Tuyet Trang Lam

Image coding with robust channel-optimized trellis-coded quantization

This paper presents a wavelet-based image coder that is optimized for transmission over the binary symmetric channel (BSC). The proposed coder uses a robust channel-optimized trellis-coded quantization (COTCQ) stage that is designed to optimize the image coding based on the channel characteristics. A phase scrambling stage is also used to further increase the coding performance and robustness to nonstationary signals and channels. The resilience to channel errors is obtained by optimizing the coder performance only at the level of the source encoder with no explicit channel coding for error protection. For the considered TCQ trellis structure, a general expression is derived for the transition probability matrix. In terms of the TCQ encoding rat and the channel bit error rate, and is used to design the COTCQ stage of the image coder. The robust nature of the coder also increases the security level of the encoded bit stream and provides a much more visually pleasing rendition of the decoded image. Examples are presented to illustrate the performance of the proposed robust image coder.

Robust hyperspectral image coding with channel-optimized trellis-coded quantization

This paper presents a wavelet-based hyperspectral image coder that is optimized for transmission over the binary symmetric channel (BSC). The proposed coder uses a robust channel-optimized trellis-coded quantization (COTCQ) stage that is designed to optimize the image coding based on the channel characteristics. This optimization is performed only at the level of the source encoder and does not include any channel coding for error protection. The robust nature of the coder increases the security level of the encoded bit stream, and provides a much higher quality decoded image. In the absence of channel noise, the proposed coder is shown to achieve a compression ratio greater than 70:1, with an average peak SNR of the coded hyperspectral sequence exceeding 40 dB. Additionally, the coder is shown to exhibit graceful degradation with increasing channel errors.

Reduced-delay selective ARQ for low bit-rate image and multimedia data transmission

The paper presents a reduced-delay selective-ARQ scheme based on a similarity check function that measures the degree of corruption in transmitted multimedia data packets. Accordingly, if the packet is found to be badly corrupted based on a specified similarity criterion, it can be considered as a lost packet and retransmitted. The degree of corruption contributed by a particular packet is measured by the proposed similarity check function at the receiver without explicit knowledge of the original source data. Simulation results and comparisons with a conventional ARQ scheme are provided to illustrate the performance of the proposed method.

Automatic network-adaptive ultra-low-bit-rate video coding

This paper presents a software-only, real-time video coder/decoder (codec) for use with low-bandwidth channels where the bandwidth is unknown or varies with time. The codec incorporates a modified JPEG2000 core and interframe predictive coding, and can operate with network bandwidths of less than 1 kbits/second. The encoder and decoder establish two virtual connections over a single IP-based communications link. The first connection is UDP/IP guaranteed throughput, which is used to transmit the compressed video stream in real time, while the second is TCP/IP guaranteed delivery, which is used for two-way control and compression parameter updating. The TCP/IP link serves as a virtual feedback channel and enables the decoder to instruct the encoder to throttle back the transmission bit rate in response to the measured packet loss ratio. It also enables either side to initiate on-the-fly parameter updates such as bit rate, frame rate, frame size, and correlation parameter, among others. The codec also incorporates frame-rate throttling whereby the number of frames decoded is adjusted based upon the available processing resources. Thus, the proposed codec is capable of automatically adjusting the transmission bit rate and decoding frame rate to adapt to any network scenario. Video coding results for a variety of network bandwidths and configurations are presented to illustrate the vast capabilities of the proposed video coding system.

Wavelet-based image coder with channel-optimized trellis-coded quantization

This paper presents a wavelet-based image coder optimized for transmission over binary symmetric channels (BSC). The proposed coder uses a channel-optimized trellis-coded quantization (COTCQ) stage that is designed to optimize the image coding based on the channel characteristics. This optimization is performed only at the level of the source encoder, and does not include any channel coding for error protection. Consequently, the proposed channel-optimized image coder is especially suitable for wireless transmission due to its reduced complexity. Furthermore, the improvement over TCQ-based image coders is significant. Examples are presented to illustrate the performance of the proposed COTCQ-based image coder.

