pareal; { (o) concealed residual }
PLClpc:pareal; { (o) concealed LP parameters }
PLI:integer; { (i) packet loss indicator
0 - no PL, 1 = PL }
decresidual:pareal; { (i) decoded residual }
lpc:pareal; { (i) decoded LPC (only used for no PL) }
inlag:integer; { (i) pitch lag }
iLBCdec_inst: piLBC_Dec_Inst_t
{ (i/o) decoder instance }
);
implementation
procedure compCorr(
cc:pareal; { (o) cross correlation coefficient }
gc:pareal; { (o) gain }
pm:pareal;
buffer:PAreal; { (i) signal buffer }
lag:integer; { (i) pitch lag }
bLen:integer; { (i) length of buffer }
sRange:integer { (i) correlation search length }
);
var
i:integer;
ftmp1, ftmp2, ftmp3:real;
begin
{ Guard against getting outside buffer }
if ((bLen-sRange-lag)<0) then
begin
sRange:=bLen-lag;
end;
ftmp1 := 0.0;
ftmp2 := 0.0;
ftmp3 := 0.0;
for i:=0 to sRange-1 do
begin
ftmp1 :=ftmp1+ buffer[bLen-sRange+i] * buffer[bLen-sRange+i-lag];
ftmp2 :=ftmp2+ buffer[bLen-sRange+i-lag] * buffer[bLen-sRange+i-lag];
ftmp3 :=ftmp3+ buffer[bLen-sRange+i] * buffer[bLen-sRange+i];
end;
if (ftmp2 > 0.0) then
begin
cc[0] := ftmp1*ftmp1/ftmp2;
gc[0] := abs(ftmp1/ftmp2);
pm[0] :=abs(ftmp1)/(sqrt(ftmp2)*sqrt(ftmp3));
end
else
begin
cc[0] := 0.0;
gc[0] := 0.0;
pm[0] := 0.0;
end;
end;
{----------------------------------------------------------------*
* Packet loss concealment routine. Conceals a residual signal
* and LP parameters. If no packet loss, update state.
*---------------------------------------------------------------}
procedure doThePLC(
PLCresidual:pareal; { (o) concealed residual }
PLClpc:pareal; { (o) concealed LP parameters }
PLI:integer; { (i) packet loss indicator
0 - no PL, 1 = PL }
decresidual:pareal; { (i) decoded residual }
lpc:pareal; { (i) decoded LPC (only used for no PL) }
inlag:integer; { (i) pitch lag }
iLBCdec_inst: piLBC_Dec_Inst_t
{ (i/o) decoder instance }
);
var
lag, randlag:integer;
gain, maxcc:real;
use_gain:real;
gain_comp, maxcc_comp, per, max_per:real;
i, pick, use_lag:integer;
ftmp, pitchfact, energy:real;
randvec:array [0..BLOCKL_MAX-1] of real;
begin
lag:=20;
{ Packet Loss }
if (PLI = 1) then
begin
iLBCdec_inst^.consPLICount := iLBCdec_inst^.consPLICount+1;
{ if previous frame not lost,
determine pitch pred. gain }
if (iLBCdec_inst^.prevPLI <> 1) then
begin
{ Search around the previous lag to find the
best pitch period }
lag:=inlag-3;
compCorr(@maxcc, @gain, @max_per,@iLBCdec_inst^.prevResidual,lag, iLBCdec_inst^.blockl, 60);
for i:=inlag-2 to inlag+3 do
begin
compCorr(@maxcc_comp, @gain_comp, @per,@iLBCdec_inst^.prevResidual,i, iLBCdec_inst^.blockl, 60);
if (maxcc_comp>maxcc) then
begin
maxcc:=maxcc_comp;
gain:=gain_comp;
lag:=i;
max_per:=per;
end;
end;
end
{ previous frame lost, use recorded lag and periodicity }
else
begin
lag:=iLBCdec_inst^.prevLag;
max_per:=iLBCdec_inst^.per;
end;
{ downscaling }
use_gain:=1.0;
if (iLBCdec_inst^.consPLICount*iLBCdec_inst^.blockl>320) then
use_gain:=0.9
else
if (iLBCdec_inst^.consPLICount*iLBCdec_inst^.blockl>2*320) then
use_gain:=0.7
else
if (iLBCdec_inst^.consPLICount*iLBCdec_inst^.blockl>3*320) then
use_gain:=0.5
else
if (iLBCdec_inst^.consPLICount*iLBCdec_inst^.blockl>4*320) then
use_gain:=0.0;
{ mix noise and pitch repeatition }
ftmp:=sqrt(max_per);
if (ftmp> 0.7) then
pitchfact:=1.0
else
if (ftmp>0.4) then
pitchfact:=(ftmp-0.4)/(0.7-0.4)
else
pitchfact:=0.0;
{ avoid repetition of same pitch cycle }
use_lag:=lag;
if (lag<80) then
begin
use_lag:=2*lag;
end;
{ compute concealed residual }
energy := 0.0;
for i:=0 to iLBCdec_inst^.blockl-1 do
begin
{ noise component }
iLBCdec_inst^.seed:=(iLBCdec_inst^.seed*69069+1) and ($80000000-1);
randlag := 50 + (iLBCdec_inst^.seed) mod 70;
pick := i - randlag;
if (pick < 0) then
begin
randvec[i] := iLBCdec_inst^.prevResidual[iLBCdec_inst^.blockl+pick];
end
else
begin
randvec[i] := randvec[pick];
end;
{ pitch repeatition component }
pick := i - use_lag;
if (pick < 0) then
begin
PLCresidual[i] :=iLBCdec_inst^.prevResidual[iLBCdec_inst^.blockl+pick];
end
else
begin
PLCresidual[i] := PLCresidual[pick];
end;
{ mix random and periodicity component }
if (i<80) then
PLCresidual[i] := use_gain*(pitchfact * PLCresidual[i] + (1.0 - pitchfact) * randvec[i])
else
if (i<160) then
PLCresidual[i] := 0.95*use_gain*(pitchfact *PLCresidual[i] +(1.0 - pitchfact) * randvec[i])
else
PLCresidual[i] := 0.9*use_gain*(pitchfact *PLCresidual[i] +(1.0 - pitchfact) * randvec[i]);
energy :=energy + PLCresidual[i] * PLCresidual[i];
end;
{ less than 30 dB, use only noise }
if (sqrt(energy/iLBCdec_inst^.blockl) < 30.0) then
begin
gain:=0.0;
for i:=0 to iLBCdec_inst^.blockl-1 do
begin
PLCresidual[i] := randvec[i];
end;
end;
{ use old LPC }
move(iLBCdec_inst^.prevLpc[0],PLClpc[0],(LPC_FILTERORDER+1)*sizeof(real));
end
{ no packet loss, copy input }
else
begin
move( decresidual[0],PLCresidual[0],iLBCdec_inst^.blockl*sizeof(real));
move( lpc[0],PLClpc[0], (LPC_FILTERORDER+1)*sizeof(real));
iLBCdec_inst^.consPLICount := 0;
end;
{ update state }
if (PLI=1) then
begin
iLBCdec_inst^.prevLag := lag;
iLBCdec_inst^.per := max_per;
end;
iLBCdec_inst^.prevPLI := PLI;
move ( PLClpc[0],iLBCdec_inst^.prevLpc[0], (LPC_FILTERORDER+1)*sizeof(real));
move ( PLCresidual[0],iLBCdec_inst^.prevResidual[0],iLBCdec_inst^.blockl*sizeof(real));
end;
end.