Some web conferencing solutions require additional software to be installed (usually via download) by the presenter and participants, while others eliminate this step by providing physical hardware or an appliance. In general, system requirements depend on the vendor. Some web conferencing services vendors provide a complete solution while others enhance existing technologies. Most also provide a means of interfacing with email and calendaring clients in order that customers can plan an event and share information about it, in advance. A participant can be either an individual person or a group. System requirements that allow individuals within a group to participate as individuals (e.g. when an audience participant asks a question) depend on the size of the group. Handling such requirements is often the responsibility of the group. Most vendors also provide either a recorded copy of an event, or a means for a subscriber to record an event. Support for planning a shared event is typically integrated with calendar and email applications. The method of controlling access to an event is provided by the vendor. Additional value-added features are included as desired by vendors who provide them. Besides exceptions (e.g. Openmeetings, TokBox, WebHuddle, BigBlueButton), web conferencing services do not apply free software but proprietary software, see Comparison of web conferencing software.
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