Multiple description channel-optimized trellis-coded quantization

This paper presents the design of multiple description trellis-coded quantizers that are optimized for transmitting data over multiple noisy channels. A multiple description channel-optimized trellis-coded quantization (MDCOTCQ) scheme is developed whereby all trellis-coded quantizers (side and central) are designed to operate over the binary symmetric channel with a given bit error rate (BER). Using the tensor product of trellises, an expression of the multi-channel transition probability matrix is derived. This formulation enables the construction of multiple description channel-optimized trellis-coded quantizers for arbitrary bit rates and arbitrary channel bit error rates. The proposed MDCOTCQ system enables the transmission of compressed data over noisy diversity or packet-based communication systems, and enables outstanding robustness to channel or packet loss. Examples are presented to illustrate the performance of the proposed MDCOTCQ-based source coder.

Robust image coding using perceptually-tuned channel-optimized trellis-coded quantization

This paper presents a perceptually tuned wavelet-based image coder that is optimized for transmission over the binary symmetric channel (BSC). The proposed coder uses a channel-optimized trellis-coded quantization (COTCQ) stage that is designed to optimize the image coding based on the channel characteristics, without using any channel coding for error protection. A perceptually-tuned rate allocation scheme controls the quantization by tuning the COTCQ quantization stage to the visual masking properties of the wavelet subbands. Examples are presented to illustrate the performance of the proposed image coder.

Selective Error Detection for Error-Resilient Wavelet-Based Image Coding

This paper introduces the concept of a similarity check function for error-resilient multimedia data transmission. The proposed similarity check function provides information about the effects of corrupted data on the quality of the reconstructed image. The degree of data corruption is measured by the similarity check function at the receiver, without explicit knowledge of the original source data. The design of a perceptual similarity check function is presented for wavelet-based coders such as the JPEG2000 standard, and used with a proposed ldquoprogressive similarity-based ARQrdquo (ProS-ARQ) scheme to significantly decrease the retransmission rate of corrupted data while maintaining very good visual quality of images transmitted over noisy channels. Simulation results with JPEG2000-coded images transmitted over the binary symmetric channel, show that the proposed ProS-ARQ scheme significantly reduces the number of retransmissions as compared to conventional ARQ-based schemes. The presented results also show that, for the same number of retransmitted data packets, the proposed ProS-ARQ scheme can achieve significantly higher PSNR and better visual quality as compared to the selective-repeat ARQ scheme.

Selective FEC for error-resilient image coding and transmission using similarity check functions

This paper introduces the concept of similarity check functions that measure the degree of corruption in transmitted multimedia data packets. Rather than directly discarding or directly retransmitting erroneous packets, the degree of corruption contributed by a particular packet is measured by a similarity check function at the receiver, which does not require explicit knowledge of the source data. Accordingly, if the packet is found to be badly corrupted based on a specified similarity criteria, it can be considered as a lost packet and recovered using forward error correcting codes or retransmission. An example of a similarity check function design and a selective forward error correction (S-FEC) scheme that allocates channel protection bits only to those packets that are in most need of correction, is presented to illustrate the proposed concept.

A perceptually-tuned image coder with Channel-Optimized Trellis-Coded Quantization

A system is presented for the compression of digital imagery over binary symmetric channels (BSC). The objective is to minimize the perceived distortion for a desired target bit rate. The proposed system utilizes wavelet decomposition, channel-optimized trellis-coded quantization (COTCQ), and a perceptually-tuned rate allocation scheme to control the quantization. Because of the inherent noise-robust properties of the COTCQ stage, no channel coding is employed. Additionally, the COTCQ design does not utilize entropy coding. Consequently, the proposed image coder is especially suitable for wireless transmission due to its reduced complexity and robustness to channel errors. Examples are presented to illustrate the performance of the proposed image coding system.