SAA7130 Philips Semiconductors, SAA7130 Datasheet - Page 30

• Manufacturer Part Number: SAA7130
• Description: PCI video broadcast decoder
• Manufacturer: Philips Semiconductors

Philips Semiconductors
7.6.7
The Vertical Blanking Interval (VBI) is often utilized to
transport data over analog video broadcast. Such data can
closely relate to the actual video stream, or just be general
data (e.g. news). Some examples for VBI data types are:
This information is coded in the unused lines of the vertical
blanking interval, between the vertical sync pulse and the
active visible video picture. So-called full-field data
transmission is also possible, utilizing all video lines for
data coding.
The SAA7130HL supports capture of VBI data by the
definition of a VBI region to be captured as raw VBI
samples, that will be sliced and decoded by software on
the host CPU. The raw sample stream is taken directly
from the ADC and is not processed or filtered by the video
decoder. The sampling rate of raw VBI can be adjusted to
the needs of the data slicing software.
7.6.8
Analog TV video signals are decoded into its components
luminance and colour difference signals (YUV) or in its
digital form Y-C
along the line (corresponding to a sampling rate of 27 MHz
divided by two), and a certain relationship from level to
number range (see Fig.13).
2002 Apr 23
Closed Caption (CC) for the hearing impaired (CC, on
line 21 of first field)
Intercast data [in US coded in North-American
Broadcast Text System (NABTS) format, in Europe in
World Standard Teletext (WST)], to transmit internet
related services, optionally associated with actual video
program content
Teletext, transporting news services and broadcast
related information, Electronic Program Guide (EPG),
widely used in Europe (coded in WST format)
EPG, broadcaster specific program and schedule
information, sometimes with proprietary coding scheme
(pay service), usually carried on NABTS, WST, Video
Programming Service (VPS), or proprietary data coding
format
Video Time Codes (VTC) as inserted in camcorders
e.g. use for video editing
Copy Guard Management System (CGMS) codes, to
indicate copy protected video material, sometimes
combined with format information [Wide Screen
Signalling (WSS)].
PCI video broadcast decoder
VBI
S
IGNAL LEVELS AND COLOUR SPACE
DATA
B
-C
R
. ITU-R BT.601 defines 720 pixels
30
The video components do not use the entire number
range, but leave some margin for overshoots and
intermediate values during processing. For the raw VBI
samples there is no official specification how to code, but
it is common practice to reserve the lower quarter of the
number range for the sync, and to leave some room for
overmodulation beyond the nominal white amplitude (see
Fig.14).
The automatic clamp and gain control at the video input,
together with the automatic chroma gain control of the
SAA7130HL, ensures that the video components stream
at the output comply to the standard levels. Beyond that
additional brightness, contrast, saturation and hue control
can be applied to satisfy special needs of a given
application. The raw VBI samples can be adjusted
independent of the active video.
The SAA7130HL incorporates the YUV-to-RGB matrix
(optional), the RGB-to-YUV matrix and a three channel
look-up table in between (see Fig.15). Under nominal
settings, the RGB space will use the same number range
as defined by the ITU and shown in Fig.13a for luminance,
between 16 and 235. As graphic related applications are
based on full-scale RGB, i.e. 0 to 255, the range can be
stretched by applying appropriate brightness, contrast and
saturation values. The look-up table supports gamma
correction (freely definable), and allows other non-linear
signal transformation such as black stretching.
The analog TV signal applies a quite strong gamma
pre-compensation (2.2 for NTSC and 2.8 for PAL).
As computer monitors exhibit a gamma (around 2.5), the
difference between gamma pre-compensation and actual
screen gamma has to be corrected, to achieve best
contrast and colour impression.
The SAA7130HL offers a multitude of formats to write
video streams over the PCI-bus: YUV and RGB colour
space, 15-bit, 16-bit, 24-bit and 32-bit representation,
packed and planar formats. For legacy requirements
(VfW) a clipping procedure is implemented, that allows the
definition of 8 overlay rectangles. This process can
alternatively be used to associate ‘alpha’ values to the
video pixels.
SAA7130HL
Product specification