Low Bit Rate Video Coding Research Articles

Content adaptive downsampling for low bitrate video coding

Content adaptive downsampling for low bitrate video coding

A FAST ALGORITHM FOR REGION-ORIENTED TEXTURE CODING

This paper addresses the framework of object-oriented image coding, describing a new algorithm, based on monodimensional Legendre polynomials, for texture approximation. Through the use of 1D orthogonal basis functions, the computational complexity which usually makes prohibitive most of 2D region-oriented approaches is significantly reduced, while only a slight increment of distortion is introduced. In the aim of preserving the bidimensional intersample correlation of the texture information as much as possible, suitable pseudo-bidimensional basis functions have been used, yielding significant improvements with respect to the straightforward 1D approach. The algorithm has been experimented for coding still images as well as motion compensated sequences, showing interesting possibilities of application for very low bitrate video coding.

A Segmentation-Based Chroma Intra Prediction Coding Scheme for H.264/AVC

In this paper, we propose a novel segmentation-based intra prediction coding scheme for low-bitrate video coding. Different coding schemes are separately designed for the luma and chroma components in our proposed method. The traditional block-based coding scheme is still used for the luma components, and the segmentation-based coding scheme is developed for the chroma components. The segmentation operation is used for the reconstructed luma components, which groups similar pixels together and produces a set of homogenous regions. Here, these local and homogenous regions are referred to superpixels. By utilizing the spatial correlation between the luma and chroma planes, we transfer the segmentation result of the luma components to the chroma components, which will not induce any side information in the chroma intra prediction coding. Instead of using the macroblock (MB) as the coding unit, the proposed method implements the chroma intra prediction in each superpixel, and the original pixels in each superpixel are employed to substitute the neighboring reconstructed samples in the prediction process. The experimental results show that the proposed method can achieve an average 0.20 dB and up to 0.63 dB coding gains in comparison to the directional intra prediction scheme for H.264/AVC low-bitrate video coding.

Low-complexity high-quality adaptive deblocking filter for H.264/AVC system

Blocking artifacts always appear on the reconstructed image, particularly in a low bit-rate video coding system. This paper presents an adaptive offset method to improve image quality for H.264 decoding. First, the histogram statistic is used to analyze the correlation between the offset and the filtering performance. The best filtering performance can mostly be found at the position of three offsets. Second, the best offset can be searched for with the minimum SAE (Summation of Absolute Error) among the three candidates. This algorithm can not only keep low computations, but it can also obtain good filtering quality. The average performance can be improved about 0.25 to 0.45dB (decibels) higher than the original H.264 deblocking filter. The blocky effect on the decoding image can be smoothed in vision.

A gaussian rate-distortion method for detecting zero-quantized blocks

AbstractAn efficient Gaussian rate-distortion approach is presented for detecting zero-quantized blocks (ZQBs) in H.264/Advanced Video Coding (H.264/AVC). ZQBs are quite common in low bit-rate video coding. To reduce the number of computations of the integer discrete cosine transform (DCT), quantization (Q), inverse quantization (IQ) and inverse DCT (IDCT), many approaches have been developed to detect ZQBs before DCT. DCT, Q, IQ and IDCT processes are not performed if the input residual data are detected as a ZQB. The proposed Gaussian rate-distortion approach greatly reduces computational cost with negligible video quality degradation. Several test video sequences are used to evaluate performance. Experimental results indicate that the proposed approach reduces the execution time of DCT, Q, IQ and IDCT by an average of 39.45% and obtains an 85.19% detection rate with a reasonable video quality loss of 0.002 dB.

A Gaussian Rate-Distortion Method For Detecting Zero-Quantized Blocks

An efficient Gaussian rate-distortion approach is presented for detecting zero-quantized blocks (ZQBs) in H.264/Advanced Video Coding (H.264/AVC). ZQBs are quite common in low bit-rate video coding. To reduce the number of computations of the integer discrete cosine transform (DCT), quantization (Q), inverse quantization (IQ) and inverse DCT (IDCT), many approaches have been developed to detect ZQBs before DCT. DCT, Q, IQ and IDCT processes are not performed if the input residual data are detected as a ZQB. The proposed Gaussian rate-distortion approach greatly reduces computational cost with negligible video quality degradation. Several test video sequences are used to evaluate performance. Experimental results indicate that the proposed approach reduces the execution time of DCT, Q, IQ and IDCT by an average of 39.45% and obtains an 85.19% detection rate with a reasonable video quality loss of 0.002 dB.

