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The H.239 protocol allows the Codian IP VCR to support an additional video stream to or from each connected H.323
endpoint. Thus, there are potentially 3 media streams between each H.323 endpoint and the IP VCR: audio, main video
and H.239 video. In general, the main video channel is used for motion video (i.e. high frame rate streams) and the
content channel for less dynamic video such as an accompanying presentation - this is typically a high resolution, low
frame rate video stream.
Support for H.239 video on the IP VCR encompasses:
• Recording H.239 video streams from H.323 endpoints, in either single-endpoint or point to point recordings
• Playing back recorded content channel data to H.323 endpoints via H.239
• Streaming the content channel to users' desktop machines
Recording H.239
When a H.323 endpoint is being recorded, that endpoint may open a H.239 content channel video stream, in addition to
its main video channel. The IP VCR records both video channels, and both are available when that recording is played
back.
When using the Recording console, the presence of H.239 video is indicated by a "H.239" icon on the right of the screen.
In a point to point recording, the nature of H.239 means that only one of the recorded endpoints is able to supply the
H.239 channel at any one time. Specifically, this means that if one endpoint is supplying the content channel stream then
it must stop transmitting H.239 video before the other endpoint can start. This is in contrast to the main video channel,
which both endpoints are able to transmit and receive simultaneously without restriction.
Playing back content channel video
If a recording includes a content channel video stream, that content channel stream (originally supplied by a H.323
endpoint via the H.239 protocol) can be played back to either other H.323 endpoints or to users viewing a recording via
streaming.
Playing back to H.323 endpoints
Stored content channel video can only be played back to a H.323 endpoint if that H.323 endpoint is capable of receiving a
H.239 video stream in addition to its main video channel. When playing back a recording which includes content channel
video, a H.323 endpoint with no H.239 receive capability will see just the main video channel.
Streaming content channel video
Recorded content channel streams can be played back to users' desktops via web browser-based streaming in addition to
the recorded main video and audio streams. When streaming, users have the choice of playing back just the audio and
main video streams, just the recorded H.239, or both together.
The play back of content channel video is accomplished through use of a Java applet, and therefore Java must be installed
on any machine wishing to view the recorded H.239 video.