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Author:Laaksonen, Arttu Matias
Title:Bandwidth Extension in High-Quality Audio Coding
Kaistanlaajennus korkealaatuisessa audiokoodauksessa
Publication type:Master's thesis
Publication year:2005
Pages:vii + 49 s. + liitt. 13      Language:   eng
Department/School:Sähkö- ja tietoliikennetekniikan osasto
Main subject:Akustiikka ja äänenkäsittelytekniikka   (S-89)
Supervisor:Välimäki, Vesa
Instructor:Ojala, Pasi
Electronic version URL: http://urn.fi/urn:nbn:fi:tkk-007914
OEVS:
Electronic archive copy is available via Aalto Thesis Database.
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Location:P1 Ark S80     | Archive
Keywords:audio coding
bandwidth extension
spectral band replication
acoustic signal analysis
acoustic signal processing
audiokoodaus
äänenpakkaus
kaistanlaajennus
äänenkäsittely
äänianalyysi
Abstract (eng):In mobile telecommunications the transmission speed is currently very limited.
Advanced coding methods are used to pack transmitted information into a smaller memory space.
The coding of audio signals has developed a lot in the past years, and one method enabling better coding efficiency has been bandwidth extension.

In this thesis, the current bandwidth extension methods are studied, and analysis is made to find out if the methods could be improved.
Two new methods have been developed by the author.
A method based on modified discrete cosine transform (MDCT) has been used to examine how different parameters affect the result of bandwidth extension.
The second method uses linear prediction (LPC) in modeling the properties of audio signals.

The new methods were compared against each other and one previous bandwidth extension method in listening tests.
The results of the tests were that the new methods can be used to improve coding efficiency in high-quality audio coding.
Abstract (fin):Langattoman viestinnän siirtonopeudet ovat tällä hetkellä varsin rajalliset.
Kehittyneiden koodausmenetelmien avulla siirrettävä tieto saadaan pakattua pienempään muistiin.
Äänisignaalien pakkaaminen on edistynyt paljon kuluneina vuosina, ja yksi tämän mahdollistanut menetelmä on ollut kaistanlaajennus.

Tässä diplomityössä tutkitaan nykyisiä kaistanlaajennusmenetelmiä.
Menetelmiä analysoidaan tavoitteena löytää keinoja niiden parantamiseen.
Diplomityön tekijä on kehittänyt kaksi uutta menetelmää.
Modifioituun diskreettiin kosinimuunnokseen (MDCT) perustuvaa menetelmää on käytetty selvittämään kuinka eri parametrit vaikuttavat kaistanlaajennuksen lopputulokseen.
Toinen menetelmä käyttää lineaarista ennustusta (LPC) äänisignaalin ominaisuuksien mallintamiseen.

Uusia menetelmiä vertailtiin toisiinsa ja yhteen olemassaolevaan menetelmään kuuntelutesteissä.
Testien tuloksina todettiin, että uusia menetelmiä voidaan käyttää pakkaustehokkuuden parantamiseen korkealaatuisessa audiokoodauksessa.
ED:2005-08-18
INSSI record number: 34429
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