Library items tagged: Videoconferencing

Anonymous
H.323 This is the umbrella standard for IP conferencing. It includes several sub-standards: H.261 defines the mandatory video Coder/Decoder (CODEC)* standard, whereas H.263 and H.264 define optional video CODECs. Similarly G.711 is the mandatory audio CODEC and G.729 one of several audio CODEC options. The complex operation of managing the data streams from the CODEC including calling, establishing a call, and controlling the various component parts i.e. video, audio and data is defined by two standards, H.225 and H.245.
Anonymous
Dr Syngen Brown of the University of London Computer Centre (ULCC) has made most helpful and detailed comments on the standards. Polycom® is a registered trademark of Polycom in the U.S. and various countries.  A videoconference link requires:
Anonymous
Anonymous
Software requirements: A modern web browser Quicktime 6.5 and above Windows Media Player (requires IE and Windows 2000, XP, Vista or 7) Java (standard edition) How to Use Live Videoconference Streaming The Streaming feature may be selected when a videoconference is being booked from the Confirm booking page (Step 3 of 3). The conference Booker should click Set conference options and tick the Videoconference streaming tick box.
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When videoconferencing over ISDN, IP and other networks, although echoes can be reduced to a manageable level delays on the sound or “Latency” remains. This introduces an unnatural element into a videoconference that participants need to be aware of. All participants have to learn to conference within the limitations of the time delay, and so interaction is less spontaneous than with a face to face meeting. As most conferences are voice switched, sharp interjections will cause the conference to switch automatically to that site; this may clip another site’s presentation.
Anonymous
To reduce echoes caused by transmission delays, special devices known as “Echo Cancellers” are used. These devices when operating efficiently can almost eliminate all traces of echo during a conference. Room acoustics and microphone positions also affect the level of echo. If a microphone is moved or its sensitivity is altered during the conference, echo could be introduced until the echo canceller has realigned itself to the new environment.
Anonymous
To keep transmission costs to a minimum, the data rate for videoconferencing is generally very low. This means that the vision signals need significant compression to squeeze into the small space available. Compression requires a considerable amount of electronic processing. One penalty to pay for this is the time taken for the vision signals to travel through all the circuitry. The delays are appreciable and can be of the order of 0.25 second. The delays introduced in compressing the sound signals are very much less, as not so much signal processing is needed.
Anonymous
Videoconferencing is a form of television so the guidelines for appearing on television are relevant. Because videoconferencing uses a reduced quality network link to keep costs down some other limitations are also introduced. Television cameras can only handle a very limited range of contrast so wear clothes in pastel shades and plain weaves. Strong saturated colours and white shirts are not recommended. Within a videoconference, faces are the focal point, so clothing must not pre-dominate the image. Avoid clothes that are brightly coloured or with a distinctive pattern.