DVD Demystified

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Introduction
Chapter 6
The DVD-Video format specification is an application of DVD-ROM
intended to provide high-quality audio and video in a format supported
worldwide by consumer electronics manufacturers, movie studios, video
publishers, and computer makers. Likewise, the DVD-Audio specification is
an application of DVD-ROM focused on high-fidelity multichannel audio. In
addition, the DVD Forum has defined recording formats for video, audio,
and generic streaming data. This chapter covers the technical details of
these application formats.
It is worth noting that the DVD application specifications are not formal
standards—that is, they have not gone through an open review process
under the auspices of a standards organization. The physical format specifications
for DVD-ROM and writable DVDs were submitted to the ECMA
and have become ISO/IEC standards, but the application formats are
controlled by the DVD Forum—a consortium of companies with vested
interests.
Variations of DVD for professional use, video games, Web-connected content,
and other areas also may beget application specifications based on
DVD-ROM or writable DVD. The DVD Forum may define some of these,
whereas other organizations may define additional applications, such as
Philips and Sony’s SACD audio format for DVD and Sony’s own PlayStation
format.
Data Flow and Buffering
Raw channel data is read off a disc at a constant 26.16 Mbps. The 16/8
demodulation process cuts it in half to 13.08 Mbps. After error correction,
the user data stream goes into the track buffer at a constant 11.08 Mbps.
Data search information (DSI) is copied from the data stream before it
reaches the track buffer. The track buffer feeds the program stream data
out at a variable rate of up to 10.08 Mbps. If the buffer fills, the input
stream is halted (while the disc continues to spin) until there is room in the
buffer for more incoming data. The program stream contains various packetized
elementary streams (PESs): video, audio, subpicture, still picture,
real-time text presentation control information (PCI), and data search
information (DSI). PCI and DSI together constitute DVD system overhead.