T. V. Laskhman, A. Ortega, and A. Reibman, "VBR video: Tradeoffs and potentials," Proc. IEEE, vol. 86, pp. 952--973, 1998.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....with means # # and # # seconds, respectively (as indicated by the empirical study in [6] # # # #, and # # # ####) We assume a talkspurt and a silence period start only at a frame boundary. Video Source Model: We use video teleconferencing as an example video source. In the model we use [10], the number of packets per video frame period (i.e. 40 msec for a 25 fps frame rate) is govern by the DAR(1) model, which is a Markov chain characterized by three parameters: the mean, the variance, and #. The transition matrix is computed as: # # ## #### ### (1) where # is the autocorrelation ....

....coefficient and I is the identity matrix. Furthermore, each row of # is identical and consists of the negative binomial probabilities ## # ###### ### # #, where ## # # ### # # , and# is the peak rate. Similar to a voice source, a video source can only tolerate a 1 packet loss rate [10]. 2 Data Source Model: The arrival time of file data generated by a mobile device is assumed to be exponentially distributed with mean equal to one second. The data size, in terms of number of packets, is also assumed to be exponentially distributed with mean equal to 100 packets. Again we assume ....

T. V. Lakshman, A. Ortega, and A. R. Reibman, "VBR Video: Tradeoffs and Potentials," Proceedings of the IEEE, vol. 86, no. 5, pp. 952--973, May 1998.

....major requirements for the video streaming process to be successful. First, the amount of lost packets in the network must not be excessive. Second, the delay experienced by a video frame as it traverses the network must be constant if the display and encoder are to operate at the same frame rate [1, 2]. Both lost packets and packets that do not arrive on time to be displayed result in degradation of the video quality. Networks that can provide Quality of Service (QoS) guarantees, such as ATM, have been developed in response to the demand for the integrated delivery of new services such as ....

T. V. Lakshman, A. Ortega, and A. Reibman, "VBR Video: Tradeoffs and Potentials," Proceedings of IEEE, vol. 86, no. 5, pp. 952--973, May 1998.

....compared to the smoothing of a xed coder output, under equivalent traf c parameters and decoding constraints. I. INTRODUCTION We consider the transmission of variable bit rate (VBR) video over a network offering a guaranteed service such as ATM VBR or the guaranteed service of the IETF [1], 2] The guaranteed service requires that the ow produced by the output device conforms with a traf c envelope #, namely over anywindow of size #, the amount of data does not exceed ####. With the Resource Reservation Protocol (RSVP) # is derived from the T SPEC eld in messages used for ....

T.V. Lakhsman, A. Ortega and A. R. Reibman, VBR video: Tradeoffs and potentials, Proceedings of the IEEE, July 1997.

.... hand, characterizing the relation that exists between network parameters such as token bucket parameters and network performance, e.g. losses or delay, is a relatively well investigated area when it comes to video, and a number of works have provided guidelines on how to select parameters, e.g. [20][21] 24] and how to measure network performance [11] 22] On the other hand, determining how these translate into different levels of video quality has received little attention. As a result, one of this paper s contributions is to provide a quantitative, even if still partial, answer to this ....

T. V. Lakshman, A. Ortega, and A. R. Reibman, "VBR Video: Trade-Offs and Potentials." Proc. IEEE, pp. 952-973, May 1998.

....performance measurements using both synthetic benchmarks and actual experiments with variable bit rate MPEG 2 streams over SCSI disks. 1 Introduction Variable Bit Rate (VBR) video streams are estimated to be smaller (by 40 or more) than Constant Bit Rate (CBR) streams of comparable quality [10, 13]. Correspondingly, media servers supporting VBR streams can be expected to concurrently serve more users than their CBR counterparts, due to reduced requirements for disk space, disk bandwidth, buffer space, and network bandwidth. Nevertheless, most of the existing experimental or commercial ....

Lakshman, T. V., Ortega, A., and Reibman, A. R. VBR Video: Tradeoffs and Potentials. Proceedings of the IEEE 86, 5 (May 1998), 952--973.

