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SAA7126H

Digital video encoder

Philips Electronics 

Philips Semiconductors

Digital video encoder

Product specification

SAA7126H; SAA7127H

7 FUNCTIONAL DESCRIPTION

The digital video encoder encodes digital luminance and

colour difference signals into analog CVBS, S-video and

simultaneously RGB or CR-Y-CB signals. NTSC-M,

PAL-B/G and sub-standards are supported.

Both interlaced and non-interlaced operation is possible

for all standards.

The basic encoder function consists of subcarrier

generation, colour modulation and insertion of

synchronization signals. Luminance and chrominance

signals are filtered in accordance with the standard

requirements of “RS-170-A” and “ITU-R BT.470-3”.

For ease of analog post filtering the signals are twice

oversampled with respect to the pixel clock before

digital-to-analog conversion.

The total filter transfer characteristics are illustrated in

Figs 3 to 8. The DACs for Y, C and CVBS are realized with

full 10-bit resolution; 9-bit resolution for RGB output. The

CR-Y-CB to RGB dematrix can be bypassed optionally in

order to provide the upsampled CR-Y-CB input signals.

The 8-bit multiplexed CB-Y-CR formats are “CCIR 656”

(D1 format) compatible, but the SAV and EAV codes can

be decoded optionally, when the device is operated in

slave mode. Two independent data streams can be

processed, one latched by the rising edge of LLC1, the

other latched by the falling edge of LLC1. The purpose of

that is e.g. to forward one of the data streams containing

both video and On Screen Display (OSD) information to

the RGB outputs, and the other stream containing video

only to the encoded outputs CVBS and S-video.

For optimum display of RGB signals through a

euro-connector TV set, an early composite sync pulse (up

to 31 LLC1 clock periods) can be provided optionally on

the CVBS output.

It is also possible to connect a Philips digital video decoder

(SAA7111, SAA7711A, SAA7112 or SAA7151B) to the

SAA7126H; SAA7127H. Via the RTCI pin, connected to

RTCO of a decoder, information concerning actual

subcarrier, PAL-ID and (with SAA7111 and newer types)

definite subcarrier phase can be inserted.

The SAA7126H; SAA7127H synthesizes all necessary

internal signals, colour subcarrier frequency and

synchronization signals from that clock.

Wide screen signalling data can be loaded via the I2C-bus

and is inserted into line 23 for standards using 50 Hz field

rate.

VPS data for program dependent automatic start and stop

of such featured VCR’s is loadable via the I2C-bus.

The IC also contains closed caption and extended data

services encoding (line 21), and supports anti-taping

signal generation in accordance with Macrovision. It is also

possible to load data for copy generation management

system into line 20 of every field (525/60 line counting).

A number of possibilities are provided for setting different

video parameters, such as:

• Black and blanking level control

• Colour subcarrier frequency

• Variable burst amplitude, etc.

During reset (RESET = LOW) and after reset is released,

all digital I/O stages are set to the input mode and the

encoder is set to PAL mode and outputs a ‘black burst’

signal on CVBS and S-video outputs, while RGB outputs

are set to their lowest output voltages. A reset forces the

I2C-bus interface to abort any running bus transfer.

7.1 Data manager

In the data manager, alternatively to the external video

data, a pre-defined colour look-up table located in this

block can be read out in a pre-defined sequence (8 steps

per active video line), achieving a colour bar test pattern

generator without the need for an external data source.

7.2 Encoder

7.2.1 VIDEO PATH

The encoder generates out of Y, U and V baseband

signals luminance and colour subcarrier output signals,

suitable for use as CVBS or separate Y and C signals.

Luminance is modified in gain and in offset (latter

programmable in a certain range to enable different black

level set-ups). A blanking level can be set after insertion of

a fixed synchronization pulse tip level in accordance with

standard composite synchronization schemes. Other

manipulations used for the Macrovision anti-taping

process such as additional insertion of AGC super-white

pulses (programmable in height) are supported by the

SAA7126H only.

In order to enable easy analog post filtering, luminance is

interpolated from a 13.5 MHz data rate to a 27 MHz data

rate, providing luminance in 10-bit resolution. The transfer

characteristic of the luminance interpolation filter are

illustrated in Figs 5 and 6. Appropriate transients at

start/end of active video and for synchronization pulses

are ensured.

2002 Oct 15

7

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