Sungdae Cho

A full-featured, error-resilient, scalable wavelet video codec based on the set partitioning in hierarchical trees (SPIHT) algorithm

Compressed video bitstreams require protection from channel errors in a wireless channel. The 3-D set partitioning in hierarchical trees (SPIHT) coder has proved its efficiency and its real-time capability in the compression of video. A forward-error-correcting (FEC) channel (RCPC) code combined with a single automatic-repeat request (ARQ) proved to be an effective means for protecting the bitstream. There were two problems with this scheme: (1) the noiseless reverse channel ARQ may not be feasible in practice and (2) in the absence of channel coding and ARQ, the decoded sequence was hopelessly corrupted even for relatively clean channels. We eliminate the need for ARQ by making the 3-D SPIHT bitstream more robust and resistant to channel errors. We first break the wavelet transform into a number of spatio-temporal tree blocks which can be encoded and decoded independently by the 3-D SPIHT algorithm. This procedure brings the added benefit of parallelization of the compression and decompression algorithms, and enables implementation of region-based coding. We demonstrate the packetization of the bitstream and the reorganization of these packets to achieve scalability in bit rate and/or resolution in addition to robustness. Then we encode each packet with a channel code. Not only does this protect the integrity of the packets in most cases, but it also allows detection of packet-decoding failures, so that only the cleanly recovered packets are reconstructed. In extensive comparative tests, the reconstructed video is shown to be superior to that of MPEG-2, with the margin of superiority growing substantially as the channel becomes noisier. Furthermore, the parallelization makes possible real-time implementation in hardware and software.

3D set partitioning coding methods in hyperspectral image compression

Hyperspectral images are generated by collecting hundreds of narrow and contiguously spaced spectral bands of data producing a highly correlated long sequence of images. Some application specific data compression techniques may be applied advantageously before we process, store or transmit hyperspectral images. This paper applies asymmetric tree 3DSPIHT (AT-3DSPIHT) for hyperspectral image compression; it also investigates and compares the performance of the AT-3DSPIHT, 3DSPIHT and 3DSPECK on hyperspectral image compression. Results show that the AT-3DSPIHT outperforms the other two by the approximate range of 0.2 to 0.9 dB PSNR. It guarantees over 4 dB PSNR improvement at all rates or rate savings at least a factor of 2.5 over 2D coding of separate spectral bands without axial transformation.

Comparison of 3D set partitioning methods in hyperspectral image compression featuring an improved 3D-SPIHT

Summary form only given. Hyperspectral images were generated through the collection of hundreds of narrow and contiguously spaced spectral bands of data producing a highly correlated long sequence of images. An investigation and comparison was made on the performance of several three-dimensional embedded wavelet algorithms for compression of hyperspectral images. These algorithms include 3D-SPIHT, AT-3DSPIHT, 3D-SPECK (three-dimensional set partitioned embedded block), and JPEG2000. 3D-SPIHT is the three-dimensional extension of the state-of-the-art SPIHT (set partitioning in hierarchical trees) image compression algorithm. AT-SPIHT uses the same coding algorithms as 3D-SPIHT, but utilizes a more efficient, asymmetric tree structure. 3D-SPECK is a version of two-dimensional SPECK modified to encode 3D subband blocks. For an image sequence, 3D-DWT was applied to obtain a wavelet coefficient prism. This prism is partitioned into small code blocks with different sizes, and each subband is treated as a code block. A block splitting algorithm is used on the individual code blocks to test their significance. Compression performance was conducted on the mentioned algorithms using several AVIRIS (Airborne Visible Infrared Imaging Spectrometer) image sequences. The rate distortion performances were compared by means of the peak signal-to noise ratio (PSNR). The visual effect is considered a primary concern of hyperspectral imagery so an analysis of every algorithms visual effect is in order. Through experimentation, AT-3DSPIHT provided high quality reconstructed images even at very low bit rate such as 0.4 bpp. A comparison was also conducted on JPEG200 and other algorithms concerning JPEG2000s multi-component images. The results have shown that AT-3DSPIHT, 3D-SPIHT and 3D-SPECK outperform JPEG2000 by the approximate range of 1 to 2.5 dB PSNR, depending on the image sequence.

