Video Port/VCXO Interpolated Control (VIC) Port User's Guide

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3.2.3 BT.656 Image Window and Capture

Capture Image

Ystart

Xstart

Ystop

Xstop

Field 1

Capture Image

Ystart

Xstart

Ystop

Xstop

Field 2

Hcount=0

Ycount=1

BT.656 Video Capture Mode

Table 3-4. Error Correction by Protection Bits (continued)

Received F, V, and H Bits

Received P

-P

Bits 000 001 010 011 100 101 110 111

1011 010 - 010 010 - 101 010 -

1100 - 001 110 - 110 - 110 110

1101 001 001 - 001 - 001 110 -

1110 - - - 011 - 101 110 -

1111 - 001 010 - 100 - - -

The BT.656 format is an interlaced format consisting of two fields. The video port allows capture of one or

both fields. The captured image is a subset of each field and can be larger or smaller than the active video

region. The captured image position is defined by the VC xSTRT1 and VC xSTOP1 registers for field 1, and

the VC xSTRT2 and VC xSTOP2 registers for field 2. The VCXSTART and VCXSTOP bits set the

horizontal window position for the field relative to the HCOUNT pixel counter. The VCYSTART and

VCYSTOP bits set the vertical position relative to the VCOUNT line counter. This is shown in Figure 3-1 .

HCOUNT increments on every chroma sample period (every other VCLKIN rising edge) for which capture

is enabled. Once VCOUNT = YSTART, line capture begins when HCOUNT = XSTART. It continues until

HCOUNT = XSTOP. A field's capture is complete when HCOUNT = VCXSTOP and VCOUNT =

VCYSTOP.

Figure 3-1. Video Capture Parameters

Table 3-5 shows common digital camera standards and the number of fields per second, number of active

lines per field, and the number of active pixels per line.

48 Video Capture Port SPRUEM1 – May 2007

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