....int (F int cur )is adopted in our experiment: DeltaF int (F int cur ) d0:3 Delta F int cur e# where dxe means the smallest integer greater than x. 4. FRAME RATE CONTROL FOR TIME VARYING CBR CHANNEL Time varying CBR channels include the feedback VBR and the renegotiated CBR channel [6], where the available bandwidth is time varying and can be modeled well with a piecewise constant function. This model will be valid if the bandwidth change speed is relatively low in comparison with the duration when the bandwidth is kept at a constantlevel. This model will be even more ....

T. V. Lakshman, A. Ortega, and A. R. Reibman, "VBR video: Tradeoffs and potentials," Proceeding of the IEEE,vol. 86, pp. 952--973, May 1998.

....across all the different disks, which leads to server throughput improved by several factors at high loads. 1. INTRODUCTION Variable bit rate encoding of video streams can achieve quality equivalent to constant bit rate encoding while requiring average bit rate that is lower by 40 or more [10, 13]. However, variable bit rate streams have high variability in their resource requirements which can lead to low utilization of disk and network bandwidth in the common case. This occurs because the aggregate bandwidth requirements of concurrently served streams can be significantly higher at ....

Lakshman, T. V., Ortega, A., and Reibman, A. R. VBR Video: Tradeoffs and Potentials. Proceedings of the IEEE 86, 5 (May 1998), 952--973.

....during compression, which causes quality degradation in the encoded video. With CBR encoding, the bit rate of the resulting encoded video actually fluctuates around the target CBR rate; but the video can be transmitted at the CBR rate and a small smoothing buffer at the client ensures continuity [8, 25]. For open loop VBR encoding, the quantization scale remains constant throughout the encoding process, which often produces highly variable bit rates. Digital video distribution systems using satellite and cable have avoided using VBR video due to its burstiness. Nevertheless, for a given movie ....

T. V. Lakshman, A. Ortega, and A. R. Reibman. VBR Video: Trade-offs and potentials. In Proceedings of the IEEE, volume 86, pages 952--973, May 1998.

....fluctuation of the TCP friendly flow should be smoothed in advance by the encoder decoder network de jitter buffers. A longer time scale variation can be successfully modeled into time varying constant bit rate (CBR) channels (including the feedback VBR and the renegotiated CBR channel) [27]. One may think of a layered or aggregated scalable coding scheme to tackle the bandwidth fluctuation problem in a more systematic manner. However, switching between layers of stream is a difficult task even for aggregated (i.e. simulcast) stream and it is out of our scope. Thus, in our approach, ....

T. V. Lakshman, A. Ortega, and A. R. Reibman, VBR video: tradeoffs and potentials, Proc. of the IEEE, vol. 86, May 1998.

....channel conditions, and develop an effective rate control scheme accordingly. Rate control of H.263 video over the Internet is the main focus of this work. It is well known that VBR (variable bit rate) video supports better quality than CBR (constantbit rate) video. Lakshman, Ortega and Reibman [2] classified VBR video into four classes: the unconstrained VBR, the shaped VBR, the constrained VBR and the feedback VBR. For the unconstrained VBR, if there are sufficient buffers at both the encoder and the decoder, rate control can be formulated as a optimization problem constrained to the bit ....

....out at the cost of some additional delay while the content of the bit stream is unaffected. Under the feedback VBR, the network state information is accessible to the encoder, and the encoder can adjust its bit rate according to the change of the network traffic condition. It was argued in [2] that the feedback to the video encoder is one of the key characteristics of video transmission over packet networks. However, it is not a trivial task for the encoder to adapt to the state of the network quickly. Furthermore, it may not be efficient that the network state is sent back to the ....

[Article contains additional citation context not shown here]

T. V. Lakshman, A. Ortega, and A. R. Reibman, "VBR video: Tradeoffs and potentials," Proceeding of the IEEE,Vol. 86, No. 5, May 1998, pp. 952--973.

