CSE 2340 Lectures

1
?13? ???????
2
??

• ????
• ???????????
• ???????????
• ???????????

3
??? ?
4
????????????

• ???????????????
• ?????????????
• ????????
• ????????
• ??(???)????
• ????(??)
• ????????????????,
• ????????????????????

5
??????????

• ???? (Perception model-based compression)
• ?? ?????????
• ?? ??????????
• ?? PCM, ADPCM, SBC
• ????,??? (Production model-based compression)
• ?? ?????
• ?? ???????
• ?? LPC
• ????(Hybrid compression)
• ?? CELP

6
???????????
7
????????

• ?? ?? ??? ?? ?? ??
• G.711 PCM 64 4.4 1972 PSTN
• ANSI 1015 LPC-10 2.4 2.7 1976 ????
• G.721 ADPCM 32 4.1 1984 PSTN
• GSM(??????) RPE-CELP 13 3.6 1991
• ANSI 1016 CELP 4.8 3.2 1991
• G.728 ???CD-CELP 16 4.0 1992
• IS 54(??TDMA) VSELP 8 3.5 1992
• IS 96(??CDMA) QCELP 1-8 3.4 1993
• ?????? VSELP 6.8 3.3 1993
• G.729A CS-ACELP 8 4.2 1995 IP??
• G.723.1(H.323, H.324) ACELP 6.3 3.98 1995 IP??
• ???GSM(??????) AMR 5-6 3.4 1995
• ?????ANSI?? MELP 2.4 3.3 1996

8
???????????
9
??????

• ??????,????,???,
• ??????,?????16 kbps??,
• ???????,
• ????,????????????,
• ???,????????
• CCITT G.711 PCM 64kb/s
• CCITT G.721 ADPCM 32Kb/s
• CCITT G.726 ADPCM 48, 32, 24, 16 Kb/s
• ????????????????

10
CCITT G.711 (??????) Pulse Code Modulation
(PCM) of Voice Frequency

• ????

??104 kbps

• ??
• ????,?????,
• ?????,
• ??????,???64kbps?

?? 8? x 8k64 kbps
11
???? Fln(x)

• ?? ???????????????

12
???????

• x(n) ???(112?) F(n) PCM?(17?)
  
• 0 0 0 0 0 0 0 W X Y Z a 0 0 0 W X Y Z
• 0 0 0 0 0 0 1 W X Y Z a 0 0 1 W X Y Z
• 0 0 0 0 0 1 W X Y Z a b 0 1 0 W X Y Z
• 0 0 0 0 1 W X Y Z a b c 0 1 1 W X Y Z
• 0 0 0 1 W X Y Z a b c d 1 0 0 W X Y Z
• 0 0 1 W X Y Z a b c d e 1 0 1 W X Y Z
• 0 1 W X Y Z a b c d e f 1 1 0 W X Y Z
• 1 W X Y Z a b c d e f g 1 1 1 W X Y Z

13
PCM ???

• ????????????(??????)
• ????????(??)
• ???? (8 KHz x 8 bit x 1),
• ??????TDM (time-division multiplexing)
• ?????????????/??
• CD-DA(CD??),DAT
• (44.1 KHz x 16 bit x 2)

14
ADPCM??????????? (Adaptive Differential PCM)

• ??
• ????????????,?????????????, ???????????????,??????
  ?????????????
• ????????????????,????????(step-size)???????,??????
  ????????,
• ????????????,??????????

15
????(DM)
16
???????? DPCM
?????
??? Q

• ???????????????????,?????????????????,????????????
  ??

?????? Xn A1Xn-1 A2Xn-2 ... AmXn-m
( m?????,A1, A2, ... , Am??????)
17
??
E ????
-255-240 -239-224 -31-16 -150 116 1732 225240 241255 -248 -232 -24 -8 8 24 232 248
130,150,140,200,230 f 130, 130, 142, 144,
167 e 0, 20, -2, 56, 63 e 0,
24, -8, 56, 56 f 130, 154, 134,
200, 223
18
?????????(APCM)
???
??? Q

• ????????????????????
• ????????,????????????????,?????????,??????????????
  ??????