고화질 비디오의 부호화 효율성 증대와 연산 복잡도 감소를 위한 디블록킹 필터

In this paper, we propose a de-blocking filter for improvement of coding efficiency and computational complexity reduction on a high definition video coding. Recently, the H.264/AVC standard-based research for high definition video coding method is under way because the amount of used of high definition videos is on the increase. The H.264/AVC de-blocking filter is designed for low bitrate video coding and it improves not only the subjective quality but also coding efficiency by minimizing the blocking artifact. However, the H.264/AVC de-blocking filter that strong filtering is performed is not suitable in a high definition video coding which occurs relatively low blocking artifact. Also, the conventional de-blocking filter has high computational complexity in decoder side. The computational complexity of the proposed method is reduced about maximum 8.8% than conventional method. Furthermore, the coding efficiency of the proposed method is about maximum 7.3% better than H.264/AVC de-blocking filter.

Very Low Bit-Rate Video Coding by Combining H.264/AVC Standard and 2-D Discrete Wavelet Transform

In this paper, we propose a new method for very low bit-rate video coding that combines H.264/AVC standard and two-dimensional discrete wavelet transform. In this method, first a two dimensional wavelet transform is applied on each video frame independently to extract the low frequency components for each frame and then the low frequency parts of all frames are coded using H.264/AVC codec. On the other hand, the high frequency parts of the video frames are coded by Run Length Coding algorithm, after applying a threshold to neglect the low value coefficients. Experiments show that our proposed method can achieve better rate-distortion performance at very low bit-rate applications below 16 kbits/s compared to applying H.264/AVC standard directly to all frames. Applications of our proposed video coding technique include video telephony, video-conferencing, transmitting or receiving video over half-rate traffic channels of GSM networks.

船舶位置情報を利用した見張り用映像の伝送方式に関する研究

Recently, the need for lookout support for seaman is now increasing. One of the useful ways to support the lookout operations is to transmit the outside images to the control center. However, the communication in the sea is still insufficient Internet bandwidth. In video coding processing, a pre-filter is often used for improving both coding efficiency and subjective image quality in low bitrate video coding. Especially, pre-filter to edge information can keep the visual impression to be clear. However, to apply these filters for the image frame entirely is inefficient in coding, because the edge information has high-frequency component. Therefore, to apply these filters for only ship's region is effective. So, in this research, a technique that transmits outboard image by using information of ship's position is proposed. The acquisition ship by RADAR/ARPA contributes to estimating the ship in the outboard image. This method is applied to an outside image, and the quality of image and its processing time is considered. By using that implementation, subjective evaluation is performed, and the effectiveness for improvement of visibility is confirmed.

超高精細映像におけるマクロブロックサイズ拡張手法に関する解析的考察

Ultra-high resolution video is expected to be one of the next-generation high quality video formats. Current video coding technology H.264 achieves the maximum amount of coding efficiency from among the existing coding standards. However, even H.264 is not sufficient enough for ultra-high resolution video distribution service due to a lack of coding efficiency. Therefore, an enhanced video coding technology is strongly required to improve the coding efficiency. In the past works, several approaches for extending the macroblock (MB) size have been proposed, and these researches showed that extended MB size technology improved the coding efficiency, especially for high resolution video. However, a clear description of the performance improvement mechanism has yet to be presented. We analytically consider the coding characteristics of an extended MB size scheme for ultra-high resolution video in this paper. We clarified the coding gain mechanism of this technology based on a R-D characteristics analysis. Furthermore, we analytically confirmed that the extended MB size scheme was most effective at high-resolution and low-bitrate video coding. Finally, we conducted a coding experiment and found that the maximum bit reduction ratio reached approximately 15% using an optimal coding control for the extended MB size scheme.

