IS MPEG-2 OUR NEW LEGACY?

Yasser Syed, Ph. D., Mukta Kar Ph.D. Cable Television Laboratories & Vinay Sathe, Ph.D. Multirate Systems

Abstract content. End users are now interested in “my 500 channels” rather than the standard “500 Cable operators have been looking at channels” on their cable networks. advanced in order to make more Proliferation of new digital services such as bandwidth available to meet ever-growing VOD, HDTV, DOCSIS, VOIP has increased user demands on cable networks, the need to be able to send more bits on the same pipe. This paper investigates the issues related to introduction of a new video compression Does the bandwidth crunch necessitate format in cable networks and how it can co- moving to new video compression exist with “legacy” MPEG-2 deployments. technologies? Yes and no. In this paper, we present the case that new compression formats should be looked at as complementing the INTRODUCTION MPEG-2 based deployments in the near term, not replacing them. The introduction of new The introduction of services video (and audio) codecs can act as a part of a using MPEG-2 over 10 years ago was done to bandwidth reclamation strategy instead of a meet several objectives: ability to provide complete overhaul of a cable network. hundreds of television programs, reduce capex and opex related to acquisition and In this paper we first list some bandwidth distribution, to name a few. The transition savings strategies in cable networks that can from analog to digital required plant upgrades, help reduce the bitrate needs without new encoders, and new STBs along with a abandoning MPEG-2 based deployments. revolutionary way of thinking. Today, MPEG- Next, we take a look at the issues involved in 2 set of standards forms the core of audio, introduction of new video compression video and transport protocols used in the formats. Unlike the analog to digital digital cable delivery system [1,2]. transition, only new encoders and STBs are required, but plant upgrades are not necessary. Over this same decade, user requirements This allows for new and old video have changed along with advances in video technologies to co-exist and many of the ideas compression technology. Recently, several originated in the earlier transition can be new video codecs have been introduced (e.g. leveraged again. WM-9 and MPEG-AVC/H.264). The powerful message of these codecs is hard to HOW FAR CAN MPEG-2 GO? ignore: 2-to-3 times the compression efficiency, Digital Rights Management MPEG-2 video standard specifies syntax support and increased interactivity with the for compressed video bitstream, but does not standardize an encoding algorithm to generate There are ways to extend the coding it. Over the years, better encoding schemes potential of MPEG-2 by adding new tools and have yielded superior picture quality at a creating new profiles. In the last few years, given bitrate using techniques such as researchers have been looking at compression improved pre and post processing, smoothing techniques beyond MPEG-2. By way of of motion vectors, better rate control (bit example, some of the potential new additions allocation) multi-pass encoding and so on. to the existing tool-kit of video compression Compared to the early days of MPEG2, the techniques include: typical bitrate required for broadcast quality • Multiple reference frames for prediction. video compression has gone down • Variable block size for significantly through competitive processes • Special prediction modes for fades built into developing advances in video • 1/4th motion estimation. encoding marketplace. However, it is • Multiple directions of prediction for I- interesting to note that certain applications , such as VOD have associated business • Loop filter to control propagation of error, agreements that dictate the bitrate to be • Usage of . constant (e.g. 3.75 Mbps) irregardless of the advances in encoding techniques. Adding these new tools, requires extensive modifications of the MPEG-2 standard and Video compression experts generally agree the creation of new products. In essence it that current state of the technology is such would be almost equivalent to creating a new that new encoding techniques to produce coding standard to handle these changes. In MPEG-2 video streams will probably not fact, some of the coding gain in advanced produce too much further improvement for codecs come from including these tools [3]. entertainment quality television programs (See Figure 1). Due to the maturity of the It should be noted that various alternatives MPEG-2 , most significant coding exist to reclaim bandwidth other than efficiencies at the main profile/main level changing the video compression codec, and (MP/ML) have already been explored through may be easier to deploy. A quick list includes: the competitive encoder development marketplace . 1. Higher QAM constellations (64 to 256: ~33%/QAM) 7 6 2. Shift analog PPV services to digital 5 (10X/QAM) 4 3. Switched broadcast Service (~1x/QAM)[4]

Mbps 3 4. Stat mux MPEG-2 VOD (~25%/QAM) 2 5. Convert all (most) analog to digital 1 (10X/QAM) 0 1995 1996 1997 1998 1999 2000 2001 2002 2003 Year STATE OF COMPETITION

