M. Ghanbari. Two-layer coding of video signals for vbr networks. IEEE JSAC, vol. 7, June 1989.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....more monitoring functionalities. In [18] Wang and Zhu made a detailed overview of error control and concealment techniques. These techniques can be characterized as follows: 1) Layered coding with transport prioritization, i.e. a combination of scalability layers and error correction codes [2, 12, 21]; 2) Multiple description coding [16, 17] 3) Joint source and channel coding [1] 4) Robust waveform coding, i.e. redundancy in the waveform coding stage [6] 5) Robust entropy coding, which places redundancy in the entropy coding stage [11, 13] 6) Postprocessing at the decoder, which ....

M. Ghanbari, "Two-layer coding of video signals for VBR networks," IEEE J. Select. Areas Comm., Vol. 7, pp. 801806, June 1989.

....in Section 3.5. Finally, a frame rate scalable extension to SVIP is presented in Section 3.6 followed by a conclusion. 3. 2 Error Resilience Bandwidth scalable video compression schemes are often designed with transport prioritization in mind and produce packets that are highly inter dependent [47, 28, 45, 134, 124, 135]. In particular, it has been shown [47, 28, 45] that by separating the source material into a base layer and an enhancement layer and by applying priority queuing [28, 45] or di#erent loss probabilities [47] results superior to the one layer approach are obtained for statistically multiplexed ....

....SVIP is presented in Section 3.6 followed by a conclusion. 3. 2 Error Resilience Bandwidth scalable video compression schemes are often designed with transport prioritization in mind and produce packets that are highly inter dependent [47, 28, 45, 134, 124, 135] In particular, it has been shown [47, 28, 45] that by separating the source material into a base layer and an enhancement layer and by applying priority queuing [28, 45] or di#erent loss probabilities [47] results superior to the one layer approach are obtained for statistically multiplexed networks. However, due to the lack of prioritized ....

[Article contains additional citation context not shown here]

M. Ghanbari. Two-layer coding of video signals for VBR networks. IEEE J. Selected Area Comm., 7(5), pp. 771--81, June 1989.

....discussion on how to build a layered encoder based on these proposed coding schemes. In addition, since SPIHT exploits cross band correlation in the wavelet domain, it is not easy to separate the generated bit stream into resolution or spatial layers. Layered coding was first proposed by Ghanbari [7] and has since then become one of the most promising techniques to facilitate video streaming or delivery over heterogeneous networks. Recently, layered coding is adopted as a means to enable video distribution over networks that consist of both high and low capacity links [8, 9, 12, 2] Layered ....

M. Ghanbari, "Two-layer coding of video signals for VBR networks", IEEE JSAC, vol. 7, pp. 771-781, June 1989.

....evidence of combined source channel coding technique exists in [28] which discusses its usage for images. More recently, works presented in [8,22,35] discussed the usage of such techniques for real time services. Particular emphasis is given to scalable coding for VBR video over ATM networks in [9,12]. Data loss is a major problem for transmitting video over wireless networks. Bit error rates of around 10 to 10 may arise for long periods of time (approximately hundreds of milliseconds) especially in mobile environments. Data loss can be prevented if we used sufficient error correction ....

M Ghanbari. Two-layer coding of video signals for vbr networks. IEEE Journal on Selected Areas in Communications, 7(5):771--781, June 1989.

....computational complexity of at least O(N3 M ) DW72] which raises the need for good approximations with polynomial complexity. The hierarchical encoding technique enables us to use the resources more eciently. This encoding method has received a lot of attention from the networking community [Gha89] [KV89] 1 and is still an active research area. Hierarchical encoding is a layered way of encoding the kind of information that can appear in di erent quality levels such as audio and video data. In hierarchical encoding, the information of a session is divided into an enumerated set of levels, ....

M. Ghanbari. Two-layer coding of video signals for VBR networks. IEEE Journal on Selected Areas on Communications, 7(5):771-781, 1989.

....traf c classes with di erent QoS in terms of loss and delay. One possible approach to exploit such diversity of QoS is to transcode the MPEG video into alternative formats that can be easily mapped to the di erent QoS parameters. For instance, transcoding MPEG video into a layered representation [1, 2] would allow natural mapping of layers to trac classes with increasing loss rates. In particular, the ability of some scalable compression techniques to produce more than two layers [3] further increases the level of achievable trac di erentiation. However, this transcoding approach su ers from ....

