Video coding standards (Cntd.) • MPEG-2 (hardware technology) has been the industry-standard digital video broadcast codec for many years for high bit rate applications. MPEG-2 requires 2 Mbps of bandwidth, which is available over coaxial lines and satellite lines, to deliver broadcast-quality, jitter-free, digital video. • MPEG-4 Simple Profile (SP) and Advanced Simple Profile (ASP) were developed for streaming video over Internet connections. MPEG-4 offers a software method to compress and decompress video over a network that provides only a best-possible connection with a wide range of data rates. The result is not what viewers have come to expect from their televisions, but enough to offer interesting services and enhance the richness of the Internet experience.
Video coding standards (Cntd.) • H.264/MPEG-4 AVC addresses the needs for greater compression, leading to lower data rates, while maintaining broadcast quality for video-on-demand (VOD) and high-definition television (HDTV) needs. H.264 meets the needs of both broadcast and the Internet by cutting the MPEG-2 bit rates in about half for digital video transmission-without a loss in video quality. This advance has followed the evolution of video compression science toward higher quality and lower bandwidth, and it opens new possibilities for service providers operating over the local copper loop infrastructure. Using H.264/MPEG-4 AVC and new H.264-enabling technology platforms for encoding, transport, and decoding, Telcos and ISPs can boost their average revenue per user (ARPU) with exciting and compelling new video-on-demand, HDTV distribution, and interactive TV services. The age of IPTV over DSL has arrived.
Codecs Source: Alcatel
H.264/AVC benefits bandwidth demand, storage requirement, and download times
5.4. IPTV main building blocks Streaming Server Streaming server resides at the head- end. It can encode and stream live streams in real-time and pre-encoded streams that are stored on the video server. Streaming server transmits the streams to the switch or router which transfers them over the backbone to the central/remote offices, and from there to the end user location.
IPTV main building blocks (Cntd.) Video Server Video servers fulfill several purposes. For store and forward transmissions, video servers store digitally encoded content and stream it through level III devices via operators’ networking infrastructure. Video serversreceive newly encoded digital content that is uploaded from the streaming server. Video servers also enable time shifted TV applications. Viewers at home can then watch any program at a time convenient to them.
IPTV main building blocks (Cntd.) Level III Device A switch or router that supports multicast transmission. The router or switch resides at the head-end, interfacing with the network. Another router or switch receives data at the central office and transmits either to DSLAMS located there, or into end-user network.
IPTV main building blocks (Cntd.) DSLAM The DSLAM (Digital Subscriber Line Access Multiplexer) resides at the central office, connecting xDSL subscribers to the backbone and subsequently to the head-end. When distributing TV over IP, the DSLAM should support multicast transmission. If it doesn’t, the switch or router at the central office has to replicate each channel for each request. This can cause congestion at the DSLAM input level. If the DSLAM supports multicast, it receives one stream for each channel and replicates the stream for each end point.
IPTV main building blocks (Cntd.) CPE (Customer Premises Equipment) The equipment located at the end-point that receives the TV/IP stream. Usually the term CPE refers to the DSL modem. The DSL modem receives the stream from the DSLAM or Level III device and transfers it directly to the PC for display on the desktop or to the IP STB.
IPTV main building blocks (Cntd.) Set-top Box (STB) Gateway between TV set/PC-TV and NT (PSTN line, satellite or cable) Signal processing – receiving, decoding/decompressing STB also accepts commands from the user and transmits these commands back to the network, often through a back channel Functions - TV signal receiver, modem, game console, Web browser, e-mail capabilities, video-conferencing, cable telephony
Set-top Box (STB)– Cntd. • Components - Electronic Program Guide (EPG), CD ROM, DVD player etc. • Many STBs are able to communicate in real time with devices such as camcorders, DVDs, CD players and music keyboards • Hardware Data network interface Decoder Buffer Synchronization hardware
Set-top Box (STB) - Cntd Types of STB (1) Broadcast TV Set-top Boxes - (Thin Boxes) More elementary level set-top box with no return channel (back-end). Some memory, interface ports and some processing power. (2) Enhanced TV Set-top Boxes - (Smart TV Set-top boxes, Thick Boxes) These have a return channel, usually through a phone line. Video on Demand, Near Video on Demand, e-commerce, Internet browsing, e-mail and chat communications (3) Advanced Set-top Boxes - (Advanced digital Set-top boxes, Smart TV Set-top box, Thick Boxes) Like a PC - processors, memory and optional large hard-drives. (4) All-in-one Set-top Boxes - (Integrated Set-top box, Super Box) A fully integrated set-top box. Features could include everything from high-speed Internet access to digital video recording to games and e-mail capacity.
