????S ? :

1
?????? ?????? ???????O??O?

• ????S ?
• ??????????O????? T?????
• ??????? ??. 3
• ???????S ?O????????S?S ??G?S
• - ? ??????OS? ??S FO??S

2
?e?????? ??d???p???s?? F????

• ??d???p???s? ????? ? p????f???a µ?a? d?a???t??
  p???? ??d???p??e?ta? µe s??p? t?? ??????µ???
  d?ad??? a?apa??stas?. ??s? t?? d?ad??as?a? a?t??
  ap????pteta? ? p?e??????sa p????f???a.
• ? ??d???p???s? ????? ap??e?e? (lossless)
  ?p??e?ta? st? ?eµe???d? pe?????sµ? ?t? µ?a p???
  µe e?t??p?a ? µp??e? ?a ??d???p????e? µe µ?de????
  p??a??t?ta sf??µat?? ef?s?? ? ???µ?? p??
  p????pte? e??a? R gt H, ?a? a?t?st??fa, e?? R lt
  H t?te, a?e???t?ta ap? t?? p???p????t?ta t??
  ??d??a ?a p?????e? µ? µ?de???? p??a??t?ta
  sf??µat?? , (1? Te???µa t?? Shannon).
• ??as???? te?????? lossless, ?e????? s??p??
• - ???????µ?? t?? Shannon
• - ???????µ?? t?? Lempel Ziv
• - ???????µ?? t?? Huffman
• ??d???p???s? a?a??????? p???? ??e?
  a?ap?fe??ta ap??e?e? (lossy) p?? ?fe????ta? st?
  d?a???t?p???s? t?? t?µ?? (?ßa?t?sµ??). ? st????
  st?? pe??pt?s? a?t? e??a? ? e?a??st?p???s? a?t??
  t?? ap??e??? ?a? e? s??e?e?a ? s?µp?es? µe
  e?e???µe?e? ?a? p??? ap??e?e?.

3
?e?????? ??d???p???s?? F????

• ??d???p???s? F???? ?d?a?te?a ???s?µ?
  d?ad??as?a a? a?a????st??µe ?t? µe???? µ???? t??
  d?a?????µe??? p????f???a? e??a? f??? ?a? ?t? µ?s?
  t?? s?µp?es?? t?? µp??e? ?a ep?te???e? s?µa?t???
  µe??s? t?? apa?t??µe??? e????? ????? (µ???? ?a?
  4-5 f???? ????? a?s??t? ?p?ß??µ?s? t??
  p???t?ta?).
• Ge???? ?at??????p???s? t?? te??????
• 1) Waveform Coding
• - Temporal
• - Spectral (Transform)
• 2) Model-based (or Source) Coding
• ?a??µ??a ?at??????p???s? ?s??e? ?a? se ?????
  t?p?? a?a??????? p???? (p.?. e????a ? video).

4
?e?????? ??d???p???s?? F????
?e?a????? ?at??????p???s? t?? d??f???? te??????
??d???p???s??
5
?e?????? ??d???p???s?? F????
?????aµµa ßa?µ?d?? e??? ??d???p???t? ADPCM (CT2
cordless telephone system)
?? s?st?µa e??a? p??sa?µ?st??? (p??ß??pt?? ?a?
?ßa?t?st??) ?a? ?ts? e??a? se ??s? ?a
pa?a??????e? t?? stat?st???? a??a??? t?? s?µat??
e?s?d?? S(k)
6
?e?????? ??d???p???s?? F????
??a???µµata ßa?µ?d?? ?p?-??????? ??d???p???t? ?a?
ap???d???p???t? Sub-band Codec (
Coder-Decoder )
- ???s? t?? filter banks QMF ??a a????s? t??
a?ad?p??s?? f?sµat??
7

?e?????? ??d???p???s?? F????
??p???? d?a????sµ?? ?p?-?????

• Adaptive Transform Coding (ADC)
• ??d???p???s? tµ?µ?t?? f???? st? ped?? s????t?t??
  
• S?????? ???s?µ?p??e?ta? ? ??a???t??
  ?etas??µat?sµ?? S???µ?t???? (DCT) t?? ?p???? ??
  s??se?? a????s?? ?a? s???es?? fa????ta? pa?a??t?
  ( g(0)1, g(k)21/2 )

