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Audio Engineering Society
Convention Paper

Transforming Ambiophonic + Ambisonic 3D Surround Sound to & from ITU 5.1/6.1
Robert E. (Robin) Miller III ©20031

Page 7 -- Stereo Recordings Compatible with PerAmbio

PerAmbio 6.1.10+ embraces Ambiophonics championed by Glasgal [13, 14] whereby 2-channel (stereo) acquires 3D ambience by convolution with the 3D impulse responses of concert halls - in MCN terms 2.0.10+.  In essence, it is unnecessary to waste mics, channels and bandwidth to žrecord the hall,Ó when its acoustic imprint is reproducible given its IR.

Reproduced Ambiophonically, many existing stereo releases sound better because Ambio solves problems inherent to 2-speaker stereo of coloration, pinna confusion, and toggling to the nearer speaker for center images.  These žerrorsÓ are not necessarily endemic to the recording - they are mainly a function of the two 60°-spaced speakers upon replay - and can be eliminated by HRTF-based Ambiophonics. 

Additionally, in 2-speaker stereo, all sounds including ambience come from the front 60° between the speakers - only 1/6 of the sonic panorama.  Since many stereo recordings have been made acoustically somewhat ždryÓ to reduce muddling the front stage with ambience, they are ripe for convolution that both restores natural ambience and places it all around - including height if reproduction in 3D.  For serious listening, an ultimate sonic experience may outweigh the inconvenience of needing to be in the žsweet spotÓ - implying only one or two listeners.  Single-person listening such as auto sound, PC-based gaming and VR, and audio-centric amusement rides are other viable fixed-position applications where the highest priority is an uncompromised aural experience.

WORK IN PERIPHONIC REPRODUCTION

6.1.10+ and 2.0.10 (Ambio with 8-channel convolved surround) are relatively economical yet effective means of full 3D periphonic reproduction.  Objectives for further work include:

  • Optimize 3D reproduction alternative(s) for both home and studio;

  • Develop DSP for crosstalk cancellation and ambience using 3D hall impulse responses;

  • Develop automobile PanAmbio reproduction (demonstrated by the author and his colleagues at 111th AES in New York, Dec 2001);

  • Encourage implementation in distribution of 6 full-range audio channels in any medium;

  • Develop a main microphone array that is more camera-friendly e.g. for live event broadcasts;

  • Introduce artists, producers, and engineers to PerAmbio to žadd a dimensionÓ to their creativity;

  • First PanAmbio 4.1 (4.1.4) broadcast, Webcast, and DVD (-V, -A, SACD, or DTS-CD) release;

  • First PerAmbio 6.1 (6.1.10+) broadcast, Webcast, and DVD (-V, -A, SACD, or DTS-CD) release.

  • ANOVA analysis to rank simultaneously made recordings by trained auditioners [19];

  • Make recordings with prototype microphones to test new approaches and explore compatibilities;

Recordings for professional evaluation and education are available (www.filmmaker.com).

CONCLUSIONS

Listening in ITU 5.1 is a more enjoyable experience than 2-speaker stereo and is driving home theater purchases by mainstream consumers.  This acceptance obviates the žchicken & eggÓ dilemma common to any introduction of new entertainment technology - i.e. consumer surround systems for music are already being installed.

If an audience to has the means for surround sound, will they demand 2D surround music recordings of higher quality?  Will they want 3D in the future?  They might if led by producers and engineers who provide them access to 3D via extensible recordings, delivery standards, and replay systems.  The choices available could add value for users, entertainment providers, and equipment manufacturers of dual-format DVD-As, SACDs, DTS-CDs for music-only, movies, virtual reality, amusement rides - and in the future for 3D ATV broadcasts, movies, and Internet Webcasts.  Issues include relearning by practitioners, providing access by updating delivery standards, and avoiding onerous complexity for users - although some will feel that ž10 speakers must be twice as good as 5!Ó

The hybrid approach PerAmbio 6.1.10+ described offers backward and forward compatibility, playing with no special decoding on standard 5.1/6.1 horizontal 2D surround systems today and with a decoder on full periphonic 3D systems tomorrow.

ACKNOWLEDGEMENTS

The author is grateful to Ralph Glasgal for his inspiration and wisdom and to the Ambiophonics Institute for support of the authorŪs work.  Additional support is by the University of Parma and colleagues Angelo Farina, Enrico Armelloni, and Anders Torger; JĖrg Wuttke and Christian Langen of Schoeps GMBH, and Buzz Turner and Scott Boland of Redding Audio.  Geoff Houser and Brad Frikkers fabricated microphone prototypes; Howard Moscovitz and Craig Greenwood assisted with recording; hundreds of musicians performed for the evaluation CDs; and DTS encoded them.  Trademarks are those of their owners: DTS of Digital Theater Systems, Dolby Digital of Dolby Laboratories, SACD of Philips and Sony, IMAX of IMAX Corp., Soundfield of Soundfield.

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