....the entire video. This alternative formulation allows maximization of reception quality for a given cost. 3 Related Work The idea of providing di erential treatment to di erent parts of compressed digital video with di erent error sensitivity is not new. In particular, it has been shown in [1, 4] that by separating the source material into a base layer and an enhancement layer, and by applying priority queuing [4] or di erent loss probabilities [1] results superior to the one layer approach can be obtained. In terms of MPEG, it has also been shown that two layer scalable MPEG outperforms ....

[Article contains additional citation context not shown here]

M. Ghanbari, \Two-layer coding of video signals for VBR networks," IEEE J. Selected Area Comm., vol. 7, no. 5, pp. 771-81, June 1989.

.... implementable congestion control schemes, including connection admission control (CAC) and usage parameter control (UPC) To minimize the impact of delay and loss, the video community has focused on developing good error concealment algorithms and designing efficient two layer coding algorithms [1,2] for use in combination with the dual priority transport provided by ATM networks. For example, while one layer MPEG 2 [3] produces generally unacceptable video quality with a cell loss ratio of 10 3 , losses at this rate with SNR scalability (one of the four standardized layered coding ....

M. Ghanbari, "Two-layer coding of video signals for VBR networks," IEEE J. Select. Areas Commun., vol. 7, p771-781, June 1989.

.... and implementable congestion control schemes, including connection admission control (CAC) and usage parameter control (UPC) To minimizethe impact of delay and loss, the video community has focused on developing good error concealment algorithms and designing efficient two layer coding algorithms [1,2] for use in combination with the dual priority transport provided by ATM networks. For example, while one layer MPEG 2 [3] produces generally unacceptable video quality with a cell loss ratio of 10 3 , losses at this rate with SNR scalability (one of the four standardized layered coding ....

....deviation s i . The modified covariance method [26] is used to evaluate the autoregressive parameters. We explored the general p th order ARP, and determined using the Akaike information criterion [26] that the optimal order was p = 1 for this data. The ARP parameters are given by a = c rr [1, 0] c rr [1, 1] 4a) and s 2 = c rr (0, 0) a c rr (0, 1) 4b) where c rr ( j, k) 1 N 1 N 1 n=1 S r(n j) r(n k) 5) is the modified covariance function and N represents the number of samples over which the covariance function is evaluated. Next, we test the hypothesis that ....

[Article contains additional citation context not shown here]

M. Ghanbari, "Two-layer coding of video signals for VBR networks," IEEE J. Select. Areas Commun. , vol. 7, p771-781, June 1989.

....# # ## # # ### # # # ### in this case. We assume that receiving a portion of the packets of a layer improves the reception quality as compared to receiving no packet of the layer. This assumption is realistic as packet loss causes a graceful degradation in signal quality in many coding schemes[6]. For example, in [6] signal exhibits a reasonable enhancement in quality above the lowest layer for ### packet loss in the next higher layer. This transition is gradual up until #### packet loss in the next higher layer. Real time transmission in internet uses these coding schemes, because packet ....

....# # ### in this case. We assume that receiving a portion of the packets of a layer improves the reception quality as compared to receiving no packet of the layer. This assumption is realistic as packet loss causes a graceful degradation in signal quality in many coding schemes[6] For example, in [6] signal exhibits a reasonable enhancement in quality above the lowest layer for ### packet loss in the next higher layer. This transition is gradual up until #### packet loss in the next higher layer. Real time transmission in internet uses these coding schemes, because packet losses are frequent. ....

M. Ghanbari. Two-Layer Coding of Video Signals for VBR Networks. IEEE Journal on Selected Areas in Communications, VOL. #. No. #. June ####

....the VBR video bit stream transmitted by the source so that it conforms to the specified UPC contract and buffer constraints, while keeping picture quality degradations within acceptable levels. This approach is known as source rate control [5, 6] and also employs DP at the source. In earlier work [9, 10, 11], DP was based on splitting the DCT coefficients at some predetermined point resulting in two partitions of the bit streams, but in recent works, adaptive DP algorithms have been proposed. Luo and El Zarki [6] designed an adaptive DP scheme within the MPEG framework, which has the capability of ....

M. Ghanbari, "Two-Layer Coding of Video Signals for VBR Networks", IEEE J. on Sel. Areas in Commun., Vol. 7, Jun. 1989.

....(ADP) Scheme. ADP splits the MPEG 2 video bitstream into two sub bitstreams. This split is done by taking into account the relevance of the different pieces of information of the original MPEG 2 encoded bitstream. ADP offers advantages over similar hierarchical schemes proposed in the past [9][10] 13] Under this scheme, low frequency coefficients together with other relevant information, are transmitted at a high priority level, also denominated base layer. High frequency coefficients and other less important information are then transmitted at a lower priority level, also denominated ....

