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Radvision High Quality Experience Over Unmanaged Networks By Face to Face Live


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Radvision High Quality Experience Over Unmanaged Networks By Face to Face Live

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Radvision High Quality Experience Over Unmanaged Networks By Face to Face Live

  1. 1. Face to Face Live 480.348.3400 www.facetofacelive.comA Radvision / Avaya Expert Partner
  2. 2. White Paper Maintaining A High Quality Experience Over Un managed Networks Quality of Service and Quality of Experience –Scalable Video Coding (SVC) – Unequal Error Protection (UEP) - RADVISION’s Error Resiliency Solution
  3. 3. White Paper White PaperThis paper is intended to describe the error resiliency and packet loss robustness featuresavailable in RADVISION’s products.These features include:  RADVISION’s SVC-based solution  Unequal Error Protection (UEP) tools  Packet Retransmission and VFUThe above mentioned features are available on the following products: SCOPIA Desktop V7.0 SCOPIA Elite SCOPIA BEEHD SCOPIA VC-240ContentsQuality of Service and Quality of Experience .......................................... 3Scalable Video Coding (SVC) .............................................................. 4Unequal Error Protection (UEP) .......................................................... 5RADVISION’s Error Resiliency Solution ................................................... 6RADVISION’s Solution vs. Existing Solutions............................................. 7 RADVISION WHITE PAPER | 2
  4. 4. White White Paper Paper Quality of Service and Quality of ExperienceIt is well-known that video quality in a videocall or video conference is tightly coupled withnetwork conditions. However, as videoconferencing infrastructure become massivelydeployed, it can no longer be assumed thatnetwork QoS is available, as use of non-dedicated lines and the public Internetbecomes more prevalent.In network topologies where QoS is notguaranteed, there are techniques that can beutilized to ensure a reliable channel regardlessof network conditions. These techniques canhelp maintain a high Quality of Experience(QoE) even when network quality is low, byovercoming transient packet loss situations andreducing the effects of network losses on videoquality.These error resilience techniques, however,come at a cost - either in latency, as a result ofincreased buffering, or in bandwidth, which isdirectly proportional to the bandwidth of theprotected stream and the excepted loss rate. RADVISION WHITE PAPER | 3
  5. 5. White White Paper Paper Scalable Video Coding (SVC) (UEP). This saves considerable bandwidth, while maintain a high levelAs explained in details in the RADVISION of resiliency.whitepaper “Delivering a Truly Scalable VisualCommunications Solution”, Scalable VideoCoding (SVC) allows senders to transmit a singlevideo stream, encoded once, supporting a Therefore SVC and other errorrange of resolutions, bitrates and quality resiliency techniques (such as Forwardlevels, by discarding selected data (a process Error Correction, or FEC) are notknown as “layer thinning”). competing techniques but complementing ones.But SVC introduces another significantadvantage over single-layer coding: temporalscalability. Temporal scalability introduces alayered structure of frame dependency, whichallows any network element, including thereceiving client, to decode the bit stream evenwhen some of the data is missing.Fig 1: a Temporal Scalabilitymulti-layered frame structure exampleThe layered frame structure in figure 1 is anexcellent illustration of the strength oftemporal scalability. Unlike single-layer coding,where each frame depends on the previousframe, and so a loss of any frame is significant,we can see in this example that the odd-numbered frames (1, 3, 5, etc.) can bediscarded from the stream without anyinfluence on the rest of the frames. Frames 2or 6, for instance, have limited dependency,and if lost, they will affect only one otherframe. Therefore, this layered stream inessence is much more resilient to errors than asimilar single-layer stream.The use of such a multi-layered SVC streamallows applying error resiliency techniques toparts of the stream (specific layers) only, atechnique known as Unequal Error Protection RADVISION WHITE PAPER | 4
  6. 6. White White Paper Paper Unequal Error Protection (UEP) RADVSION employs Unequal ErrorExisting error resilience techniques can be Protection (UEP) methods, designed forcategorized into two general groups: protective data protection over erroneouscoding and correction codes. Both are used to networks. UEP allows the sender toprotect data against possible data loss. protect different levels of data in different ways - therefore optimallyUsing protective coding, the encoder may protecting the SVC stream. Importantselect not to exploit all the redundancy in the data, located in the base layer of thestream for compression purposes. As a result, multi-layered stream, is highlythe stream has more redundancy, and is protected; less important data, locatedtherefore much more resilient to packet loss. in higher layers, is less protected or notOn the other hand, the compression is much protected at all.less efficient, which adversely affects quality. In case of re-transmission, only theA typical way to implement protective coding is important data will be increase the INTRA macro-block frequency in Due to the specific layer structure ofthe video stream. the RADVISION SVC stream, retransmission can be used withoutUsing correction codes, such as Forward Error introducing additional delay.Correction (FEC), an