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Standardisation group: ITU-R WP6C RG25

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New methods for perceptual evaluation of next generation sound systems

 Af Nick Zacharov

As part of DELTA SenseLab’s ongoing participation within the International Telecommunication Union (ITU), Nick Zacharov, Senior Technologist at DELTA SenseLab, was nominated to chair the rapporteur group (RG25, 2015-2016) on audio quality assessment within the Radio Communication Sector.

This group oversees all ITU Recommendations relating to audio quality matters, including the ITU-R BS.1534 and ITU-R BS.1116 Recommendations. Both of these recommendations are widely used throughout the audio industry for the selection of audio codec, watermark technologies and so forth, through subjective listening tests.

Next generation sound systems

Presently there is a big move across the audio, broadcast and cinematographic industries to introduce so-called next generation sound systems (also known as advanced sound systems). Such systems allow for a scalable reproduction of the sound into a user’s environment whether they are using a 2-channel stereo system (headphone or loudspeaker) or a large number of loudspeaker channels, e.g. 5.1, 10.2, 22.2 channels of loudspeakers. This is achieved using a so-called channel-based or object-based technology, whereby the sound field is rendered according to the nature of the loudspeaker configuration (number, loudspeakers location, etc.).

With the advent of such next generation advanced sound systems come a wide range of new quality characteristics that are hard to capture with the existing listening test recommendations. The need to developed new means for the assessment of audio quality such highly immersive spatial sound applications has thus emerged.

Novel methods for perceptual evaluation of sound systems

As part of this effort, DELTA SenseLab has worked on the development of novel methods for the perceptual evaluation of next generation sound systems. The Multiple Stimulus Ideal Profile Method has been developed with the aim of efficiently evaluating overall quality of such technologies as well as characterising the perceptual nature of the technologies.

In order to validate the method, joint evaluation tests were performed in collaboration with BBC Research and Development (Salford UK) and QI Statistics (UK). The excellent results of this work were contributed to the ITU-R WP6C RG25 group and have resulted in a work plan to further refine the method with the hope of approving a new ITU-R Recommendation. Presently the method is in a “preliminary draft new recommendation”.

In order to get further input and review of the method, a conference paper was prepared [1] for the Quality of Multimedia Experience (QoMEX) conference held in Lisbon. The paper was well received and led to good discussion and further received the best paper award from the conference (see figure 1).

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 Figure 1. QoMEX 2016, best paper award.

The invention of the sound quality wheel

In addition to this work, DELTA SenseLab has been working on unifying the sound quality terminology used in perceptual evaluation. Whilst the wine aroma wheel was already formalised in the early 80’s for the wine industry, no equivalent lexicon has existed in the field of audio until now.

The sound quality wheel (see figure 2) has been in recent development and published, providing a lexicon for generic reproduced sound quality evaluation. This work has been progressing within DELTA SenseLab and has been now been published [2,3]. The sound attribute wheel has also been contributed into the ITU-R WP6C RG25 for consideration as part of new methods for perceptual audio evaluation.

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Figure 2. Version 2.0 of the sound quality wheel, Audio Engineering Society, 2016 [2].

The work continues in the development of such a new recommendation with the hope of finalisation within the next 12-18 months. The next meeting of the group is in October 2017, where we hope to see progress towards a new Draft Recommendation.

Virtual reality and broadcasting

ITU-R is studying the important of VR for broadcasting and has found rapporteurs to study what aspects of VR will benefit from ITU-R Recommendations. On 17 October 2016, the virtual reality (VR) workshop “Seminar on Virtual Reality and 360 in Broadcasting” was held at ITU’s Headquarters in Geneva. Presentations from the seminar can be found here.

Further information

For further information about ITU rapporteur group (RG25) and the new methods for perceptual evaluation of sound systems, contact Nick Zacharov, Senior Technologist, DELTA SenseLab (nvz@delta.dk).

[1] Nick Zacharov, Chris Pike, Frank Melchior and Thierry Worch. “Next Generation Audio System Assessment using the Multiple Stimulus Ideal Profile Method”, Quality of Multimedia, Experience (QoMEX), Lisbon, Portugal, 2016.

[2] Pedersen, Torben H., Zacharov, Nick. “The Development of a Sound Wheel for Reproduced Sound”, Audio Engineering Society 138th Convention, May, 2015.

[3] Zacharov, Nick, Pedersen, Torben H. “Spatial Sound Attributes — Development of a Common Lexicon”, Audio Engineering Society 139th Convention, October, 2015.

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DANSK VERSION


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Standardiseringsgruppe: ITU-R WP6C RG25

Nye metoder til perceptuel evaluering af næste generation af lydsystemer.

Af Nick Zacharov

Som et led i DELTA SenseLabs løbende deltagelse i International Telecommunication Union (ITU) blev Nick Zacharov, Senior Technologist hos DELTA SenseLab (en del af FORCE Technology), i 2015 udnævnt til formand for rapportørgruppen (RG25, 2015-2016) for evaluering af lydkvalitet inden for radiokommunikationssektoren.