Lossless Compression of Volumetric Medical Images with Improved Three-Dimensional SPIHT Algorithm

This article presents a lossless compression of volumetric medical images with the improved three-dimensional (3-D) set partitioning in hierarchical tree (SPIHT) algorithm that searches on asymmetric trees. The tree structure links wavelet coefficients produced by 3-D reversible integer wavelet transforms. Experiments show that the lossless compression with the improved 3-D SPIHT gives improvement about 42% on average over two-dimensional techniques and is superior to those of prior results of 3-D techniques. In addition, we can easily apply different numbers of decomposition between the transaxial and axial dimensions, which is a desirable function when the coding unit of a group of slices is limited in size.

Error-resilient video coding with improved 3D SPIHT and error concealment

This paper first introduces an asymmetric tree structure for utilization with an error resilient form 3-D SPIHT, called ERC-SPIHT. Then, we present a fast error concealment scheme, borrowed from Rane et al.s work with images, for embedded video bitstream using ERC-SPIHT. In addition to using simple averaging method in the root subband, we detect the presence or absence of edges in the lost block of every image. Then we use an interpolation scheme to recover the lost edge information.

Optimal error protection for real-time image and video transmission

In this paper a novel and computationally inexpensive analytic mean square error (MSE) distortion rate (D-R) estimator for SPIHT which generates a nearly exact distortion rate (D-R) function for the 2D and 3D SPIHT algorithm is presented. The analytical formula is derived from the observations that for any bit-plane coder, the slope of the D-R curve is constant for each level of the bit plane. Furthermore the slope of D-R curve reduces by a factor proportional to the level of the bit plane. An application of the derived results is presented in the area of 2D SPIHT transmission employing a binary symmetric channel (BSC) and Reed Solomon (RS) forward error correction (FEC) codes. Utilizing our D-R estimate, we employ unequal error protection (UEP) and equal error protection (EEP) in order to minimize the end to end mean square error (MSE) distortion of the transform domain. UEP yields a significant performance gain relative to EEP only when the average number of parity bits for a group of packets is constrained. When both the source rate and channel code rate varied under a bit budget constraint, optimal UEP yields only a slight improvement over the optimal EEP. A major contribution of this paper is the simple and extremely accurate analytical D-R model which potentially improves upon pre-existing methodologies and applications that rely on an accurate and computationally inexpensive D-R estimate. Another important contribution is that the optimum EEP, which requires almost no header information and can easily be computed using our method, is only slightly worse than the optimum UEP.

Error resilience and recovery in streaming of embedded video

The three-dimensional (3-D) SPIHT coder is a scalable or embedded coder that has proved its efficiency and its real-time capability in compression of video. A forward-error-correcting (FEC) channel (RCPC) code combined with a single automatic repeat request (ARQ) proved to be an effective means for protecting the bitstream. There were two problems with this scheme: the noiseless reverse channel ARQ may not be feasible in practice; and, in the absence of channel coding and ARQ, the decoded sequence was hopelessly corrupted even for relatively clean channels. In this paper, we introduce a new method of partitioning wavelet coefficients into spatio-temporal (s-t) tree blocks to achieve error resilience. Each of these s-t blocks corresponds to the full 3-D image region, because roots of these trees are wavelet coefficients taken at fixed intervals in the root low-frequency subband. Previously, we reported on grouping contiguous root subband coefficients to generate s-t tree blocks that correspond to local 3-D regions. The new procedure brings higher error resilience, since lost coefficients can be concealed with the surrounding coefficients even if some of the coded s-t blocks are totally missing. The bitstreams of the coded s-t blocks are packetized and encoded with a channel code to correct errors and to prevent decoding of erroneous data after errors are detected. Because the separately encoded s-t blocks produce embedded bitstreams, the packets from the bitstreams are interleaved to generate an embedded composite bitstream. The embedded property, whereby successive compressed bits convey successively smaller value information, suggests unequal error protection, where earlier bits are more strongly protected by the channel code than later bits. Therefore, unequal error protection is also incorporated into our video bitstreams to bring an even higher degree of resilience to channel bit errors. Our claims are supported by extensive simulations with decoding of the various 3-D SPIHT bitstreams compared to each other and to MPEG-2. Superiority to MPEG-2 in noiseless and noisy channels, nnder equal conditions with or without FEC, is clearly demonstrated by the results of these simulations.

