Datasheet

TVP5154A

www.ti.com

SLES214C–DECEMBER 2007–REVISED SEPTEMBER 2010

3.4 Color Low-Pass Filter

In some applications, it is desirable to limit the Cb/Cr bandwidth to avoid crosstalk. This is especially true

in the case of video signals that have asymmetrical Cb/Cr sidebands. The provided color LP filters limit the

bandwidth of the Cb/Cr signals. Color LP filters are needed when the comb filtering turns off, due to

extreme color transitions in the input image. See Chrominance Control #2 Register (Section 7.2.27), for

the response of these filters. The filters have three options that allow three different frequency responses

based on the color frequency characteristics of the input video as shown in Figure 3-3.

Figure 3-3. Color Low-Pass Filter with Filter Characteristics, NTSC/PAL ITU-R BT.601 Sampling

3.5 Luminance Processing

The luma component is derived from the composite signal by subtracting the remodulated chroma

information. A line delay exists in this path to compensate for the line delay in the adaptive comb filter in

the color processing chain. The luma information is then fed into the peaking circuit, which enhances the

high-frequency components of the signal, thus, improving sharpness.

3.6 Chrominance Processing

For NTSC/PAL formats, the color processing begins with a quadrature demodulator. The Cb/Cr signals

then pass through the gain control stage for chroma saturation adjustment. An adaptive comb filter is

applied to the demodulated signals to separate chrominance and eliminate cross-chrominance artifacts.

An automatic color-killer circuit is also included in this block. The color killer suppresses the chrominance

processing when the burst amplitude falls below a programmable threshold (see I

C subaddress 06h,

Section 7.2.7). The SECAM standard is similar to PAL except for the modulation of color, which is FM

instead of QAM.

3.7 Timing Processor

The timing processor is a combination of hardware and software running in the internal microprocessor

that serves to control horizontal lock to the input sync pulse edge, AGC and offset adjustment in the

analog front end, and vertical sync detection.

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