Susie J. Wee

Secure scalable streaming enabling transcoding without decryption

We present a method of secure scalable streaming (SSS) that enables low-complexity and high-quality transcoding to be performed at intermediate, possibly untrusted, network nodes without compromising the end-to-end security of the system. SSS encodes video into secure scalable packets using jointly designed scalable coding and progressive encryption techniques. This combination allows downstream transcoders to perform transcoding operations such as bitrate reduction and spatial downsampling by simply truncating or discarding packets, and without decrypting the data. Secure scalable packets have unencrypted headers that can provide hints such as optimal truncation points to downstream transcoders. Using these hints, downstream transcoders can perform RD-optimal transcoding for fine-grain bitrate reduction. The SSS transcoding operation has low complexity and is stateless, so SSS transcoders can support many simultaneous transcoding sessions. SSS works with existing scalable image and video compression standards and systems including Motion JPEG-2000, 3D subband coding, and MPEG-4 FGS.

Unbalanced multiple description video communication using path diversity

Multiple description (MD) coders provide important error resilience properties. Specifically, MD coders are designed to provide good performance when the loss is limited to a single description, but it is not known in advance which description. Apostolopoulos (2001) combined MD video coding with a path diversity transmission system for packet networks such as the Internet, where different descriptions are explicitly transmitted through different network paths, to improve the effectiveness of MD coding over a packet network by increasing the likelihood that the loss probabilities for each description are independent. The available bandwidth in each path may be similar or different, resulting in the requirement of balanced or unbalanced operation, where the bit rate of each description may differ based on the available bandwidth along its path. We design a MD video communication system that is effective in both balanced and unbalanced operation. Specifically, unbalanced MD streams are created by carefully adjusting the frame rate of each description, thereby achieving unbalanced rates of almost 2:1 while preserving MDs effectiveness and error recovery capability.

Secure scalable video streaming for wireless networks

We present a wireless video streaming system that securely and efficiently streams video to heterogeneous clients over timevarying communication links. Clients may differ in their display, power, communication, and computational capabilities and wireless channels may have time-varying bandwidths and quality levels that depend on channel usage and channel conditions. End-to-end system efficiency is achieved by placing transcoders at intermediate network nodes; these transcoders can easily adapt the video stream for particular client capabilities and network conditions. This system uses our proposed method of secure scalable streaming (SSS) to simultaneously achieve scalability, efficiency, and security. Specifically, an SSS coder encodes video into secure scalable packets by using jointly designed scalable video coding, packetization, and progressive encryption techniques. This allows downstream SSS transcoders to transcode the secure scalable packets by simply truncating or eliminating packets, and without decrypting the coded video. A key feature of SSS is that it enables low-complexity transcoding operations to be performed at intermediate network nodes without compromising the security of the end-to-end wireless streaming system.The conference proceedings are published in six volumes. Volume I deals with speech processing. Volume II deals with: speech processing; industry technology track; design and implementation of signal processing systems; neural networks for signal processing. Volume III deals with: image and multidimensional signal processing; multimedia signal processing. Volume IV deals with signal processing for communications. Volume V deals with:signal processing education; sensor array and multichannel signal processing; audio and electroacoustics. Volume VI deals with signal processing theory and methods

Rate-distortion hint tracks for adaptive video streaming

We present a technique for low-complexity rate-distortion (R-D) optimized adaptive video streaming based on the concept of rate-distortion hint track (RDHT). RDHTs store the precomputed characteristics of a compressed media source that are crucial for high performance online streaming but difficult to compute in real time. This enables low-complexity adaptation to variations in transport conditions such as available data rate or packet loss. An RDHT-based streaming system has three components: 1) information that summarizes the R-D attributes of the media; 2) an algorithm for using the RDHT to predict the distortion for a feasible packet schedule; and 3) a method for determining the best packet schedule to adapt the streaming to the communication channel. A family of distortion models, denoted distortion chains, are presented which accurately predict the distortion produced by arbitrary packet loss patterns. Two distortion chain models are examined which lead to two RDHT-based techniques. We evaluate the proposed techniques for two canonical problems in streaming media, adaptation to available data rate and to packet loss. Experimental results demonstrate that for the difficult case of nonscalably coded H.264 video, the proposed systems provide significant performance gains over conventional low-complexity streaming systems, and achieve this gain with a comparable level of complexity making them suitable for online R-D optimized streaming.

