Voice Packetization, Codecs and Voice Quality
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The "nuts and bolts" of Voice over IP:
• How voice is digitized and coded,
• Time stamps applied with the RTP protocol, and
• How the result is carried in UDP, IP packets and MAC frames.
You'll learn about codecs and compression, and understand factors like delay, jitter and packet loss, what causes them, and how they affect sound quality.
VoIP Module 4
Detailed Outline
4. Voice Packetization, Codecs and Voice Quality
4.1 Voice Packetization
...... 4.1.1 Microphone Produces a Voltage Analog
...... 4.1.2 Digitization
...... 4.1.3 Coding
...... 4.1.4 Segmentation and Packetization
4.2 Measuring Voice Quality
...... 4.2.1 Mean Opinion Score
...... 4.2.2 Toll-Quality Speech
4.3 Factors Affecting Voice Quality
...... 4.3.1 Codec, Delay, Jitter and Packet Loss
...... 4.3.2 Network Load
4.4 Codecs and Compression
...... 4.4.1 Coder / Decoder
...... 4.4.2 Tradeoffs
...... 4.4.3 CBR vs. VBR
...... 4.4.4 Standards
4.5 Delay
...... 4.5.1 Coding Delay
...... 4.5.2 Network Delay
...... 4.5.3 Design Goal
4.6 Jitter
...... 4.6.1 IP: No Guarantees
...... 4.6.2 Variable Delivery Time
...... 4.6.3 Variable Network Loading
...... 4.6.4 Jitter Buffer
4.7 RTP
...... 4.7.1 Real-Time Transport Protocol
...... 4.7.2 Segmentation
...... 4.7.3 Time Stamp
...... 4.7.4 Error Recovery
4.8 VoIP Protocol Stack: RTP, UDP, IP, MAC
...... 4.8.1 Moving the RTP PDU
...... 4.8.2 UDP Error Detection and Recovery
...... 4.8.3 Port Number
...... 4.8.4 RTP/UDP/IP/Ethernet Protocol Stack
...... 4.8.5 Header Compression
4.9 Packet Loss
...... 4.9.1 Packet Loss Mechanism
...... 4.9.2 Recovery
4.10 Tips for Maximizing Voice Quality
...... 4.10.1 Network Level Testing
...... 4.10.2 VoIP Application Level Testing
...... 4.10.3 Strategies
O autoru
Eric Coll is an international expert in telecommunications, broadband and networking, and has been actively involved in the telecom industry since 1983. He holds Bachelor of Engineering and Master of Engineering (Electrical) degrees.
Mr. Coll has broad experience, and broad knowledge of telecom developed working as an engineer in the telecommunications industry.
He has used his knowledge of telecom to develop and teach telecommunications technology training seminars to wide acclaim across North America since 1992... and answering questions at seminars for companies and organizations ranging from Bell Labs to the Department of Justice keeps things up to date.
In his spare time, Mr. Coll authors textbooks and online courses based on the latest updates to the seminar courses.
Mr. Coll also provides consulting services as a Subject Matter Expert in telecommunications to government, carriers, and their customers.