모바일 화상통신을 위한 오류강인 부호화 기법

영상을 통신망에서 실시간 전송하려면 압축된 비디오 비트열이 필요하다. 비디오 압축 알고리즘은 시간적, 공간적, 확률적 중복성을 제거하기 때문에 부호화된 비트열은 전송과정 중에 발생하는 전송에러에 매우 민감한 특성을 보인다. 본 논문에서는 저 전송률 비디오 코딩에서 에러의 확산을 막기 위한 에러 복원코딩 방식을 제안한다. 이런 에러 복원 코딩 기술의 성능은 전송에러를 얼마나 정확하게 탐지해 내느냐에 달려 있는데, 전송 에러를 검출하기위해 데이터 숨김이라는 방식을 제안한다. 그리고 에러가 발생한 매크로블록을 복원하기 위해 인트라 매크로블록 갱신 기술과, 움직임 벡터 예측을 이용한 움직임 보상 기술을 적용하여 성능을 비교 및 평가한다. 이 방식은 WCDMA와 같이 에러가 발생할 확률이 있는 비디오 전송망에서 사용할 경우 매우 효과적이다. Compressed video bitstreams are intended for real-time transmission over communication networks. Because video compression algorithms eliminate the temporal, spatial, and statistical redundancies, the coded video bitstreams are very sensitive to transmission errors. We propose an error resilient video coding technique to limit the effect of error propagation in low bit-rate video coding. The success of error resilient coding techniques relies on how accurately the transmission errors can be detected. To detect the transmission error, we propose a very simple error detection technique based on data hiding Next, we conceal the corrupted MB data using intra MB refresh and motion compensation with the estimated motion vector and compare the simulation results. This method will be useful in video communication in error Prone environment such as WCDMA networks.

Moving Objects Detection Method Based on Brightness Distortion and Chromaticity Distortion

This paper addresses a new background subtraction algorithm for detecting moving objects from a static background scene. The algorithm is proposed on the basis of brightness distortion and chromaticity distortion in RGB color space. For a given video sequence, a background frame is first extracted. Statistical analysis of chromaticity value is used in background frame extraction. It can solve the problem of deleting moving traces of moving objects in the case of few frames and slow movement. Gaussian model is used to calculate the threshold of brightness distortion in object detection. It can solve the problem of manually setting the brightness distortions of different video sequences. Experimental results show that the method proposed in this paper can detect moving objects exactly and effectively. It has been used in intelligent video surveillance system and region of interest (ROI) based low-bitrate video coding system.

An adaptive preprocessing algorithm for low bitrate video coding

At low bitrate, all block discrete cosine transform (BDCT) based video coding algorithms suffer from visible blocking and ringing artifacts in the reconstructed images because the quantization is too coarse and high frequency DCT coefficients are inclined to be quantized to zeros. Preprocessing algorithms can enhance coding efficiency and thus reduce the likelihood of blocking artifacts and ringing artifacts generated in the video coding process by applying a low-pass filter before video encoding to remove some relatively insignificant high frequent components. In this paper, we introduce a new adaptive preprocessing algorithm, which employs an improved bilateral filter to provide adaptive edge-preserving low-pass filtering which is adjusted according to the quantization parameters. Whether at low or high bit rate, the preprocessing can provide proper filtering to make the video encoder more efficient and have better reconstructed image quality. Experimental results demonstrate that our proposed preprocessing algorithm can significantly improve both subjective and objective quality.

Low complexity deblocking method for DCT coded video signals

A new method to remove blocking artefacts in low bit-rate block-based video coding, such as MPEG-4 and H.264, is presented. A low computational deblocking filter with five modes is proposed, including three frequency-related modes (smooth mode, intermediate mode, and complex mode for low-frequency, mid-frequency, and high-frequency regions, respectively), one special mode (steep mode for a large offset between two blocks) and a refined mode (corner mode for the corner of four blocks). A mode decision procedure is also needed to decide which mode is given by observing pixel behaviour around the block boundary. To take the masking effect of the human visual system (HVS) into consideration, the filter for smooth mode is designed to be much stronger than that for complex mode, because human eyes are more sensitive to smooth regions. Experimental results show that, in most cases, the proposed algorithm removes more blocking artefacts than MPEG-4 deblocking filters do, and improves both subjective and objective image quality. The proposed algorithm keeps the computation lower than MPEG-4 and is suitable for most block-based image and video coding systems.

