Documents disponibles écrits par cet auteur

Secure transcoders for single layer video data / Nithin Thomas in Signal processing. Image communication, Vol. 25 N° 3 (02 ex.) (Mars 2010) 

Public ISBD [article]  in Signal processing. Image communication > Vol. 25 N° 3 (02 ex.) (Mars 2010) . - pp. 196–207 Titre : Secure transcoders for single layer video data Type de document : texte imprimé Auteurs : Nithin Thomas, Auteur ; David Redmill, Auteur ; David Bull, Auteur Année de publication : 2010 Article en page(s) : pp. 196–207 Note générale : Electronique Langues : Anglais (eng) Mots-clés : H.264/AVC  Video  coding  TV  broadcasting  Security  Cryptography Index. décimale : 621.382 Dispositifs électroniques utilisant les effets des corps solides. Dispositifs semi-conducteurs Résumé : This paper considers the use of selective encryption systems for compressed video data that can support transcoding of the encrypted bit-streams without the need for decryption and re-encryption. The focus is on the use of the H.264 video codec. However, the concepts can be easily extended to any video coding standard. I-frame encryption encrypts only the intra frames, making it suitable for use with modified interframe transcoders that operate only on P and B frames. These interframe transcoders are found to offer improved performance for un-encrypted data, due to the temporal propagation of the higher quality of I-frames. The operations of both interframe open loop transcoding and Fast Pixel Domain Transcoding (FPDT) are unaffected by I-frame encryption yielding identical results. However, the lack of I-frame data causes a significant drift problem when I-frame encryption is used with a more complete Cascaded Pixel Domain Transcoder (CPDT). A modified CPDT is proposed, called Intra Block Copy (IBC) transcoding, which offers improved performance at the expense of a reduced range of possible output bitrates. Sign bit encryption systems such as Real-time Video Encryption Algorithm (RVEA) offer improved security compared to I-frame encryption. However transcoding this data can result in some sign bits being omitted causing a loss of cipher synchronization. A novel sign bit encryption technique called Synchronous Video Encryption Algorithm (SVEA) is proposed that preserves the cipher synchronization. While the operation of open loop transcoding systems is unaffected, the encryption interferes with the drift compensation in the more complex transcoders, leading to reduced performance. DEWEY : 361.382 ISSN : 0923-5965 En ligne : http://www.sciencedirect.com/science/article/pii/S0923596509001386 [article] Secure transcoders for single layer video data [texte imprimé] / Nithin Thomas, Auteur ; David Redmill, Auteur ; David Bull, Auteur . - 2010 . - pp. 196–207. Electronique Langues : Anglais (eng) in Signal processing. Image communication > Vol. 25 N° 3 (02 ex.) (Mars 2010) . - pp. 196–207 Mots-clés : H.264/AVC  Video  coding  TV  broadcasting  Security  Cryptography Index. décimale : 621.382 Dispositifs électroniques utilisant les effets des corps solides. Dispositifs semi-conducteurs Résumé : This paper considers the use of selective encryption systems for compressed video data that can support transcoding of the encrypted bit-streams without the need for decryption and re-encryption. The focus is on the use of the H.264 video codec. However, the concepts can be easily extended to any video coding standard. I-frame encryption encrypts only the intra frames, making it suitable for use with modified interframe transcoders that operate only on P and B frames. These interframe transcoders are found to offer improved performance for un-encrypted data, due to the temporal propagation of the higher quality of I-frames. The operations of both interframe open loop transcoding and Fast Pixel Domain Transcoding (FPDT) are unaffected by I-frame encryption yielding identical results. However, the lack of I-frame data causes a significant drift problem when I-frame encryption is used with a more complete Cascaded Pixel Domain Transcoder (CPDT). A modified CPDT is proposed, called Intra Block Copy (IBC) transcoding, which offers improved performance at the expense of a reduced range of possible output bitrates. Sign bit encryption systems such as Real-time Video Encryption Algorithm (RVEA) offer improved security compared to I-frame encryption. However transcoding this data can result in some sign bits being omitted causing a loss of cipher synchronization. A novel sign bit encryption technique called Synchronous Video Encryption Algorithm (SVEA) is proposed that preserves the cipher synchronization. While the operation of open loop transcoding systems is unaffected, the encryption interferes with the drift compensation in the more complex transcoders, leading to reduced performance. DEWEY : 361.382 ISSN : 0923-5965 En ligne : http://www.sciencedirect.com/science/article/pii/S0923596509001386

