Adaptive time division multiplexing transmission scheme for the distributed video coding

Summary form only given. Distributed video coding (DVC) has been intensively studied in recent years. This new coding paradigm substantially differs from conventional prediction-based video codecs such as MPEG and H.26x, which are characterized by a complex encoder and simple decoder. The conventional DVC codec, e.g., DISCOVER codec, uses advanced frame interpolation techniques to create SI based on adjacent decoded reference frames. The quality of SI is a well-recognized factor in the RD performance of WZ video coding. A high SI quality implies a high correlation between the created SI and the original WZ frame, which then decreases the rate required to achieve a given decoded quality. Clearly, the performance of an SI creation process based on adjacent previously decoded frames is limited by the quality of the past and the future reference frames as well as the distance and motion behavior between them. The correlation between high-motion frames is low and vice versa. That is, SI quality in the conventional codecs depends on the temporal correlation of key frames, which affects the bitrate and PSNR of the compression process. In this work, a novel DVC architecture for dealing with the cases of high-motion and large GOP-size sequences is proposed to better the rate-distortion (RD) performance. For high-motion video sequences, the proposed architecture generates SI by using subsampled spatial information instead of interpolated temporal information. the proposed approach separates the video sequence into subsampled key frames and corresponding WZ frames, which changes the creation of SI. That is, all successive frames on the encoder side are downsized to sub-frames, which are then compressed by an H.264/AVC intra encoder. Experimental results reveal that the subsampling input based DVC codec can gain up to 1.47 dB in the RD measures and maintains the most important characteristic of the DVC codec, the encoder is lightweight, as compared with the conventional WZ codec, respectively. The novel DVC architecture evaluated in this study exploits spatial relations to create SI. The experimental results confirm that the RD performance of the proposed approach is superior to that of the conventional one for high-motion and/or large GOP-size sequences. The quality of spatial interpolation based SI is higher than that of the temporal interpolation one, which leads to a high-PSNR reconstructed WZ frame. The subsampled key frames are also decoded by LDPCA decoder to recover the information lost when H.264/AVC intra coding is used to increase PSNR gain. Since many spatial domain interpolation and super resolution schemes have been proposed for use in the fields of image processing and computer vision, the performance of the proposed DVC codec can be further enhanced by using better schemes to generate even better SI.

In this paper, we propose a simple in-service delay time estimation method and two adaptive transmission schemes, that is, adaptive GI length transmission scheme and adaptive modulation transmission scheme, based on the estimation method for broadband vehicular OFDM transmissions. The simple in-service delay time estimation method uses the characteristic that the symmetry of received signal point distribution collapses in multipath propagation environments, obtains the useful information about the delay spread and average BER from the accumulative average value of the detector outputs of sub-carriers of OFDM signals. The proposed adaptive transmission schemes utilize the measured delay time relative information to adaptively change the GI length or modulation method of OFDM signals, achieving high transmission quality and efficiency simultaneously. Assuming a two-ray Rayleigh fading multipath channel model, the effectiveness of these proposed schemes has been confirmed by computation simulations.

The ongoing research on Distributed Video Coding (DVC) is focused on flexibility and increased rate distortion (RD) performance. Besides Slepian-Wolf (SW) coding and coder control, a good side information (SI) quality is essential for high RD performance. The SI is typically extracted by temporal inter-/extrapolation. Fast motion is still a challenge. Two global motion guided adaptive temporal inter-/extra-polation (GTIE/GpTIE) schemes are proposed. They incorporate fast camera motion by global motion estimation and subsequent refinement. The issue of occlusion and revelation at the frame border is solved by an adaptive temporal inter-/extrapolation method. Simulation results show an RD performance increase of up to 3.1 dB.

