Acoustic Quadraphony:
a new meta-format for cinema surround audio



                               Dr. Diego Gonzalez
   ...
What should be the future of sound for Digital Cinema?


    • Cinema    sound has gone through many quality jumps along i...
From the point of view of the audience, the new systems shall
   improve quality, overcoming current limitations such as:
...
From the point of view of the industry, new
              systems should feature:

• cost effectiveness of baseline servic...
Acoustic Quadraphony is a very promising approach
      to tackle many of these requirements!

A fundamental problem in de...
Acoustic Quadraphony implementation

Contrarily to the measurement of pressure, developed in the 19th
century, the direct ...
Rendering procedure

• Thanks to the linearity of the acoustic environment
response, it is possible to generate quadraphon...
The quadraphonic audio workflow
        Quadraphonic audio Workflow

        Production                                  Po...
Acoustic Quadraphony:
the right approach to audio virtual reality
Direct measurement of
        sound pressure and air particle velocity
                                                   ...
Direct recording
       The recording of the dry sound of actors and
       musical sources can be made in anechoic chambe...
Video:
       Pseudo-anechoic recording of a choir




Back                                          Next
Quad IR measurement
 FSSG-CNR has implemented a procedure for
 the measurement of pressure and velocity
 impulse responses...
Video:
        Measurement of quadraphonic impulse
       responses in San Giorgio Church - Venice




Back               ...
Intensimetric indices
                                                                                                    ...
Post-processing
                     Quadraphonic convolution




 Anechoic source                                Virtual ...
dvd authoring

       Surround sound produced
       with Acoustic Quadraphony
       can be delivered in any
       stand...
Playback
       Quad audio is suitable to be
       reproduced by any standard and future
       playback system. Realisti...
Active playback of Quad sound
 FSSG-CNR developed a prototype system that allows for the faithful
 reconstruction of the o...
Thank you for your attention!
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iDiff 2008 conference #04 IP-Racine FSSG

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iDiff 2008 conference #04 IP-Racine FSSG

  1. 1. Acoustic Quadraphony: a new meta-format for cinema surround audio Dr. Diego Gonzalez Dr. Davide Bonsi
  2. 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. 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. 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. 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. 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. 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. 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. 9. Acoustic Quadraphony: the right approach to audio virtual reality
  10. 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 Back Next
  11. 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. Back Next
  12. 12. Video: Pseudo-anechoic recording of a choir Back Next
  13. 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 Back Next
  14. 14. Video: Measurement of quadraphonic impulse responses in San Giorgio Church - Venice Back Next
  15. 15. Intensimetric indices From the Quad IR it is possible to )*+,,-*+./01-2,+.3+,145,+ ()*+,-./01234*5)06)53+75)8090,+23+7)7. ' !quot;% !quot;$ derive intensimetric indices that !quot;( !quot;# :*;quot;.-576, <=>quot;047-.5 ! describe the energetic properties ! !!quot;( !!quot;# of a sound field, such as the sound !' !!quot;$ ! !quot;# !quot;$ !quot;% !quot;& ' ! !quot;# !quot;$ !quot;% !quot;& ' )*+,-./012345+6*17*64,86*91:1-,34,8*8/ 670+.8,9 )*+,-./012345+6*17*64,86*91:1-,34,8*8/ .-2)0:5; ' ' energy flow directions, the energy !quot;( !quot;( ! =>?quot;158./6 =>?quot;158./6 ! decay curves and the reverberation !!quot;( !!quot;( !' !' ! !quot;# !quot;$ !quot;% /.3*1;6< !quot;& ' !'quot;( ! !quot;# !quot;$ !quot;% /.3*1;6< !quot;& ' time Adimensional index *+,-./01,23/ 1 ! ;< 0.9 ;=> !quot;! ;=/ 0.8 ;=? ;04@4 0.7 !#! 1: 0.6 !$! 0.5 0.4 !%! eta 0.3 sigma !&! Back Next 0.2 62.5 125 250 500 1000 2000 4000 8000 ! quot; # $ % & ' ( ) Centre Frequency (Hz) 456,0789
  16. 16. Post-processing Quadraphonic convolution Anechoic source Virtual acoustic environment Transcoding to Quadraphonic consumer format acoustic (mono, stereo, sound surround) Back Next
  17. 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! Back Next
  18. 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. Back Next
  19. 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) Back Next
  20. 20. Thank you for your attention!
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