DemoVideoMulticast en

Multicast Hierarchical Video

Context

IP multicast is a group communication mechanism. When several users want to receive the same content, the multicast mechanism permits the server to send it only once. Then, the routeurs are in charge to duplicate the packets. Thereby, a minimal number of copies travel over the network links, which allows to reduce the bandwidth usage. In example, the multicast has democratized the IP-TV.

To generalize the deployment and the use of multicast, a congestion control mechanism is compulsory. Moreover, this mechanism must be fair with TCP. Several receiver-driven layered multicast congestion control scheme have been proposed. They are scalable to very large groups, but none of these are yet fully satisfying. The "Networking & Protocols" research team works on this problematic with the aim of improving:

• The fairness between multcast streams and TCP.
• The convergence quickness to the fair rate.

Principles

We want to show the possibilities given by the multicast associated with a congestion control. Thereby, we have designed a live time video streaming software, which allows several users to receive the same stream, but with an image quality fitted to the bandwidth available for each receiver.

Thus, the congestion control allows each receiver to calculate his own maximal rate and to receive the matching image quality. Therefore, when the received rate grows, each receiver improve its own the image quality.

Demonstration

Goal

This demonstration shows the capacity of each multicast client to auto-regulate his reception rate, depending on the network conditions. And consequently receive an optimal image quality.

Test bed

The test bed demonstration allows the dynamic rate modification of the congestioned link. That permits to highlight the relation between the image quality an the network bandwidth.

Fig.1 Test bed

Scenario

This demonstration use one video server and one receiver. During the reception, we changed the link bandwidth:

• Test 1 : The bandwidth allows to receive the first layer.
• Test 2 : The bandwidth allows to receive the 4 first layers.
• Test 3 : The bandwidth allows to receive the 16 first layers.
• Test 4 : The bandwidth allows to receive the 64 first layers.

Results

Fig.2 : Video resolutions depending on the number of layers received

Test 1 - 1 layer : <videoflash>K4VR1vCs63c|300</videoflash>	Test 2 - 4 layers : <videoflash>5_i5V9TKaB4|300</videoflash>
Test 3 - 16 layers : <videoflash>2JYch0Fpieg|300</videoflash>	Test 4 - 64 layers : <videoflash>PM3PYnuahxc|300</videoflash>

Software sources

The software is available under GPLv2 Licence at the following address: MuVi-Channel