introduction to audio post-processing ivan lee, jun. 2005
TRANSCRIPT
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
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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.
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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.
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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
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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
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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
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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.
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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
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Dolby Pro Logic II
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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
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Dolby Virtual Speaker
Crosstalk Cancellation
Listening Zone
Sonic Signatures
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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
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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
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Dolby Virtual Speaker
Reference Mode Wide Mode
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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
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BBE & BBE ViVA
3D Stereo of BBE ViVA
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BBE & BBE ViVA
Compressor / AGC in BBE ViVA
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BBE & BBE ViVA
Block Diagram of BBE ViVA
─ Center Filter
─
┼BBE
AGC
L
R
Lo
Ro
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SRS WOW & TruSurround XT (TBD)
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Q & A