A video error resilience redundant slices algorithm and its performance relative to other fixed redundancy schemes / Pierre Ferré in Signal processing. Image communication, Vol. 25 N° 3 (02 ex.) (Mars 2010) 

Public ISBD [article]  in Signal processing. Image communication > Vol. 25 N° 3 (02 ex.) (Mars 2010) . - pp. 163–178 Titre : A video error resilience redundant slices algorithm and its performance relative to other fixed redundancy schemes Type de document : texte imprimé Auteurs : Pierre Ferré, Auteur ; Dimitris Agrafiotis, Auteur ; David Bull, Auteur Année de publication : 2010 Article en page(s) : pp. 163–178 Note générale : Electronique Langues : Anglais (eng) Mots-clés : Error  resilience  Video  coding  Redundant  slices  Macroblock  selection  Distortion  Forward  error  correction Index. décimale : 621.382 Dispositifs électroniques utilisant les effets des corps solides. Dispositifs semi-conducteurs Résumé : In this paper, a redundant picture formation algorithm that takes into account a given redundancy rate constraint is presented for error resilient wireless video transmission without reliance on retransmissions. The algorithm assigns priorities to macroblocks (MBs) according to two suggested metrics and ranks MBs accordingly. The first metric is based on an end-to-end distortion model and aims at maximising the reduction in distortion per redundancy bit. The end-to-end distortion accounts for the effects of error propagation, mismatch between the primary and redundancy description and error concealment. MBs providing large distortion reduction for fewer bits spent are assigned a higher priority. The second metric employs the variance of the motion vectors of a macroblock and those of its neighbouring blocks. Results show that the rate distortion metric outperforms other examined metrics by up to 2 dB. A comparison with other error resilience schemes, such as loss adaptive-rate distortion optimisation (LA-RDO) and cross packet forward error correction (FEC), is also presented. Results show that our approach outperforms the LA-RDO solution. Cross packet FEC provides better performance in the presence of random packet losses. However, results show that our approach can tackle bursty losses better. With bursty errors, the correction capabilities of the Reed-Solomon codes can be exceeded, and the availability of a coarse representation of the coded macroblocks, through a redundant slice scheme, can offer performance gains of up to 1 dB. DEWEY : 361.382 ISSN : 0923-5965 En ligne : http://www.sciencedirect.com/science/article/pii/S0923596509001404 [article] A video error resilience redundant slices algorithm and its performance relative to other fixed redundancy schemes [texte imprimé] / Pierre Ferré, Auteur ; Dimitris Agrafiotis, Auteur ; David Bull, Auteur . - 2010 . - pp. 163–178. Electronique Langues : Anglais (eng) in Signal processing. Image communication > Vol. 25 N° 3 (02 ex.) (Mars 2010) . - pp. 163–178 Mots-clés : Error  resilience  Video  coding  Redundant  slices  Macroblock  selection  Distortion  Forward  error  correction Index. décimale : 621.382 Dispositifs électroniques utilisant les effets des corps solides. Dispositifs semi-conducteurs Résumé : In this paper, a redundant picture formation algorithm that takes into account a given redundancy rate constraint is presented for error resilient wireless video transmission without reliance on retransmissions. The algorithm assigns priorities to macroblocks (MBs) according to two suggested metrics and ranks MBs accordingly. The first metric is based on an end-to-end distortion model and aims at maximising the reduction in distortion per redundancy bit. The end-to-end distortion accounts for the effects of error propagation, mismatch between the primary and redundancy description and error concealment. MBs providing large distortion reduction for fewer bits spent are assigned a higher priority. The second metric employs the variance of the motion vectors of a macroblock and those of its neighbouring blocks. Results show that the rate distortion metric outperforms other examined metrics by up to 2 dB. A comparison with other error resilience schemes, such as loss adaptive-rate distortion optimisation (LA-RDO) and cross packet forward error correction (FEC), is also presented. Results show that our approach outperforms the LA-RDO solution. Cross packet FEC provides better performance in the presence of random packet losses. However, results show that our approach can tackle bursty losses better. With bursty errors, the correction capabilities of the Reed-Solomon codes can be exceeded, and the availability of a coarse representation of the coded macroblocks, through a redundant slice scheme, can offer performance gains of up to 1 dB. DEWEY : 361.382 ISSN : 0923-5965 En ligne : http://www.sciencedirect.com/science/article/pii/S0923596509001404