Internet Communications Using SIP : Delivering VoIP and Multimedia Services With Session Initiation Protocol {2Nd Ed.}

Requirements for Accessibility The requirements to support rich communications for the hearing- or speech- disabled can be divid ...

Figure 17.1 Example of finger spelling Courtesy of Omnitor AB The example in Figure 17.1 is interesting for designers, since it ...

■■ Impaired users require a fast-response real-time text application, whereby, just as with voice, users can follow the thoughts ...

Figure 17.3 RTP packet example for text/t140with one redundant block The text blocks may contain one or more text characters tha ...

■■ (P) is one bit to indicate padding of the payload. ■■ (V) is a 2 bit indicator of the version for RTP. An SDP example that de ...

Transcoding Services Transcoding services are provided by a human or machine acting as a third party to replace one media set wi ...

Note in Figure 17. 5 that the transcoding function can be located in the end- point PC if no human is required to perform the tr ...

It is interesting to note that SIP-based communications for the disabled are also compatible with the legacy text phones used on ...

Figure 17.8 Example for relay service invocation by a caller In the example shown in Figure 17.8, the caller may be on a 2G mobi ...

B sends an ACKto T indicating the SDP data sent by T are OK. Only now will B reply with a 200 OKmessage to A and include the SD ...

Internet communication based on SIP is ideally suited to provide impaired users all the rich multimedia communications available ...

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301 Quality of Service (QoS) for voice is a critical feature for real-time Internet communications. QoS for VoIP is also a much- ...

As far as the issue of bandwidth versus QoS, QoS in the endpoints and the critical requirements of communications to/from anywhe ...

Voice Quality Metrics There are three basic categories of quality for voice [2]: ■■ Listening quality—How users rate what they h ...

Some wireless SIP based features such as Push to Talk may have slightly dif- ferent specifications for delay. Burst vs. Average ...

The elements that influence the quality of interactive voice shown in Fig- ure 18.1, from the left to the right are: ■■ Far end ...

A comparison of the Internet Low Bit Rate Codec (iLBC) with legacy ITU-T codecs is shown in Figure 18.2 [5]. The iLBC codec is d ...

Codecs in Wireless Networks and Transcoding A wide variety of codecs are deployed in 2G and 3G wireless networks, and it is beyo ...

The Endpoint Quality for Voice It can be argued that, in the absence of notable network-induced impairments, the QoS for voice r ...