Temporal Concealment Method Research Articles

Error Resilience Scheme for Real-Time Video

The quality of decoded video in erroneous environment depends on efficient detection and concealment of errors. In this paper, an improved error detection technique and a novel temporal error concealment technique for MPEG-4 video are proposed. The proposed detection technique can detect efficiently some transmission error as well locate the exact position of the first error. The proposed temporal concealment method can mask the impairments caused by the detected error significantly with very low computation complexity. Experimental results show the improved detection technique combining with the proposed temporal concealment method can increase the video quality efficiently.

정보숨김과 주변 움직임 벡터의 적응적 선택에 의한 에러은닉 알고리즘의 설계 및 구현

In this paper, we propose an error resilience video coder which uses a hybrid error concealment algorithm. Firstly, the algorithm uses the error concealment with data hiding. If the hiding information is lost, the motion vector of lost macroblock is computed with adaptive selection of adjacent motion vectors and OBMC (Overlapped Block Motion Compensation) is applied with this motion vector. We know our algorithm is more effective in case of continuous GOB. The results show more significant improvement than many temporal concealment methods such as MVRI (Motion Vector Rational Interpolation) or existing error concealment using data hiding.

Modeling of transmission-loss-induced distortion in decoded video

This paper analyzes the distortion in decoded video caused by random packet losses in the underlying transmission network. A recursion model is derived that relates the average channel-induced distortion in successive P-frames. The model is applicable to all video encoders using the block-based motion-compensated prediction framework (including the H.261/263/264 and MPEG1/2/4 video coding standards) and allows for any motion-compensated temporal concealment method at the decoder. The model explicitly considers the interpolation operation invoked for motion-compensated temporal prediction and concealment with sub-pel motion vectors. The model also takes into account the two new features of the H.264/AVC standard, namely intraprediction and inloop deblocking filtering. A comparison with simulation data shows that the model is very accurate over a large range of packet loss rates and encoder intrablock rates. The model is further adapted to characterize the channel distortion in subsequent received frames after a single lost frame. This allows one to easily evaluate the impact of a single frame loss.

Vector Rational Interpolation Schemes for Erroneous Motion Field Estimation Applied to MPEG-2 Error Concealment

A study on the use of vector rational interpolation for the estimation of erroneously received motion fields of MPEG-2 predictively coded frames is undertaken in this paper, aiming further at error concealment (EC). Various rational interpolation schemes have been investigated, some of which are applied to different interpolation directions. One scheme additionally uses the boundary matching error and another one attempts to locate the direction of minimal/maximal change in the local motion field neighborhood. Another one further adopts bilinear interpolation principles, whereas a last one additionally exploits available coding mode information. The methods present temporal EC methods for predictively coded frames or frames for which motion information pre-exists in the video bitstream. Their main advantages are their capability to adapt their behavior with respect to neighboring motion information, by switching from linear to nonlinear behavior, and their real-time implementation capabilities, enabling them for real-time decoding applications. They are easily embedded in the decoder model to achieve concealment along with decoding and avoid post-processing delays. Their performance proves to be satisfactory for packet error rates up to 2% and for video sequences with different content and motion characteristics and surpass that of other state-of-the-art temporal concealment methods that also attempt to estimate unavailable motion information and perform concealment afterwards.

주변 움직임 벡터의 적응적 선택을 이용한 효율적인 에러은닉 알고리즘

통신 기술의 발전으로 무선 채널을 이용한 멀티미디어 서비스를 제공하기 위한 방법이 활발히 연구되고 있다. 이에 따라 최근 무선망이나 인터넷과 같이 오류가 많이 발생하는 채널을 통한 비디오의 전송이 급격히 증가하면서 채널 상에서 발생하는 전송에러로 인한 데이터의 손실이 심각한 문제로 대두되고 있으며, 이에 따라 에러 은닉이 주된 관심사로 부각되었다. 에러 은닉 기법은 부가 정보가 필요 없으며, 부호화 기법의 변형 없이 적용이 가능하기 때문에 널리 연구되고 있다. 본 논문에서는, 손실된 블록 주위의 정상블록들 중 움직임 벡터들의 적응적 선택을 이용하여 중간 값을 취한 후, 손실된 블록의 새로운 움직임 벡터로 할당하고, OBMC(Overlapped Block Motion Compensation)을 통해 최종적으로 손실영역을 은닉하게 된다. 이 방법은 연속된 GOB(Group Of Block)의 손실에 있어서 효과적임을 알 수 있었다. 실험 결과 PSNR 성능평가 면에서 제안한 방법의 결과가 기존의 방법들 중 우수한 에러은닉 결과를 내는 MVRI(Motion Vector Rational Interpolation)이나 메디안<TEX>$.$</TEX>중첩 에러 은닉 기법에 비해 약 3db정도 향상된 결과를 얻을 수 있었다. In the wireless communication systems, transmission errors degrade the reconstructed image quality severely. Error concealment in video communication is becoming increasingly important because transmission errors can cause single or multiple loss of macroblocks in video delivery over unreliable channels such as wireless networks and internet. Among various techniques which can reduce the degradation of video quality, the error concealment techniques yield good performance without overheads and the modification of the encoder. In this paper, lost image blocks can be concealed with the OBMC(Overlapped Block Motion Compensation) after new motion vectors of the lost image blocks are allocated by median values using the adaptive selection with motion vectors of adjacent blocks. We know our algorithm is more effective in case of continuous GOB loss. The results show a significant improvement over the zero motion error concealment and other temporal concealment methods such as Motion Vector Rational Interpolation or Median＋OBMC by 3dB gain in PSNR.

Robust error concealment for visual communications in burst-packet-loss networks

Compressed video sequences are very vulnerable to channel disturbances when they are transmitted through the burst-packet-loss networks such as a wireless channel. An effective solution for packet loss is to perform concealment at the receiver. Most of the spatial and/or temporal concealment methods estimate the true motion vector (MV) associated with a missing block by using the MV's of the adjacent blocks. However, these methods cannot conceal effectively the missing blocks, since the neighboring blocks can be easily lost by the burst packet losses destroying a large area of coded video. In this paper, we present a robust error concealment method of estimating the true MV of the missing block by using the bidirectional motion tracking technique within neighboring frames of a damaged frame. This motion tracking technique uses the linear trajectory feature of the image block in the forward and backward prediction directions. Experimental results sow that the proposed algorithm has superior subjective and objective video quality than conventional error concealment methods in the burst-packet-loss environments.