Secure scalable streaming and secure transcoding with JPEG-2000

Secure scalable streaming (SSS) enables low-complexity, high-quality transcoding at intermediate, possibly untrusted, network nodes without compromising the end-to-end security of the system S. J. Wee, J. G. Apostolopoulos (2001). SSS encodes, encrypts, and packetizes video into secure scalable packets in a manner that allows downstream transcoders to perform transcoding operations such as bitrate reduction and spatial downsampling by simply truncating or discarding packets, and without decrypting the data. Secure scalable packets have unencrypted headers that provide hints such as optimal truncation points to downstream transcoders. Using these hints, downstream transcoders can perform near-optimal secure transcoding. This paper presents a secure scalable streaming system based on motion JPEG-2000 coding with AES or triple-DES encryption. The operational rate-distortion (R-D) performance for transcoding to various resolutions and quality levels is evaluated, and results indicate that end-to-end security and secure transcoding can be achieved with near R-D optimal performance. The average overhead is 4.5% for triple-DES encryption and 7% for AES, as compared to the original media coding rate, and only 2-2.5% overhead as compared to end-to-end encryption which does not allow secure transcoding.

Field-to-frame transcoding with spatial and temporal downsampling

We present an algorithm for transcoding high-rate compressed bitstreams containing field-coded interlaced video to lower-rate compressed bitstreams containing frame-coded progressive video. We focus on MPEG-2 to H.263 transcoding, however these results can be extended to other lower-rate video compression standards including MPEG-4 simple profile and MPEG-1. A conventional approach to the transcoding problem involves decoding the input bitstream, spatially and temporally downsampling the decoded frames, and re-encoding the result. The proposed transcoder achieves improved performance by exploiting the details of the MPEG-2 and H.263 compression standards when performing interlaced to progressive (or field to frame) conversion with spatial downsampling and frame-rate reduction. The transcoder reduces the MPEG-2 decoding requirements by temporally downsampling the data at the bitstream level and reduces the H.263 encoding requirements by largely bypassing H.263 motion estimation by reusing the motion vectors and coding modes given in the input bitstream. In software implementations, the proposed approach achieved a 5/spl times/ speedup over the conventional approach with only a 0.3 and 0.5 dB loss in PSNR for the Carousel and Bus sequences.

Reversing motion vector fields

We examine the problem of estimating a reverse motion vector field from a given forward motion vector field and its motion-compensated residual. This problem has practical importance when providing reverse-play functionality in compressed video environments, where video data is stored, processed, and transported in compressed form. We present a family of algorithms that trade off motion vector accuracy for computational efficiency. Experimental results demonstrate the performance of these algorithms.

Performance of a multiple description streaming media content delivery network

Content delivery networks (CDN) have been widely used to provide reduced delay and packet loss, fault tolerance, and improved scalability for Web content delivery. Additional benefits are provided for video streaming when one designs a streaming media CDN (SM-CDN) for either conventional single description (SD) or multiple description (MD) coding. Specifically, when precise network conditions and topology are known, simulations show that an MD-SM-CDN can provide 20 to 40% reduction in distortion over a conventional SD-SM-CDN, even when the underlying CDN is not designed with MD streaming in mind. This paper examines the performance of an MD-SM-CDN as a function of different network topologies and loss conditions, and compares it with a conventional SD-SM-CDN. This examination provides insight into an MD-SM-CDNs performance when knowledge of network topology and conditions is imprecise or uncertain. Our simulations indicate that an MD-SM-CDN can provide improved performance over a conventional SD-SM-CDN over a wide range of network topologies and loss conditions.

JPSEC for Secure Imaging in JPEG 2000

In this paper, we first review the on-going JPSEC standardization activity. Its goal is to extend the baseline JPEG 2000 specification to provide a standardized framework for secure imaging, in order to support tools needed to secure digital images, such as content protection, data integrity check, authentication, and conditional access control. We then present two examples of JPSEC tools. The first one is a technique for secure scalable streaming and secure transcoding. It allows the protected JPSEC codestream to be transcoded while preserving the protection, i.e. without requiring unprotecting (e.g. decrypting) the codestream. The second one is a technique for conditional access control. It can be used for access control by resolution or quality, but also by regions of interest.

Secure transcoding with JPSEC confidentiality and authentication

The emerging JPEG-2000 part 8 security standard (JPSEC) is being defined to provide security services for JPEG-2000 images. This paper describes how confidentiality and authentication can be applied in a manner that allows mid-network adaptation of protected JPSEC streams while preserving end-to-end security. We achieved this by designing the JPSEC syntax to support the principles of secure scalable streaming and secure transcoding. Specifically, we designed JPSEC encryption methods and signaling syntax that enable an entity to securely adapt or transcode the resulting JPSEC-protected stream without requiring decryption. We discuss tradeoffs in protection, transcoding flexibility, and complexity for the different encryption methods. Furthermore, we show how authentication can be applied to verify that the secure transcoding operation was performed in a valid and permissible manner.