audionumérique -
Transcript of audionumérique -
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● Chaîne d'acquisition/traitement/restitution de l'information audio● Musique vs parole● Streaming internet● Audio embarqué● Audionumérique pour la radio, le cinéma, la production musicale● Architectures – algorithmes – normes
audionumérique
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Architectures standards
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L'oreille
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La dynamique de l'oreille
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Les bandes critiques
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Le masquage fréquentiel
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Les harmoniques
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Les harmoniques
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Le spectre des sources sonores
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L'équilibre spectral
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Architecture du TSA
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Mixers virtuels
● Floating point vs Integer● Ex : float 32 bit = 1 bit de signe + 23 bits de
mantisse + 8 bits exposant
→144 dB de dynamique et non 1638 dB
● 1.0 correspond à 0 dBr● Dithering (ex: 1.0 / 3 = 0.333333334)
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Dithering
● Problèmatique : erreurs d'arrondi lorsqu'on passe de “floating point” à “integer”.
● [1 2 3 4 5] * 0.8 = [0.8 1.6 2.4 3.2 4.0]
-> [1 1 2 3 4]● Distortion corrélée avec le signal !● Stratégie : ajouter un bruit uniforme avant
conversion, pour décorréler. ● Exemple : 3.2 = Ent{3.2 + [0-1]}
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Dithering
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Dithering
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Buffering
● Influence de la taille des buffers● Double buffering● Low latency mode● Plugin delay compensation & problèmes liés à
la phase (filtres en peigne)
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Double Buffering & DMA
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Sur-échantillonnage
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EQ : filter design
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EQ : filter design
● Direct form I (instable si N grand, 2N délais)
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Compression
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Compression
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Réverbération
● Emulation : réponse impulsionnelle.
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L'API Java Sound
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L'API Java MIDI