Error-resilient compression and transmission of scalable video

Compressed video bitstreams require protection from channel errors in a wireless channel and protection from packet loss in a wired ATM channel. The three-dimensional (3-D) SPIHT coder has proved its efficiency and its real-time capability in compression of video. A forward-error-correcting (FEC) channel (RCPC) code combined with a single ARQ (automatic- repeat-request) proved to be an effective means for protecting the bitstream. There were two problems with this scheme: the noiseless reverse channel ARQ may not be feasible in practice; and, in the absence of channel coding and ARQ, the decoded sequence was hopelessly corrupted even for relatively clean channels. In this paper, we first show how to make the 3-D SPIHT bitstream more robust to channel errors by breaking the wavelet transform into a number of spatio-temporal tree blocks which can be encoded and decoded independently. This procedure brings the added benefit of parallelization of the compression and decompression algorithms. Then we demonstrate the packetization of the bit stream and the reorganization of these packets to achieve scalability in bit rate and/or resolution in addition to robustness. Then we encode each packet with a channel code. Not only does this protect the integrity of the packets in most cases, but it also allows detection of packet decoding failures, so that only the cleanly recovered packets are reconstructed. This procedure obviates ARQ, because the performance is only about 1 dB worse than normal 3-D SPIHT with FEC and ARQ. Furthermore, the parallelization makes possible real-time implementation in hardware and software.

Multilayered protection of embedded video bitstreams over binary symmetric and packet erasure channels

This paper presents a multilayered protection of embedded video bitstreams over bit errors and packet erasure channels using Error Resilient and Error Concealment 3-D SPIHT (ERC-SPIHT) algorithm, which is based on the 3-D SPIHT concepts. A robust source coder is created to give error resilience in source level of the codestream. This robustness is achieved by partitioning the wavelet coefficients into many independent sub-bitstreams while maintaining spatio-temporal tree structures. For higher protection against channel noise, we use a product code. In each packet, the concatenation of a rate compatible punctured convolutional (RCPC) code and an error detecting parity check (CRC) code is used. Across the packets, Reed-Solomon codes are used. These steps provide the robust source coder with additional layers of protection against channel noise. Finally, in the decoder side, an error concealment function is performed for the lost blocks. Simulations show that the multilayered protection of 3-D SPIHT outperforms the methods that use single layer protection in terms of average PSNRs and the PSNR ranges, and provides higher average PSNRs and lower PSNR variances.

Robust image transmission using a new joint source channel coding algorithm and dual adaptive OFDM

In this paper we consider the problem of robust image coding and packetization for the purpose of communications over slow fading frequency selective channels and channels with a shaped spectrum like those of digital subscribe lines (DSL). Towards this end, a novel and analytically based joint source channel coding (JSCC) algorithm to assign unequal error protection is presented. Under a block budget constraint, the image bitstream is de-multiplexed into two classes with different error responses. The algorithm assigns unequal error protection (UEP) in a way to minimize the expected mean square error (MSE) at the receiver while minimizing the probability of catastrophic failure. In order to minimize the expected mean square error at the receiver, the algorithm assigns unequal protection to the value bit class (VBC) stream. In order to minimizes the probability of catastrophic error which is a characteristic of progressive image coders, the algorithm assigns more protection to the location bit class (LBC) stream than the VBC stream. Besides having the advantage of being analytical and also numerically solvable, the algorithm is based on a new formula developed to estimate the distortion rate (D-R) curve for the VBC portion of SPIHT. The major advantage of our technique is that the worst case instantaneous minimum peak signal to noise ratio (PSNR) does not differ greatly from the averge MSE while this is not the case for the optimal single stream (UEP) system. Although both average PSNR of our method and the optimal single stream UEP are about the same, our scheme does not suffer erratic behavior because we have made the probability of catastrophic error arbitarily small. The coded image is sent via orthogonal frequency division multiplexing (OFDM) which is a known and increasing popular modulation scheme to combat ISI (Inter Symbol Interference) and impulsive noise. Using dual adaptive energy OFDM, we use the minimum energy necessary to send each bit stream at a particular probability of bit error. An added benefit of OFDM over serial transmission schemes is that some degree of progressiveness of SPIHT is preserved by transmitting both the VBC and LBC streams in parallel.