Texas Instruments TMS320DM648 manual Y/C Video Capture Mode, 1 Y/C Capture Channels

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Y/C Video Capture Mode

Figure 3-2. 8-Bit BT.656 FIFO Packing

VCLKINA / VCLKINB

VDIN[9−2] / VDIN[9−12]

Cb 0 Y 0

Cr 0

Y 1

Cb 1

Y 2

Cr 1

Y 3

Cb 2

Y 4

Cr 2

Y 5

63

56

55

48

47

40

39

32

31

24

23

16

15

8

7

0

Y 31

Y 30

Y 29

Y 28

Y 27

Y 26

Y 25

Y 24

Y 23

Y 22

Y 21

Y 20

Y 19

Y 18

Y 17

Y 16

Y 15

Y 14

Y 13

Y 12

Y 11

Y 10

Y 9

Y 8

Y FIFO

Y 7

Y 6

Y 5

Y 4

Y 3

Y 2

Y 1

Y 0

63

56

55

48

47

40

39

32

31

24

23

16

15

8

7

0

Cb 15

Cb 14

Cb 13

Cb 12

Cb 11

Cb 10

Cb 9

Cb 8

Cb FIFO

Cb 7

Cb 6

Cb 5

Cb 4

Cb 3

Cb 2

Cb 1

Cb 0

48

47

40

39

16

15

8

7

0

63

56

55

32

31

24

23

Cr 15

Cr 14

Cr 13

Cr 12

Cr 11

Cr 10

Cr 9

Cr 8

Cr FIFO

Cr 7

Cr 6

Cr 5

Cr 4

Cr 3

Cr 2

Cr 1

Cr 0

Little-Endian Packing

3.3Y/C Video Capture Mode

The Y/C capture mode is similar to the BT.656 capture mode but captures 8-bit 4:2:2 data on separate luma and chroma data streams. One data stream contains Y samples and the other stream contains multiplexed Cb and Cr samples co-sited with every other Y sample. The Y samples are written into a Y FIFO and the chroma samples are de-multiplexed and written into separate Cb and Cr FIFOs for transfer into Y, Cb, and Cr buffers in DSP memory.

The Y/C capture mode supports HDTV standards such as SMPTE260, SMPTE296, and BT.1120 with embedded EAV and SAV codes. It also supports SDTV YCbCr modes that use separate control signals (sometimes called CCIR601 mode)

As with the BT.656 capture mode, data bytes where the 8 most-significant bits are all set to 1 (FFh) or are all cleared to 0 (00h) are reserved for data identification purposes and consequentially only 254 of the possible 256 8-bit words may be used to express signal value.

3.3.1 Y/C Capture Channels

Because Y/C mode requires the entire VDATA bus, only single channel operation is supported. If the DCHDIS bit in VPCTL is set, then Y/C mode cannot be selected. Y/C capture takes place on channel A only. Both embedded timing references and external control inputs are supported.

3.3.2 Y/C Timing Reference Codes

Many high-resolution Y/C interface standards provide for embedded timing reference codes. These codes are identical to those used in the BT.656 standard except that they appear on both the luma (Y) and chroma (CbCr) data streams in parallel.

3.3.3 Y/C Image Window and Capture

The SDTV Y/C format (CCIR601) is an interlaced format consisting of two fields just like BT.656. HDTV Y/C formats may be interlaced or progressive scan. For interlaced capture, the capture windows are programmed identically to BT.656 mode. For progressive scan formats, only field1 is used.

In Y/C mode, HCOUNT increments on every luma sample period (every VCLKINA rising edge) for which capture is enabled. Once YCOUNT = YSTART, line capture begins when HCOUNT = XSTART. It continues until HCOUNT = XSTOP. A field'scapture is complete when HCOUNT = VCXSTOP and

VCOUNT = VCYSTOP.

50 Video Capture Port SPRUEM1 –May 2007

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