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STV0118

PAL/NTSC HIGH PERFORMANCE DIGITAL ENCODER

STMicroelectronics 

STV0118

IV - FUNCTIONAL DESCRIPTION

The STV0118 can operate either in master mode,

where it supplies all sync signals, or in 6 slave

modes, where it locks onto incoming sync signals.

The main functions are controlled by a micro-con-

troller via an I2C 2-wire bus. Refer to the “User’s

Register Description” for an exhaustive list of the

control possibilities available.

IV.1 - Data Input Format

The digital input is a time-multiplexed ITU-R656

/D1-type [Cb, Y, Cr, Y] 8-bit stream. Note that

“ITU-R” was formerly known as “CCIR”. Input sam-

ples are latched in on the rising edge (by default)

of the clock signal CKREF, whose nominal fre-

quency is 27MHz. Figure 1 illustrates the expected

data input format. Alternatively, a 54-Mbit/s stream

can be fed to the STV0118, refer to Section IV.17

(“dual encoding”) for details.

The STV0118 is able to encode interlaced and

non-interlaced video. One bit is sufficient to auto-

matically direct the STV0118 to process non-inter-

laced video. Update is performed internally on the

first frame sync active edge following the program-

ing of this bit. The non-interlaced mode is a

624/2 = 312 line mode or a 524/2 = 262 line mode,

where all fields are identical.

An ‘autotest’ mode is available by setting 3 bits

(sync[2:0]) within the configurations register0.

In this mode, a color bar pattern is produced, inde-

pendentlyfrom video input, in the adequate stand-

ard. As this mode sets the STV0118 in master

mode, VSYNC/ODDEV and HSYNC pins are then

in output mode.

IV.2 - Video Timing

The STV0118 outputs interlaced or non-interlaced

video in PAL-B, D, G, H, I, PAL-N, PAL-M or

NTSC-M standards and ‘NTSC- 4.43’ is also pos-

sible.

The 4-frame (for PAL) or 2 frame (for NTSC) burst

sequences are internally generated, subcarrier

generation being performed numerically with

CKREF as reference. Rise and fall times of syn-

chronizationtips and burst enveloppeare internally

controlled according to the relevant ITU-R and

SMPTE recommendations.

Figures 2 to 7 depict typical VBI waveforms.

It is possible to allow encoding of incoming YCrCb

data on those lines of the VBI that do not bear line

sync pulses or pre/post-equalisation pulses (see

Figures 2 to 7). This mode of operation is refered

to as “partial blanking” and is the default set-up. It

allows to keep in the encoded waveform any VBI

data present in digitized form in the incoming

YCrCb stream (e.g. WSS data, VPS, supplemen-

tary Closed-Captions line or StarSight data, etc.).

Alternatively,the complete VBI may be blanked(no

incoming YCrCb data encoded on these lines, “full

blanking”).

The complete VBI comprises of the following lines :

- for 525/60 systems (SMPTE line numbering con-

vention) : lines 1 to 19 and second half of line 263

to line 282.

- for 625/50 systems (CCIR line numbering con-

vention) : second half of line 623 to line 22 and

lines 311 to 335.

The ‘partial’ VBI consists of :

- for 525/60 systems (SMPTE line numbering con-

vention) : lines 1 to 9 and second half of line 263

to line 272.

- for 625/50 systems (CCIR line numbering con-

vention) : secondhalf of line 623 to line 5 and lines

311 to 318.

Full or partialblanking is controlledby configuration

bit ‘blkli in configuration register1’.

Note that :

- line 282 in 525/60/SMPTEsystems is either fully

blanked or fully active.

- line 23 in 625/60/CCIR systems is always fully

active.

In an ITU-R656-compliant digitalTV line, the active

portion of the digital line is the portion included

between the SAV (Start of Active Video) and EAV

(End of Active Video) words. However, this digital

active line starts somewhat earlier and may end

slightly later than the active line usually defined by

analog standards. The STV0118 allows two ap-

proaches :

- It is possible to encode the full digital line (720

pixels / 1440clock cycles). In this case, the output

waveform will reflect the full YCrCb stream in-

cluded between SAV and EAV.

- Alternatively, it is possible to drop some YCrCb

samples at the extremities of the digital line so

that the encoded analog line fits within the ‘ana-

log’ ITU-R/SMPTE specifications.

Selection between these two modes of operation

is performed with bit ‘aline’ in configuration regis-

ter 4.

In all cases, the transitions between horizontal

blanking and active video are shaped to avoid too

steep edges within the active video. Figure 8 gives

timings concerning the horizontal blanking interval

and the active video interval.

6/42

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