Introduction Listening Test Results Summary End
Subjective Audio Quality Impairments ofPlayout Adaptation with AAC RTP
Communication
J. Issing1 N. Farber2
1Department of Computer Science 7Computer Networks and Communication Systems
University of Erlangen-Nuremberg
2Audio DepartmentFraunhofer IIS
IEEE CQR 2011, Naples, Florida, USA
Issing, Farber University Erlangen, Fraunhofer IIS
AAC Playout Adaptation Impairments
Introduction Listening Test Results Summary End
Audio Communication
Our Vision
I We want to connect two sites to enable conversation as ifyou were in the same room.
Example: Cisco Telepresence
Issing, Farber University Erlangen, Fraunhofer IIS
AAC Playout Adaptation Impairments
Introduction Listening Test Results Summary End
Audio Communication
To pursuit this vision we...
I focus on full band (20 Hz to 22 000 Hz) speech & audioI can not rely on existing time stretching techniques, as
audio has neither talk spurts, nor silence periodsI use 48 kbit/s (AAC-ELD) stereo
Issing, Farber University Erlangen, Fraunhofer IIS
AAC Playout Adaptation Impairments
Introduction Listening Test Results Summary End
Network Packet Delay
Network Packet DelayI Packets traversing a network suffer from two main effects:
random jitter floor and delay spikes
0
0.05
0.1
0.15
0.2
0.25
9600 9700 9800 9900 10000 10100 10200 10300 10400 10500
delay [s]
seq
Issing, Farber University Erlangen, Fraunhofer IIS
AAC Playout Adaptation Impairments
Introduction Listening Test Results Summary End
Time Scale Modification
ACE Time ScalingI Shrinking is performed by dropping frames
1 2 4 5
I Stretching is performed by inserting a concealed frame
1 2 3 C 4 5
I Adjacent audio frames overlap
0 1 2 3 4 5
0
1
Access Unit No.
Am
plitu
de
1 2 3 4
Issing, Farber University Erlangen, Fraunhofer IIS
AAC Playout Adaptation Impairments
Introduction Listening Test Results Summary End
Concealment vs Stretching
gj
Issing, Farber University Erlangen, Fraunhofer IIS
AAC Playout Adaptation Impairments
Introduction Listening Test Results Summary End
Concealment vs Stretching
Concealment vs Stretching Listening Test
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excellent 90
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speech 10%
stretch_010
stretch_050
stretch_100
stretch_200
conceal_010
conceal_050
conceal_100
conceal_200
hr
lp35
I No significant difference between stretching andconcealment
I Speech item performed admirably well for stretching(10 ms)
Issing, Farber University Erlangen, Fraunhofer IIS
AAC Playout Adaptation Impairments
Introduction Listening Test Results Summary End
Time Shrinking
Time Stretching Listening Test
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excellent 90
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squam
drop_01
drop_02
drop_04
drop_10
logic_01
logic_02
logic_04
logic_10
hr
lp35
I Dropping performs very well for small drop ratesI Tonal signal suffer from phase shift artifacts (SQUAM)
Issing, Farber University Erlangen, Fraunhofer IIS
AAC Playout Adaptation Impairments
Introduction Listening Test Results Summary End
Further Information
The paper provides addition information aboutI The network pattern file anatomyI Oscillation resultsI Evaluation of the impairment addition model, as used by
the E-Model
Issing, Farber University Erlangen, Fraunhofer IIS
AAC Playout Adaptation Impairments