Error-resilient Schemes for Efficient Transmission of Embedded Wavelet Coded Images

The reliable transmission of compressed images across noisy transmission channels and networks prone to packet losses is considered. The problem is viewed from a source coding perspective, where the main constraints are maximum coding efficiency and minimum redundancy. Error-resilient mechanisms are incorporated into wavelet-based image encoding schemes to obtain robust data streams that withstand significant bit errors and packet losses. The basic design starts with the well known SPIHT image compression algorithm and makes the resulting bit-stream resilient to network packet losses by modifying the encoding structure and partitioning the coefficients. The robust encoder in its basic form requires no additional redundancy and relies on an edge-directed interpolation method for error concealment of lost data. Coding improvements of 0.5-1.5 dB in SNR values over other similar methods have been observed. Wavelet-based image encoding schemes involve quantization of the image wavelet coefficients. Redundant sets of wavelet coefficients generated by overcomplete discrete wavelet transform are used as side information to improve error-resilience at high packet loss rates. Unlike other error protection schemes, the use of redundant wavelet sets not only improves the robustness of the encoding scheme but also improves image quality. The error-resilient encoding scheme is extended to encompass a wide range of images including color images. Efficient implementations are also developed to account for different situations arising due to various types of errors and losses in transmission channels. The different error-resilient mechanisms that have been implemented require minimal redundancy and maintain a high source coding efficiency for the selected image quality. The implementations are flexible and can be easily adapted to any type of transmission channel with different network parameters.