Introduction toAudio Post-Processing

Ivan Lee, Jun. 2005

22

Outline

Overview Dolby Pro Logic II Dolby Virtual Speaker BBE & BBE ViVA SRS WOW & TruSurround XT (TBD) Q & A

33

Overview

Tech.

Comp.2 channel

Enhancement

2–to-multi ch.

Matrix Decode

Multi-to-2 ch.

Virtual Surround

Proprietary Sound

DolbyPro Logic II,

Bass Management

Virtual Speaker

Headphone

SRS WOW Circle Surround II TruSurround XT

BBE BBE, ViVA

Realtek EQ,Bass,Treble

Collection of the APP Technology

44

Overview - Dolby Dolby Pro Logic II

Sophisticated, matrix decoding technology that expands any two-channel source audio, such as CDs and stereo-encoded videocassettes, video games and TV broadcasts, to a five-channel full bandwidth (range) playback (Left/Center/Right/Left surround/Right surround), resulting in a surround experience.

Dolby Virtual SpeakerHighly advanced signal processing technology that delivers 5.1-channel surround sound from just two speakers. It's ideal for PCs and spaces where a full 5.1 home theater is not practical.

55

Overview - Dolby Dolby Headphone

Revolutionary signal processing technology that delivers 5.1-channel surround sound over any pair of headphones for a richer, more spacious and less fatiguing listening experience.

66

Overview - BBE BBE HD Sound

Natural Musical Realism Speech intelligibility Truly lifelike movie experience Improves simulated “surround” effects

BBE Mach3Bass Extends the bass response

BBE ViVA Integrates a 3D enhancement effect with BBE HD Soun

d BBE MP

Integrates BBE with MP harmonic and restoration.For MP3 and all lossy audio compressions

77

Overview - SRS SRS

The SRS® (Sound Retrieval System) 3D Stereo system is designed to retrieve and restore spatial information, directional cues, and other sonic nuances which are either missing or altered by the electronic reproduction of stereo and/or the microphone mixing process.

SRS WOW FOCUS : Clarity Improvement TruBass : Bass Enhancement SRS : 3D-Audio

88

Overview - SRS

SRS TruSurroundSRS TruSurround delivers a compelling, virtual surround sound experience through any two-speaker, including internal television speakers and headphones.

SRS TruSurround XT SRS TruSurround SRS Dialog Clarity Enhancement TruBass WOW

99

Dolby Pro Logic II Pro Logic II matrix decoder receives 2 channels and

delivers feeds for three, four or more loudspeakers.

To express Lt and Rt in terms of the intended directiTo express Lt and Rt in terms of the intended direction of a source,independent of the magnitude.on of a source,independent of the magnitude.

1010

Dolby Pro Logic II

Source Analysis

Lt2 + Rt

2 = 1

Lt(α) = cos((α – 90)/2) , Rt(α) = sin((α – 90)/2)

1111

Dolby Pro Logic II

1212

Dolby Pro Logic II

1313

Dolby Pro Logic II

1414

Dolby Pro Logic II

1515

Dolby Pro Logic II

Parameter Movie Music Virtual ProLogic Matrix

Surround delay 10 – 25ms 0 –15ms No 10 – 25ms 0 – 15ms

Surround filter No Shelf No 7 kHz LPF Shelf

Surround coherence On Off Off On Off

Panorama control Off Opt. Off Off Off

Dimension control Off Opt. Off Off Off

Center-Width control Off Opt. Off Off Off

Auto-Balance On Off On On Off

1616

Dolby Virtual Speaker

Crosstalk Cancellation

Listening Zone

Sonic Signatures

1717

Dolby Virtual Speaker

I. Update Delay-Line

Biquad IIR +

Biquad IIR +

Mixer

Read from Delay-Line

Write to Delay-Line

Read form Input Channels

Write to Output Channels

Ls (s4)

Rs (s5)

u2

u1

u0

u3

G

Delay-Line Buffer

G

1818

Dolby Virtual Speaker

Read from Delay-Line

Write to Delay-Line

Read form Input Channels

Write to Output Channels

II. Synthesize 5 channels to 2 channels

Ls (s4)

Rs (s5)Mixer

Mixer

u0

u1

G1

G2

G3

G4

+ +

FIR4

FIR4

s12 s13

L (s2)

R (s3)

G1

G2

G3

G4

+ +

FIR4

FIR4

s10 s11

G

G

Mixer

s10

s11

s13

s12

FIR3

FIR3

+

+

C (s1) G

L

R

u2 G

u3 G

FIR

FIR

FIR

FIR

1919

Dolby Virtual Speaker

Reference Mode Wide Mode

2020

BBE & BBE ViVA

The state variable filter has several advantages of biquads as a synthesizer filter. Lowpass, highpass, bandpass, and band reject are available simultaneously. Also, frequency and Q control are independent and their values calculated easily.

f = 2 sin(PI Fc/Fs) , q = 1/Q‧ ‧

2121

BBE & BBE ViVA

Block Diagram of BBE

┼ X ┼ X ┼

X

┼

f f

q

Input

Highpass Bandpass Band reject

Lowhpass

BBE : Output = LP‧ Contour_Coef + HP‧ Process_Coef - 0.94‧ q‧ BP

f = 2‧ sin(PI‧ Fc/Fs) , q = 1/Q

Z -1

Z -1

2222

BBE & BBE ViVA

3D Stereo of BBE ViVA

2323

BBE & BBE ViVA

Compressor / AGC in BBE ViVA

2424

BBE & BBE ViVA

Block Diagram of BBE ViVA

─ Center Filter

─

┼BBE

AGC

L

R

Lo

Ro

2525

SRS WOW & TruSurround XT (TBD)

2626

Q & A