Error Resilient Entropy Coding Research Articles

Iterative Soft Decoding of Multiple Description Image over Wireless Channel

Motivated by recent results in multiple description image coding over wireless networks, we propose a scheme for transmission of multiple descriptions through hybrid packet loss and additive white Gaussian noise channel. Each description is coded into multiple bitstreams by applying SPIHT coding on wavelet trees along spatial orientations and each stream is further compressed using arithmetic code. Use of error resilient entropy coding (EREC) is proposed in literature for synchronization requirement of variable length codes, but EREC is not compatible with iterative soft-in soft-out decoding of arithmetic code at the receiver. We propose the application of EREC assisted by state and tail bits (ERECST) in conjunction with iterative decoding of arithmetic code at receiver for reconstructing the multiple description coded image over packet loss and Gaussian noise channel. Experimental results demonstrate that an additional gain of 7 dB in PSNR is obtained over existing scheme.

Parallel design for error-resilient entropy coding algorithm on GPU

The error-resilient entropy coding (EREC) algorithm is an effective method for combating error propagation at low cost in many compression methods using variable-length coding (VLC). However, the main drawback of the EREC is its high complexity. In order to overcome this disadvantage, a parallel EREC is implemented on a graphics processing unit (GPU) using the NVIDIA CUDA technology. The original EREC is a finer-grained parallel at each stage which brings additional communication overhead. To achieve high efficiency of parallel EREC, we propose partitioning the EREC (P-EREC) algorithm, which splits variable-length blocks into groups and then every group is coded using the EREC separately. Each GPU thread processes one group so as to make the EREC coarse-grained parallel. In addition, some optimization strategies are discussed in order to obtain higher performance using the GPU. In the case that the variable-length data blocks are divided into 128 groups (256 groups, resp.), experimental results show that the parallel P-EREC achieves 32× to 123× (54× to 350×, resp.) speedup over the original C code of EREC compiled with the O2 optimization option. Higher speedup can even be obtained with more groups. Compared to the EREC, the P-EREC not only achieves a good speedup performance, but it also slightly improves the resilience of the VLC bit-stream against burst or random errors.

EREC-Based Length Coding of Variable-Length Data Blocks

This paper investigates error-resilient transmission of variable-length-coding bitstream. We propose a method for coding the lengths of variable-length data blocks based on the error-resilient entropy coding (EREC). The idea is converting the problem of coding VLB lengths into the problem of coding the number of blank bits in fixed-length EREC slots. We give the upper bound of side information (SI) cost. To combat error propagation in SI bits, we rearrange SI bits into EREC structure. Detailed decoder design is given, which reveals that the proposed algorithm simplifies EREC decoder design by decomposing the decoder into three serially concatenated components. Experimental results show that the proposed method is economical and robust.

State-Information-Assisting EREC

This paper proposes an improved algorithm of the error-resilient entropy coding (EREC). The idea is to record and transmit the states of variable-length data blocks (VLBs) and fixed-length data slots (FLSs) during EREC encoding process. The state information (SI) of VLBs and FLSs is used at the receiver to resynchronize VLBs during EREC decoding process. It is proved that the cost of SI is fewer than 3 bits per VLB. To combat errors in SI bits, we propose to code SI bits into EREC structure. Experimental results show that our proposed method improves recovery quality of VLC bitstream significantly.

Robust multiple description image coding over wireless networks based on wavelet tree coding, error resilient entropy coding, and error concealment

In this paper, we propose an integrated robust multiple description coding (MDC) scheme for compressed still images over error-prone channels with both packet loss and random bit errors. Multiple descriptions are first generated independently by using multiple description scalar quantizer (MDSQ). To achieve an excellent error resilient capability for each description, multiple bitstreams are then generated based on wavelet trees along the spatial orientations. The spatial orientation trees in the wavelet domain are individually encoded using SPIHT. Error propagation is thus limited within each bitstreams. However, synchronization words are usually needed to avoid error propagation across multiple independent bitstreams. In order to maintain high compression efficiency robust synchronization, we adopt error resilient entropy coding (EREC) to re-organize these variable-length bitstreams into fixed-length data slots before multiplexing and transmission. Therefore, the synchronization of the start of each bitstream can be automatically obtained at the receiver. Finally, to alleviate the devastating image degradation resulted from errors in the beginning of the bitstreams, we propose an error concealment technique to both constrain the EREC/MDC decoding and post-process the decoded wavelet coefficients. With analysis and experimental results, we have demonstrated how each of these components has contributed to the overall robustness of the proposed transmission of compressed images over wireless channels.

