Juan Carlos De Martin

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— We present a new cross-layer ARQ algorithm for video streaming over 802.11 wireless networks. The algorithm combines application–level information about the perceptual and temporal importance of each packet into a single priority value, which drives packet selection at each retransmission opportunity. Hence, only the most most perceptually important(More)
—Mobile multimedia applications, the focus of many forthcoming wireless services, increasingly demand low-power techniques implementing content protection and customer privacy. In this paper low complexity perception-based partial en-cryption schemes for speech are presented. Speech compressed by a widely-used speech coding algorithm, the ITU-T G.729(More)
The IEEE 802.11 standard currently does not offer support to exploit the unequal perceptual importance of multimedia bitstreams. All packets affected by channel errors, in fact, are simply discarded, irrespective of the position and percentage of corrupted bits. The objective of this paper is to investigate the effect of bit error tolerance in WLAN speech(More)
This paper presents an analysis-by-synthesis technique to evaluate the perceptual importance of multimedia packets for rate-distortion optimized streaming. The proposed technique, instead of relying on a priori information, computes the distortion that would be caused by the loss of each single packet, including the effects of error propagation and(More)
We present a new algorithm to dynamically identify perceptually important regions in pictures of a video sequence. For each macroblock, the distortion that its loss would cause at the decoder is computed. High-distortion macroblocks are then grouped together into slices to be protected with forward error correction or to be sent as " premium " packets. We(More)
— This paper evaluates the performance of video streaming in inter-vehicular environments using the 802.11 ad hoc network protocol. We performed transmission experiments while driving two cars equipped with 802.11b standard devices in urban and highway scenarios. Different sequences, bitrates and packetization policies have been tested. The experiments show(More)
This paper presents simulation results outlining the behavior of rate-adaptive voice communications over IP networks. In the considered architecture, voice coders adapt their rate to the current state of the network so as to generate only the bandwidth that the network is capable of carrying. An algorithm is proposed for driving the transmission rate of(More)
We present a source-driven approach to packet marking for speech transmission over packet networks implementing the Differentiated Services model. Packets generated by the speech coder are examined: if deemed perceptually critical, they are marked as premium and sent on a " virtual wire; " otherwise, they are sent as regular best-effort traffic. Applied to(More)
— In video communications over IP networks, quality of service (QoS) guarantees must be introduced to limit the effect of packet losses. In particular, end–to–end QoS can be improved if packets are protected according to the distortion that would be introduced at the receiver by their loss. In the traditional Analysis–by–Synthesis (AbS) approach, each(More)