M. Ghanbari "Two-Layer Coding of Video Signals for VBR Networks" IEEE Journal on Selected Areas in Communications, Vol. 7, No. 5, June 1989, pp. 771-781.

....to achieve better results. I. INTRODUCTION N ETWORKED multimedia services, such as teleconferencing, video on demand, and distance learning are emerging. In these applications, it is often needed to adapt the bitrate of the coded video bit streams to the available bandwidth of various channels [1] [5] In a heterogeneous network, the bitrate adaptation allows different end users with different subnetworks to have different quality of service (QoS) based on their available network bandwidths. For some real time video coding applications, the adaptation of the bitrates can be achieved ....

M. Ghanbari, "Two-layer coding of video signals for VBR networks," IEEE J. Select. Areas Commun., vol. 7, pp. 771--781, June 1989.

.... the previous frame and interpolations from the adjacent blocks of the current frame [22] A second approach divides the discrete cosine transform (DCT) coefficients of a frame into layers so that in overload situations the lower layers can be discarded, resulting in an image of a lower quality [5, 11]. The third technique involves sending adjacent pixels in different packets, so that lost packets do not imply localized pixel loss, and each lost pixel usually has undamaged neighbors [19, 20] l PB FF Rew Figure 1: Model of a user watching a video 3 QoS Metrics This section describes the ....

GHANBARI, M. Two-Layer Coding of Video Signals for VBR Networks. IEEE Journal on Selected Areas in Communications 7, 5 (June 1989), 771--781.

....For example, video using interframe compression produces much lower information rates when there is little motion or change between frames, but generates very high bit rate peaks when there are scene changes or fast motion. Peak to mean bit rate ratio for VBR codecs is usually very high. In [Ghanbari89] the value 4.7 is reported for one particular codec. The use of VBR coding is based on the capability of packet switching networks to use statistical multiplexing for efficient utilization of network resources. One can then economize on resources when the information content of the signal is low ....

....important in the future. Hierarchically coded media transmission is ideally positioned to take advantage of these developments. 3. Hierarchical Coding Hierarchical coding techniques (also referred to as component, layered, or sub band coding) split signals into components of varying importance [Ghanbari89, Karlsson89]. The aggregation of these components reconstructs the original data, but subsets of them can also provide various degrees of approximation to the original signal. For example, a simple form of hierarchical coding could decompose a video frame into two sub frames: 1) a low resolution component ....

[Article contains additional citation context not shown here]

M. Ghanbari, "Two-Layer Coding of Video Signals for VBR Networks," IEEE Journal on Selected Areas in Communications Vol. 7(5), pp. 771-781 (June 1989).

....and produce heavy volumes of bursty network traffic. In addition, interactive real time applications, e.g. teleconferencing, introduce strict delay constraints. Hierarchical Coding (HC) also referred to as layered coding, techniques split signals into components of varying importance [1] [2]. The aggregation of these components reconstructs the original data, but subsets of the components can also provide various degrees of approximation to the original signal. HC is very important for the efficient use of high speed packet switching networks such as the emerging Broadband Integrated ....

....with Fig. 2(c) V. Networking Applications of HJPEG The advantages of hierarchical coding for various applications, e.g. congestion control in high speed networks, accommodation for heterogeneous end devices, and error resiliency in network transmission have been presented in many papers [2], 12] 6] In this section, some potential applications of HJPEG are discussed. A. Multimedia Database Browsing As multimedia databases, dealing mostly with images, are widely used, content based information retrieval [16] has gained attention in the database community. This trend of treating ....

M. Ghanbari, "Two-Layer Coding of Video Signals for VBR Networks," IEEE Journal on Selected Areas in Communications, Vol 7, No. 5, pp. 771-781, June 1989.

.... Layered encoding is founded on the notion that the output of a source coder can be partitioned into an essential layer (which is critical for conveying basic information content of the image) and enhancement layers (which when added to the the essential layer recreate the signal more fully) [3, 4, 5, 6, 7, 11]. Consequently, transport protocols that employ layered encoding techniques arrange the contents of the essential and enhancement layers into packets of high and low priority, respectively, and then ensure that all the high priority packets are timely delivered to each of the client sites. Since ....