Distributed video coding (DVC) suits the light weight encoder and complex decoders, shifting the motion estimation to the decoder, in contrast to the conventional encoding scheme. Mode decision is one of the factor affecting the Rate Distortion (RD) performance due to the varying statistics of the sequence in the DVC. In this paper, we propose to introduce coding modes and the Side Information (SI) refinement modes at the decoder in the pixel domain multi resolution refinement(MRR) Wyner-Ziv scheme. During the decoding process, the mode decision of the current decoding layer of the block is based on the information from the previous decoded layers of the block and the updated SI. We further propose the adaptive weighted reconstruction scheme using the neighbor pixels. RD performance of the proposed scheme is tested with several sequences. The results shows significant performance improvement.

This letter investigates the impact of reference frames in Distributed Video Coding (DVC) on the Rate-Distortion (RD) performance and reveals that reference frames have the potential to be better side information (SI) than the extensively used interpolated frames. Based on this investigation, we also propose a motion range prediction (MRP) method to exploit reference frames and precisely guide the statistical motion learning process. Extensive simulation results show that choosing reference frames as SI performs competitively, and sometimes even better than interpolated frames. Furthermore, the proposed MRP method is shown to significantly reduce the decoding complexity without degrading any RD performance.

Smart spaces is a scenario that is ideal for the application of wireless communication technology to benefit non-expert users. A prime example of such an application would be low-cost and real-time video surveillance of hallways or video conferencing. Traditional solutions for these scenarios use state-of-the-art video codecs like H.264/AVC in order to achieve the low bitrate which is essential in wireless communication. On the flip side, such encoders are computationally complex and need expensive hardware to run on thus making them inefficient choices for being deployed in clusters. Recent research has resulted in distributed video coding (DVC) being proposed as a solution for applications that have limited battery resources and low hardware complexity, thus necessitating a low-complexity encoder. It is now a popular topic in the research community and the past years have seen several implementations. However, current DVC solutions use iteratively decodable channel codes like low-density parity check – accumulate (LDPCA) codes or Turbo codes that have large latencies. In order to make real-time communication possible, the proposed architecture makes efficient use of skip blocks to reduce the bitrate, eliminates the iterative decoding nature of the Wyner-Ziv (WZ) channel and uses a simple data-hiding-based compression algorithm. This drastically cuts down on the time complexity of the decoding procedure while still maintaining a rate–distortion performance better than that of H.264/AVC intra-coding and other current DVC solutions.

Distributed Video Coding (DVC) is a new compression paradigm in video coding, which is receiving lots of interests nowadays. Side information creation is a key function in the DVC decoder, and plays a key-role in determining the performance of the codec. This paper proposes a novel framework to create side information at the block level with two modes: Wyner-Ziv mode and Intra/WZ mode, corresponding to Motion Compensated Frame Interpolation and motion compensated quality enhancement technique, respectively. While in the second mode, a low quality Intra block sent by the encoder is used to generate side information by doing motion estimation with the help of the reference frames. Experimental results demonstrate that the proposed scheme can achieve up to 2.1dB improvement in rate-distortion performance when compared to state-of-the-art DVC codec, especially for high motion video sequences and long group of pictures sizes.

Error-resilient scalable compression based on distributed video coding

The common distributed video coding (DVC) systems treat input video frames group by group. In each group of pictures (GOP), usually the first frame, called key frame, is intra-coded and the others are Wyner-Ziv (WZ)-coded. This GOP coding structure presents a fixed and inefficient coding mode switch (key or WZ) at group boundaries, thus preventing a DVC system from adapting the rate-distortion (R-D) performance to varying video content. In this work, a structure of temporal group of blocks (TGOB) with dynamic coding mode (key/WZ) decision is presented. This dynamic TGOB coding architecture determines each image block to be a key block or a WZ block based on spatiotemporal image analysis, resulting in a mode switch of fine granularity in both the spatial and temporal domains. As a consequence, not only the overall coding efficiency is improved, but also the temporal flickering artifacts for the reconstructed video are reduced substantially. Experimental results show that our proposed DVC scheme with block mode decision achieves up to 2.85 dB of quality gain and also up to 51% of temporal flickering reduction, compared to the well-known DISCOVER system.

