Distortion Policy of Buffer-Constrained Rate Control for Real-Time VBR Coder
For fixed capacity (or bandwidth) networks, e.g., circuit switching networks, constant bit rate (CBR) coders are quite common for speech or video signals transmission. By increasing interest in packet switching networks, e.g., asynchronous transfer mode (ATM) networks, variable bit rate (VBR) coders are now highly desirable7. A major advantage of the VBR coder is constant quality (or distortion). Since speech or video/image signals are nonstationary, bit rate cannot be fixed to keep constant quality. In this case, the VBR coder can provide nearly constant quality by allowing VBR. For CBR links, the buffer has been used at the output side of the VBR coder to absorb fluctuation of bit rate. It is well known that overflow or underflow of buffer cannot be prevented without buffer control methods.
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