Robust video transmission using block-interleaved error-resilient entropy coding

Variable-length coding (VLC) is widely used in video coding to improve compression efficiency. However, suffering from loss of synchronization, the VLC bit stream is much more sensitive to random errors than a fixed-length coding (FLC) bit stream. Error-resilient entropy coding (EREC) is a valid tool combating random errors in a VLC bit stream. Due to its intrinsic property of error propagation, when EREC is applied to a video bit stream, those blocks placed later become much more likely to be lost. We propose a simple method to further improve the error robustness of a video bit stream by interleaving transform coefficients of blocks so that low-frequency information is always placed ahead of high-frequency information. Thus, low-frequency information of greater significance is less likely to be lost. Experimental results prove the superiority of the proposed method. In addition, block interleaving can also be used in a data-partitioned video bit stream with ease.

A Mathematical Analysis on Error Propagation of EREC and Its Application to Optimal Channel-Matched Searching Pattern for Robust Transmission of Coded Video

The error resilient entropy coding (EREC) provides efficient resynchronization method to the coded bitstream, which might be corrupted by transmission errors. The technique has been given more prominence, nowadays, because it achieves fast resynchronization without sizable overhead, and thereby provides graceful quality degradation according to the network conditions. This paper presents a novel framework to analyze the performance of EREC in terms of the error probability in decoding a basic resynchronization unit (RU) for various error prone networks. In order to show the feasibility of the proposed framework, this paper also proposes a novel EREC algorithm based on the slightly modified H.263 bitstream syntax. The proposed scheme minimizes the effect of errors on low frequency DCT coefficients and incorporates near optimal channel-matched searching pattern (SP), which guarantees the best possible quality of reproduced video. Given the number of bits generated for each RU, the near optimal SP is produced by the proposed iterative deterministic partial SP update method, which reduces the complexity of finding optimal solution, O((N - 1)!), to O(m . N 2 ). The proposed EREC algorithm significantly improves the decoded video quality, especially when the bit error rate is in the rage of 10 -3 -10 -4 . Up to 5 dB enhancement of the PSNR value was observed in a single video frame.

Fast and robust fixed-length packetization algorithm for set partitioning in hierarchical trees bit stream over packet erasure channels

We consider the robust packetization scheme for set par- titioning in hierarchical trees (SPIHT) embedded bit stream over packet erasure channels and propose a fast and robust fixed-length packetization scheme using a two-step process. In the first step, a multiplexer is used to partition the embedded bit stream into multiple variable-length blocks with block sizes close to the fixed packet size. In the second step, a packetized error-resilient entropy code (PEREC) algorithm is proposed to reorganize these variable-length blocks into fixed-size packets to be transmitted over the physical network. Any lost packets have only minor effects on other received packets. Computer simulations show that the proposed method pro- vides both excellent compression performance with fast speed and graceful degradation under serve packet losses. © 2007 SPIE and

Bi-directional error-resilient entropy coding (BEREC)

In this paper, a new bi-directional error-resilient entropy coding (BEREC) technique is proposed which uses the beginnings and ends of fixed-length slots to synchronize variable-length blocks of data in two directions. In BEREC frames, every two variable-length blocks of data are grouped to generate one block-pair and placed in one fixed-length slot back-to-back using the similar searching strategy to that of the error-resilient entropy coding (EREC). Therefore, two blocks in one block-pair can be decoded in forward and backward directions separately. Compared to the EREC, the BEREC shows a significantly better performance of error robustness for noisy channels.

The Efficient and Robust Error Resilient Entropy Coding of Compressed Image for Wireless Communications

Many image and video compression algorithms work by splitting the image into blocks and producing variable-length code bits for each block data. If variable-length code data are transmitted consecutively over error-prone channel without any error protection technique, the receiving decoder cannot decode the stream properly. So the standard image and video compression algorithms insert some redundant information into the stream to provide some protection against channel errors. One of such redundancy is resynchronization marker, which enables the decoder to restart the decoding process from a known state in the event of transmission errors, but its frequent use should be restricted not to consume bandwidth too much. The Error Resilient Entropy Code (EREC) is well known method which can regain synchronization without any redundant information. It can work with the overall prefix codes, which many image compression methods use. This paper proposes an improvement to FEREC (Fast Error-Resilient Entropy Coding). It first calculates initial searching position according to bit lengths of consecutive blocks. Second, initial offset is decided using statistical distribution of long and short blocks, and initial offset is adjusted to insure all possible offset value can be examined. The proposed algorithm can speed up the construction of EREC slots, and can preserve compressed image quality in the event of transmission errors. The simulation result shows that the quality of transmitted image is enhanced about 0.3--3.5 dB compared with the existing FEREC when random channel error happens.

