Audio Engineering Society
Convention Paper

Scalable Tri-play Recording for Stereo, ITU 5.1/6.1 2D, and Periphonic 3D (with Height) Compatible Surround Sound Reproduction
Robert E. (Robin) Miller III ©2003^{1 /} www.filmaker.com
Acrobat PDF (0.7M) here

Presented at the 115th Convention
2003 October 10ñ13 New York, New York

This convention paper has been reproduced from the author's advance manuscript, without editing, corrections, or consideration by the Review Board. The AES takes no responsibility for the contents. Additional papers may be obtained by sending request and remittance to Audio Engineering Society, 60 East 42nd Street, New York, New York 10165-2520, USA; also see www.aes.org. All rights reserved. Reproduction of this paper, or any portion thereof, is not permitted without direct permission from the Journal of the Audio Engineering Society.  For a PDF version of this paper (0.7 MG), click here.

ABSTRACT

Objectives: Take the next step toward reproducing human hearing AND make better recordings in 5.1. In life, we hear sources we see ñ but also reflections and reverberation we don't see. Each sonic arrival is individually direction-stamped by our unique HRTF, including height, tonally colored by our pinna. Preserving 3D directionality is key to life-like hearing. A practical, scalable approach is presented (pat.pend.) ó a way to ìtransformî 3D (full sphere) recordings for uncompromised 2D reproduction in stereo or 5.1/6.1 without any decoding. By adding a decoder and speakers, full 3D is losslessly ìreconstitutedî from 6-channel media. Experimental ìtri-playî 6-channel ìPerAmbio 3D/2Dî recordings have been made and demonstrations presented (AES 114th Amsterdam 3/2003 & AES 24th Banff 6/2003) with praised results.

1. EVOLVING REALISM FOR MUSIC & MOVIES

Just as monaural sound reproduction had finally to yield to stereo and stereo to 5.1, so two-dimensional (2D) surround in the horizontal plane will progress toward life-like 3D (with height). In essence, the more the directionality of sound is preserved in 3-space, the more natural the result, as determined by our unique HRTF.
However to date, recording practice in 5.1, like stereo, favors spaciousness and simulating timbre (tonality) at the price of accurate localization ñ as though mutually exclusive [1, 2, 3, 4, 5]. Progress is needed to realize all three, as in real life. A new system [6, 7] from microphones to media to speakers, ìPerAmbio 3D/2D,î takes a step toward life-like 3D sound with correct spatial impression, timbre AND localization, and that plays compatibly in stereo, 5.1/6.1 2D, and full 3D using available 6-channel media and 10 or more speakers in a home theater or height-modified cinema.

2. GOALS: COMMERCIAL & ARCHIVAL

Musicians, record labels, and home theater owners have much to gain from lifelike 3D reproduction that is compatible with well-accepted stereo and 5.1/6.1 [8]:

• Priceless performances can be preserved;

• Producersí libraries are more future-proof;

• Consumersí collections will not become obsolete.

For music-only, these objectives translate into future value to musicians, producers, hardware manufacturers, and consumers ñ deliverable today on DVD-A, SACD, and DTS-ES Discrete CD. DVD-V movies could also provide an alternate mix in PerAmbio 3D (DTS-ES 6.1 Discrete). Other applications for 3D reproduction are:

• Multi-media/Virtual Reality

• Amusement rides

• Simulation/training

• Auto sound

• Cinema/TV (ATV requires AAC implemented)

3. HISTORY, HEARING, & HEIGHT

Human hearing is unique to us as individuals due to our own HRTF (head-related transfer function), learned at an early age, re-learned after trauma or loss with age, and thus difficult to generalize with auralization. In acoustic spaces, hearing is bound by perceptions called psychoacoustics. Musicians, who ìplay acousticsî as extensions of their instruments, and recordists are likely to be most sensitive; consumers can learn to be.

When stereo caught on in the 1950s, the author recalls that musicians often favored monaural ó Why? Described as the ìstage doorî effect, mono sounded correct tonally AND was localized at a point in 2D for coming through a narrow opening in the orchestra shell wall. The ìsweet spotî included the entire stage wing. Mono sounded like live listening backstage!

On-stage, stereo fell short of localizing instruments, as Blumlein himself knew in the 1930s, bunching the panorama of sounds at the speakers (the ìhole in the middleî) and confusing the pinna about important central soloists, because their sound was coming from speakers far from center. Add that ambience was redirected to frontal speakers, far from around and behind. But consumers, therefore producers, cared more that it sounded spacious. Acoustic music recordists (classical, jazz, folk, etc.) adapted by choosing to get the timbre ìcorrectî and the ìsweet areaî large by using spaced omnidirectional microphones in various layouts. More accurate but less spacious sounding coincident M-S 2D and Ambisonic 3D approaches were less successful.

ITU 5.1/6.1 surround sound (2D) extends stereo to envelop listeners, but only horizontally, lacking height (3D) and therefore not fully realizing the illusion of live human hearing, explored next. New research into surround sound such as 2D Wavefield Synthesis (WFS) and 3D High Order Ambisonics (HOA) are important work and the author finds demonstrations impressive and their potential great. However, their application to home theater may wait for resolution of impracticalities such as large numbers of high quality microphones, channels, speakers, higher noise, limited frequency range, etc.

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