SPATIAL SOUND DISTRIBUTION, LEADING THE 6TH MEETING OF UHD SPAIN

For more than an hour and a half of lectures, 50 professionals participated in the sixth virtual meeting on the perception, classification, and distribution of spatial sound.

• The meeting, in virtual format, has been led by José Javier López, professor of telecommunications at the Polytechnic University of Valencia, and has been restricted to members of the association.
• The classification of spatial sound reproduction systems, the concept of object-oriented audio, and current proposals for spatial sound distribution were the main topics addressed during the masterclass. 
• Also, the Vice President of the Spanish section of the Audio Engineering Society shared with the attendees his experiences in audio research and made special emphasis on applications in high-definition television.

UHD Spain hosted last April 5th a second masterclass on next-generation audio, restricted to members of the association. On this occasion, the meeting, the sixth organized by the association, was led by José Javier López, professor of telecommunications at the Polytechnic University of Valencia, who with over 25 years of experience has focused his research work on topics of sound processing and multimedia, especially in the field of spatial sound. Pioneer in Spain in Wave-Field Synthesis system and object-oriented audio, currently his research is based in the field of customization of the HRTF for interactive sound and virtual reality in the research center iTEAM, Institute of Telecommunications and Multimedia Applications, integrated with the Polytechnic City of Innovation in Valencia. 

The Vice President of the Spanish section of the Audio Engineering Society explained the hearing ability of humans as the foundation of spatial sound in a didactic introduction.

“Just as we use two eyes to see in three dimensions, we use two ears to create a complete understanding of the sound world around us. Only through binaural hearing is it possible to obtain a spatial hearing. This is the primitive ability that, intuitively and due to a survival factor, humans have possessed since the beginning of time to react to danger signals approaching from a distance. Obviously, as engineers, music producers, or content creators, we have exploited this ability for creative purposes,” explains Lopez, pointing out the importance of knowing the basics of spatial sound in order to understand it.

“The purpose of an immersive sound system that is used in virtual reality, broadcast, music, or theater is to transfer the sensations that we would have in a listening environment, to the playback environment,” says Lopez.

Classification of spatial sound reproduction systems in three distinct groups was another of the concepts addressed during the masterclass. In an instructive way, Lopez explained binaural systems, based on the transfer function related to the head and the way we hear, which are generally oriented to headphone listening.

There are also those based on Panning, known as Surround or multichannel systems, such as surround sound systems or slightly more evolved systems such as Vector Base Amplitude Panning or VBAP. In the third group are classified the more advanced, but also more complex, systems that synthesize the acoustic field in a realistic way, where the best known are Ambisonics and Wave Field Synthesis. 

The concept of object-oriented audio and current proposals for spatial sound distribution were other topics addressed during the master class on spatial sound distribution in NGA, where Lopez based his presentation on the ITU standard.

The BS.2076: Audio Definition Model – ITU norm attempts to standardize the description of a sound scene, and provides different key elements for using the various spatial sound formats in one file (DVMM). Audio Definition Mode includes multichannel sound or channel orienting (5.1 and later), binaural sound, scene-based sound (Ambisonic, High Order Ambisonic, or SPS), and an object-oriented system.

“Up to recently, production was oriented to a single ecosystem, either stereo or multichannel, Ambisonic… ideally, we would like to produce completely object-oriented, but we know that this is not likely to be feasible yet. Reality suggests that we can mix recording and playback methods and make hybrid systems, which include not only objects but also binaural systems, multichannel, stereo, Ambisonic, etc., and thus have greater creative freedom. Allowing to combine several systems in a single production sounds great, but of course, it presents even more problems… But, thanks to current audio research, all these problems have a solution,” says the UPM professor

In reference to UHD, Lopez explains that there are some limitations such as the required bandwidth of compression codecs, which can be commercial or open-source codecs such as Opus, or the number of channels limited to 16.

Another concept addressed is ‘fidelity vs creativity’. “Before a creative process, you have to take into account, what you want to achieve, how it’s going to be heard, and what you can actually do. Because spatial sound is wonderful, but the reality is what it is… you have to ask yourself what you are looking for with immersive sound: if what you are looking for is fidelity to reality (as in the case of virtual reality), impressing the listener, as is the case with theatrical movies and special effects, enhancing a live show or complementing the shortcomings of inconsequential music, complementing it with some effects.”

“Next Generation Audio generates many expectations, but its application to UHD has some limitations and we must be aware of them, such as economic constraints, the uses, and customs of the sector, complexity, and changes between formats. In the future, the trend will be towards personal audio,” concludes Lopez.

This initiative of the non-profit association UHD Spain consists of meetings of its members with experts from the audiovisual sector and responds to the commitment to promote Ultra High Definition in Spain, at all levels: both for consumers and professionals.

UHD Spain is a non-profit association created on January 26, 2021, to promote Ultra High Definition (UHD) in Spain. There are currently 38 associated companies: ADM, Agile Content, Ametic, Ateme, Atresmedia, Axión, Canal Sur, Canon, CCMA, Cellnex, Cires21, COITT, Dolby, Egatel, Fecotel, Fenitel, Forta, Fraunhofer, Gsertel, Henneo, Hispasat, Hurí, Lavinia, Mediapro, Medina Media, Rohde &. Schwarz, RTVE, Sapec, Secuoya, Synamedia, Tedial, Telecom CLM, Televés, TRedess, UPM, Uteca, Vestel and Video-MOS.