Digital Video on CD and DVD
Find out more information about digital video
on CD and DVD including MPEG coding
Video and film must be converted to a digital format for
storing on CD or DVD. The following formats use digital video:
CD-ROM applications use a range of digital
video options including MPEG-1, depending on the requirements.
Video CD and CD-i use
for full screen video on a compact disc with playing times of over
Super Video CD
(SVCD) uses MPEG-2 for higher
quality video but with playing times of only 40 minutes.
DVD-Video uses MPEG-2 for the highest quality
video and playing times of up to several hours.
MPEG encoded video normally conforms to PAL/SECAM (625
line) or NTSC (525 line) video, although the number of lines may be
reduced particularly for MPEG-1 encoding.
NTSC stands for the National Television Systems Committee of the Electronic Industries
Association (EIA), which prepared the TV standard for the USA, Canada, Japan, Central America, half of the Caribbean & half
of South America. When referring to NTSC video what is normally
meant is 525 line 60 Hz. The number of active lines is 480.
PAL (Phase Alternation Line) is the TV format
used in most of Western
Europe, Australia and other countries. When referring to PAL
video, what is normally meant is 625 line 50 Hz video, since PAL only
refers to the way colour signals are coded for broadcast purposes. The
number of active lines is 576.
SECAM ("SEquential Couleur A Memoire"
or sequential colour with memory) is the TV format used in France, Eastern Europe and other
countries. Like PAL SECAM video means 625 line 50 Hz. The number
of active lines is 576.
DVD players, games consoles and other hardware that
provides a video output for a TV will use one of these video
standards. PCs will use other display resolutions and the video
will be displayed either in a window or scaled to full screen. The
old VGA resolution of 640 x 480 is NTSC compatible but larger sizes will
need the video to be scaled upwards to fill the screen. As a
result artefacts may occur if not correctly filtered and aspect ratios
may not be maintained.
CCIR-601 Video Standard
CCIR (the International Radio Consultative Committee)
recommendation 601 specifies the image format, and coding for digital television signals.
The main parameters of CCIR 601 are listed below:
|Sampling frequency for Y (MHz)
|Sampling frequency for U and V (MHz)
|No of samples per line
|No of levels for Y component
|No of levels for U,V components
The number of levels is less than 256 because black is defined as 16
and white as 235 to allow for overshoot in the analogue signal to be
digitally coded. Most digital video recording systems comply with CCIR 601 or a subset
CCIR 601 video can be converted to a lower resolution called SIF (Standard
Interchange Format) with 240 lines with 360 pixels each for NTSC,
and 288 lines by 360 pixels for PAL and SECAM.
For Video CD the number of samples per line is reduced further to 352 as
this is a multiple of 16, the size of a macroblock.