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4.2 BT.656 Video Display Mode
The BT.656 display mode outputs 8-bit or 10-bit 4:2:2 co-sited luma and chroma
data multiplexed into a single data stream. Pixels are output in pairs with each
pair consisting of two luma samples and two chroma samples. The chroma
samples are associated with the first luma pixel of the pair. Output pixels are
valid on the positive edge of VCLKOUT in the sequence CbYCrY as shown in
Figure 4–8.
Figure 4–8. BT.656 Output Sequence
VCLKOUT
VDOUT[9–0]
4.2.1
Display Timing Reference Codes
The end active video (EAV) code and start active video (SAV) code are issued
at the start of each video line. EAV and SAV codes have a fixed format. The
format is shown in Table 3–2 (page 3-4). The EAV and SAV codes define the
end and start of the horizontal-blanking interval, respectively, and they also
indicate the current field number and the vertical blanking interval. The SAV
and EAV codes have a 4-bit protection field to ensure valid codes. The video
display module generates these protection bits as part of the SAV and EAV
codes. Table 3–3 (page 3-5) shows possible combinations of valid SAV and
EAV codes with their protection bits. The video display pipeline generates SAV
and EAV sync codes and inserts them into the output video stream according
to the BT.656 specification.
The BT.656 line timing is shown in Figure 4–9 and Figure 4–10. Each line
begins with an EAV code, a blanking interval, an SAV code, followed by the line
of active video. The EAV code indicates the end of active video for the previous
line, and the SAV code indicates the start of active video for the current line.
Figure 4–9. 525/60 BT.656 Horizontal Blanking Timing
FPCOUNT
720 721 722 723
VCLKOUT
4
VDOUT[9–0]
EAV
Blanking Data
SPRU629
Cb0
Y0
Cr0
One Line
855 856 857
0
268
4
Blanking
SAV
BT.656 Video Display Mode
Y1
Cb1
Y2
Cr1
Y3
1
2
718 719 720 721 722 723
1440
Active Video
Video Display Port
Cb2
Y4
Next Line
EAV
4-9
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