Parallelized ACO based Routing for Stagnation Mitigation and Avoidance of Multimedia Traffic Over MANETs

2. Multimedia Networks (Sharma & Kotecha, 2011; Sharma, Karkhanawala, & Kotecha, 2011)

MPEG-1 provides near-VCR quality with typical rates between 1.5 to 3 Mbps and MPEG-2 achieves broadcast-TV and higher qualities at rates 5-30Mbps (or higher). MPEG-4 provides a wide range of quality and data transfer rates. Its initial commercial focus is video-on-demand, video conferencing, streaming at a quality higher than that of MPEG-1 but at only 300-400 Kbps. However, multimedia being compressed is not always a good solution for providing better utilization of the available bandwidth. If higher compression is needed to accommodate for more bandwidth limited networks, then the delay due to encoding may interfere with interactivity. The main goal of transmission of video in lossy environments is to maintain quality of transmission, in spite of losses during communication. In order to understand, the loss of what types of frames will adversely affect the quality of video broadcast by how much amount, we need to understand the frame types of MPEG. MPEG-2 has the following Frames:

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  Intra or I-frames, carry a complete video picture. They are coded without reference to other frames and might use spatial compression but do not use temporal compression. Spatial compression uses the property that pixels within a single frame, are related to their neighbors; by removing spatial redundancy, the size of the encoded frame can be reduced and prediction can be used at the decoder to reconstruct the frame. A received I-frame provides the reference point for decoding a received MPEG stream;

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  Predictive-coded, or P-frames, predict the frame to be coded from a preceding I-frame or P-frame using temporal compression. P-frames can provide increased compression compared to I-frames, with a P-frame typically 20%-70% the size of an associated I-frame. However, for theoretical analysis, they can be assumed to be half of the size of I-frames;

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  Bi-directionally predictive-coded, or B-frames, uses the previous and next I-frame or P-frame as their reference points for motion compensation. B-frames provide further compression, typically 5%-40% percent the size of an associated I-frame. For theoretical analysis, the B frames are assumed to be 1/4^th of the size of I-frames.