MPEG SURROUND

Student: Shang-Yu Yeh Adviser : H.-M. Hang

2007/12/17

Outline MPEG Surround Introduction T/F Resolution and DataMode Adaptive Parameter Smoothing Experimental Results

MPEG Surround Introduction Low-bitrate parametric coding technology

for multi-channel audio signal Backward compatibility to stereo

equipment Exploits inter-channel differences in level,

phase and coherence equivalent to the spatial cues to capture the spatial image of a multi-channel audio signal

Spatial cues: CLD, ICC, CPC

Spatial Audio CodingEncoder:

Decoder:

MPEG Surround EncoderArchitecture:

T/F TransformT/F Transform

T/F Transform

Downmix

SpatialParameterEstimation

AudioEncoder

CompressedAudio

Bitstream

Spatial Parameters

1s

2s

1x2x

Nx

F/T Transform

F/T Transform

MPEG Surround Encoder

T/F Resolution and DataMode Parameter extraction

reduce the accuracy of samples

71 hybrid subbands

parameterbands

parametersets

T/F Resolution and DataMode

New Architecture:

T/F TransformT/F Transform

T/F Transform

Downmix

SpatialParameterEstimation

AudioEncoder

CompressedAudio

Bitstream

Spatial Parameters

1s

2s

1x2x

Nx

F/T Transform

F/T Transform

MPEG Surround Encoder

TimeResolutionDecision

DataMode & Freq

ResolutionDecision

Adaptive Parameter

Smooth

T/F Resolution “Resolution” refers to the number of

parameters 0 1 2 3 0

Time(ps)

Frequency(pb)

pbStride

Time Resolution Decision Choose the number of parameter sets

for a frame Can be fixed or variable

0 1 2 3

0 1 2 3

DataMode Decision Exploit the correlation between

subsequent sets 4 modes: default, keep, interpolation

and lossless 0 1 2 3

parameter set

0 1 2

data set

Freq Resolution Decision Choose a stride that make the decoding

error minimum Exploit correlation between bands pbStride can be: 1, 2, 5, 28 0 1 2

data set

stride

stride

stride

Freq Resolution Decision Pairing: grouping of 2 parameter

subsets to share some data (QP, pbStride…)

Pairing of non-neighboring sets will not have gain 0 1 2

data set

pair

Combination of 2 modules

Adaptive Parameter Smoothing For artifacts from coarse quantization

and low up-date rate of spatial cues Especially in the case of stationary and

tonal signals First order IIR filtering of the parameter

bands

Adaptive Parameter Smoothing

1lW

lWlkonjW

BASdelta

A

B

)( 11 llkonjdelta

ll WWSWW

Smooth strengh:

Adaptive Parameter Smoothing Configure for each parameter set Error estimation:

Parameter normalization:

set

set

stddevmeanbpbp

)()( '

parametersresolutionhighestthefbpCPCICCCLDpbforparametersnormalizedpbp

bandfullfbbandparameterpb

fbppbpError

bandfull

boxIdx pbbandfullps

___:)'(,,:___:)'(

)28(_:_:

)'()'(

_

_

Experimental Results Add DataMode and Freq Resolution

Decision Modules without any loss Bitrate reduction(%):

ps1 ps2 ps4

Input01 4.22 2.52 2.36Input02 25.12 21.09 20.07Input03 6.67 3.89 3.54Input04 3.88 2.52 2.28Input05 4.63 2.77 2.57

(pb=10)

Experimental Results DataMode Decision:

Bitrate reduction(%):1 2 3 4 5

0%

20%

40%

60%

80%

100%

ps1_pb10

losslessinterpolationkeepdefault

1 2 3 4 50%

20%

40%

60%

80%

100%

ps1_pb10_dm7_111

losslessinterpolationkeepdefault

Theoretical Experimental

Input01 59.03 44.70Input02 75.74 55.68Input03 66.85 48.05Input04 59.52 44.11Input05 63.37 47.07

(ps=1, pb=10)1 2 3 4 5

0%10%20%30%40%50%60%70%80%90%

100%

exp_ps1theo_ps1

Experimental Results Freq Resolution Decision:

Bitrate reduction(%):Theoretical Experimental

Input01 30.08 16.29Input02 20.83 8.58Input03 14.11 6.80Input04 32.35 17.29Input05 28.11 15.35

1 2 3 4 50%

20%

40%

60%

80%

100%ps1_pb10

stride28stride5stride2stride1

1 2 3 4 50%

20%

40%

60%

80%

100%ps1_pb10_dm7_111

stride28stride5stride2stride1

(ps=1, pb=10) 1 2 3 4 50%

10%20%30%40%50%60%70%80%90%

100%

exp_ps1theo_ps1

Experimental Results Overall Bitrate reduction(%):

ps1 ps2 ps4

Input01 53.71 40.20 28.99Input02 59.49 56.66 55.97Input03 51.58 41.24 30.34Input04 53.77 42.47 29.96Input05 55.19 46.59 35.34

(pb=10)

Experimental ResultsInput01 (LS) Input02 (L) Input02(R)

Original

No smooth

Smooth with normalized error

Additional bit rate 0.005 kB/s 0.00498 kB/s 0.00498 kB/s