M. Ghanbari. Two-Layer Coding of Video Signals for VBR Networks. IEEE Journal on Selected Areas in Communications, 7(5):771--781, June 1989.

....evidence of combined source channel coding technique exists in [24] which discusses its usage for images. More recently, works presented in [7,18,31] discussed the usage of such techniques for real time services. Particular emphasis is given to scalable coding for VBR video over ATM networks in [8,11]. Data loss is a major problem for transmitting video over wireless networks. Bit error rates of around 10 Gamma3 to 10 Gamma2 may arise for long periods of time (approximately hundreds of milliseconds) especially in mobile environments. Data loss can be prevented if we used sufficient ....

M Ghanbari. Two-layer coding of video signals for vbr networks. IEEE Journal on Selected Areas in Communications, 7(5):771--781, June 1989.

....produced by the coding scheme, but instead, an effort is made to produce constant quality signal at a given average bit rate (or level of quality) by using Variable Bit Rate (VBR) schemes. Peak to mean bit rate ratios for VBR codecs is usually high; a 4. 7 value is reported for one particular codec [2]. 2 HAN POLYZOS The use of VBR coding is based on the capability of packet switching networks to use statistical multiplexing for efficient utilization of network resources. One can then economize on resources when the information content of the signal is low and expend them at a higher rate ....

.... many facets of image and video transmission [5] 6] 7] LC with a variable spatial resolution [8] has received less attention than LC with a fixed resolution, despite its adoption in some popular coding standards [9] 10] 11] Two layer coding has been mostly considered in the literature [2], 5] 7] 12] 13] with the first, coarse or low frequency, subsignal usually referred to as the base layer, and the second, higher resolution, subsignal termed the enhancement layer. We use the term Multi resolution Layered Coding (MLC) to refer to LC with more than two layers of spatial ....

M. Ghanbari, "Two-layer coding of video signals for VBR networks, " IEEE Journal on Selected Areas in Communications, Vol. 7, No. 5, pp. 771-781, June 1989.

....modes in H.263, independent segment decoding, and dynamic reference picture selection [14, 79] These schemes can only limit adverse effects of error propagation due to prediction coding. Layered coding (LC) has been an area of active research in the past decade in the context of ATM [3, 23, 48, 85] and wireless networks [30, 32, 84] Layered coding partitions data into a base layer and a few enhancement layers. The base layer contains visually important video data that can be used to produce output of acceptable quality, whereas the enhancement layers contain complementary information that ....

M. Ghanbari. Two-layer coding of video signals for VBR networks. IEEE journal on Selected Areas in Communications, 7:801-806, June 1989.

....out that the base flow decoded by itself yields a low quality picture. Another way is to encode the n DCT coefficients with the highest energy in the base flow. Another way is to encode in the base flow only those coefficients with energy higher than some threshold. Yet other ways are described in [9, 4, 8]. Recent work indicates that the energy threshold approach yields good quality video flows yet requires little CPU power [6] However, layered coding is useful if the nodes in the multicast tree are able to selectively forward one or both flows to a specific branch. Furthermore, it should also be ....

....Using a higher priority for packets from the base flow guarantees a minimal video quality even during periods of network congestion. If one such packet is lost, then corresponding data sent in the other flow is useless, and the quality of the video delivered to the destinations is disappointing [9]. Unfortunately, current routers in the Internet are not smart enough to handle selective forwarding and or priority queues. Furthermore, we note that video flows encoded with layered coding might not be compatible with hardware codecs. Consider for example the frequency truncation scheme ....

M. Ghanbari, "Two-layer coding of video signals for VBR networks", IEEE JSAC, vol. 7, no 5, pp. 771781, June 1989.

.... the previous frame and interpolations from the adjacent blocks of the current frame [22] A second approach divides the discrete cosine transform (DCT) coefficients of a frame into layers so that in overload situations the lower layers can be discarded, resulting in an image of a lower quality [4, 10]. The third technique involves sending adjacent pixels in different packets, so that lost packets do not imply localized pixel loss, and each lost pixel usually has undamaged neighbors [19, 20] 3 QoS Metrics This section describes the performance metrics we have used to evaluate the proposed ....

GHANBARI, M. Two-Layer Coding of Video Signals for VBR Networks. IEEE Journal on Selected Areas in Communications 7, 5 (June 1989), 771--781.

