Robust Audio Tool (RAT) Speaker : Wei-Shin Pan DATE : 09/07/02

2009 Graduate Institute of Communication Engineering 2 OutLine Introduction RAT DEMO Keep going

2009 Graduate Institute of Communication Engineering 3 Introduction An open-source audio conferencing and streaming application RAT transmission – Unicast (Point-to-point streaming) – Multicast (conference) –

2009 Graduate Institute of Communication Engineering 4 Architecture(1) Three components RAT Ratmedia Ratui

2009 Graduate Institute of Communication Engineering 5 Architecture(2) RAT –arguments analyzing and controls the other components. RATmedia – voice processing and transmisstion RATui –Graphical user Interface

2009 Graduate Institute of Communication Engineering 6 RAT How to start –RAT Get ! Choose the build platform The stable version : RAT4 (4.4.01) –Installation –Start it ! RAT launched from the command line Syntax : – > rat address/port

2009 Graduate Institute of Communication Engineering 7 User interface

2009 Graduate Institute of Communication Engineering 8 Configuration Options –Personal –Transmission –Reception –Audio –Codecs –Security –Interface

2009 Graduate Institute of Communication Engineering 9 Personal

2009 Graduate Institute of Communication Engineering 10 Transmission

2009 Graduate Institute of Communication Engineering 11 Codecs G.711 u-law & a-law 64kbit/s, MOS 4.3 Linear kbit/s (RAW) GSM 13.2kbit/s, MOS 3.5

2009 Graduate Institute of Communication Engineering 12 Loss protection(1) Loss protection

2009 Graduate Institute of Communication Engineering 13 Loss protection(2) Redundancy

2009 Graduate Institute of Communication Engineering 14 Loss protection(3) Layering

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2009 Graduate Institute of Communication Engineering 16 Repair scheme Pattern-Match – 將遺失的部份聲音, 以它前後的聲音透過 interpolate 來回 復, 需較大的計算量 Repeat – 基於人聲沒有快速變化的特性, 將遺失掉的封包用前一 個封包來代替, 但當封包長度和封包遺失率太大時, 就沒 辦法利用人聲的特性了 Noise – 透過隨機分佈雜訊聲音來取代遺失的聲音區塊, 會被封 包長度跟封包遺失率大小所影響

2009 Graduate Institute of Communication Engineering 17 Sample rate conversion If local’s soundcard can’t support sample rate of received packets, and converting the sample rate by this option.

2009 Graduate Institute of Communication Engineering 18 Limit Playout delay Jitter – jitter buffer Adjustable range : ms IF value is high, the voice packets will play smoothly and poor quality (high delay) IF value is low, some voice packets can’t play because the delay too short.

2009 Graduate Institute of Communication Engineering 19 Jitter Buffer (With Playout buffer )is designed to remove the effects of jitter from a decoded voice stream and buffer each arriving packet for a short interval before playing out. This compensates an additional delay and packet loss for jitter. Jitterbuffer

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2009 Graduate Institute of Communication Engineering 21 Silence suppression Much silence gaps (No talking) in a conversation Background Noise – No packet sending will reduce 50% bandwidth

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2009 Graduate Institute of Communication Engineering 23 DES (data encryption standard)

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2009 Graduate Institute of Communication Engineering 26 DEMO

2009 Graduate Institute of Communication Engineering 27 Reference [1] The Study and Analysis of the Robust-Audio Tool for Real-Time Audio Conference, Ting-Yu Chiu [2] Robust Audio Tool official website