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Bandwidth for Video
Electronic-Video, or “e-Video”, includes all audio/video clips that are distributed and played over the Internet, either by direct download or streaming video. The problem with video, however, has been its inability to travel over networks without clogging the lines. If you’ve ever tried to deliver video, you know that even after heroic efforts on your part (including optimizing the source video, the hardware, the software, the editing and the compression process) there remains a significant barrier to delivering your video over the Web. That is the “last mile” connection to the client.
So before we explain the details of how to produce, capture, edit and compress video for the Web, we had better begin by describing the near term opportunities for overcoming the current bandwidth limitations for delivering video over the Internet.
In this chapter, we will describe how expanding broadband fiber networks will reach out to the “last mile” to homes and businesses creating opportunities for video delivery. In order to accomplish this, we will start by quantifing three essential concerns:
the file size requirements for sending video data over the Internet,
the network fiber capacity of the Internet for the near future and
the progress of narrowband (28.8Kbps) to broadband (1.5 Mbps) over the “last mile.”
This will provide an understanding of the difficulties being overcome in transforming video from the current limited narrowband streaming video to broadband video delivery.
Transitioning from Analog to Digital Technology
Thomas Alva Edison’s contributions to the telegraph, phonograph, telephone, motion pictures and radio helped transform the 20th Century with analog appliances in the home and the factory. Many of Edison’s contributions were based on the continuous electrical analog signal.
Today, Edison’s analog appliances are being replaced by digital ones. Why? Let’s begin by comparing the basic analog and digital characteristics.
Analog signals move along wires as electromagnetic waves. The signal’s frequency refers to the number of time per second that a wave oscillates in a complete cycle. The higher the speed, or frequency, the more cycles of a wave are completed in a given period of time. A baud rate is one analog electric cycle or wave per second. Frequency is also stated in hertz (Hz). (Kilohertz or kHz represents 1000 Hz, MHz represents 1,000,000 Hz and GHz represents a billion Hz).
Analog signals, such as voice, radio, and TV involve oscillations within specified ranges of frequency. For example:
Voice has a range of 300 to 3300 Hz
Analog cable TV has a range of 54 MHz to 750MHz
Analog microwave towers have a range of 2 to 12 GHz
Sending a signal along analog wires is similar to sending water through a pipe. The further it travels the more force it loses and the weaker it becomes. It can also pick up vibrations, or noise, which introduces signal errors.
Today, analog technology has become available world-wide through the following transmission media:
1/. Copper wire for telephone (one-to-one communication).
2/. Broadcast for radio & television (one-to-many communication).
3/. Cable for television (one-to-many communication).
Most forms of analog content, from news to entertainment, have been distributed over one or more of these methods. Analog technology prior to 1990, was based primarily on the one-to-many distribution system as show in the Table below where information was primarily directed toward individuals from a central point.
Table 1-1 Analog Communication Prior to 1990
Prior to 1990, over 99% of businesses and homes had content reach them from any one of the three transmission delivery systems. Only the telephone allowed two-way communication, however. While the other analog systems where reasonably efficient in delivering content, the client could only send feedback, or pay bills, through ordinary postal mail. Obviously, the interactivity level of this system was very low.
The technology used in Coaxial Cable TV (CATV) is designed for the transport of video signals. It is comprised of three systems: AM, FM, and Digital. Since the current CATV system with coaxial analog technology is highly limited in bandwidth new technology is necessary for applications requiring higher bandwidth. In the digital system, a CATV network will get better performance than AM/FM systems and ease the migration from coaxial to a fiber based system. Fiber-optics in CATV networks will eliminate most bottlenecks and increase channel capacity for high speed networks.
Analog signals are a continuous variable waveform that are information intensive. They require considerable bandwidth and care in transmission. Analog transmissions over phone lines have some inherent problems when used for sending data. Analog signals lose their strength over long distances and often need to be amplified. Signal processing introduces distortions and become amplified raising the possibility of errors.
In contrast to the waveform of analog signals, digital signals are transmitted over wire connections by varying the voltage across the line between a high and a low state. Typically, a high voltage level represents a binary digit 1 and a low voltage level represents a binary digit 0. Because they are binary, digital signals are inherently less complex than analog signals and over long distances they are more reliable. If a digital signal needs to be boosted, the signal is simply regenerated rather than being amplified.
