Home > Articles > Information Technology

📄 Contents

  1. 1 VCR Control Functions
  2. 2 Near Video on Demand
  3. 3 Near Video on Demand with VCR Functions
  • Print
  • + Share This
Like this article? We recommend

Like this article? We recommend

7.5.3 Near Video on Demand with VCR Functions

The ideal combination would be near video on demand (for the efficiency) plus full VCR controls for every individual viewer (for the user convenience). With slight modifications to the model, such a design is possible. Below we will give a slightly simplified description of one way to achieve this goal (Abram-Profeta and Shin, 1998).

We start out with the standard near video-on-demand scheme of Fig. 7-2. However, we add the requirement that each client machine buffer the previous DT min and also the upcoming DT min locally. Buffering the previous DT min is easy: just save it after displaying it. Buffering the upcoming DT min is harder, but can be done if clients have the ability to read two streams at once.

One way to get the buffer set up can be illustrated using an example. If a user starts viewing at 8:15, the client machine reads and displays the 8:15 stream (which is at frame 0). In parallel, it reads and stores the 8:10 stream, which is currently at the 5-min mark (i.e., frame 9000). At 8:20, frames 0 to 17,999 have been stored and the user is expecting to see frame 9000 next. From that point on, the 8:15 stream is dropped, the buffer is filled from the 8:10 stream (which is at 18,000), and the display is driven from the middle of the buffer (frame 9000). As each new frame is read, one frame is added to the end of the buffer and one frame is dropped from the beginning of the buffer. The current frame being displayed, called the play point, is always in the middle of the buffer. The situation 75 min into the movie is shown in Fig. 7-3(a). Here all frames between 70 min and 80 min are in the buffer. If the data rate is 4 Mbps, a 10-min buffer requires 300 million bytes of storage. With current prices, the buffer can certainly be kept on disk and possibly in RAM. If RAM is desired, but 300 million bytes is too much, a smaller buffer can be used.

Figure 7-3 (a) Initial situation. (b) After a rewind to 12 min. (c) After waiting 3 min. (d) After starting to refill the buffer. (e) Buffer full.

Now suppose that the user decides to fast forward or fast reverse. As long as the play point stays within the range 70–80 min, the display can be fed from the buffer. However, if the play point moves outside that interval either way, we have a problem. The solution is to turn on a private (i.e., video-on-demand) stream to service the user. Rapid motion in either direction can be handled by the techniques discussed earlier.

Normally, at some point the user will settle down and decide to watch the movie at normal speed again. At this point we can think about migrating the user over to one of the near video-on-demand streams so the private stream can be dropped. Suppose, for example, that the user decides to go back to the 12 min mark, as shown in Fig. 7-3(b). This point is far outside the buffer, so the display cannot be fed from it. Furthermore, since the switch happened (instantaneously) at 75 min, there are streams showing the movie at 5, 10, 15, and 20 min, but none

The solution is to continue viewing on the private stream, but to start filling the buffer from the stream currently 15 minutes into the movie. After 3 minutes, the situation is as depicted in Fig. 7-3(c). The play point is now 15 min, the buffer contains minutes 15 to 18, and the near video-on-demand streams are at 8, 13, 18, and 23 min, among others. At this point the private stream can be dropped and the display can be fed from the buffer. The buffer continues to be filled from the stream now at 18 min. After another minute, the play point is 16 min, the buffer contains minutes 15 to 19, and the stream feeding the buffer is at 19 min, as shown in Fig. 7-3(d).

After an additional 6 minutes have gone by, the buffer is full and the play point is at 22 min. The play point is not in the middle of the buffer, although that can be arranged if necessary.

  • + Share This
  • 🔖 Save To Your Account

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020