....layer is added, there is an improvement of quality of the received signal and additional bandwidth is needed to transport the combined stream. Hierarchical coding was first suggested for packet voice transmission[6] and subsequently several coding schemes have been proposed for video, e.g. 1] [15], 32] to name a few. Some of these are amenable to tuning of layer bandwidths. Tuning of layer bandwidths become trivial if an embedded code is used. In an embedded code, any prefix of a valid codeword is a valid codeword and if the code is chosen appropriately, the prefix codeword corresponds ....

....queueing for example, with different weights for different layers[8] The required weights can be computed easily with the knowledge of layer bandwidths and the maxmin fair session link rates. For certain coding schemes, packet loss causes a graceful degradation in signal quality. For example, in [15] signal exhibits a reasonable enhancement in quality above the base layer for 10 enhancement layer packet loss. This transition is gradual up until 100 enhancement layer packet loss. This mechanism will be useful in these coding schemes. We would like to comment on our assumption that all ....

M. Ghanbari. Two-Layer Coding of Video Signals for VBR Networks. IEEE Journal on Selected Areas in Communications, VOL. 7. No. 5. June 1989:

....source encodes its signal into a number of layers that can be incrementally combined to provide progressive refinement in quality. Hierarchical coding was first suggested for packet voice transmission[7] Subsequently, several hierarchical coding schemes have been proposed for video, e.g. 1] [16], 33] to name a few. Layer structure may be fixed and predetermined because of several reasons. Certain coding schemes are not amenable to dynamic layer bandwidths because of their inherent structure, e.g. perceptually weighted wavelets using hierarchical vector quantization with wavelet ....

M. Ghanbari. Two-Layer Coding of Video Signals for VBR Networks. IEEE Journal on Selected Areas in Communications, VOL. 7. No. 5. June 1989.

....is added, there is an improvement of quality of the received signal and additional bandwidth is needed to transport the combined stream. Hierarchical coding was first suggested for packet voice transmission[5] Subsequently, several hierarchical coding schemes have been proposed for video, 1] [9], 22] to name a few. Here, 19] assumes that the source coder is programmable, and the source can modify its signals hierarchical structure. Once the fair rates are computed, the source partitions its signal to form as many layers as there are distinct receiver rates and tunes the layer ....

....source encodes its signal into a number of layers that can be incrementally combined to provide progressive refinement in quality. Hierarchical coding was first suggested for packet voice transmission[5] Subsequently, several hierarchical coding schemes have been proposed for video, e.g. 1] [9], 22] to name a few. Layer structure may be fixed and predetermined because of several reasons. Certain coding schemes are not amenable to dynamic layer bandwidths because of their inherent structure, e.g. perceptually weighted wavelets using hierarchical vector quantization with wavelet ....

M. Ghanbari. Two-Layer Coding of Video Signals for VBR Networks. IEEE Journal on Selected Areas in Communications, VOL. 7. No. 5. June 1989:

....encoded via zig zag scanning, run length encoded and then a VLC table. See [4, 3, 1] for more details. Previous researchers have applied the idea of partitioning the data into higher and lower priority data in the context of ATM or other packetized networks to achieve better error resilience [5, 6]. However, this may not be possible over channels such as existing analog phone lines or wireless networks where it may be difficult, if not impossible, to prioritize the data being transmitted. Hence, it becomes necessary to resort to other error concealment techniques to mitigate the effects of ....

M. Ghanbari, "Two-layer coding of video signals for vbr networks," IEEE Journal Selected Areas in Communications, vol. 7, pp. 771--781, June 1989.

....coding algorithms maintain a constant bit rate regardless of the contents of the frames [11, 38, 78, 81] Thus, the image quality varies from frame to frame. In VBR video coding algorithms, the size of the compressed frame varies from frame to frame and a constant image quality can be maintained [21, 26, 75]. 3 VBR video coding algorithms are tailor made for packet switched networks for several reasons [36, 50, 58] First, packet switched networks provide the flexibility of statistical resource sharing by several VBR video sources [39] Thus, if a video source does not use up all the bandwidth, ....

....Care must be taken to see that the processing overheads at the end users do not delay the video traffic too much and that the loss is not significant enough to affect the end user s satisfaction with the received image. 3. 4 Video Coding Algorithms Various coding schemes are available for video [15, 21, 53, 76]. This section presents some of the video coding algorithms based on the image compression techniques discussed in the previous section. Video coding algorithms can be classified as intraframe and interframe coding algorithms. Intraframe coding algorithms encode an image based on the redundant ....

M. Ghanbari, "Two-layer coding of video signals for VBR networks", IEEE Journal on Selected Areas in Communications, Vol. 7, No. 5, pp. 771-781, June 1989.

