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????S ? :

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Title: ????S ? :


1
?????? ?????? ???????O??O?
  • ????S ?
  • ??????????O????? T?????
  • ?????S??S? ??. 4
  • ???????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).
  • ??ass???? 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? Subband Codec (
Coder-Decoder )
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) CELP (Code Excited LP)
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) (Long Term Short Term Prediction)
- ???es? t?? ß??t?st?? d???e?s?? (ap? t?
codebook)
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. 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
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