[show abstract][hide abstract] ABSTRACT: Streaming of precoded video, which is both source and channel coded, over wireless networks faces challenges of time-varying packet loss rate and fluctuating bandwidth. Rate shaping has been proposed (Chen, T.P.-C. and Chen, T., ICASSP, 2002) to "shape" the precoded video to adapt to the real-time bandwidth requirement and the packet loss rate. We now propose a novel "fine-grained rate shaping" (FGRS) scheme to allow for bandwidth adaptation over a wide range of bandwidth and packet loss rate. The video is precoded with fine granularity scalability (FGS) followed by forward error correction (FEC) coding with erasure codes. Utilizing the fine granularity property of FGS and FEC, FGRS selectively drops part of the precoded video and still yields a decodable bitstream at the decoder. A new two-stage rate-distortion (R-D) optimization, with model-based hyper-plane and hill-climbing based refinement, is proposed to select which part of the precoded video to drop. Promising results for FGRS are shown.
[show abstract][hide abstract] ABSTRACT: Streaming of precoded video, which is both source- and channelcoded, over packet-loss networks faces challenges of the timevarying packet loss rate and fluctuating bandwidth. Rate shaping has been proposed to reduce the bit rate of a precoded video bitstream to adapt to the real-time bandwidth variation. In our earlier work, rate shaping was extended to consider not only the bandwidth but also the packet loss rate variations. In practice, the reconstructed result of the previous frame will affect the following frames if the video is predictive coded, and/or the error concealment method performed at the receiver utilizes temporal information.
[show abstract][hide abstract] ABSTRACT: Streaming of video, which is both source- and channel-coded, over wireless networks faces the challenge of time-varying packet loss rate and fluctuating bandwidth. Rate shaping (RS) has been proposed to reduce the bit-rate of a precoded video bitstream to adapt to the real-time bandwidth variation. In our earlier work, rate shaping was extended to consider not only the bandwidth but also the packet loss rate variations. Rate-distortion optimized rate adaptation is performed on the precoded video that is a scalable coded bitstream protected by forward error correction codes. In this paper, we propose an RS scheme that further takes into account the error concealment (EC) method used at the receiver. We refer to this scheme as EC aware RS (ECARS). When performing ECARS, first ECARS needs to know the benefit/gain of sending each part of the precoded video, as opposed to not sending it but reconstructing it by EC. Then given a certain packet loss probability, the expected gain can be derived and be included in the rate-distortion optimization problem formulation. Finally, ECARS performs rate-distortion optimization to adapt the rate of the precoded video. A two-stage rate-distortion optimization approach is proposed to solve the ECARS rate-distortion optimization problem. In addition to ECARS, the precoding process can be EC aware to prioritize the precoded video based on the gain. We present an example EC aware precoding process by means of macroblock prioritization. Experiment results of ECARS together with EC aware precoding are shown to have excellent performance.
[show abstract][hide abstract] ABSTRACT: We present in this paper an adaptive joint source-channel coding scheme using rate shaping on pre-coded video data. Rate shaping selectively drops portions of the video bitstream before transmitting them in order to satisfy the network bandwidth requirement. In wireless multimedia transport over heterogeneous networks, limited bandwidth is not the only issue. The high error rate of the channel should be considered as well, so channel coding is often applied. We propose a rate shaping method that drops not only the source-coding segments of the video bitstream, but also the channel-coding segments of the video bitstream, adaptively according to the network condition, in order to achieve the optimal rate-distortion performance. The proposed method is based on discrete rate-distortion combination to accomplish joint source-channel coding. We consider both the simulcast and multicast scenarios and show promising results.
[show abstract][hide abstract] ABSTRACT: Video transport over error prone channels may result in loss or erroneous decoding of the video. Error concealment is an effective mechanism to reconstruct the video content. In this paper, we review different error concealment methods and introduce a new framework, which we refer to as second-generation error concealment. All the error concealment methods reconstruct the lost video content by making use of some a priori knowledge about the video content. First-generation error concealment builds such a priori in a heuristic manner. The proposed second-generation error concealment builds the a priori by modeling the statistics of the video content. Context-based models are trained with the correctly decoded video content, and then used to replenish the lost video content. Trained models capture the statistics of the video content and thus reconstruct the lost video content better than reconstruction by heuristics.
Image Processing. 2002. Proceedings. 2002 International Conference on; 02/2002
[show abstract][hide abstract] ABSTRACT: This paper is organized as follows. In Section 2, we formulate the proposed UMPC method for modeling non- stationary and multi-modal data. Both MPC and UPC are shown to be special cases of the proposed UMPC model. We apply UMPC to error concealment in Section 3. The experiment results in Section 4 show the performance of UMPC for error concealment over conventional methods. We then conclude in Section 5. In this paper, we present a new statistical modeling technique called "updating mixture of principal components" (UMPC). UMPC specifically captures the non-stationary as well as the multi-modal characteristics of the data. Real-world data such as video data typically have these two characteristics. The video content changes over time and has a multi-modal probability distribution. We apply UMPC to perform error concealment for video data transmitted over networks with losses, and show that UMPC outperforms conventional error concealment methods.
[show abstract][hide abstract] ABSTRACT: Is there life after video coding standards? One might think that re- search has no room to advance with the video coding standards already defined. On the contrary, exciting research opportunities arise after the standards are specified. In this paper, we introduce two standard-related research areas: rate shaping and error concealment, as examples of interesting research that finds its context in standards. Experiment results are also shown.
Recent Advances in Visual Information Systems, 5th International Conference, VISUAL 2002 Hsin Chu, Taiwan, March 11-13, 2002, Proceedings; 01/2002
[show abstract][hide abstract] ABSTRACT: We propose a general framework for blind watermark detection. This framework contains a maximum-likelihood detector that utilizes the probability distribution of the original image. Other watermark detectors in literature are shown to be special cases of this framework. We demonstrate this framework in both the pixel domain and the transform domain, and show that our detector outperforms others because of 1) better modeling of the probability distribution of the original image, and 2) consideration to the human visual system in this framework.
[show abstract][hide abstract] ABSTRACT: Progressive transmission of images is very useful in many
applications, especially in image transmission over the Internet. To
view an image, people would want to see part of the image while the
image transmission is in progress, rather than having to wait until the
end of the image transmission. On the other hand, the ease of
transmission and copying of images creates the need to use digital
watermarking to embed the copyright information seamlessly into the
media. We propose a progressive image watermarking scheme. In this
scheme, the watermark is embedded in such a way that we can retrieve
part of it even when the watermarked image is still being transmitted.
As transmission progresses, the retrieved watermark has a decreasing bit
error rate. Our proposed methods not only transmit the watermarked image
progressively, but also intelligently select watermark embedding
locations robust to various attacks
Multimedia and Expo, 2000. ICME 2000. 2000 IEEE International Conference on; 02/2000