Digital Video Recording SystemMark LewisAndrew LevineENPM 643Fall 2006Final ProjectProject descriptionThe goal of this project is to apply systems engineering principles to develop the scenarios and use cases, requirements and specifications, system level design, and verification and validation of a digital video recording (DVR) system. Lastly, a subset of a system test plan will be presented.A DVR system is a common hardware set and service provided by cable TV companies (i.e. Comcast, Cox, Time Warner), or 3rd party services such as TiVo, who typically charge a monthly fee for the service portion. The service (and corresponding hardware) allows users to record TV, set a recording, search a schedule for programs to record, set a schedule to record programs, watch recorded programs, watch and record live TV, and configure the DVR system. Once the system is configured and set up, the system will run automatically according to user settings. Goals of this project include fully identifying the system requirements, use cases, system specifications, and validating and verifying the system design. For the purposes of this project, several common DVR characteristics will be ignored. These functions and characteristics include full menu functionality, ability to record multiple channels simultaneously, links to personal computers to transfer media, video, pictures, audio, links to web applications and podcast subscriptions, interactive games, DVD burner, and HD compatibility.Stakeholder and Scenario IdentificationOne of the first steps towards requirements capture and development is the identification of stakeholders and the analysis of their high-level concerns and needs of the system. For a basic DVR system, we identified the following stakeholders:Stakeholder Name DescriptionCustomer The end user of the system who has purchased the DVR system and will be the one who most interacts with the system.Retailer The store or company who is responsible for selling system units to customers.Data Service ProviderThe entity that provides and maintains a data service needed by the DVR system.System Developer The group that designed, tested, and produced the DVR system, both hardware and software.System Maintenance PersonnelThe group that is responsible for handling failed units and providing repair services.Content Provider A group (typically a television programming provider) whose product access is controlled via the DVR usage.As this table is examined, it is clear that some stakeholders could be combined into one in certain situations. For instance, one company could design, sell, and repair DVR units, as well as provide the data service, effectively combining four stakeholders into one.The primary focus for this section (and most subsequent ones) is on the requirements of the end user of the system. Our original intent had been to conduct a survey of known DVR users to determine their concerns and needs of these systems. However, time limits and a concern over producing a survey that didn’t lead the respondent to certain answers ended this endeavor. In lieu of the surveys, both team members provided inputs from the end user standpoint as both of us use and own DVR systems.Each stakeholder in this system is involved in a group of scenarios that can help determine the high-level requirements of the system. The table below shows some scenarios for the system and the associated stakeholders linked to the scenario:ScenarioNumberScenario Description StakeholdersAffected1 Customer purchases DVR systemCustomer, Retailer2 Customer configures DVR systemCustomer, Data Service Provider3 Customer schedules recording Customer, Data Service Provider, Content Provider4 Customer watches recording Customer5 Customer uses DVR to watch “live” TVCustomer, Data Service Provider, Content Provider6 Customer experiences system failureCustomer, Retailer, System Maintenance PersonnelUse Case ModelingFrom the scenarios described in the previous section, use case analysis was performed in order to reach high-level requirements for the system.The first step in use case modeling is to identify actors who interact with the system (either provide input or receive output from the system). For a typical DVR system, three actors were identified. The first is the customer who purchased the system and interacts with it to record and watch television. The second is the DVR data service that is required to update schedule information on the system. The third is the television provider (typically a cable or satellite TV company) used by the customer and whose signal is connected to the DVR unit.Below is the use case diagram for the DVR system:Figure 1. Use Case Diagram.High-Level RequirementsBased on the scenarios and use cases, the initial high-level requirements are as follows:RequirementNumberRequirement Description1 System must provide video I/O of formats and using connectors that are compatible with consumer video standards.2 System must have a remote control.3 System must have menu-based software interface that can be navigated by the user.4 System must have displayable and searchable schedules of all programs.5 System must provide user standard video player functions.6 System must provide user ability to specify programs to record.7 System must have digital storage media for recording programs for future retrieval.8 System must be able to access a recording as it is being written to the storage media.9 System must have a data link to connect to a data service.10 System must provide user the ability to get and set system configuration parameters.11 System must be built from Commercial Off-The-Shelf (COTS) components.12 System must be capable of digitizing, recording, and displaying a standard video signal input.Use Case AnalysisUse Case #1 – Show Broadcast Schedule1. Description: The user wants to view the program broadcast schedule.2. Pre-Condition: The user has set up the DVR system and a connection to the cable feed has been established.3. Actors: User4. Flow of Events: a) User chooses to display broadcast schedule through interface.b) DVR shows schedule by set organization method on TV screen.c) User can navigate schedule using interface and select a specific program to watch or record.d) Schedule display terminates upon user request or timeout.5. Post-Condition: Recording scheduled if requested, program displayed if requested; otherwise previous display restored.Use Case #2 – Show