As a result, digital signals have the following advantages over analog:
Higher transmission speeds
Less complex equipment
The excitement over converting analog to digital media is, therefore, easy to explain. It is motivated by cost-effective higher quality digital processing for data, voice and video information.
In transitioning from analog to digital technologies however, several significant changes are also profoundly altering broadcast radio and television. The transition introduces fundamental changes from one way broadcast to two-way transmission, and thereby the potential for interactivity, and scheduling of programming to suit the user’s needs.
Not only is there an analog to digital shift, but a synchronous to asynchronous shift as well. Television and radio no longer needs to be synchronous and simultaneous. Rather the viewer and listener can control the time of performance.
In addition, transmission can be one of three media: copper wire, cable, or wireless. Also, the receiver is transitioning from a dumb device, such as the television, to an intelligent set-top box with significant CPU power. This potentially changes the viewer from a passive to an interactive participant.
Today, both analog and digital video technologies coexist in the production and creative part of the process leading up to the point where the video is broadcast.
Currently, businesses and homes can receive content from one to six delivery systems:
copper wire (telephones),
coaxial cable (TV cable), or
broadcast (TV or radio);
copper wire (modem, DSL),
Ethernet modem, or
At the present time, analog systems still dominate, but digital systems are competing very favorably as infrastructure becomes available. Analog/digital telephone and digital cable allow two-way communication and these technologies are rapidly growing. The digital systems are far more efficient and allow greater interactivity with the client.
The race is on as cable, data, wireless, and telecommunications companies are scrambling to piece together the broadband puzzle and to compete in future markets. The basic infrastructure of copper wire, cable and satellite, as well as, the packaged contents are in place to deliver bigger, richer data files and media types.
In special cases, data transmission over the developing computer networks within corporations and between universities, already exist. Groups vying to dominate have each brought different technologies and standards to the table. For the logical convergence of hardware, software and networking technology to occur the interface of theses industries must meet specific inter-operational capabilities and must achieve customer expectations for quality of service.
Long distance and local Regional Bell Operating Companies (RBOC) telephone companies started with the phone system designed for point-to-point communication, POTS (plain old telephones) and have evolved into a large switched, distributed network, capable of handling millions of simultaneous calls. They track and bill accordingly with an impressive performance record. They have delivered 99.999% reliability with high quality audio. Their technology is now evolving toward DSL (Digital Subscriber Line) modems.
AT&T has made significant progress in leading broadband technology development now that it has added the vast cable networks of Tele-Communications Inc. and MediaOne Group to telephone and cellular. Currently, AT&T with about 45% of the market can plug into more U.S. households than any other provider. But other telecommunications companies, such as Sprint and MCI, as well as, the regional Bell operating companies, are also capable of integrating broadband technology with their voice services.
Although both routing and architecture of the telephone network has evolved since the AT&T divestiture, the basics remain the same. About 25,000 central offices in the U.S. connect through 1200 intermediate switching nodes, called access tandems. The switching centers are connected by trunks designed to carry multiple voice frequency circuits using frequency division multiplexing (FDM), or synchronous time-division multiplexing (TDM), or wavelength division multiplexing (WDM) for optics.
The cable companies Time Warner, Comcast, Cox Communications and Charter Communications have 60 million homes wired with coaxial cable primarily one-way cable offering one-to-many broadcast service. Their technology competes through the introduction of cable modems and the upgrade of their infrastructure to support two-way communication. The merger between AOL and Time Warner demonstrates how Internet and content companies are finding ways to converge.
Cable television networks currently reaches 200 million homes. On the other hand, satellite television can potentially reach 1 billion homes. These will offer nearly complete coverage of the U.S., digital satellite is also competing. DirecTV, has DirecPC, which can beam data to a PC. Its rival, EchoStar Corp., is working with interactive TV player, TiVo Inc., to deliver video and data service to a set-top box. However, satellite is currently not only a one-way delivery system, but is also the most expensive in the U.S. In regions of the world outside the U.S. where the capital investment in copper wires and cable has yet to be made, satellite may have a better competitive opportunity.
The Internet itself doesn’t own its own connections. Internet data traffic passes along the copper, fiber, coaxial cable, and wireless transmission of the other industries as a digital alternative to analog transmissions.
The new media is being built to include text, graphics, audio, and video across platforms of television, Internet, cable and wireless industries. The backbone uses wide area communications technology, including satellite, fiber, coaxial cable, copper and wireless. Data servers mix mainframes, workstations, supercomputers, and microcomputers and a diversity of clients populate the end-points of the networks including; conventions PCs, palmtops, PDAs, smart phones, set-top boxes, and TVs.