8
?e?????? ??d???p???s?? F????
???t??? pa?a????? f????
?pa?te?ta? ? e?t?µ?s? t?? e??? pa?aµ?t??? -
?? t? f???µa e??a? e?f??? (voiced) ? ?f???
(unvoiced) - - Teµe???d?? s????t?ta
(pitch) - ??s? ?s??? t?? f???µat??
9
?e?????? ??d???p???s?? F????
??d???p???t?? f???? (Vocoders) t?p?? LPC (Linear
Predictive Coding)
??a? LPC Vocoder µ??te??p??e? t? f???t??? ?d? ??
??a ??aµµ??? s?st?µa t?p?? all-pole µe s????t?s?
µetaf????
???sd????sµ?? t?? s??te?est?? t?? LPC Vocoder
To t????? de??µa ???feta? ?? ??aµµ????
s??d?asµ?? p??????µ???? de??µ?t??
minS e2n w.r.t. ak ? R a r (R
Toeplitz) (Levinson-Durbin Algorithm)
10
?e?????? ??d???p???s?? F????
?????aµµa ßa?µ?d?? e??? ??d???p???t? LPC
?pa?t??µe?? p????f???a st?? d??t? -
S??te?est?? LPC (?ßa?t?sµ????) -
Voiced/unvoiced decision - Pitch period
- Gain
11
?e?????? ??d???p???s?? F????
???f??e? e?a??a?t???? µ???d?? d?µ??????a? t??
s?µat?? d???e?s?? st?? ap???d???p???t? LPC
LPC Vocoder MPE-LPC (Multipulse
Excitation) ???s? p????? pa?µ?? a?? pe???d? µe
µetaßa???µe?a p??t? ?a? ??se?? CELP (Code
Excited LP) ???s? e??? p???a????sµ???? codebook
µe s?µata d???e?s??
12
?e?????? ??d???p???s?? F????
?????aµµa ßa?µ?d?? t?? d?ad??as?a? code book
search t?? s?st?µat?? ??d???p???s?? CELP (Code
Excited Linear Predictive)
?? ßas???? d?ad??as?e? st?? ??d???p???t? CELP
- ?p?????sµ?? t?? d?? p??ß?ept?? (LTP,
STP) ap? t? e??st?te tµ?µa f????
(Long Term Short
Term Prediction) - ???es? t??
ß??t?st?? d???e?s?? (ap? t? codebook). ??
a?t??e?µe???? sf??µa a?a?atas?e???
(error) ?f?stata? pe?a?t??? µetas??µat?sµ?
a?????? t?? a?t???pt???? µ??a??sµ??
µa? (perceptual masking)
13
?e?????? ??d???p???s?? F????
?????aµµa ßa?µ?d?? t?? s?st?µat?? ??d???p???s??
RELP (Residual
Excited Linear Predictive)

To s?st?µa ??d???p???s?? RELP ßas??eta?
??s?ast??? st?? ?d?a ?????? µe a?t? t??
s?st?µat?? ADPCM µe ep?p???? st???e?a t??
e?s?µ?t?s? ?a?a?t???st???? t?? t?????t??
de??µat?? (v/u, gain, pitch) . S??µat??eta? t?
s?µa sf??µat?? (residual) t? ?p??? ?ßa?t??eta?
?a? µetad?deta?.
14
?e?????? ??d???p???s?? F????
?????aµµa ßa?µ?d?? t?? ??d???p???t? f???? t??
s?st?µat?? GSM ( Regular Pulse Excited - Long
Term Prediction RPE-LTP )
To s?st?µa RPE-LTP s??d???e? ta p?e??e?t?µata
t?? RELP ?a? t?? MPE-LTP. ??s?ast??? e??a?
s?st?µa t?p?? RELP p?? ??e? e?s?µat?se? t?
d?ad??as?a LTP.
15
?e?????? ??d???p???s?? F????
?????aµµa ßa?µ?d?? t?? ap???d???p???t? f???? t??
s?st?µat?? GSM
- H a????s? STP (st?? ??d???p???t?) d??e? t???
?e??µe???? reflection coefficients ?a? ??? t???
?d???? t??? s??te?est?? p??ß?e???. ???a?
µa??µat??? ?s?d??aµ? pa?aµet??p???s?. - St?
s????e?a ap? t??? r.c. ?p????????ta? ??
s??te?est?? L.A.R. (logarithmic area ratios)
µ?s? e??? ap??? µ?-??aµµ???? µetas??µat?sµ??. ??
s??te?est?? p?? p????pt??? ????? ?a??te?e?
?d??t?te? ?ß??t?s??.
16
?e?????? ??d???p???s?? F????
?e?????? ??d???p???s?? p?? ???s?µ?p?????ta? se
d??f??a s?st?µata ????t?? ep??????????
17
?e?????? ??d???p???s?? F????
????????s? t?? ap?d?s?? d?af???? te??????
??d???p???s?? µe ß?s? t?? de??t? MOS (Mean
Opinion Score)

• ??a??et??? p???t?ta (5) ?ata??pt?t?ta
  ????? ?aµµ?a p??sp??e?a
• ?a?? p???t?ta (4) ?ata??pt?t?ta
  ????? ?d?a?te?? p??sp??e?a
• ??t??a p???t?ta (3) ?ata??pt?t?ta
  µe s?et??? p??sp??e?a
• ??epa???? p???t?ta (2) ?ata??pt?t?ta µe
  s?µa?t??? p??sp??e?a
• ?a?? p???t?ta (1) ????
  pe?????sµ??? ?ata??pt?t?ta pa?? t??
• 
  s?µa?t??? p??sp??e?a