....compared to the smoothing of a xed coder output, under equivalent traf c parameters and decoding constraints. I. INTRODUCTION We consider the transmission of variable bit rate (VBR) video over a network offering a guaranteed service such as ATM VBR or the guaranteed service of the IETF [1], 2] The guaranteed service requires that the ow produced by the output device conforms with a traf c envelope , namely over any window of size t, the amount of data does not exceed (t) With the Resource Reservation Protocol (RSVP) is derived from the T SPEC eld in messages used for ....

T. V. Lakhsman, A. Ortega and A. R. Reibman, VBR video: Tradeoffs and potentials, Proceedings of the IEEE, July 1997.

....to constrain the output of a variable bit rate (VBR) encoder to the bit rate provided by the network without sacrificing too much on the quality of the decoded video. This target bit rate that we have to achieve may be constant or variable depending on the nature of the network. Lakshman et al. [5] classify VBR video into unconstrained, shaped, constrained and feedback depending on the design of buffers for rate control, or algorithms used by the encoder to change the coding parameters using feedback information from the network. Chen and Wong [6] and Choi and Park [7] try to solve the rate ....

T. V. Lakshman, A. Ortega and A. R. Reibman, "VBR video: Tradeoffs and potentials," Proc. IEEE, vol. 86, no. 5, pp. 952-73, January 1998.

.... hand, characterizing the relation that exists between network parameters such as token bucket parameters and network performance, e.g. losses or delay, is a relatively well investigated area when it comes to video, and a number of works have provided guidelines on how to select parameters, e.g. [19][20] 23] and how to measure network performance [10] 21] On the other hand, determining how these translate into different levels of video quality has received little attention. As a result, one of this paper s contributions is to provide a quantitative, even if still partial, answer to this ....

T. V. Lakshman, A. Ortega, and A. R. Reibman, "VBR Video: Trade-Offs and Potentials." Proc. IEEE, pp. 952-973, May 1998.

....compared to the smoothing of a fixed coder output, under equivalent traffic parameters and decoding constraints. I. INTRODUCTION We consider the transmission of variable bit rate (VBR) video over a network offering a guaranteed service such as ATM VBR or the guaranteed service of the IETF [1], 2] The guaranteed service requires that the flow produced by the output device conforms with a traffic envelope , namely over any window of size t, the amount of data does not exceed (t) With the Resource Reservation Protocol (RSVP) is derived from the T SPEC field in messages used for ....

T. V. Lakhsman, A. Ortega and A. R. Reibman, "VBR video: Tradeoffs and potentials," Proceedings of the IEEE, July 1997.

....framework allows us to design and analyze a number of content adaptation strategies. We illustrate this content adaptation with a multimedia news delivery system that adapts to clients ranging from workstations to cellular phones. 1. 1 RELATED WORK Much work (for a small sampling, see [3,4,5,6]) has been done on adapting video to bandwidth variations, and sometimes screen size, by selecting a suitable compression scheme. These systems consider only a single type of media, not composite multimedia documents. Also, while a range of bandwidth variations is accounted for, drastically ....

T.V. Lakshman, A. Ortega and A.R. Reibman, VBR video: Trade-offs and potentials, Proceedings of the IEEE, to appear.

....720 x 576 pixels. The group of pictures (GOP) structure is IBBPBBPBBPBBI. i.e. it comprises 12 frames between I frames (N=12) and 3 frames between anchor frames (M=3) The picture structure is frame structure. The sequence is encoded with an openloop Variable Bit Rate (VBR) control scheme [11]; we use a fixed quantizer step size Q for I and P pictures and 1.4Q for B pictures. Motion estimation is performed with full search, 16 pixel frame (H) 16 pixel frame (V) The slice size is 45 macroblocks, which corresponds to an entire row of macroblocks in the picture. A corrupted frame is ....

T.V.Lakshman, A. Ortega, and A.R. Reibman, "VBR video: Tradeoffs and potentials", Proceedings of the IEEE., Vol. 86, No.5, May 1998

.... the use of B pictures at the expense of higher bit rates but better video quality [13] Conversely with one way video services, some experiments demonstrate the advantage of increasing the end to end delay for the purpose of smoothing the video traffic to improve the multiplexing performance [14]. When the end to end delay increases to up to two frame times, the SGM increases significantly to 35 percent. Further increases of the delay beyond three or four frames yield marginal improvements (only 2.6 percent) Other empirical measurements of MPEG over TCP and ATM recorded only 7 percent of ....

