PDF of this tutorialDefinition
Digital video, using Moving Pictures Expert Group (MPEG2) compression technology (standardized in International Standards Organization [ISO]/International ElectroTechnical Commission [IEC] 13818), presents new testing challenges. Digital video will be transported over both traditional core telecom networks and a variety of emerging residential-access networks. This requires a testing strategy which will isolate problems to the specific network (core or access) and transmission layer. Transmission problems may be either analog or digital in nature. MPEG2 data is subject to a number of different impairments in each type of network. For example, in the core synchronous optical network (SONET) or synchronous digital hierarchy (SDH) network, asynchronous transfer mode (ATM) impairments may dominate, while in hybrid fiber coax (HFC), access networks’ non-linear distortion and ingress noise may dominate.
Overview
Testing digital video is challenging because:
- MPEG2 is a new standard and technology.
- The core network transport of MPEG2 utilizes ATM, also a new technology.
- The access networks which deliver the MPEG2 signal to the home are either partially new technology (i.e., quadrature amplitude modulation [QAM] modulation over HFC networks) or completely new technology (i.e., switched digital video [SDV] networks).
And, just so we don't forget, the reasons for deploying digital video in general and specifically MPEG2 digital video are:
- Digitized video can be edited using non-linear editors.
- Digitized video can be stored on servers; compression allows more efficient storage.
- A number of digital video programs can be transmitted in the bandwidth of a single analog TV channel.
- higher video and audio quality, scalable quality by varying the bit rate of the encoder
- inclusion of data such as electronic programs guides within the MPEG transport stream
- enhanced interactivity
- local content insertion
