Digital Video Broadcasting and Compression Standards Explained

Digital Video Broadcasting (DVB)

DVB (Digital Video Broadcasting) is the most established digital television system, which transmits signals via cable (QAM), satellite (QPSK), and terrestrial (COFDM) networks.

Core Digital Television Concepts

• Flow Program: A digital raster that contains a single digital TV program.
• Transport Stream: A digital raster that contains multiple video programs, services, audio, and data transmitted together.
• Trama Digital: A set of digital signals comprising a header for synchronization and identification, plus a data block with information.

Video Compression and Image Types

MPEG encompasses several image compression systems with varying resolutions and binary streams.

• Group of Pictures (GOP): A set of images interpreted together, formed by an I-frame, which can include several P and B frames.
• Image Type I: An image containing compressed information of all the points it contains.
• P-type Image: A screen formed using a predictive system based on information from a previously transmitted image.
• B-type Image: A screen formed using two-way extrapolation from both a previous and a later image in time.
• Discrete Cosine Transform (DCT): A mathematical operation that decomposes an image area into frequency coefficients, serving as the basis for image compression.

Technical Specifications and Interfaces

• IEEE 1394: A port for transferring digital video, audio, and data in series. Also known as i-Link or FireWire.
• Digital Active Line: The time period in which samples are taken from a TV line during scanning, with a duration of 53.33 microseconds.
• Sampling: The action of sampling a signal for digitization. Depending on the number of samples taken from luminance and chrominance signals, various sampling schemes exist.

Modulation Techniques

• QAM (Quadrature Amplitude Modulation): A type of digital amplitude modulation that uses two carriers of the same frequency separated in phase by 90 degrees.
• QPSK (Quadrature Phase Shift Key): A type of phase modulation for digital modulators that uses two quadrature carriers, encoding one bit on the horizontal axis and another on the vertical.