....ability to adapt to different qualities of service, and may be willing to reduce their quality requirements in cases of network saturation. For example, some video coders are designed with tunable parameters so that the compression ratio can be adjusted to output streams with different bit rates [17, 29, 26]. When the network is less loaded, we would 7 The maximum bandwidth of each link in the network is 100 Mbps. For the sake of simplicity, we assume that only one performance parameter, the throughput, is guaranteed; however, this example can be applied to other performance parameters such as ....

M. Ghanbari. Two-layer coding of video signals for VBR networks. IEEE Journal on Selected Areas in Communications, 7(5):771--781, June 1989.

....such as conferencing. Thus, the scheduling discipline chosen should reflect this difference in performance criteria. Another example scenario could be hierarchical source coding for video applications wherein the digitized video signal is separated into subsignals of differing importance [7, 8]; the relatively stable background information in a picture is separated from the information pertaining to motion. The information content of a scene, in terms of bits needed to represent it, would depend on the degree of activity in the scene. While the volume of information content could be ....

Ghanbari, M., "Two-Layer Coding of Video Signals for VBR Networks", IEEE, Journal on Selected Areas in Communications, vol. 7, pp. 771-789, June 1989.

....in layers, so that the participants can receive the stream partially (only a subset of total number of layers) if there is not enough capacity to receive the full stream. Such streams are said to be hierarchically encoded. Extensive research has been conducted on hierarchical coding in the past [3, 5, 4, 7, 15]. In most of these approaches, a stream (audio or video) is partitioned into a base layer and a number of enhancement layers. The base layer comprises of the information that is needed to represent the lowest fidelity video (or audio) and each enhancement layer improves upon the reception fidelity ....

M. Ghanbari. Two-layer coding of video signals for VBR networks. IEEE Journal on Selected Areas in Communication, 7(5):771--781, June 1989.

.... various approaches have been proposed to combat the cell loss problem in Discrete Cosine Transform (DCT) based as well as other coding systems [1] One popular method is to exploit the insensitivity of the human visual system to the high frequency component of video signals by using layered coding [2] [3] 4] With such schemes, the lowfrequency coefficients and other more important information (such as coding modes and motion vectors) are transmitted with a higher level of priority and protection than for the less important high frequency components. To limit error propagation in coders using ....

M. Ghanbari, "Two-layer coding of video signals for vbr networks," IEEE Journal Selected Areas in Communications, vol. 7, pp. 771--781, June 1989.

....to receive all these broadcasts simultaneously, it might want to emphasize only on certain broadcasts at a given time (like receiving full quality video from the football game and only the audio from the presidential debate) Moreover, these preferences may change over time. Hierarchical encoding [3, 5, 4, 6, 11] is an efficient technique to cater to the requirements of such heterogeneous receivers. In this technique the source encodes the audio or video stream into various partitions, or layers (typically a base layer and a number of enhancement layers) Each of the layers are transmitted separately, ....

....Figure 2: Transmission of image data in layers 3. 1 Hierarchical Encoding Decoding Service There are several hierarchical encoding techniques that exploit the fact that video signals are composed of a series of video frames with intra frame spatial correlation and inter fame temporal correlation [3, 5, 4, 6, 11]. These techniques differ with respect to their susceptibility to errors and packet losses, error recovery features, state information and bandwidth requirements of different layers. However, their software implementations tend to be computationally intensive and no system level hardware is ....

M. Ghanbari. Two-layer coding of video signals for VBR networks. IEEE Journal on Selected Areas in Communication, 7(5):771--781, June 1989.

....forwarding of streams scheme allows us to use the standard UNI signaling in ATM networks, and utilize end to end functionality to provide transport of layered streams. We do not focus on the various schemes for hierarchical encoding. Readers can refer to the past research done in in this area [4, 6, 5, 8, 15]. The rest of the paper is organized as follows. Section 2 gives an overview of the HMC architecture over ATM. Section 3 describes the deficiencies in UNI 2 and describes some mechanisms which are required in addition to UNI signaling to deal with hierarchically encoded streams. Section 4 ....

M. Ghanbari. Two-layer coding of video signals for VBR networks. IEEE Journal on Selected Areas in Communication, 7(5):771--781, June 1989.