Figure 1-1 Connecting the backbone of the Internet to Your Home
Web-television hybrids, such as, WebTV provide opportunities for cross-promotion between television and Internet. Independent developers may take advantage of broadcast-Internet synergy by creating shows to targeted audiences
Clearly, the future holds a need for interaction between the TV and the Internet. But will it appear as TV quality video transmitted over the Internet and subsequently displayed on a TV set. Or, alternatively, as URL information embedded within existing broadcast TV set pictures. Perhaps both.
Streaming is the ability to play media, such as audio and video, directly over the Internet without downloading the entire file before play begins. Digital encoding is required to convert the analog signal into compressed digital format for transmission and playback.
Streaming videos send a constant flow of audio/video information to their audience. While streaming videos may be archived for on-demand viewing, they can also be shown in real-time. Examples include play-by-play sports events, concerts and corporate board meetings. But a streaming video offers more than a simple digitized signal transmitted over the Internet. It offers the ability for interactive audience response and unparalleled form of two-way communication. The interactive streaming video process is referred to as
Widespread Web-casting will be impractical, however, until audiences have access rates of a minimum of 100 Kbps or faster. Compression technology can be expected to grow more powerful, significantly reducing bandwidth requirement. By 2006 the best estimates indicate that 40 Million homes will have cable modems and 25 Million DSL connections with access rates of 1.5 Mbps.
We shall see in Chapters 5, 6 and 7 how the compression codecs and software standards will competitively change “effective” Internet bandwidth and the quality of delivered video.
The resultant video quality at a given bandwidth is highly dependent upon the specific video compressor. The human eye is extremely non-linear and its capabilities are difficult to quantify. The quality of compression, specific video application, typical content, available bandwidth, and user preferences all must be considered when evaluating compressor options. Some optimize for “talking heads” while other optimize for motion.
To date, the value of streaming video has been primarily the rebroadcast of TV content and redirected audio from radio broadcasts. The success of these services to compete with traditional analog broadcasts will depend upon the ability of streaming video producers to develop and deliver their content using low cost computers that present a minimal barrier to entry. Small, low cost independent producers will effectively target audiences previously ignored. Streaming videos steadily moving toward the integration of text, graphics, audio, and video with interactive on-line chat will find new audiences. In Chapter 2, we present business models to address business’s video needs.
Despite these promising aspects, streaming video is still a long way from providing a satisfactory audio/video experience in comparison to traditional broadcasts. The low data transmission rates are a severe limitation on the quality of streaming videos. While a direct broadcast satellite dish receives data at 2 Mbps, an analog modem is currently limited to 0.05 Mbps. The new cable modems and ADSL are starting to offer speeds competitive with satellite, but they will take time to penetrate globally. Unlike analog radio and television, streaming videos requires a dynamic connection between the computer providing the content to the viewer. Current computer technology limits the viewing audience to up to 50,000. While strategies to overcome this with replicating servers may increase audiences, this too will take effort.
The enhancement of data compression reduces the required video data streaming rates to more manageable levels. The technology has only recently reached the point where video can be digitized and compressed to levels which allow reasonable appearance during distribution over digital networks. Advances continue to come, improving look and delivery of video.
Calculating Bandwidth Requirements
So far we have presented the advantages of digital techology, unfortunately there is one rather large disadvantage - bandwidth limitations. Let’s try some simple math that illustrates the difficulties.
Live, or on-demand, streaming video and/or audio is relatively easy to encode. The most difficult part is not the encoding of the files. It is determining what level of data may be transmitted. The following Table contains information that will help with some basic terms and definitions:
Why the difference between Kbps and KB/sec? File sizes on a hard drive are measured in Kilobytes (KB). But the data that transferred over a modem is measured in Kilobits per second (Kbps) because it's comparatively slower than a hard drive.
In the case of a 28.8Kbps modem the maximum data transfer rate is 2.5 KB/sec even through the calculated rate is 28.8Kbs / 8 bits in a byte = 3.6KB/sec. This is because there is approximately a 30% losses of transmission capabilities lost due to Internet “noise.” This is due to traffic congestion on the web and more than one surfer requesting information on the same server.
The following Table 1-4 provides information concerning the characteristics of video files. This includes pixels per frame and frames per file (film size file).
