TW2864D datasheet(21/110 Pages) RENESAS

21 / 110 page

TW2864

FN7745 Rev. 0.00

Page 21 of 110

September 28, 2012

Following is an example using pixel ratio to determine the horizontal scaling ratio. These equations should be used to

determine the scaling ratio to be written into the 12-bit HSCALE register assuming HACTIVE is programmed with 720

active pixels per line:

NTSC:

HSCALE = [720/Npixel_desired] * 256

PAL:

HSCALE = [(720/Npixel_desired)] * 256

Where: Npixel_desired is the nominal number of pixel per line.

For example, to output a CCIR601 compatible NTSC stream at SIF resolution, the HSCALE value can be found as:

HSCALE = [(720/320)] * 256 = 576 = 0x0240

However, to output a SQ compatible NTSC stream at SIF resolution, the HSCALE value should be found as:

HSCALE = [(640/320)] * 256 = 512 = 0x200

In this case, with total resolution of 768 per line, the HACTIVE should have a value of 640.

The vertical scaling determines the number of vertical lines output by the TW2864. The vertical scaling register

(VSCALE) is a 12-bit register, which is the concatenation of a 4-bit register SCALE_HI and an 8-bit register VSCALE_LO.

The maximum scaling ratio is 16:1. Following equations should be used to determine the scaling ratio to be written

into the 12-bit VSCALE register assuming VACTIVE is programmed with 240 or 288 active lines per field.

60Hz system:

VSCALE = [240/ Nline_desired] * 256

50Hz system:

VSCALE = [288/ Nline_desired] * 256

Where: Nline_desired is the number of active lines output per field.

The scaling ratios for some popular formats are listed in

Table 2. Error! Reference source not found. shows Horizontal Scaler Pre-Filter Curves.

SCALING RATIO

FORMAT

TOTAL

RESOLUTION

OUTPUT

RESOLUTION

HSCALE

VALUES

VSCALE

(FRAME)

1:1

NTSC SQ

NTSC CCIR601

PAL SQ

PAL CCIR601

780x525

858x525

944x625

864x625

640x480

720x480

768x576

720x576

0x0100

2:1 (CIF)

NTSC SQ

NTSC CCIR601

PAL SQ

PAL CCIR601

390x262

429x262

472x312

432x312

320x240

360x240

384x288

360x288

0x0200

4:1 (QCIF)

NTSC SQ

NTSC CCIR601

PAL SQ

PAL CCIR601

195x131

214x131

236x156

216x156

160x120

180x120

192x144

180x144

0x0400

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