.... approaches have been proposed to combat the cell loss problem in Discrete Cosine Transform (DCT) based as well as other coding systems [24] One popular method is to exploit the insensitivity of the human visual system to the high frequency component of video signals by using layered coding [25] [26] 27] With such schemes, the low frequency coefficients and other more important information (such as coding modes and motion vectors) are transmitted with a higher level of priority and protection than for the less important high frequency components. To limit error propagation in coders ....

M. Ghanbari, "Two-layer coding of video signals for vbr networks," IEEE Journal Selected Areas in Communications, vol. 7, pp. 771--781, June 1989.

....adapt to different qualities of service, and may be willing to reduce their quality requirements in cases of network saturation. For example, some video coders are designed with tunable parameters so that the compression ratio can be adjusted to output streams with different bit rates [DB89, KV88, Gha89] When the network is less loaded, we would like the compression ratio to be small so that we can have higher video quality; however, when the network is close to saturation, we would like to increase the compression ratio so that we can admit more connections. Such adaptation, also known as ....

M. Ghanbari. Two-layer coding of video signals for VBR networks. IEEE Journal on Selected Areas in Communications, 7(5):771--781, June 1989.

....of the video signal are placed in separate packets. There will only be a small degradation in picture quality if these packets are lost because the human eye is relatively insensitive to the higher frequency components of a video signal. Other applications of multiversion messages are discussed in (Ghanbari 1989; Karlsson and Vetterli 1989; Kim and Towsley 1986; Vetterli and Garrett 1990; Yemini 1983) 4.3.1. Issues in Version Selection for Multiversion Messages When using multiversion messages, the transmission control process employs a version selection scheme to decide which version of a message ....

Ghanbari, M. 1989. Two-layer coding of video signals for VBR networks. IEEE Journal on Selected Areas in Communications, 7(5):771--781.

....redundancies uses error correction codes [1, 2, 7] to add redundancy into packets before transmitting them and recovers data in case of loss. These schemes consume more bandwidth and are not effective for high loss rate and bursty losses. Non redundant transmission and error concealment schemes [3, 4, 6, 8, 9, 11], on the other hand, recover lost pixels from those received within a tolerable range by using the inherent redundancies of source data. These schemes 800 600 400 200 0 200 0 2 4 6 8 10 12 14 Sample Number original signal simple averaging trans. averaging original samples received ....

M. Ghanbari. Two-layer coding of video signals for vbr networks. IEEE journal on Selected Areas in Communications, 7(5):771--781, June 1989.

.... retransmission query protocols sacrifice visual quality for higher compression by lowering the data transmission rate while resending requested data [2] Although some networks provide layered transmission, in which high priority data experiences a lower packet loss rate than low priority data [3, 4], packet loss is still experienced to some extent by all data. When subband coded images are transmitted over a lossy packet network, lost coefficients have varying effects on the synthesized image. Lost high frequency coefficients may result in aliasing, blurring, or have negligible visual ....

M. Ghanbari, "Two layer coding of video signals for VBR networks," IEEE J. Select. Areas Comm., Vol. 7, No. 5, pp. 771-781, June 1989.

.... active voice cells. Once the cell priority has been determined using one of the above methods, low priority cells can be discarded when congestion occurs. Discarding cells based on the importance of their contents may also be applied to video traffic. For example, embedded coding techniques 2 [42, 43, 44] can be used to separate image information into two streams: a stream containing essential information, and a stream containing picture enhancement information. Cells containing essential information are given higher priority than those containing picture enhancements. Even when networks become ....

M. Ghanbari, "Two-Layer Coding of Video Signals for VBR Networks," IEEE J. Select. Areas Commun., Vol. 7, No. 5, pp. 771-781., June 1989.

....out that the base flow decoded by itself yields a low quality picture. Another way is to encode the n DCT coefficients with the highest energy in the base flow. Another way is to encode in the base flow only those coefficients with energy higher than some threshold. Yet other ways are described in [9, 4, 8]. Recent work indicates that the energy threshold approach yields good quality video flows yet requires little CPU power [6] However, layered coding is useful if the nodes in the multicast tree are able to selectively forward one or both flows to a specific branch. Furthermore, it should also be ....

....Using a higher priority for packets from the base flow guarantees a minimal video quality even during periods of network congestion. If one such packet is lost, then corresponding data sent in the other flow is useless, and the quality of the video delivered to the destinations is disappointing [9]. Unfortunately, current routers in the Internet are not smart enough to handle selective forwarding and or priority queues. Furthermore, we note that video flows encoded with layered coding might not be compatible with hardware codecs. Consider for example the frequency truncation scheme ....