19
CCITT G.721 ADPCM???
13???????????
??? Q

• 6????????,
• 4????????,
• ???? 8k x 4 32 kbps

20
ADPCM ??

• PCM???? 4.5?
• ADPCM???? 4.34?,??????(32 kbps)?
• ADPCM??
• ??????
• ?????????(???)

21
Sub-band coding (????)

• ????
• ???????(BPF)???????????????????(???,??)
• ?????????,??????,????????
• ???????????,???????,?????????
• ?????????ADPCM????,?????????

22
G.722 64 kbps???????
??1??64kbps???? 0 ??2??56kbps???? 8
kbps ??3??48kbps???? 16kbps
23
???????????
24
????(???)?????

• ???????????????????,
• ?????????(??)??,
• ?????????????????????
• ???????????,?????????????

25
??????(1)

• ???????,????,????,???????,?????
• ???????????(????1 ms??)
• ????????,???,????????,????????,??10 100 ms????
• ???????????????????,???????????,???????????(transf
  er function)????20ms?????????

26
??????(2)

• ?????????????????,???????,?????2?

• ??Voiced sounds (????,??????????????,????)

• ??Unvoiced sounds(?????,?????????,??????????????
  ?????????)

27
????????????(1)
28
????????????(2)
LPC?? (a1, a2, a3, a4, a5, a6, a7, a8, a9, a10,
G, V/UV, T)
29
???????(LPC??) ???????????????

• ??????????(1030ms)??????,LPC?????A (a1, a2,
  a3, a4, a5, a6, a7, a8, a9, a10, G, V/UV,
  T)?????, ???20ms????
• ????????????8kHz,??????50?,?? 20ms(???20x8160???)
  ,?????????????????,??????????????????
• ??????(1?)
• ?????T(6?)
• ?????G(5?)
• ????????(10???,????6?,?60?)

??,??????50 x 72 bits 3600 bps 3.6kbps
30
????LPC???(1)

• ???????????????????????????,????????????LPC?
• ?????????10???????????
• spre(n) - a1s(n-1)a2s(n-2)a10s(n
  -10)
• ??s(n)??????
• e(n) s(n) - spre(n) s(n) a1s(n-1)a2s(n-2)
  a10s(n-10)

31
????LPC???(2)

• ??????????s(n) ,n0..159,??????ai
  ??????e(n)????????
• ? E?s(n)a1s(n-1)a2s(n-2)
  a10s(n-10)2 ??
• ??,???a1, a2, , a10 ??????????????
• dE/da1 0, ?s(n)a1s(n-1)a2s(n-2)
  a10s(n-10)s(n-1)0
• dE/da2 0, ?s(n)a1s(n-1)a2s(n-2)
  a10s(n-10)s(n-2)0
• .. ,
• dE/da10 0, ?s(n)a1s(n-1)a2s(n-2)
  a10s(n-10)s(n-10)0

32
???? ai??????

• R(1,1) R(1,2) R(1, 3) ..
  R(1,10) a1 -R(0,1)
• R(2,1) R(2,2) R(2, 3) ..
  R(2,10) a2 -R(0,2)
• R(3,1) R(3,2) R(3, 3) ..
  R(3,10) a3 -R(0,3)
• . . . . . . . . .
• R(10,1)R(10,2) R(10, 3) ..
  R(10,10) a10 -R(0,10)

33
????LPC???(3)
??????3???(V/UV,G,T)

• ??/?????
• ????,???????????????
• ???????????????
• 
  
• 
  i?12,140
• ????T???
• ???????????????
• ????SIFT?????,AMDF?????
• ???????G

34
?1 2.4kb/s LPC?????