Distributed video coding (DVC) is a new video coding paradigm, which allows a reverse complexity codec in which the complexity is shifted from the encoder toward the decoder. Many DVC implementations have to make a prediction of the encoded frame at the decoder side using only the other frames as reference, in a process called side information (SI) generation. This process is crucial to any DVC framework a better SI will lead to a better rate distortion performance. In this work, we propose a linear motion mode to produce SI associated with, and a way to deal with the common problems of this model. Results are presented to support the proposed method. Keywords—Side Information, Wyner-Ziv Video Coding, Motion Compensation Frame Interpolation.

Publication in the conference proceedings of EUSIPCO, Poznan, Poland, 2007

Nowadays, distributed video coding (DVC) has been receiving more and more attention due to its contribution to the low complexity encoding. This paper presents a new DVC using an optimized trellis coded quantization (TCQ) to improve the current schemes. In the scheme, the improved quadtree scanning firstly removes the zero trees of the Wyner-Ziv frame, and then the non-zero trees are quantized by an optimized TCQ. Finally, the quantized coefficients are compressed by Slepian-Wolf coder. Experimental results show that the proposed scheme outperforms the referenced in rate-distortion performance, and the goal of low-complexity encoding is achieved.

Distributed video coding (DVC) is a coding paradigm that entails low complexity encoding by exploiting the source statistics at the decoder. To improve the DVC coding efficiency, this paper presents a novel adaptive technique for mode decision to control and take advantage of skip mode and intra mode in DVC initially proposed by Luong et al. in 2013. The adaptive mode decision (AMD) is not only based on quality of key frames but also the rate of Wyner–Ziv (WZ) frames. To improve noise distribution estimation for a more accurate mode decision, a residual motion compensation is proposed to estimate a current noise residue based on a previously decoded frame. The experimental results, integrating AMD in two efficient DVC codecs, show that the proposed AMD DVC significantly improves the rate distortion performance without increasing the encoding complexity. For a GOP size of 2 on the set of six test sequences, the average (Bjøntegaard) bitrate saving of the proposed codec is 35.5% on WZ frames compared with the DISCOVER codec. This saving is mainly achieved by AMD.

Distributed Video Coding (DVC) is an encoding mode that uses decoder-side information to reduce encoder complexity. The coding efficiency of DVC depends critically on the quality of side information generation and the accuracy of correlated noise modeling. Based on the transformation domain Wyner-Ziv (TDWZ) coding, block matching and optical flow method are used to generate initial side information frames, and a WZ reconstruction algorithm based on side information improvement and a method to improve the accuracy of correlated noise modeling are proposed by gradually updating the noise residual coefficient. Experimental results show that for WZ frames with GOP size 2, the proposed scheme can significantly improve the coding efficiency compared with TDWZ and DISCOVER while reducing the complexity of the decoding end. The system's rate distortion (RD) performance has also been improved.

Distributed video coding (DVC) architecture designs, based on distributed source coding principles, have benefitted from significant progresses lately, notably in terms of achievable rate-distortion performances. However, a significant performance gap still remains when compared to prediction-based video coding schemes such as H.264/AVC. This is mainly due to the non-ideal exploitation of the video sequence temporal correlation properties during the generation of side information (SI). In fact, the decoder side motion estimation provides only an approximation of the true motion. In this paper, a progressive DVC architecture is proposed, which exploits the spatial correlation of the video frames to improve the motion-compensated temporal interpolation (MCTI). Specifically, Wyner-Ziv (WZ) frames are divided into several spatially correlated groups that are then sent progressively to the receiver. SI refinement (SIR) is performed as long as these groups are being decoded, thus providing more accurate SI for the next groups. It is shown that the proposed progressive SIR method leads to significant improvements over the Discover DVC codec as well as other SIR schemes recently introduced in the literature.