Algebraic code-excited linear prediction

<h2 id="features">Features</h2>
The main advantage of ACELP is that the <a href="/facts/Algebra/nMdqczjo">algebraic</a> codebook it uses can be made very large (> 50 bits) without running into storage (<a href="/facts/Random-access_memory/DuD4bxh6">RAM</a>/<a href="/facts/Read-only_memory/P9QMuDLH">ROM</a>) or complexity (<a href="/facts/CPU/Jxp1bqMV">CPU</a> time) problems.

<h2 id="technology">Technology</h2>
The ACELP algorithm is based on that used in <a href="/facts/Code-excited_linear_prediction/Shkm4bjo">code-excited linear prediction</a> (CELP), but ACELP codebooks have a specific algebraic structure imposed upon them.
A 16-bit algebraic codebook shall be used in the innovative codebook search, the aim of which is to find the best innovation and gain parameters. The innovation vector contains, at most, four non-zero pulses.
In ACELP, a block of N speech samples is synthesized by filtering an appropriate innovation sequence from a codebook, scaled by a gain factor g c, through two time-varying filters.
The long-term (pitch) synthesis filter is given by:

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            1
            
              1
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                g
                
                  p
                
              
              
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                  T
                
              
            
          
        
      
    
    {\displaystyle {\frac {1}{B(z)}}={\frac {1}{1-g_{p}z^{-T}}}}

The short-term synthesis filter is given by:

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              A
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            1
            
              1
              +
              
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                  1
                
                
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    {\displaystyle {\frac {1}{A(z)}}={\frac {1}{1+\sum _{i=1}^{P}a_{i}z^{-i}}}}

<h2 id="references">References</h2>

<ol>
<li id="fn:1">"Transfer of technology". <a href="https://www.usherbrooke.ca/recherche/fr/partenariats/pour-les-entreprises/transfert-de-technologie/exemples-de-transferts/technologie-de-compression-de-la-parole-acelpr/" target="_blank">https://www.usherbrooke.ca/recherche/fr/partenariats/pour-les-entreprises/transfert-de-technologie/exemples-de-transferts/technologie-de-compression-de-la-parole-acelpr/</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></li>
<li id="fn:2">ACELP map, VoiceAge Corporation, Archive.org <a href="https://web.archive.org/web/20071014224013/http://www.voiceage.com/image/ACELPMAP.jpg" target="_blank">https://web.archive.org/web/20071014224013/http://www.voiceage.com/image/ACELPMAP.jpg</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></li>
<li id="fn:3">"Related Standards Specifications". 14 October 2007. Archived from the original on 14 October 2007. <a href="https://web.archive.org/web/20071014095716/http://www.voiceage.com/relatedstandards.php" target="_blank">https://web.archive.org/web/20071014095716/http://www.voiceage.com/relatedstandards.php</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></li>
<li id="fn:4">VoiceAge Corporation (13 October 2007). "Codec Technologies". Archived from the original on 13 October 2007. Retrieved 20 September 2009. <a href="https://web.archive.org/web/20071013162836/http://www.voiceage.com/technologies.php" target="_blank">https://web.archive.org/web/20071013162836/http://www.voiceage.com/technologies.php</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></li>
<li id="fn:5">VoiceAge Corporation. "Codec Technologies". VoiceAge Corporation. Archived from the original on 18 October 2009. Retrieved 20 September 2009. <a href="https://web.archive.org/web/20091018020920/http://www.voiceage.com/technologies.php" target="_blank">https://web.archive.org/web/20091018020920/http://www.voiceage.com/technologies.php</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></li>
<li id="fn:6">VoiceAge Corporation. "ACELP.net — Beyond the Standards". Archived from the original on 14 October 2007. Retrieved 3 January 2010. <a href="https://web.archive.org/web/20071014035312/http://www.voiceage.com/acelpnet.php" target="_blank">https://web.archive.org/web/20071014035312/http://www.voiceage.com/acelpnet.php</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></li>
<li id="fn:7">US patent 5717825, "Algebraic code-excited linear prediction speech coding method", issued 10 February 1998
 <a href="https://worldwide.espacenet.com/textdoc?DB=EPODOC&IDX=US5717825" target="_blank">https://worldwide.espacenet.com/textdoc?DB=EPODOC&IDX=US5717825</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></li>
</ol>

Algebraic code-excited linear prediction open-in-new

Algebraic code-excited linear prediction