Fast construction of dynamic and multi-resolution 360° panoramas from video sequences

This paper presents a unified approach to automatically build dynamic and multi-resolution 360° panoramic (DMP) representations from image sequences captured by hand-held cameras mainly undertaking rotation and zooming for natural scenes with moving targets. A simple (yet stable) rigid motion model and a closed-loop-based mosaicing algorithm are proposed to generate cylindrical mosaics automatically. Multi-resolution representations are built for interesting areas by separating zooming sub-sequences from a pan/zoom sequence. Moving objects are detected and separated from images based on motion information, and then more accurate contours are extracted using a modified active contour algorithm. The DMP construction method is fast, robust, and automatic, achieving five frames per second for image sequences with 384×288 color images on a Pentium III 800 MHz PC. The construction of the DMP representation can be used in virtual reality, video surveillance, and very low bit-rate video coding.

Adaptive frame skipping based on spatio-temporal complexity for low bit-rate video coding

Conventional rate control schemes focus on the adjustment of quantization values to retain a certain buffer level, and buffer adaptive frame skippings are used to avoid buffer overflow at low bit-rates. In this paper, an adaptive frame-skipping scheme is proposed to achieve the balance between spatial and temporal quality, and to maintain the buffer level. The occurrence of frame skipping is jointly dependent on the temporal and spatial complexity of the video, and on the fullness of the buffer. This helps to achieve a balanced spatial and temporal quality and to enhance the overall perceptual quality. Experimental results show that the new scheme is simple but very effective, with large average PSNR gains and consistently improved visual quality, and the improvement in perceptual quality is much significant than that in average PSNRs.

Residual motion coding method supporting error concealment in low bitrate video coding

A residual motion coding (RMC) method supporting error concealment (EC) in low bitrate video coding is proposed. In the RMC method, the residual motion vector (RMV) is interleaved into the bitstream at the encoder to improve the error resilience of MVs. Experimental results show that the EC using RMV performs better than conventional EC methods.

Spiral intra macroblock refresh with motion vector restriction for low bit-rate video telephony over a 3G network

A method to limit the effect of error propagation in low bit-rate error resilient video coding has been proposed and implemented on a 3G prototype videophone. In conventional methods, the effect of the bit-stream error does not vanish rapidly since the refreshed macroblocks are affected by the errors in the unrefreshed macroblocks. To overcome this ineffectiveness, two techniques are used; one is motion vector restriction that limits the error propagation, and the other is the spiral intra macroblock refresh that minimizes coding efficiency degradation caused by the motion vector restriction. Further, the latter technique concentrates on the center area in the screen, where the subjective preference is closely related. Experiments show that the proposed method removes the effect of the error more rapidly than the conventional methods.

Automatic scalable face model design for 2D model-based video coding

Scalable low bit-rate video coding is vital for the transmission of video signals over wireless channels. A scalable model-based video coding scheme is proposed in this paper to achieve this. This paper mainly addresses automatic scalable face model design. Firstly, a robust and adaptive face segmentation method is proposed, which is based on piecewise skin-colour distributions. 43 million skin pixels from 900 images are used to train the skin-colour model, which can identify skin-colour pixels reliably under different lighting conditions. Next, reliable algorithms are proposed for detecting the eyes, mouth and chin that are used to verify the face candidatures. Then, based on the detected facial features and human face muscular distributions, a heuristic scalable face model is designed to represent the rigid and non-rigid motion of head and facial features. A novel motion estimation algorithm is proposed to estimate the object model motion hierarchically. Experimental results are provided to illustrate the performance of the proposed algorithms for facial feature detection and the accuracy of the designed scalable face model for representing face motion.

“MPEG-4 Very Low Bitrate Video Coding System by Adaptively Using Sprite”

“MPEG-4 Very Low Bitrate Video Coding System by Adaptively Using Sprite”