encoder can protect Exploiting these techniques, RADVISIONstreams without directly affecting coding is able to protect the stream withoutefficiency. FEC involves sending additional adding a substantial amount ofpackets to protect the data. In case data is bandwidth, as in the protective codingmissing, it can be fully restored using the FEC approach, while maintaining a verypackets. This, however, dramatically increases high quality of experience, as in thethe bandwidth required, due to the addition of correction code approach.FEC packets, and can introduce latency due tothe extra processing needed. Also, as theoverall bandwidth is limited, it may affectquality.On top of these, packet retransmission can beused, to compensate for packets lost.Depending on the senders’ and receivers’capabilities, a specific packet, or even a wholeframe, can be resent. With single-layer codingthis technique usually introduces substantiallatency and is not suitable for interactivecommunication. With the use of multi-layercoding technique, such as SVC, re-transmissioncan be used without introducing latency.The most common technique used forrecalibrating sender and receiver involvesgenerating a new key frame (INTRA frame)upon request from the receiver, using a VideoFast Update (VFU) command. RADVISION WHITE PAPER | 5
  7. 7. White Paper White Paper solution maintains the same excellent RADVISION’s Error Resiliency Solution quality at a much higher packet loss rates.RADVISION’s error resiliency solution employsthese technologies in a unique combination to As the RADVISION solution is embeddedcreate the highest quality of experience, even in all of the RADVISION product line,in error-prone network conditions. from desktop to infrastructure, users can benefit from these error-resiliencyThese technologies include: techniques in every aspect of their  Temporal Scalability, as part of the communication: H.264/SVC implementation  Point-to-point calling between  UEP using FEC desktop client, even when one (or  Packet retransmission both) of the parties are not inside the corporate LAN.  Video Fast Update (VFU)  Making a conference call using theAnother important component, required for a MCU via desktop client, even whenhigh quality experience, especially overunmanaged networks, is bandwidth the MCU or the desktop client is notmanagement. While the techniques described located in the same this document are designed to recover from  Making a video call using the VC-packet loss, effective bandwidth management 240, either point-to-point orcan help users abstain from packet loss. A through the MCU.follow-up whitepaper will cover this important  In MCU to MCU cascading, whichaspect of the RADVISION solution. allow enterprises to deploy MCUsCombining these technologies, the RADVISION across their campuses (distributedsolution guarantees high quality, regardless of model) and still maintain thethe level of packet loss, as shown in figure 2below: highest quality of experience, using a “virtual” MCU. All of these are practically impossible to achieve with traditional solutions, setting annoying and unnecessary boundaries for video conferencing deployment. RADVISIONs solution allows all the video conferencing components to communicate with one other in great synergy, even over unmanaged lines and networks.Fig 2: Quality in different Packet Loss ratesconditionsFigure 2 illustrates how H.264 offers excellentquality (shown here in terms of Peak Signal-to-Noise Ratio, or PSNR), but declines significantlywhen packet loss rate increases. RADVISION’s RADVISION WHITE PAPER | 6
  8. 8. White Paper RADVISION’s Solution vs. Existing Solutions enables an increased uptake of visual communication solutions in the enterprise arena.As seen in figure 2, video from a single layer coder,even H.264, typically cannot be used over networkswith more than 1% packet loss. State-of-the-arterror correction schemes, on top of single-layercoders, can help the video handle packet loss of upto 5%. But an H.264/SVC stream protected by UEPtechnologies can offer great unprecedented visualquality, with no artifacts, even at a packet lossrate of up to 40% packet loss.Moreover, existing error resiliency schemes, whichare applied on top of single-layer coders, yield asignificant bitrate overhead. Some protect theentire Group of Pictures (GOP), resulting in up to30% overhead and an increase in the number ofpackets, which increases the chance for packetloss. Others protect certain frames or certain areaswithin a frame, resulting in limited resiliency,especially over public Internet and networks withpacket loss rates higher than 5%.RADVISION’s protection of the SVC stream adds only10-15% overhead. The strength of the solution,however, is unrivaled. For instance, for a 512Kbpscall, with 3% packet loss, the RADVISION output isflawless, without any visible artifacts apart from anoccasional drop of frame rate to 28fps.In addition, as mentioned above, the RADVISIONsolution is embedded in all of the RADVISIONproduct line, from desktop to infrastructure. Thisallows users to benefit from these error-resiliencytechniques, without a need for specific software orhardware, offering a real high quality experience toall users at any time or location. In addition to itsinfrastructure products powered by SVC, RADVISIONwill soon introduce the SVC SDK, for vendors whowish to deploy a ready-made Scalable Video Codingengine within their products.Scalable Video Coding and Unequal Error Protectionoffer many benefits to video network infrastructure,improving error resiliency and overcoming thechallenges of maintaining a high quality experience,even over unmanaged networks. The RADVISION solution RADVISION WHITE PAPER | 7