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TANDBERG MPS User Manual
Automatic bandwidth adjustment
When H.239/Duo Video
is sent to the sites, the TANDBERG MPS will automatically use approximately 1/2 of the
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original video bandwidth for the main video stream and the other half for H.239/Duo Video
. When H.239/Duo Video
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is not transmitted, the TANDBERG MPS will automatically upspeed the main video stream its original bandwidth.
8... The ITU standard H.
Provides considerably better video quality at lower bandwidths. It has been developed with strong TANDBERG
participation in joint workgroups of ITU-T and ISO. H.264 is based on the ISO standard MPEG-4.
ISO standard MPEG-4.
The TANDBERG MPS supports H.264 video compression in both CIF and SIF resolutions. An
encoding and decoding rate of a high-quality 30 frames per second is achieved. H.264 may be used on the
TANDBERG MPS for endpoint up to 768kbps.
8.. Other Features
8...1 IP adaptive bandwidth management
The MCU never produces more traffic than needed, for better utilization of network resources. Most of the data sent in
a videoconference is video data. Thus, by incorporating smart video algorithms, the codec sends no more video data
than necessary. Little movement in the picture gives low bit rate; while a lot of movement gives higher bit rate.
The MCU regulates outgoing and incoming media bit rates by means of flow control signalling.
An example of this is automatic adjustment of total bandwidth used when Duo Video is opened.
8... Asymmetrical Encoders and Decoders
Realizing there are many different types of videoconferencing units in the world that do not support the same video
and audio algorithms, TANDBERG has implemented asymmetrical encoders and decoders. This feature allows
different systems with different video and audio algorithms to communicate with the TANDBERG MPS without having
to settle on the best common protocols. The asymmetrical nature of the TANDBERG MPS allows the MCU to accept
any of its supported algorithms in any combination from any site and will always transmit the highest possible quality
video and audio to the far end.
E.g., the TANDBERG MPS can send H.263 and receive H.264 at the same time.
8... Lip Sync
IP is an asynchronous network that sends audio and video separately. It is easy to see that these two streams may
not arrive at their destination at the same time. Lip sync problems are a certainty if precautions are not taken in the
implementation of the codec.
TANDBERG MPS supports sequencing of the video and audio IP packets and the reassembly and reordering of these
packets at the destination if they are received out of order. If the video stream is received before the audio stream,
the TANDBERG MPS will buffer this data until the necessary audio is received and reassemble the data that the
destination codec will use to reproduce a clear image with exceptional sound quality and lip sync.
8... Intelligent Packet Loss Recovery (IPLR
)
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IPLR is an ITU standard based packet loss compensation for H.323 that improves received video into the TANDBERG
MPS. IPLR supports all video protocols and resolutions that TANDBERG MPS already has implemented and is
compatible with all terminals and Gateways. This method works with other vendors' endpoints as well as MCUs. Video
quality is improved on the transmitted and received video streams.
IPLR is a special algorithm developed at TANDBERG that will make efforts to reconstruct the lost packets and reduce
the visual effects caused by packet losses.
If the TANDBERG MPS experiences packet loss from an endpoint, it will ask the endpoint to handle packet loss. This
requires Intelligent Packet Loss Recovery functionality on the endpoint.
Please see
on http://www.tandberg.net for details on the IPLR
for details on the IPLR
feature.
Whitepaper TANDBERG and Packet Loss
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1
February 2006
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