Abstract
Problem statement: The bitrate scalability is an important functionality that is defined in the Moving Picture Expert Group (MPEG-4) requirements. Since the traffic in a communication network varies with time, the capability of varying the bitrate of a speech coder is needed. Approach: This study proposes an approach to vary the bitrate by using a bitrate scalable tool which is attached with the core section of Multi-Pulse based Code Excited Linear Predictive (MP-CELP) coder. The bitrates scalable tool employs multi-stage excitation coding based on an embedded-coding approach. The multi-pulse excitation codebook at each stage is adaptively produced depending on the selected excitation signal at the previous stage. Results: The experimental results show that the speech quality of the proposed coder with the bitrate scalable tools is improved above the speech quality of the conventional coder. Conclusion: From the study, the proposed approach gives a tool to improve the speech compression and can also support a variety of coder bitrates.
Highlights
Nowadays, the digital communications are widely developed (Jabrane et al, 2007)
One of standardization activities for such areas is undergoing at the MPEG-4 (Nomura et al, 1998; Chomphan, 2010b)
The input speech of 10 ms frame is processed through Linear Prediction (LP) and pitch analysis
Summary
The digital communications are widely developed (Jabrane et al, 2007). The audio, still image, video or text information can be transmitted through wire and wireless networks, the number of users to access these networks increases considerably. Channel capacity should be increased, signal compression aims at treating this situation (Chompun et al, 2000). The multimedia applications such as videophone and videoconference on ATM and Internet are widely used, the high quality speech codes are highly demanded. These kinds of applications require specific considerations for packet loss. To treat this problem, a bitrate-scalable coder is realized where the synthesized speech signal can be decoded from the received packets, which contain only a part of the whole encoded bitstream. One of standardization activities for such areas is undergoing at the MPEG-4 (Nomura et al, 1998; Chomphan, 2010b)
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