STW8019 datasheet(12/66 Pages) STMICROELECTRONICS

12 / 66 page

STw8009/STw8019

Functional description

11/65

4.5

Video timing

The DENC outputs video in PAL-B,D,G,H,I, PAL-N, PAL-M or NTSC-J, M standards (‘NTSC-

4.43’ is also possible).

The burst sequences are internally generated, subcarrier generation being performed

numerically with PIX_CLK as reference. 4-frame bursts are generated for PAL or 2-frame

bursts for NTSC. Rise and fall times of synchronization tips and burst envelope are internally

controlled according to the relevant ITU-R and SMPTE recommendations.

Figure 5, 6, 7 and 8 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-equalization pulses (

Figure 5, 6, 7 and 8). This mode of

operation is referred 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.

Alternatively, the complete VBI may be fully blanked, so no incoming YCrCb data encoded

on these lines.

The ‘complete’ VBI comprises of the following lines:

–

for 525/60 systems (SMPTE line numbering convention): lines 1 to 19 and second

half of line 263 to line 282

–

for 625/50 systems (CCIR line numbering convention): 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 convention): lines 1 to 9 and second

half of line 263 to line 272

–

for 625/50 systems (CCIR line numbering convention): second half of line 623 to

line 5 and lines 311 to 318

Full or partial blanking is controlled by configuration bit ‘

blkli in configuration register1’.

Note:

line 282 in 525/60/SMPTE systems is either fully blanked or fully active.

line 23 in 625/60/CCIR systems is always fully active.

In an ITU-R656-compliant digital TV 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 DENC permits two approaches:

●

Encodes the full digital line (720 pixels / 1440 clock cycles). In this case, the output

waveform will reflect the full YCrCb stream included between SAV and EAV.

●

Drops some YCrCb samples at the extremities of the digital line so that the encoded

analog line fits within the ‘analog’ ITU-R/SMPTE specifications.

Selection between these two modes of operation is performed with bit ‘aline’ in configuration

In all cases, the transitions between horizontal blanking and active video are shaped to

avoid too steep edges within the active video. Figure 11 on page 15 gives timings

concerning the horizontal blanking interval and the active video interval.

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