User manual

RC200/203 Manual
www.celoxica.com Page 59
Parameters:
Standard: A code selecting the TV colour-encoding standard.
Possible values
RC200VideoInStandardPALNTSC or
RC200VideoInStandardSECAM
The first code selects PAL or NTSC and the second selects
SECAM. The default value is
RC200VideoInStandardPALNTSC.
Timing: 1 or more clock cycles.
Description:
Selects which colour-encoding standard to expect at the
selected input.
You need to call
RC200VideoInSetInput() before using this
macro. The video input is capable of decoding both PAL and
NTSC from the same setting.
5.12.4 Reading a pair of YCrCb pixels
extern macro proc RC200VideoInReadPixelPairYCrCb (XPtr, YPtr, YCrCbPtr);
Parameters: XPtr: Pointer to an lvalue of type unsigned 9.
YPtr: Pointer to an lvalue of type unsigned 9.
YCrCbPtr: Pointer to an lvalue of type unsigned 32.
Timing: 1 or more clock cycles (read blocks until data is ready).
Description:
Reads a pair of YCrCb encoded pixels from the video input
selected by
RC200VideoInSetInput(). YCrCb is the native
output from the video decoder and therefore requires the
least hardware.
After the macro returns,
(*XPtr, *YPtr) are the coordinates
of the most recently sampled pixel, which has the colour
value (
*YCrCbPtr). Each pixel pair is presented at most once
(pixels can be missed if they are not read quickly enough), at
a rate of 6.75 MHz during the visible portion of the input
video. The YCrCb data is formatted as follows:
(*YCrCbPtr)[31:24] - Overall Cb (blue chrominance) value
(*YCrCbPtr)[23:16] - Left-hand pixel Y (luminance) value
(*YCrCbPtr)[15: 8] - Overall Cr (red chrominance) value
(*YCrCbPtr)[ 7: 0] - Right-hand pixel Y (luminance) value
The chrominance and luminance values follow the CCIR601
standard ranges. The value in
XPtr ranges from 0 to 718 (in
2-pixel increments) for an entire video line of 720 pixels. The
value returned in
YPtr varies from 0 to the number of visible
lines – 1: 0-575 for PAL and 0-479 for NTSC.