• 20ms??1?,??????
• LPC????????34 bit
• ??G 7 bit
• ??/??????????T7 bit
• ?? 48x502.4kb/s

35
? LPC-10???(ANSI 1015 , 2.4kb/s)

• 22.5ms??1?,?????????,
• LPC???10?,?????????,
• ???????T??????????(AMDF)??,?60??,??51.3-400Hz,????
  ?,
• ????????????????
• ??54 x 1000/22.5 2.4 kb/s

36
????????????

• ???? ????
• 1 ???
  ???
• 2 ???
  ???
• 3 ????
  ????
• 4 ????????? ???????
• ?????????2-4 kbps??,???????????,??????????????????
  ????,????????,???????????????.

37
???????????
38
???????

• ????????????????,???????????????????????????????
  
• ??????????????????????
• ????????????,?????????

??????????????
????
????
???????
??
(????)
??
???????
(?????)
????
39
???????

• ?? ????-???AbS(Analysis-by-Synthesis)???????,
  ???????????LPC???????,????????(??/??)?????????????
  ??,??????,??????u(n), ???????s(n)??????????e(n)???
  ?

• ????????????????????????,??????-??????)

40
??????u(n)?????

• ?????????
• ?????????MPLPC(multiple pulse LPC)
• ???????RPE (regular-pulse excited)
• ???????CELP (code excited linear predictive)

41
????????? --MPLPC

• ???????20ms????, ???????LPC???
• ???????k?????,????????????
• ??1?????,????????
• ?1,,i-1?????????????,????i?????????
• ??????k?,???

42
???????LPC??? Regular-Pulse Excited LPC

• ?????4?????(??5 ms?1?????), ?????????13???,??????,
  
• ????5ms???????????(?1??????????????????),????40-12
  0????????????????????

• ?20ms????????,??LPC???(?36??)

?20ms?4x5636260bit, ??0.26x5013kb/s
43
? GSM (13kbps)????? (Global System for Mobile
communications)
LPC????8???,?36bit,?20 ms ????
?5ms?????13????????????(56bit)
?5ms????,?40-120??????????????????????
?20ms??4x5636260bit, ??0.26x5013kb/s
44
?????????? ( CELP,Code Excited
LPC )

• CELP??, 1985?????????????????????(????),??????????
  ?????????????????,?????????????
• ?CELP????????????
• ??? ANSI? 4.8 kbps codec
• ITU?low-delay 16 kbps codec

45
? ?(1)
"A lathe is a big tool. Grab every dish of
sugar." ????(PCM) ADPCM CELP LD-CELP CS-ACELP LPC
-10
46
? ?(2)
?? ?? 1 min
Sample 11,025Hz 16bit PCM
176.4kbs 1292k 11k16bitpcm.wav 8000Hz 16bit PCM
128kbs 937.5k 8k16bitpcm.wav 11,0
25Hz 8bit PCM
88.2kbs 646k 11k8bitpcm.wav 11,025Hz u-Law
88.2kbs 646k 11kulaw.wav 8,000Hz
8bit PCM 64kbs 468.8k 8k8bitpc
m.wav 8,000Hz u-Law
64kbs 468.8k 8kulaw.wav toll quality
telephone 11,025Hz 4bit ADPCM
44.1kbs 323k 11kadpcm.wav 8000Hz 4bit ADPCM
32kbs 234.4k 8kadpcm.wav 11,025Hz
GSM6.10 18kbs 131.8k 11kgsm.wa
v 8,000Hz GSM6.10
13kbs 102.5k 8kgsm.wav cell phone
quality 8000Hz Lernout Hauspie SBC
12.0kbs 87.9k 8ksbc12.wav 8,000Hz DSP Group
TrueSpeech 9kbs 65.9k 8ktruespeech.wav 8,000Hz
Lernout Hauspie CELP 4.8kbs 35k 8kcelp.wav
47
????
48
????????????

• ????(??)???,??????????????????????????????????
  ???????

• ?????????????????,???????????????(?????)
• ??????????????,??????????,????????????????????(???
  ??)
• ????????????????????????,??????????????????(?????)
  ?