Bit rate optimization of composited video frames for multi-point video conferencing is implemented. Rate control problems can be generally characterized as the determination of the appropriate coding parameters by pre-coding and decoding processes so that the decoded video quality is optimized according to a certain bit rate. By using zerotree coding we obtain exact target bit rate. In order to obtain best quality for a video, target bit rate is allocated to each video frame optimally by using convex rate-distortion model and Lagrangian optimization.
In this paper we investigate DCT-based embedded zerotree coding of composited videos for multi-point video conferencing. Zerotree coding is a progressive coding method which encodes a video or image into a bit stream with increasing precision. The embedded property is accomplished that all encodings of the same image or video at lower bit rates are embedded in the beginning of the bit stream for the target bit rate [9]. By using the embedded zerotree coder, quality of the composited videos is improved when compared to a conventional encoder.
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