Gruppen fører tilsyn med alle ITU’s anbefalinger på området for lydkvalitet, herunder ITU-R BS.1534- og ITU-R BS.1116-anbefalingerne. Begge anbefalinger anvendes bredt i audioindustrien til udvælgelse af audiocodecs, vandmærketeknologi osv. ved subjektive lyttetests.

Næste generation af lydsystemer

Netop nu ser vi en hurtig udvikling indenfor audio-, tv- og biografindustrierne med introduktion af den såkaldte næste generation af lydsystemer (eller avancerede lydsystemer). Systemerne giver mulighed for skalérbar lydgengivelse i brugerens lydmiljø, uanset om de benytter 2-kanals stereosystem (hovedtelefoner eller højttaler) eller et højt antal højttalerkanaler, fx 5.1, 10.2, 22.2 højttalerkanaler. Det sker ved brug af en såkaldt kanalbaseret eller objektbaseret teknologi, hvor lydfeltet dannes ud fra højttalerkonfigurationen (antal, højttalernes placering osv.).

Med den nye generation af avancerede lydsystemer introduceres en lang række nye kvalitetskarakteristika, der er vanskelige at opfange og evaluere med de nuværende lyttetestanbefalinger. Der er altså behov for at udvikle nye redskaber til evaluering af lydkvaliteten i de nye typer avancerede rumlige lydapplikationer.

Nye metoder til perceptuel evaluering af lydsystemer

På den baggrund har DELTA SenseLab arbejdet med at udvikle nye metoder til perceptuel evaluering af den næste generation af lydsystemer. Multiple Stimulus Ideal Profile-metoden er blevet udviklet til effektiv evaluering af de nye teknologiers generelle lydkvalitet og til at fastlægge de nye teknologiers perceptuelle egenskaber.

Til validering af metoden er der gennemført fælles evalueringstest i samarbejde med BBC Research and Development (Salford UK) og QI Statistics (UK). De gode resultater er fremlagt for ITU-R WP6C RG25-gruppen, og der er opstillet en arbejdsplan til yderligere forfining af metoden med henblik på godkendelse af en ny ITU-R-anbefaling. I øjeblikket har metoden status af “foreløbigt udkast til ny anbefaling”.

Med henblik på indhentning af yderligere kommentarer og gennemgang af metoden er et konferenceindlæg blevet udarbejdet [1] til Quality of Multimedia Experience (QoMEX) konferencen i Lissabon. Indlægget fik en god modtagelse og førte til en god diskussion – og modtog desuden prisen for bedste indlæg på konferencen (se figur 1).

 

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 Figur 1. QoMEX 2016, pris for bedste indlæg.

Lydkvalitetshjulet

Ud over ovenstående arbejde har DELTA SenseLab arbejdet på en ensretning af den terminologi, der anvendes ved perceptuel evaluering af lydkvalitet. Vinindustrien fik allerede i 1980’erne fastlagt det såkaldte vinaromahjul, men det er først nu, at der bliver fastlagt et tilsvarende terminologileksikon for audioindustrien.

Lydkvalitetshjulet (se figur 2) er for nylig blevet udviklet og publiceret og skal anvendes som terminologileksikon for generisk evaluering af reproduceret lydkvalitet. DELTA SenseLab har arbejdet med opgaven, og resultatet er nu klar til offentliggørelse [2,3]. Lydattributhjulet er også indarbejdet i ITU-R WP6C RG25 til overvejelse som et element i de nye metoder til perceptuel audioevaluering.

 

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Figur 2. Version 2.0 af lydkvalitetshjulet, Audio Engineering Society, 2016 [2].

Arbejdet med udvikling af en ny anbefaling fortsætter, og målet er at færdiggøre arbejde i løbet af de næste 12-18 måneder. Gruppens næste møde finder sted i oktober 2017, og der håber vi at se fremskridt i udarbejdelsen af et nyt udkast til anbefaling.

Virtual reality og broadcasting

ITU-R undersøger betydningen af virtual reality i forbindelse med broadcasting og har udpeget rapportører til at undersøge, hvilke aspekter af virtual reality der vil drage fordel af ITU-R anbefalingerne. Den 17. oktober 2016 blev der afholdt en virtual reality workshop “Seminar om Virtual Reality og 360 i Broadcasting” på ITU’s hovedkvarter i Genève. Præsentationer fra seminaret kan downloades her.

Mere information

For yderligere information om ITU-rapportørgruppen (RG25) og de nye metoder til perceptuel evaluering af lydsystemer kontakt Nick Zacharov, Senior Technologist, DELTA SenseLab (nvz@delta.dk).

[1] Nick Zacharov, Chris Pike, Frank Melchior and Thierry Worch. “Next Generation Audio System Assessment using the Multiple Stimulus Ideal Profile Method”, Quality of Multimedia, Experience (QoMEX), Lisbon, Portugal, 2016.

[2] Pedersen, Torben H., Zacharov, Nick. “The Development of a Sound Wheel for Reproduced Sound”, Audio Engineering Society 138th Convention, May, 2015.

[3] Zacharov, Nick, Pedersen, Torben H. “Spatial Sound Attributes — Development of a Common Lexicon”, Audio Engineering Society 139th Convention, October, 2015.

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