We can use the information in Table 1-4 to compare to some simple calculations. We will use the following formula to calculate the approximate size in Megabytes of a digitized video file:
(pixel width) x (pixel height) x (color bit depth) x (fps) x (duration in seconds)
8,000,000 (bits / MB)
For three minutes of video at 15 frames per second with a color bit depth of 24-bit in a window that is 320x240 pixels, the digitized source file would be approximately 622 Megabytes:
(320) x (240) x (24) x (15) x (180) / 8,000,000 = 622 Megabytes
We will see in chapter 4, how data compression will significantly reduce this burden.
Now that we have our terms defined, let's take the case of a TV station that wants to broadcast their channel live 24hrs a day for a month over the web to a target audience of 56 Kbps modem users. In this case, a live stream generates a 4.25KB/sec since a 56Kbps file transfers at 4.25KB/sec. So how much data would be transferred in a 24 hr period if one stream was constantly being used?
ANSWER = 4.25 KB/sec * (number of seconds in a day) * 30 days per month
= 11 GB/month
So, one stream playing a file encoded for 56 Kbs for 24hrs a day will generate 11 gigabytes in a month. How is this figure useful?
This figure becomes important if you can estimate the average number of viewers in a month, then you can estimate the total amount of data that will be transferred from your process.
Ultimately the issue becomes one of the need for sufficient backbone infrastructure to carry many broadcasts to many viewers across the networks.
For HDTV with a screen size of 1080x1920 and 24-bit color, a bandwidth of 51.8 Mbps is required. This is a serious amount of data flow to route around the Internet to millions of viewers.
Transitioning from Narrowband to Broadband
In telecommunications, bandwidth refers to data capacity of a channel. For an analog service, the bandwidth is defined as the difference between the highest and lowest frequency within which the medium carries traffic.
For example, cabling that carries data between 200 MHz and 300 MHz has a bandwidth of 100MHz.
In addition to analog speeds in hertz (Hz) and digital speeds in bits per second (bps), the carrying rate is sometimes categorized as narrowband and broadband. It is useful to relate this to an analogy in which wider pipes carry more water. TV and cable are carried at broadband speeds. However, most telephone and modem data traffic from the central offices to individual homes and businesses are carried at slower narrowband speeds. This is usually referred to as the “last mile” issue.
The definitions for narrowband and broadband vary within the industries, but are summarized for our purposes as:
Narrowband refers to rates less than 1.5 Mbps
Broadband refers to rates at or beyond 1.5 Mbps
A major bottleneck of analog services exists between cabling of residents and telephone central offices. Digital
Subscriber Line (DSL) and cable modem are gaining in availability. Cable TV companies are investing heavily in converting their cabling from one-way only cable TV to two-way systems for cable modems and telephones.
In contrast to the “last-mile” for residential areas, telephones companies are laying fiber cables for digital services from their switches to office buildings where the high-density client base justifies the additional expense.
We can appreciate the potential target audience for video by estimating; how fast the “last mile” bandwidth demand is growing. Because installing underground fiber costs more than $20,000 per mile, fiber only makes sense for businesses and network backbones. Not for “last mile” access to homes. Table 1-5 shows the estimated number of users connected at various modem speeds in 1999 and 2006. High-speed consumer connections are now being implemented through cable modems and digital subscriber lines (DSL).
Approximately 1.3 million home had cable modems by the end of 1999 in comparison to 300,000 DSL connections primarily to businesses. By 2006, we project 40 million cable modems and 25 million DSL lines.
Potentially data at the rate of greater than one megabit per second could be delivered to over 80 per cent of more than 550 million residential telephone lines in the world. Better than one megabit per second can also be delivered over fiber/coax CATV lines configured for two-way transmission, to approximately 10 million out of 200 million total users (though these can be upgraded).
In2000, the median bandwidth in the U.S. is less than 56. This is de facto a narrowband environment.
But worldwide there is virtually limitless demand for communications as presented by the following growth rates:
The speed of computer connections is soaring. The number of connections at greater than 1.5 Mbps is growing at 45% per year in residential areas and at 55% per year in business areas.
Because of improving on-line experience, people will stay connected about 20% longer per year.
As more remote areas of the world get connected, messages will travel about 15% father a year.
The number of people online worldwide in 1999 was 150 million, but the peak Internet load was only 10% and the actual transmission time that data was being transferred, was only 25% of that number. With the average access rate of 44 kbps this indicates an estimate of about 165 Gbps at peak load.
