1

Multichannel Audio Technologies Dr. Gavin Kearney

gpkearney@ee.tcd.ie http://www.mee.tcd.ie/~gkearney/MCAT

Room 23, Top Floor, Printing House

What is multichannel audio? 1.  A way of expanding and enriching the

sound of audio playback

2.  Recording additional sound channels that can be reproduced on additional speakers. (e.g. two and 3 channel stereo)

3.  Most commonly used in SURROUND sound applications (e.g. 5.1, 7.1 surround sound)

Where can we find it? 1.  Cinema

2.  Home entertainment

3.  Video games

4.  Live sound reinforcement

5.  Audio Visual Installations

2

Why do we need it?

1.  Enhancement and spatialisation of music!

2.  Enhanced cinematic experience (Spatial effects)

3.  Perception of Naturalness (Sound field reconstruction)

….. IMMERSION!!!

Enhancement and spatialisation of music!

- Surround sound allows us to set up new musical perspectives

Audience View

Enhancement and spatialisation of music!

- Surround sound allows us to set up new musical perspectives

Ensemble View

3

Enhancement and spatialisation of music!

- It frees us to position and move audio for greater emotive effect…more immersive music!

Enhancement and spatialisation of music!

- We can (with reasonable effect) superimpose one acoustic environment onto another

Why do we need it?

1.  Enhancement and spatialisation of music!

2.  Enhanced cinematic experience (Spatial effects)

3.  Naturalness (Sound field reconstruction)

4

Enhanced cinematic experience

Enhanced cinematic experience

-  Usually consist of 5 channels (Front left, front centre, front right, rear left, rear right) and a Low Frequency Effects channel (LFE).

Enhanced cinematic experience

-  Not designed for accurate full surround imaging, just good frontal imaging with rear sound effects.

5

Why do we need it?

1.  Enhancement and spatialisation of music!

2.  Enhanced cinematic experience (Spatial effects)

3.  Naturalness (Sound field reconstruction)

Naturalness -  Good ‘spatialisation’ can give the feeling that

‘you’re there’!

-  Huge applications in music, gaming, 3-D cinema, teleconferencing, interactive installations

-  Involves sound field reconstruction!

How do we create the ‘spatialised’ audio?

1.  Multichannel recording techniques!

2.  Multichannel spatialisation techniques!

3.  Loudspeaker Layouts

4.  Codec choices

6

Recording Techniques?

Spatialisation? Amplitude Based Systems e.g. VBAP

Soundfield Based: Ambisonics

+

=

+

Spatialisation?

7

Physical Based: Wave Field Synthesis Spatialisation?

Loudspeaker Layouts? Commercial Solutions: - 2 Channel Stereo

Loudspeaker Layouts? Commercial Solutions: - 2 Channel Stereo - Quadraphony

8

Loudspeaker Layouts? Commercial Solutions: - 2 Channel Stereo - Quadraphony -  Dolby Stereo, Surround and Pro Logic

Loudspeaker Layouts? Commercial Solutions: - 2 Channel Stereo - Quadraphony -  Dolby Stereo, Surround and Pro Logic -  Dolby Surround Pro Logic II

Loudspeaker Layouts? Commercial Solutions: - 2 Channel Stereo - Quadraphony -  Dolby Stereo, Surround and Pro Logic -  Dolby Surround Pro Logic II -  5.1 Discrete: Dolby Digital, DTS

9

Loudspeaker Layouts? Commercial Solutions: - 2 Channel Stereo -  Quadraphony -  Dolby Stereo, Surround and Pro Logic -  Dolby Surround Pro Logic II -  5.1 Discrete: Dolby Digital, DTS -  6.1 Dolby Pro Logic IIx, Dolby Digital EX, DTS ES

Loudspeaker Layouts? Commercial Solutions: - 2 Channel Stereo -  Quadraphony -  Dolby Stereo, Surround and Pro Logic -  Dolby Surround Pro Logic II -  5.1 Discrete: Dolby Digital, DTS -  6.1 Dolby Pro Logic IIx, Dolby Digital EX, DTS ES -  7.1 Dolby Digital Plus, DTS-HD

Loudspeaker Layouts? Commercial Solutions: - 2 Channel Stereo - Quadraphony -  Dolby Stereo, Surround and Pro Logic -  Dolby Surround Pro Logic II -  5.1 Discrete: Dolby Digital, DTS -  6.1 Dolby Pro Logic IIx, Dolby Digital EX, DTS ES -  7.1 Dolby Digital Plus, DTS-HD -  SDDS (Sony Dynamic Digital Sound)

10

Loudspeaker Layouts? Cinematic Solutions:

- 10.2: “Twice as good as 5.1!” - Actually has 14 discrete channels: Five front speakers: Five surround channels: Two LFE channels: LFE Left, LFE Right Two Height channels: Left Height, Right Height

Loudspeaker Layouts? Cinematic Solutions: Ultra-High Definition (NHK Corp)

Codecs?

-  Most commercial surround sound systems utilise specific audio codecs….

11

-  Multichannel audio is an effective medium for enhancement of music, cinema, and other auditory presentations.

- The application and desired auditory effect determines the loudspeaker layout and decoding scheme.

- The aims of this course are to aid the audio engineer/ spatial musician in determining which multichannel scheme works best for a given application and environment, and to motivate further innovation in multichannel audio technologies.

Conclusions

Multi-channel Audio Technologies: 12, 2 Hour Lectures, 2 Assignments

Week 1: Introduction to Multichannel Audio Technology Week 2: Mixing for Discrete 5.1 Surround Sound Week 3: Mastering for Discrete 5.1 Surround Sound Week 4: Up-mixing and Down-mixing surround sound Week 5: Surround Sound Recording Techniques 1 Week 6: Surround Sound Recording Techniques 2. Week 7: Mixing Recorded surround Audio/ Surround Sound with Height Week 8: Introduction to Ambisonics Week 9: More about Ambisonics Week 10: Spatial Impulse Response Rendering Week 11: Binaural and Transaural Surround Sound Technology Week 12: The future of Multichannel Audio

Course Outline

Extra Spatial Music Seminar before Christmas