T.V Lakshman, A. Ortega and A.R. Reibman, 'VBR Video: Tradeoffs and Potentials', Proceedings of the IEEE, Vol.86, No.5, May 1998, pp.952-973.

....during compression, which causes quality degradation in the encoded video. With CBR encoding, the bit rate of resulting encoded video actually fluctuates around the target CBR rate; but the video can be transmitted at the CBR rate and a small smoothing buffer at the client ensures continuity [8] [9] For open loop VBR encoding, the quantization scale remains constant throughout the encoding process, which often produces highly variable bit rates. Digital video distribution systems using satellite and cable have avoided using VBR video due to its burstiness. Nevertheless, for a given ....

T. V. Lakshman A. Ortega A. R. Reibman, "VBR Video: Trade-offs and potentials," in Proceedings of the IEEE, May 1998, vol. 86, pp. 952--973.

....rate seems to be a desirable objective, since it would match the variable rate output of a coder to a variable transmission rate over the channel. Substantial activity in exploring VBR transmission of video dates back to the mid to late eighties (for example [21, 22, 23] and is still ongoing [24]. However, researchers have used the term VBR to describe different types of transmission modes, ranging from modes that guarantee quality of service (QoS) in the data delivery, to approaches with best effort performance, as is the case with transmission over the Internet. Each of these VBR ....

....bandwidth allocation is possible. While these potential advantages were heavily emphasized in early packet video papers, further research has shown that no design can maximize them simultaneously. In this chapter we concentrate on video coding aspects, but it is clear that, as argued in [24], a VBR transport design can have advantages for both video and network sharing and thus it would have to be evaluated based on both types of metrics. 4.2 QoS Guarantees vs Best Effort Much of the early work on packet video assumed transmission under some sort of Quality of Service (QoS) ....

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T. V. Lakhsman, A. Ortega, and A. R. Reibman, "VBR video: Trade-offs and poten- tials," Proceedings of the IEEE, vol. 86, pp. 952-973, May 1998.

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T. V. Laskhman, A. Ortega, and A. Reibman, "VBR video: Tradeoffs and potentials," Proc. IEEE, vol. 86, pp. 952--973, 1998.

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T.V. Lakshman. A. Ortega, and A. Reibman, "VBR video: Tradeoffs and Potentials ", Proc, IEEE, vol. 86, pp. 952-973, 1998.

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T.V. Laskhman. A. Ortega, and A. Reibman, "VBR video: Tradeoffs and Potentials," Proceedings of the IEEE, vol. 86, no.5, pp. 952-973, 1998.

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T. Lakshman, A. Ortega, and A. Reibman, "VBR video: Tradeoffs and potentials," Proceedings of the IEEE, vol. 86, no. 5, pp. 952--973, May 1998.

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T. Lakshman, A. Ortega, and A. Reibman, "VBR video: Tradeoffs and potentials," Proceedings of the IEEE, vol. 86, no. 5, pp. 952--973, May 1998.

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T. V. Lakshman, A. Ortega, and A. Reibman, "VBR video: tradeoffs and potentials," Proc. IEEE, vol. 86, pp. 952--973, May 1998.

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T.V. Laskhman. A. Ortega, and A. Reibman, "VBR video: Tradeoffs and Potentials ", Proc. Of IEEE, vol. 86, no.5, pp. 952-973, 1998.

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T. V. Lakshman, A. Ortega, and A. Reibman, "VBR video: tradeoffs and potentials," Proc. IEEE, vol. 86, pp. 952--973, May 1998.

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T. V. Lakshman, A. Ortega and A. R. Reibman, "VBR: Video Tradeoffs and Potentials," Proceedings of the IEEE, vol. 86, no. 5, pp. 952-73, 1998.

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