5.5. QoS issues for different types of traffic • Voice traffic is smooth, bandwidth-benign, drop-sensitive, and delay-sensitive, and is typically UDP-based. Bandwidth per call depends on the particular codes adopted, sampling rate, and Layer 2 media employed. Voice quality is directly affected by all three QoS quality factors (loss, delay, and delay variation). • Data traffic is much more varied. It can be smooth or bursty, bandwidth- benign or bandwidth-greedy, or drop- and delay-insensitive, and involves Transmission Control Protocol (TCP) for send/receive acknowledgment and retransmit. Traffic patterns vary by application, and data classes must support several different priorities or application categories. • Video traffic is bursty, bandwidth-greedy, drop-sensitive, and delay-sensitive. IP-based videoconferencing has some of the same sensitivities as voice traffic.
QoS issues for different types of traffic (Cntd.) Data trafficis typically handled with multiple classes, where each class can be defined and given the appropriate support based on the priority requirement of the application that is generating the traffic. In general, enterprises should restrict themselves to about five main traffic classes, such as: • Mission-critical and real-time - Transactional and interactive applications with high business priority; in some cases, real-time traffic such as voice over IP (VoIP) can be subdivided into a separate class • Transactional/interactive - Client-server applications, messaging applications (typically foreground activities that directly affect employee productivity) • Bulk - Large file transfers, e-mail, network backups, database synchronization and replication, and video content distribution (background activities that do not directly affect employee productivity and are generally time-insensitive) • Best-effort - Default class for all unassigned traffic; typically at least 25 percent of bandwidth is reserved for best-effort traffic • Scavenger (optional)—Peer-to-peer media sharing applications, gaming traffic, and entertainment traffic
QoS issues for different types of traffic (Cntd.) QoS requirements for video applications There are two main types of video applications—interactive video (such as videoconferencing) and streaming video (such as IP/TV content, which may be either unicast or multicast). Provisioning for interactive video traffic: # Packet loss should be no more than 1 percent. # One-way latency should be no more than 150 ms. # Jitter should be no more than 30 ms. # The minimum priority bandwidth guarantee is the size of the video conferencing session plus 20 percent. (For example, a 384 kbps video conferencing session requires 460 kbps of guaranteed priority bandwidth.)
QoS issues for different types of traffic (Cntd.) Streaming video applications have more tolerant QoS requirements, as they are delay insensitive and are largely jitter insensitive (due to application buffering). However, streaming video may contain valuable content, such as e-learning applications or multicast company meetings, and therefore may require service guarantees through QoS. Provisioning for streaming video traffic: # Loss should be no more than 2 percent. # Latency should be no more than 4-5 seconds (depending on video application's buffering capabilities). # There are no significant jitter requirements. # Guaranteed bandwidth requirements depend on the encoding format and rate of the video stream.
QoS issues for different types of traffic (Cntd.) Streaming video is typically unidirectional and, therefore, remote branch routers may not require provisioning for streaming video traffic on the customer edge (CE) in the direction of branch to campus. Non-important streaming video applications (either unicast or multicast), such as entertainment video, content may be provisioned in the Scavenger traffic class and assigned a minimal bandwidth percentage.
Scavenger Class The Scavenger class is intended to provide deferential services, or “less-than Best-Effort” services, to certain applications. Applications assigned to this class have little or no contribution to the organizational objectives of the enterprise and are typically entertainment- oriented. These include: • Peer-to-peer media-sharing applications (KaZaa, Morpheus, Groekster, Napster, iMesh, etc.) • Gaming applications (Doom, Quake, Unreal Tournament, etc.), and any entertainment video applications. Assigning a minimal bandwidth queue to Scavenger traffic forces it to be squelched to virtually nothing during periods of congestion, but allows it to be available if bandwidth is not being used for business purposes, such as might occur during off-peak hours.
Appendix: Bandwidth consumption of video over IP traffic in the face of competing web surfing traffic (No traffic shaping is present)
With QoS From Packet Shaper (guaranteed bandwidth of 820k for video traffic)