In 2006 there will be about 300 million users and about 65 million of these will have broadband (>1.5 Mbps) access. With the addition of increased peak load and increased actual transmission time, this will result in an estimated usage of about 16.5 Tera-bits per second of data processing.
It all adds up to a lot of bits. It leads to a demand for total data communications in 2006 of nearly a100-fold increase over 1999. With the number of new users connecting to the Internet growing this fast can the fiber backbone meet this demand? Figure 1-2 answers this question.
Figure 1-2 shows the growth in Local Area Networks (LANs) from 1980 to 2000 with some projection into the next decade. In addition, the Internet capacity is shows that over the last few decades and indicates the potential growth rate into the next decade. The jump up in Internet capacity due to Dense Wavelength Division Multiplexing (DWDM) is a projection of the multiply effect of this new technology. As a result this figure shows that we can expect multi-Tera-bit per second performance from the Internet backbone in the years ahead. This will meet the projected growth in demand.
Great! But, what about that “last mile” of copper, coax, and wireless?
The “last mile” involves servers, networks, content and transitions from narrow to broadband. Initially, the “last mile” will convert to residential broadband not as fiber optics, but as a network overlaid on existing telephone and cable television wiring. One megabit per second can be delivered to over 80 % or more of 550 million residential telephone lines in the world. It can also be delivered over all fiber/coax CATV lines configured for two-way service. The latter represents a small fraction of the worldwide CATV lines however, requiring only 10 million homes out of 200 million. But upgrade programs will convert the remainder in 5 years.
The endgame of the upgrade process may be fiber directly to the customer’s home, but not for the next decade or two. A fiber signal travels coast to coast in 30 ms and human latency (period to achieve recognition) is about 50 milliseconds. Thus fiber is the only technology to deliver viewable HDTV video. However, due to the cost and man-power involved, we’re stuck with the “last mile” remaining copper, coax and wireless for a while yet.
The Table 1-7 below summarizes how the five delivery approaches for analog and digital technologies will co-exist for the next few years. In chapter 8, we will present network background on the technologies and standards and revisit this table in more detail.
* (FFTH is fiber to the home, FTTC is fiber to the curb, MPEG-2 is a compression standard see chapter 4, ATM is Asynchronous Transfer Mode see chapter 8, TDM is Time Division Multiplexing see chapter 8).
Preparing to Converge
To be fully prepared to take advantage of the converging technologies, we must ask and answer the right questions. This is not as easy as it might seem.
We could ask, “Which company will dominate the broadband data and telecommunication convergence?” But this would be inadequate because the multi-trillion dollar world e-commerce market is too big for any one company to monopolize.
We could ask, “Which broadband networks will dominate the Internet backbone?” But this would be inadequate because innovative multiplexing and compression advances will make broadband ubiquitous and subservient to the “last mile” problem.
We could ask, “Which transmission means (cable, wireless, or copper) will dominate the “last mile”?” But this would be inadequate because the geographical infrastructure diversity of these technologies throughout the world will dictate different winners in different regions of the world demonstrating this as a “local” problem.
Individually, these questions address only part of the convergence puzzle. It is e-commerce’s demand for economic efficiency that will force us to face the important qestion of the telecommunication convergence puzzle.
“What are meaningful broadband cross-technology standards?”
Without globally accepted standards, hardware and software developers can’t create broad solutions for consumer demand. As a result, we will be concerned throughout this book in pointing out the directions and conflicts that various competing standards are undertaking.
In this chapter, we presented the background of analog technology’s transition toward digital technology. This chapter provided a calculation that illustrated why digital video data is such a difficult bandwidth problem. It evaluated the rate of change of conversion from narrowband connections to broadband. This rate establishing a critical perspective on the timeline of the demand for Internet video.
On the basis of this chapter, you should conclude that:
The Internet backbone combination of fiber and optical multiplexing will perform in the multi-Tera-bps range and provide plenty of network bandwidth in the next few years.
The “last mile” connectivity will remain twisted pair, wireless, and coax cable for the next few years, but broadband (1.5Mbps) access through cable modems and x-DSL will grow to 40 million users in just a few years.
Streaming video was identified as the crossroads of technology convergence. It is the bandwidth crisis of delivering video that will prove decisive in setting global standards and down-selecting competing technologies. The success of streaming video in its most cost-effect and customer satisfying form will define the final technology convergence model into the 21st Century
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