Cyril Bergeron

Unequal Error Protection for H.263+ bitstreams over a wireless IP network

This paper presents an original solution to efficiently transmit video bitstreams over an IP networked wireless channel via an unequal rate allocation protection scheme. The originality of this scheme is that it proposes a sensitivity estimation not only for the video stream itself as classically done, but also for the network headers used over the IP wireless network, here considered in their compressed version. Based on this sensitivity measure, the protection allocation algorithm is able to propose an efficient unequal rate allocation scheme using rate compatible punctured codes. Numerical results obtained in the case of H.263+ bitstreams transmitted over an error prone wireless compressed RTP/UDP/IP network show that taking into account both video and headers sensitivity allows this unequal error protection (UEP) scheme to provide PSNR improvements of about 5 dB when compared to equal error protection (EEP) scheme with a low additional complexity

Complaint Selective encryption for H.264/AVC video streams

This paper presents a novel selective encryption scheme that allows for secure transmission of video streams such as H.264/AVC ones, while keeping complete backward compatibility with the corresponding video standard. This compatibility allows consequently any standard compliant decoder to decode the ciphered stream without specific provision in terms of resynchronization procedure, albeit incorrectly from the visual point of view. The bits to be encrypted are chosen with respect to the video standard, the full compatibility being achieved by encrypting bits for which the impact of each of the encrypted configurations gives a non-desynchronized and fully standard compliant bitstream. Numerical results obtained with this partial ciphering algorithm in the context of H.264/AVC show that PSNR degradations of about 25 to 30 dB are obtained when the ciphering key is unknown

Temporal scalability through adaptive M-band filter banks for robust H.264/MPEG-4 AVC video coding

This paper presents different structures that use adaptive-band hierarchical filter banks for temporal scalability. Open-loop and closed-loop configurations are introduced and illustrated using existing video codecs. In particular, it is shown that the H.264/MPEG-4 AVC codec allows us to introduce scalability by frame shuffling operations, thus keeping backward compatibility with the standard. The large set of shuffling patterns introduced here can be exploited to adapt the encoding process to the video content features, as well as to the user equipment and transmission channel characteristics. Furthermore, simulation results show that this scalability is obtained with no degradation in terms of subjective and objective quality in error-free environments, while in error-prone channels the scalable versions provide increased robustness.

Modelling H.264/AVC sensivitity for error protection in wireless transmissions

A simple method is proposed to optimise the protection levels on the different parts of an H.264/AVC bitstream for transmission over an error-prone channel. This method relies on a semi-analytical model of the video stream sensitivity, that allows to predict the resulting distortion depending on the channel errors viewed by the video decoder. Valid for a frame, a partition or a group of pictures (GOP) by taking into account the dependencies existing between partitions and frames, the model allows to set the adapted protection for each partition or frame to minimise the overall sequence distortion for a given erroneous context by joint source channel optimisation of the compression and protection mechanisms. The method is then applied to determine the best trade-off of channel and source coding rates for a given operating point or protection rate, with equal or unequal error protection

Real-time multimedia communications in medical emergency - the CONCERTO project solution

The management of medical emergency, in particular cardiac emergency, requests prompt intervention and the possibility to communicate in real time from the emergency area / ambulance to the hospital as much diagnostic information as possible about the patient. This would enable a prompt emergency diagnosis and operation and the possibility to prepare the appropriate actions in the suitable hospital department. To address this scenario, the CONCERTO European project proposed a wireless communication system based on a novel cross-layer architecture, including the integration of building blocks for medical media content fusion, delivery and access. This paper describes the proposed system architecture, outlining the developed components and mechanisms, and the evaluation of the proposed system, carried out in a hospital with the support of medical staff. The technical results and the feedback received highlight the impact of the CONCERTO approach in the healthcare domain, in particular in enabling a prompt and reliable diagnosis in challenging medical emergency scenarios.

A robust content-based JPWL transmission over a realistic MIMO channel under perceptual constraints

This paper proposes a global approach of JPWL (ISO/IEC 15444-11) image transmission over a realistic wireless channel able to ensure the best Quality of Service (QoS). In order to exploit the channel diversity, we consider a Closed-Loop MIMO-OFDM scheme with different precoder designs. In particular, the high flexibility of QoS precoder allows taking into account the scalability of JPWL jointly with the instantaneous MIMO channel status. This increases the visual quality of received images. The monitoring of the quality is made by a reduced-reference metric (QIP) based on objects saliency and interest point, both linked to human perception. It is performed in association with a robust JPWL decoder to determine the optimal decoding configuration in terms of PSNR. The proposed scheme provides very good results and its performance is shown through a realistic wireless channel.

A real-time ciphering transcoder for H.264 and HEVC streams

This paper presents a novel approach for real-time encryption of both H.264 and HEVC encoded streams. Our method relies on structure-preserving Selective Encryption (SE) managed by a symmetric ciphering/deciphering transcoder. Developped as an autonomous tool, it can be implemented within any existing software and hardware architecture and requires very low computational cost. The Advanced Encryption Standard (AES) manages the encryption step to guarantee the protection of encrypted streams. Our method preserves source format and overall bitrate, which ensures undetectable ciphering and suitability for streaming over heterogeneous networks. Experimental evaluation of our proposed transcoder is provided in this paper and a demonstrator of an implementation on a mobile device will support these theoretical results.

Extrinsic distortion based source-channel allocation for wireless JPEG2000 transcoding systems

In this paper, we propose an extrinsic distortion-based source-channel allocation for JPWL transcoding systems. The distortion based approach is possible thanks to the extrinsic distortion estimation using information contained in the compressed bitstream. The proposed estimation method gives a coarse grain estimator of the true distortion, but keeping the same relative order of magnitude for distortion. Although coarse, this estimation can be used efficiently in a distortion based source-channel allocation strategy. Simulation results are provided in the context of JPEG2000 bitstream wireless transmissions using JPWL tools.

Adaptive M-band hierarchical filterbank for compliant temporal scalability in H.264 standard

The paper presents a solution of temporal scalability for video encoded H.264/MPEG-4 AVC bitstreams. Achieved through the concept of adaptive M-band hierarchical filterbanks, the temporal scalability is performed thanks to the application of a frame shuffling operation which allows backward compatibility with the standard to be kept. Simulation results show that this scalability is obtained with no degradation in terms of subjective and objective quality.

Extended Selective Encryption of H.264/AVC (CABAC)- and HEVC-Encoded Video Streams

This paper proposes an extended selective encryption (SE) method for both H.264/advanced video coding (AVC) (CABAC) and High Efficiency Video Coding (HEVC) streams, addressing the main security issue that SE is facing: content protection, related to the amount of information leakage through a protected video. Our contribution is the improvement in the visual distortion induced by SE approaches. Previous works on both H.264/AVC (CABAC) and HEVC limit encryption to bins treated by one specific mode of CABAC—its bypass mode—which has the advantage of preserving the overall bitrate, we propose here to also rely on the encryption of the more widely used mode of CABAC—its regular mode. This allows encryption of a major codeword for video reconstruction, the prediction modes for intra blocks/units. Disturbing their statistics may cause bitrate overhead, which is the tradeoff for improving the content security level of the SE approach. A comprehensive study of this compromise between the improvement in the scrambling efficiency and the undesirable aftereffects is presented in this paper, and a specific security analysis of the proposed CABAC regular mode encryption is conducted.