For years, the mainstay video signal used by the consumer market has been composite video. Attempts have been made to support s-video,
but it has been limited primarily to high-end S-VHS VCRs and TVs.
With the introduction of DVD players and digital settop boxes,
there has been renewed interest in providing high quality video to the consumer market. This new equipment not only supports very high
quality composite and s-video signals, but are also allowing consumers the option of using component video.
Using analog RGB or YUV
video interfaces eliminates NTSC/PAL encoding and decoding artifacts, such as crawling dots on highly-saturated vertical edges and color
strobing on moving tweed patterns. As a result, the picture is sharper and has less noise. More intensity (Y) bandwidth is also available,
increasing the horizontal detail.
Typically, the video IC that generates the composite and s-video signals can also generate the analog RGB and YUV video signals.
PAL Consumer Markets
Most consumer video components in Europe support one or two 21-pin SCART connectors (also known as Peritel and Euroconnector). This
connection allows S-Video, RGB analog video, composite video, and analog stereo audio to be transmitted between equipment using a single
cable. The composite video signal must always be present, as it provides the basic video timing for the RGB video signals. It is important
to note that the 0.7V RGB signals do not have a blanking pedestal or sync information.
There are now several types of SCART
pinouts, depending on the specific functions implemented. Two of the most popular ones are shown in Tables 1 and 2. Pinout details are
shown in Figure 1.
NTSC Consumer Markets
High-end consumer video equipment for NTSC countries, such as projection TVs and line doublers, usually support analog RGB video signals.
To support these markets and applications, the video IC usually has the option of generating 0.714V RGB video signals (including a
7.5 IRE blanking pedestal). A additional 0.286V sync signal is also present on the green video signal, and may optionally be present on
the red and blue video signals.
Separate R, G, and B video cables are used rather than a SCART connector.
With the introduction of DVD players, an analog YUV video interface was developed for the North American consumer market. This
interface is also being incorporated on higher end TVs. Since it is such a new standard, there is some confusion of what to the label the
connector. For now, it may be labeled YUV, Y R-Y B-Y, or YCbCr. Three separate video cables with RCA connectors are used.
YUV Color Space
YUV is a scaled version of Y B'-Y R'-Y
Y B'-Y R'-Y is derived from gamma-corrected RGB as follows:
Y = 0.299R' + 0.587G' + 0.114B'
The B'-Y and R'-Y components are then scaled to generate the desired U and V amplitudes.
YUV Video Signals
The 1V Y signal includes a 0.3V sync and no blanking pedestal. The U and V color
difference video signals have a peak-to-peak amplitude of 0.7V
For flexibility, the option of generating a 1V Y signal with a
0.286V sync and a 7.5 IRE blanking pedestal is usually done.
This Application Note presented some of the analog RGB and YUV signal interfaces for the consumer video market. Some, such as SCART, have
been used for years. Others, such as YUV, are recent developments. Both are an attempt to improve the quality of video consumers
experience at home.
Using NTSC/PAL encoder that support analog RGB and YUV component video generation, allow
the design of DVD players and settop boxes that support these new interfaces in a cost-effective manner.