Not surprisingly, the need for bandwidth is Figure 1: MPEG-2 Generational felt by DBS operators too. Due to the need to Encoder Improvements carry local programming, offer HD services and making bandwidth available for

personalized 2-way video services, satellite operators have been looking at various options including migration to higher algorithms used do not need to be constellation modulation, use of turbo codes standardized (the exception to this is targeting and adoption of advanced video codecs. to portable personal devices). Over time, as Satellite operators have very little margin left the needed to deliver in reducing per-channel bandwidth used by entertainment quality video decreasesthe take their MPEG-2 video programming and it is rate on these services will rise. Whether or not inevitable that they have to commit to a new this is an opportunity or threat to cable compression standard in near future. operators remains to be seen [7]. However, to date, there are no announced plans of migration to a new . Wireless network operators have also recognized the new market opportunities in With MPEG-2 technology, DSL providers being able to offer video services. Recently, have not been able to establish a firm foothold there is a renewed interest in MMDS in the video delivery market. The desire to technology (e.g. WiMAX consortium) that adopt an advanced video codec for video provides fixed wireless broadband access to delivery has also been reported in the DSL subscribers. At the bitrates of transmission industry because it can open up these markets. (1.5 Mbps), advanced video codec will be the Recently approved ADSL-2 standard enables logical choice for entertainment quality video transmission of data at 1.5 Mbps over existing services. It is too early to speculate if the existing phone networks [5]. This channel rate wireless operators will provide data and voice is not enough for entertainment quality video only or if they will provide data, voice and transmission if one is using MPEG-2 video with broadcast television quality video compression, but is plenty for advanced codec services. based transmission. However, High Definition programming still poses a problem because In terms of ability to offer converged 1.5 Mbps is not enough bandwidth for HD services (streaming, video conferencing, transmission, even for advanced video codecs. video cellphone, and traditional video using Clever attempts have been made to meet that same codec and protocols) MPEG-2 transport need by a very fancy arrangement of multiple and video technology is at a disadvantage. phone lines. For example, UK based Net-to- Migration to advanced codecs and new Net Technologies and Tandberg TV standards potentially gives a competitive edge experiment using two lines ADSL loop to the above network operators by enabling bonding, as referenced in an Internet report converged service offering. [6]. IMPLEMENTATION COSTS Another recent shift in business model due to availability of high bandwidth DOCSIS is Due to the broadcast nature of the video the content providers directly doing business signal, and number of decoder units; the cost with consumers by bypassing the need to have of equipment on the decode side far business relationship with network operators. outweighs the costs associated with upgrading Currently, there are only a couple of high encoding equipment. We therefore only talk profile (and many smaller) TV-over-the- about cost of implementation related to the Internet type services available. Two things to set-top box side. note here – decoders used for these services are typically software-based (WM9 or Real), In anticipation of a future move away from with DRM enhancements to the liking of each MPEG-2 technology to another video codec, content provider, and video compression several IC manufacturers have already started building their decoder ICs based on flexible and can be used to support carriage of both platform (e.g. TI, Equator, ST, Philips etc.) codecs. The concepts of modulation, Obeying Moore’s law, providing backward , buffering, insertion, and compatibility becomes a less pricey option. caroseling can be reused and intermixed with the new video codec. As an example, MPEG decoder ICs are sold at approximately <$12 price range. The real analog legacy that still exists Current MPEG4 decoder pricing is very high today is not the plant and equipment (almost a $15 premium over MPEG2 upgrades; but the reluctance of a sizeable (MP@ML) only decoders), but the premium group of people (approx. 63 million paying in is expected to go down to less than 7 dollars 2003 [9]), who get basic cable service to all in 3-4 years [8]. the TVs in their household for one low fee, to switch to a digital service that requires a box H.264 w/MPEG- for each TV. The fear is that they may opt out 2 30 of cable altogether. Alternatively there is

25 constant pressure to shift from analog due to extensive piracy, bandwidth demands, and 20 less robust security mechanisms. This 15 ‘analog’ legacy is what in one part is creating 10 the bandwidth crunch on plant systems and 5 much study through the “all-digital efforts”, 0 including using new codecs, are 2003 2004 2005 2006 2007 being considered for resolving this problem.

