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Pitch-shifting algorithm design and applications in music
KTH, School of Electrical Engineering and Computer Science (EECS).
2019 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

Pitch-shifting lowers or increases the pitch of an audio recording. This technique hasbeen used in recording studios since the 1960s, many Beatles tracks being producedusing analog pitch-shifting effects. With the advent of the first digital pitch-shiftinghardware in the 1970s, this technique became essential in music production. Nowadays,it is massively used in popular music for pitch correction or other creative purposes.With the improvement of mixing and mastering processes, the recent focusin the audio industry has been placed on the high quality of pitch-shifting tools. Asa consequence, current state-of-the-art literature algorithms are often outperformedby the best commercial algorithms. Unfortunately, these commercial algorithms are”black boxes” which are very complicated to reverse engineer.In this master thesis, state-of-the-art pitch-shifting techniques found in the literatureare evaluated, attaching great importance to audio quality on musical signals.Time domain and frequency domain methods are studied and tested on a wide rangeof audio signals. Two offline implementations of the most promising algorithms areproposed with novel features. Pitch Synchronous Overlap and Add (PSOLA), a simpletime domain algorithm, is used to create pitch-shifting, formant-shifting, pitchcorrection and chorus effects on voice and monophonic signals. Phase vocoder, amore complex frequency domain algorithm, is combined with high quality spectralenvelope estimation and harmonic-percussive separation to design a polyvalentpitch-shifting and formant-shifting algorithm. Subjective evaluations indicate thatthe resulting quality is comparable to that of the commercial algorithms.

Abstract [sv]

Pitch-shifting sänker eller ökar tonhöjden för en ljudinspelning. Denna teknik har använts i inspelningsstudior sedan 1960-talet, många Beatles-spår produceras med hjälp av analoga pitch-shifting effekter. Med ankomsten av den första digitala pitchshifting hårdvaran på 1970-talet blev denna teknik avgörande för musikproduktionen. Numera används det massivt i populärmusik för pitchkorrigering eller andra kreativa ändamål. Med förbättringen av blandningsoch masteringsprocesser har det senaste fokuset inom ljudindustrin placerats på högkvalitativa pitch-shiftingverktyg. Till följd av detta är nuvarande toppmoderna litteraturalgoritmer ofta överträffade av de bästa kommersiella algoritmerna. Tyvärr är dessa kommersiella algoritmer svarta lådor som är väldigt komplicerade att vända sig om.I den här mastersuppsatsen utvärderas toppmoderna pitch-shifting-tekniker som finns i litteraturen och lägger stor vikt vid ljudkvaliteten på musikaliska signaler. Tiddomäner och frekvensdomänmetoder studeras och testas på ett brett spektrum av ljudsignaler. Två offline-implementeringar av de mest lovande algoritmerna föreslås med nya funktioner. Pitch Synchronous Overlap and Add (PSOLA), en enkel tidsdomänalgoritm, används för att skapa pitch-shifting, formant-shifting, pitch-korrigeringoch kör-effekt på röstoch monofoniska signaler. Fas vocoder, en mer komplexfrekvensdomänalgoritm, kombineras med högkvalitativt spektralhöljeuppskattning och harmonisk-perkussiv separation för att designa en flervärd pitch-shifting och formant-shifting algoritm. Subjektiva utvärderingar indikerar att den resulterandekvaliteten är jämförbar med den av kommersiella algoritmerna.

Place, publisher, year, edition, pages
2019. , p. 83
Series
TRITA-EECS-EX ; 2019:674
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-266118OAI: oai:DiVA.org:kth-266118DiVA, id: diva2:1381398
Educational program
Master of Science in Engineering - Electrical Engineering
Examiners
Available from: 2019-12-20 Created: 2019-12-20 Last updated: 2019-12-20Bibliographically approved

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