M. Ghanbari, "Two-layer coding of video signals for VBR networks", IEEE JSAC, vol. 7, no 5, pp. 771781, June 1989.

....5. I B B P B B P B B P B B P B B I Figure 3.1: A typical MPEG group of pictures (The direction of arrows indicate which picture depends on which) Mapping of the H. 261 encoding onto a hierarchical scheme has already been suggested in a number of papers dealing with error control of VBR video on ATM [52 54]. In these schemes, conventional H.261 encoding is used as the base layer which is said to be given a guaranteed delivery service. Then an enhancement layer is created on top of the base level that increases the fidelity of the coding. In the proposed schemes of Ghanbari and Morrison, the ....

....of Service flags discussed previously, the minimum base level being classified as more important . This is used by the switches to decide which packets to trash when the switch buffers overflow because of increasing queue sizes. This method of error control for video has been discussed before in [54]. When a stream first starts transmitting, it transmits only the base level of the coded video, and transmits this at the lower level of importance for a given period. It is also transmitted with the low delay option of the ToS field set. We can thus model the start of the new flow as a step ....

[Article contains additional citation context not shown here]

M Ghanbari, "Two-Layer Coding of Video Signals for VBR Networks," IEEE Journal on Selected Areas in Communications 7,5 (June 1985), 771--781.

....function that permit to translate the user frame rate to the corresponding X transport throughput for X assuming max, min, average value. Frame rate may represent the video frame rate, the audio sample rate, etc. requested by the user. However with the emergence of layered variable rate (VBR) [GAN89] coding for video the server can send different video qualities depending on the user wishes. Indeed the video layered coding consists of coding video data in several layers. High resolution information (e.g chrominance) is contained in the high layers while low resolution information The QoS ....

M.Ghanbari, Two-Layer Coding of Video Signals for VBR Networks, IEEE Journal on Selected Areas in Communications, Volume 7 No.5, 1989

....schemes. For example, video using interframe compression produces much lower information rates when there is little motion or change between frames, but generates very high bit rate peaks when there are scene changes or fast motion. Peak to mean bit rate ratio for VBR codecs is usually high. In [4] the value 4.7 is reported for one particular codec. VBR coding is used in order to take advantage of the capability of packet switching networks to use statistical multiplexing for efficient utilization of network resources. One can then economize on resources when the information content of the ....

....quality at a given cost. A more complete discussion of VBR video coding in a high speed network environment is provided in [8] 1. 1 Hierarchical Coding Hierarchical coding techniques (also referred to as component, layered, or sub band coding) split signals into components of varying importance [4, 5]. The aggregation of these components reconstructs the original data, but subsets of them can also provide various degrees of approximation to the original signal. For example, a simple form of hierarchical coding could decompose a video frame into two sub frames: 1) a low resolution component ....

M. Ghanbari, "Two-Layer Coding of Video Signals for VBR Networks," IEEE Journal on Selected Areas in Communications, Vol. 7(5), pp. 771-781 (June 1989).

No context found.

M. Ghanbari. Two-layer coding of video signals for vbr networks. IEEE JSAC, vol. 7, June 1989.

No context found.

M. Ghanbari. Two-layer coding of video signals for VBR networks. IEEE Journal on Selected Areas in Communications, 7(5):771--781, June 1989.

No context found.

M. Ghanbari, "Two-layer coding of video signals for VBR networks," IEEE J. Select. Areas Commun., vol. 7, pp. 801-806, June 1989.

No context found.

M. Ghanbari, "Two-layer coding of video signals for VBR networks," IEEE Journal on Selected Areas in Communications, vol. 7, pp. 771--781, June 1989.

No context found.

M.Ghanbari. Two-Layer Coding of Video Signals for VBR Networks. IEEE Trans. Selected Areas in Commun., Vol. 7, No. 5, June 1989.

No context found.

M. Ghanbari, Two-layer coding of video signals for VBR networks, IEEE JSAC, 1989

No context found.

H. Ghanbari, "Two-layer coding of video signals for VBR networks ", IEEE JSAC, vol. 7, no 5, pp. 771-781, June 1989.

No context found.

M. Ghanbari, "Two layer coding of video signals for VBR networks," IEEE J. Select. Areas Comm., Vol. 7, No. 5, pp. 771-781, June 1989.

First 50 documents  Next 50

Online articles have much greater impact   More about CiteSeer.IST   Add search form to your site   Submit documents   Feedback  

CiteSeer.IST - Copyright Penn State and NEC