STV2310 datasheet(19/112 Pages) STMICROELECTRONICS

19 / 112 page

19/112

STV2310

Functional Description

The practical value of the 4 x fSC frequency depends on the actual input TV standard.

4.4

Luminance and Chrominance Separation

4.4.1

General Description

The Y/C Separator separates the chrominance (C) component from the composite signal which

also includes the luminance (Y), synchronization and color burst (subcarrier) components. In

normal operation (NTSC and PAL standards), this is done through comb or notch filtering which

relies on the correlation of consecutive lines. For SECAM inputs, a Chroma Bandpass/Trap filter

system is required. If an S-Video input is selected, Y/C separation is not required and the Y/C

Separator operates in Bypass mode. Y/C delay adjustment can be done with both pixel and sub-

pixel accuracy.

4.4.2

Programming

Once the samples processed by the input SRC have been stored in RAM, the type of input signal

(Y/C or CVBS) must be specified before the chroma component can be separated from the CVBS

input signal. This is done by setting the SVIDEOSEL bit in the DDECCONT0 register.

The Y/C separator block can either operate in auto-adaptive mode (Default mode) or Forced

Separation mode (notch). This operating mode is selected by the COMB_MODE bit in the

DDECCONT18 register:

● Chroma Bandpass/Trap filtering is forced

● Adaptative Comb Filtering mode is forced. (This applies to PAL/NTSC signals only. SECAM

signals remain processed by Chroma Bandpass/Trap filter)

The notch filter width used in the Y/C separation can be adjusted from narrow to wide by the

BW_SEL[2:0] bits in the DDECCONT18 register. Luma Chroma delay can be adjusted by the

DEM_YC_DELAY[3:0] bits in the DDECCONT15 register and DDECCONT1A register, bit [5:0].

Figure 10: SECAM Trap Filter Frequency Response

STV2310 データシート(PDF) 19 Page - STMicroelectronics