bt829bkrf ETC-unknow, bt829bkrf Datasheet - Page 37

• Manufacturer Part Number: bt829bkrf
• Description: Video Streamii Decoders
• Manufacturer: ETC-unknow

Bt829B/827B
VideoStream II Decoders
Vertical Scaling Ratio Register (VSCALE)
vertical scaling ratio. It defines the number of vertical lines output by the Bt829B.
The following formula should be used to determine the value to be entered into
this 13-bit register. The loaded value is a two’s-complement, negative value.
For example, to scale PAL/SECAM input to square pixel QCIF, the total number
of vertical lines for PAL square pixel is 156 (see Table 1-8).
NOTE:
Only the 13 least significant bits (LSBs) of the VSCALE value are used.
The five LSBs of VSCALE_HI and the 8-bit VSCALE_LO register form
the 13-bit VSCALE register. The three MSBs of VSCALE_HI are used to
control other functions. The user must take care not to alter the values of
the three most significant bits when writing a vertical scaling value. The
following C-code fragment illustrates changing the vertical scaling value:
VSCALE = ( 0x10000 – { [ ( scaling_ratio ) – 1] * 512 } ) & 0x1FFF
VSCALE = ( 0x10000 – { [ ( 4/1 ) –1 ] * 512 } ) & 0x1FFF
#define BYTE unsigned char
#define WORD unsigned int
#define VSCALE_HI 0x13
#define VSCALE_LO 0x14
BYTE ReadFromBt829B( BYTE regAddress );
void WriteToBt829B( BYTE regAddress, BYTE regValue );
void SetBt829BVScaling( WORD VSCALE )
{
BYTE oldVscaleMSByte, newVscaleMSByte;
/* get existing VscaleMSByte value from */
/* Bt829B VSCALE_HI register */
oldVscaleMSByte = ReadFromBt829B( VSCALE_HI );
/* create a new VscaleMSByte, preserving top 3 bits */
newVscaleMSByte = (oldVscaleMSByte & 0xE0) | (VSCALE >> 8);
/* send the new VscaleMSByte to the VSCALE_HI reg */
WriteToBt829B( VSCALE_HI, newVscaleMSByte );
/* send the new VscaleLSByte to the VSCALE_LO reg */
WriteToBt829B( VSCALE_LO, (BYTE) VSCALE );
}
= 0x1A00
D829BDSA
1.7 Video Scaling, Cropping, and Temporal Decimation
VSCALE is programmed with the
1.0 Functional Description
27