IP-Racine presentation of FSSG results

1. Acoustic Quadraphony:
a new meta-format for cinema surround audio
Dr. Diego Gonzalez
Dr. Davide Bonsi

2. What should be the future of sound for Digital Cinema?
• Cinema sound has gone through many quality jumps along its
history, from mono to current multi-channel surround systems,
to follow the evolution of image quality
• With the advent of Digital Cinema, a major quality jump
regarding the audio experience is expected
• What requisites shall the new systems accomplish to satisfy the
market requirements?

3. From the point of view of the audience, the new systems shall
improve quality, overcoming current limitations such as:
• limitations of the optimal listening area (sweet spot)
• lack of naturalness in acoustic environment rendering
• lack of third spatial dimension (vertical component)

4. From the point of view of the industry, new
systems should feature:
• cost effectiveness of baseline service, backwards compatibility
with existing systems and sufficient flexibility for forward
compatibility with possible future developments
• universality of the format, allowing for effective data
encryption and compression
• improvement of theatrical playback for the quality of the
audio experience
• relevant metadata support

5. Acoustic Quadraphony is a very promising approach
to tackle many of these requirements!
A fundamental problem in developing a universal format is
being able to provide a signal that contains all the
information about the sound event, including the acoustic
environment.
This challenge can be solved by means of a physical
approach that consists of capturing the pressure and the
three components of the air velocity related to the sound
event. These four signals are the quadraphonic data.

6. Acoustic Quadraphony implementation
Contrarily to the measurement of pressure, developed in the 19th
century, the direct measurement of air velocity has been possible
only recently, thanks to the invention of intensimetric probes at
Twente University

7. Rendering procedure
• Thanks to the linearity of the acoustic environment
response, it is possible to generate quadraphonic data by a
4-dimensional convolution between quadraphonic metadata
(4-impulse responses) and a target anechoic sound.
• This approach allows for the implementation of a
complete audio workflow for Digital Cinema

8. The quadraphonic audio workflow
Quadraphonic audio Workflow
Production Post-production Exhibition
Quadraphonic Recording Quad Post-prod. Quadraphonic Processing
& Metadata Measurement Real&Virtual Environments Up-Downwards Conversion
5.1 and others
P Pseudo Quad
Acoustic Anechoic Signal
Data Decoding
Vx
Post-processing
Vy Deconvolution
(pressure signal) Exhibition
4-Convolution
Up-downwards
Vz (pressure signal)
Compatibility
Rendering of Proprietary
Direct recording extended System
Anechoic source Monophonic
pressure signal Active control
gp Quadraphonic
Pseudo-anechoic
- one-dimensional
Metadata - three-dimensional
gx
4-Impulse Responses
gy Wave-field
Other Quad Synthesis
& other
gz Related Metadata prototype
-relative position systems
Library of Quad Impulse-responses Centre channel Stereo 5.1
(source-receiver) (Dialogs) (Music) (Sound effects)
-source movement Real environments Virtual environments
-absolute source
reference
From the From pre- From From
-intensimetric recording recorded Simulation Calculation DTS® or Dolby® Acoustic 3rd
indices,etc. location environments (Effects) Ambience Dimension
encoding

9. Acoustic Quadraphony:
the right approach to audio virtual reality

10. Direct measurement of
sound pressure and air particle velocity
The Microflown ® USP
probe combines three
Air velocity sensors
orthogonal velocity
are based on double
transducers and a pressure
hot-wire anemometry
microphone in coincident
configuration
The air flow produces a
variation of the temperature
profile near the wires, causing
a change in their electrical
resistance, generating a voltage
difference that is proportional
to the air velocity
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11. Direct recording
The recording of the dry sound of actors and
musical sources can be made in anechoic chambers
or in reflection-free environments.
As an alternative, direct quadraphonic recordings
can be made live on location capturing both sound
pressure and velocity.
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12. Video:
Pseudo-anechoic recording of a choir
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13. Quad IR measurement
FSSG-CNR has implemented a procedure for
the measurement of pressure and velocity
impulse responses, allowing for the complete
characterization and the faithful
reconstructions of the acoustic properties of
the environments
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14. Video:
Measurement of quadraphonic impulse
responses in San Giorgio Church - Venice
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15. Intensimetric indices
From the Quad IR it is possible to
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derive intensimetric indices that
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describe the energetic properties
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energy flow directions, the energy
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decay curves and the reverberation
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time
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Centre Frequency (Hz) 456,0789

16. Post-processing
Quadraphonic convolution
Anechoic source Virtual acoustic environment
Transcoding to
Quadraphonic
consumer format
acoustic
(mono, stereo,
sound
surround)
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17. dvd authoring
Surround sound produced
with Acoustic Quadraphony
can be delivered in any
standard format, including
Dolby® and DTS® for DVD-
Video and DVD-Audio.
Quad audio can be encoded
in any file format with any
number of channels and
configuration: future proof
compatibility is guaranteed!
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18. Playback
Quad audio is suitable to be
reproduced by any standard and future
playback system. Realistic surround
sound can be reproduced in 5.1 home
theatre systems and cinemas as well.
Moreover, quad technology allows for
the assessment of the playback quality.
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19. Active playback of Quad sound
FSSG-CNR developed a prototype system that allows for the faithful
reconstruction of the original sound field (pressure & velocity) and its
energetic properties based on the solution of the acoustic inverse
problem.
Quad audio signals are sent to the speakers through a feed-forward
control unit processing metadata previously measured in the listening
room. This ensures the best reconstruction of the natural timbre and
spatial characteristics of the recorded sound.
The process, tested and validated on one-
dimensional fields, has recently been
e x t e n d e d t o s t a n d a rd s u rro u n d
configurations and other 3D systems with an
arbitrary number of channels (Patent
Pending)
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20. Thank you for your attention!