Texas Instruments TVP5147M1PFP manual Digital Video Processing, 1 2⋅ Decimation Filter

Functional Description

2.2Digital Video Processing

Figure 2−2 is a block diagram of the TVP5147M1 digital video decoder processing. This block receives digitized video signals from the ADCs and performs composite processing for CVBS and S-video inputs and YCbCr signal enhancements for CVBS and S-video inputs. It also generates horizontal and vertical syncs and other output control signals such as genlock for CVBS and S-video inputs. Additionally, it can provide field identification, horizontal and vertical lock, vertical blanking, and active video window indication signals. The digital data output can be programmed to two formats: 20-bit 4:2:2 with external syncs or 10-bit 4:2:2 with embedded/separate syncs. The circuit detects pseudosync pulses, AGC pulses, and color striping in Macrovision-encoded copy-protected material. Information present in the VBI interval can be retrieved and either inserted in the ITU-R BT.656 output as ancillary data or stored in internal FIFO and/or registers for retrieval via the host port interface.

CH1 A/D

CH2 A/D

2⋅

Decimation

2⋅

Decimation

Copy		VBI Data	Slice VBI Data
Protection
		Processor
Detector
	CVBS/Y	Composite	YCbCr
	C/CbCr
		Processor
XTAL1		FID
XTAL2	Timing	VS/VBLK
RESETB		HS/CS
	Processor

PWDN	GLCO
DATACLK	AVID

Output

Formatter

Host

Interface

Y[9:0]

C[9:0]

SCL

SDA

Figure 2−2. Digital Video Processing Block Diagram

2.2.1 2⋅ Decimation Filter

All input signals are typically oversampled by a factor of 2 (27 MHz). The A/D outputs initially pass through decimation filters that reduce the data rate to 1⋅ the pixel rate. The decimation filter is a half-band filter. Oversampling and decimation filtering can effectively increase the overall signal-to-noise ratio by 3 dB.

2.2.2 Composite Processor

Figure 2−3 is a block diagram of the TVP5147M1 digital composite video processing circuit. This processing circuit receives a digitized composite or S-video signal from the ADCs and performs Y/C separation (bypassed for S-video input), chroma demodulation for PAL/NTSC and SECAM, and YUV signal enhancements.

The 10-bit composite video is multiplied by the subcarrier signals in the quadrature demodulator to generate color difference signals U and V. The U and V signals are then sent to low-pass filters to achieve the desired bandwidth. An adaptive 5-line comb filter separates UV from Y based on the unique property of color phase shifts from line to line. The chroma is remodulated through a quadrature modulator and subtracted from line-delayed composite video to generate luma. This form of Y/C separation is completely complementary, thus there is no loss of information. However, in some applications, it is desirable to limit the U/V bandwidth to avoid crosstalk. In that case, notch filters can be turned on. To accommodate some viewing preferences, a peaking filter is also available in the luma path. Contrast, brightness, sharpness, hue, and saturation controls are programmable through the host port.

SLES140A—March 2007 TVP5147M1PFP 11