Robust image transmission based on wavelet tree coding, error resilient entropy coding, and error concealment

A scheme with three key components including wavelet tree coding, error resilient entropy coding (EREC), and error concealment is proposed for robust image coding and transmission over noisy channels. First, we individually encode the spatial-orientation trees in the wavelet domain using the algorithm of set partitioning in hierarchical trees (SPIHT). Error propagation is thus limited because multiple independent bit streams are generated. Meanwhile, a high source coding efficiency is also preserved because the self-similarity property in each wavelet tree remains intact. Next, we use EREC to reorganize these variable-length bit streams into fixed-length data slots before multiplexing and transmission. Therefore, the synchronization of the start of each bit stream can be automatically obtained at the receiver. Finally, to alleviate the possible catastrophic image degradation that may result from errors in the beginning of the bit streams, we propose an error concealment technique to constrain the EREC decoding as well as to postprocess the decoded wavelet coefficients. As a result of the error concealment, the EREC decoding complexity is reduced and the reconstructed image quality is significantly improved. Experimental results demonstrate an excellent error resilient performance of the proposed scheme.

Error-resilient zero-tree wavelet image coding technique over noisy channels

A zero-tree wavelet image coding technique with resiliency to transmission errors that typically occur on noisy channels is proposed. Key tools employed consist of the bit partitioning algorithm, and the bit reorganization algorithm, which is called the error resilient entropy code (EREC). To take full advantage of the bit reorganization algorithm, the bit partitioning algorithm divides the data into separate code blocks, although the zero-tree wavelet coding algorithm is not a block-based compression method. The bit reorganization algorithm requires a very low redundancy for the sequential transmission of variable length blocks, offering a virtually guaranteed code and block synchronization. The wavelet transform and the wavelet packet transform are used. Simulation results verify the error resiliency of the proposed algorithm for image coding. The experimental data show that the proposed coders outperform the existing error resilient coders over both noise-free channels and noisy channels. In addition, it is confirmed that the proposed algorithm is more error resilient than previously reported error-resilient coders for various channel error conditions.

Error-resilient image and video coding for wireless communication systems

Current techniques for coding images and video sources with resilience to channel errors can remove much of the need for complex high-redundancy channel coding and provide a graceful degradation of performance with decreasing channel quality. The main function of these error-resilient techniques is to reduce the propagation of errors within the decoded data. Two main techniques are discussed in detail: the error-resilient entropy code (EREC) and pyramid vector quantisation (PVQ). The paper concludes with a comparison of the relative merits of these systems and areas for further consideration.

Bandwidth efficient transmission of MPEG-II video over noisy mobile links

We consider the performance of MPEG-II compressed video when transmitted over noisy channels. We present the results of bit sensitivity and resynchronisation sensitivity measurements, and propose techniques for substantially improving the resilience of MPEG-II to transmission errors without the addition of any extra redundancy into the bitstream. We find that it is errors in variable length encoded data which cause the greatest artifacts as errors in these data can cause loss of bitstream synchronisation. We develop the concept of a ‘black-box transcoder’ where we losslessly transcode MPEG-II into a different structure for transmission. We achieve bitstream-resynchronisation using a technique known as error-resilient entropy coding (EREC). Finally we improve the error-resilience of differentially coded information by replacing the standard 1D-DPCM with a more resilient hierarchical pyramid predictor. We consider the transmission of MPEG-II over three separate channels: a channel subject to random bit errors, a channel subject to burst errors, and a channel subject to ATM cell losses.

Adaptive quantization and fast error-resilient entropy coding for image transmission

There has been an outburst of research in image and video compression for transmission over noisy channels. Channel matched source quantizer design has gained prominence. Further, the presence of variable-length codes in compression standards like the JPEG and the MPEG has made the problem more interesting. Error-resilient entropy coding (EREC) has emerged as a new and effective method to combat catastrophic loss in the received signal due to burst and random errors. We propose a new channel-matched adaptive quantizer for JPEG image compression. A slow, frequency-nonselective Rayleigh fading channel model is assumed. The optimal quantizer that matches the human visibility threshold and the channel bit-error rate is derived. Further, a new fast error-resilient entropy code (FEREC) that exploits the statistics of the JPEG compressed data is proposed. The proposed FEREC algorithm is shown to be almost twice as fast as EREC in encoding the data, and hence the error resilience capability is also observed to be significantly better. On average, a 5% decrease in the number of significantly corrupted received image blocks is observed with FEREC. Up to a 2-dB improvement in the peak signal-to-noise ratio of the received image is also achieved.

The EREC: an error-resilient technique for coding variable-length blocks of data

Many source and data compression schemes work by splitting the input signal into blocks and producing variable-length coded data for each block. If these variable-length blocks are transmitted consecutively, then the resulting coder is highly sensitive to channel errors. Synchronization code words are often used to provide occasional resynchronization at the expense of some added redundant information. This paper introduces the error-resilient entropy code (EREC) as a method for adapting existing schemes to give increased resilience to random and burst errors while maintaining high compression. The EREC has been designed to exhibit graceful degradation with worsening channel conditions. The EREC is applicable to many problems and is particularly effective when the more important information is transmitted near the start of each variable-length block and is not dependent on following data. The EREC has been applied to both still image and video compression schemes, using the discrete cosine transform (DCT) and variable-length coding. The results have been compared to schemes using synchronization code words, and a large improvement in performance for noisy channels has been observed.