The important thing to realize is switching from an MPEG-2 Digital Video platform to a Figure 2 Average Sale Price of decoder IC new type of digital video codec does not (Courtsey: In-stat/MDR) create the same type of legacy and may, in New design and advances in hardware such as part, actually be a solution to this analog one. Media processors, VLIW processors are changing the traditional “hard-coded” nature The challenges created by switching to a of video decompression platform, making it new digital video codec are buying new more flexible to adapt to new video codecs. encoder equipment at headends or regional centers and replacing the millions of digital IS MPEG-2 VIDEO REALLY LEGACY? STBs already deployed. The most significant cost is replacing these STBs (approx 29 The transition to a new digital video codec million in 2003 [10]), but this could be argued is not the same as the earlier transition from as not insurmountable and actually somewhat carrying just an analog Cable TV signal to less of an effort than what has been launched using a new digital transmission platform. The in the past. There are a number of strategies earlier digital migration was much more that can mitigate and justify these costs, but physically involved than just replacing a much of this depends on being able to carry video codec; fortunately this time there is no both types of codecs in the same cable plant need to rebuild the digital platform. The and developing new boxes that can decode network infrastructure put in place for both MPEG-2 and the candidate digital video establishing MPEG-2 technology is still codec. With this and the inherent advantages useable; the cables, connectors, amplifiers, of the local distribution in cable systems, and transport mechanisms are already in place cable service providers can take several steps technology and services for a cost-effective to ease the burden of this transition: transition. Some factors to consider for this would be: • They can deploy new services on a region-by-region basis using an ROI to • New boxes need to bring in additional justify the deployment of new STBs. revenue • The type of video service is agnostic • Room for bandwidth needs to be to kind of digital codec used. This made. This can happen through means that MPEG-2 can initially be bandwidth reclamation strategies as used with a deployment of service to mentioned previously. build up demand to justify a box • Analog PPV services must be phased upgrade and then switch the codec out by replacing these boxes with used for the service. MPEG-2 STBs • Alternatively new codecs can be introduced in new tiers of services. A place on the cable plant where a total • Initial deployment of a few STBs to be replacement of MPEG-2 with the advanced used in a slow rollout can help codec could be beneficial, and less of a decrease the new STB costs for future hardship, is in the backend storage and larger rollouts. transport systems. With the projected • Existing MPEG-2 only STBs can be increases of Video-on-Demand (VOD) cable redeployed in other parts of the system services, larger amounts of content will need to assist in digital upgrades. to be stored, replenished and distributed in the backend plant. A content catalog of 10,000 New advanced codec products can be hours with 25% of it being replaced once a designed to decode both the new codec and week would require at least a continuous 56 MPEG-2 given an additional 10-15% extra mbps transport link to the headend along with performance in the chip. Though the new 17,000 GB of storage (this does not include codecs are not backwards compatible with storing multiple copies or transport to edge MPEG-2, the product can effectively support servers). To deal with this, more server farms both. The STB can be deployed to operate on will need to be added along with leasing of traditional MPEG-2 systems. As the new more bandwidth to transport content to one or codec gets deployed on the plant, the same many headends. These costs can be reduced box can be used to decode these new services. through the use of advanced codecs that will This strategy can allow MPEG-2 to be effectively halve the storage and transport complemented by the newer codec and can needs. To take advantage of these cost savings allow services to exist before a decision is real-time technologies between needed to switchover the codec. the new codec and MPEG-2 should be encouraged. There are already a large number digital MPEG-2 STBs out there, but this number will continue to grow due to a dramatic EXAMPLE USAGE SCENARIO: NEW increasefrom demand of MPEG-2 HD Boxes. VOD SERVICE TIER Given that new product deployments will be at least 1-2 years away, there will be a The introduction of a new video codec significant installed base of MPEG-2 boxes. needs to be part of an overall bandwidth Any new codec will have to work in reclamation strategy. A single RF QAM complement with the MPEG-2 existing Channel can have a tremendous range in video capacity depending on how it is being There are several new revenue sources to used (see Figure 3). Effective management of cable being captured by the on-demand this bandwidth can lead to new services as services: One is replacing the local video well as a cost-effective way to deploy an store (“watch a movie without the late fees”), advanced video codec. There are many ways the other is competing against the burgeoning to accomplish this, but this section will PVR market but with some extra features like attempt to describe one possible approach. an unlimited hard drive, access to unaired content, and never needing to record a show. The High Definition offering basically MPEG-2 Adv. Codec provides a “gotta have” service that can

35 increase customer loyalty (“I gotta have a feed

30 for my new HD set and cable has it”). The

25 problem is on the cable plant, the bandwidth

20 is disproportionately dished out. An HD

15 request can replace 4 or more SD requests, but the price is not that much different. The Video Programs 10 SVOD service can take up bandwidth that 5 could have been used by someone who didn’t 0 SD SD-VoD HD HD-VoD want to go to the video store to see the latest RF 256-QAM Channel movie releases. These situations can create either more contention or a disproportionate Figure 3: Codec Video Program increase in bandwidth demand on the node Capacity for Single 256 QAM Channel level to accommodate peak use. Some ways to deal with this is to limit the amount of HD Presently VoD services (projected to be a requests and constrict the size of the content 4-5 billion dollar market by 2007 [11]) catalog of an SVOD service to allow enough contain several different types of streams that take-up rates in the traditional MOD service. have radically different bandwidth behaviors. An alternative to this is to create a new tier of Two potentially bandwidth intensive services on-demand services. are High Definition (HD-VOD) deliveryand Subscription (SVOD). A This new tier would have a combined local High Definition program in MPEG-2 requires SVOD offering with an HD-VOD service that approximately 4 times the of the same requires a new STB capable of doing both channel in SD format. Besides needing a MPEG-2 and the new codec. The lower on- larger bit rate, HD-VOD creates a demand on demand tier for renting SD movies would be bandwidth resources by effectively blocking supported by MPEG-2 and the new tier would potentially 4 or more SD streams for each HD be supported by the new codec. With the stream in use. The SVOD service also creates doubling of bandwidth from the new codec, a demand on bandwidth resources by the SVOD service can have an expanded and effectively blocking pay-per-transaction SD localized content catalog with a predictable streams especially when ‘channel surfing’ monthly income source. Additionally enabling behaviors occur. As the take-up on these HD-VOD on this tier provides incremental services becomes more popular, a need to income other than the monthly fee as well as create a bandwidth resource policy based on freeing up bandwidth on the lower on-demand these different behaving streams will be tier for the SD MPEG-2 movie rental market. necessary.

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