Nevion DAC-AVA-DMUX - Manual (Page 21)

DAC-AVA-DMUX Rev. A
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4.3 Detailed control in Gyda mode
4.3.1 Video DAC
The video DAC has three configurable outputs, with the following combinations available:
- CVBS/CVBS/CVBS
- CVBS/Y/C
- Y/Pb/Pr
- R/G/B
This setting only applies to SD video. When HD video is routed to the video DAC, the
output will always be YPbPr. For CVBS and S-Video the following modulations are
available:
- PAL B/G
- NTSC
- PAL M
- PAL N
The board can handle 50Hz-based input signals as well as 60Hz-based with and without
pulldown, but can’t convert a 50Hz-based input to a 60Hz-based output and vice versa. The
modulation setting is therefore split in two, one to select between NTSC and PAL M output
for 60Hz-based sources, and one to select between PAL B/G and PAL N for 50Hz-based
sources.
It is also possible to turn black setup (“pedestal”) on or off. This setting only applies to
NTSC.
PAL Wide Screen Signaling (WSS) is also supported, and while the HD input is always
16:9, SD inputs can have WSS values already embedded. The user can select to strip off
any existing WSS information by setting mode to Off, or to override the current WSS value
by setting mode to On and specifying a new value, or set the mode to Auto. The Auto mode
will signal 4:3 or 16:9 based on the aspect ratio bit in SMPTE 352M byte 3, or turn WSS off
if no SMPTE 352M packages are available.
When specifying WSS values, the user should observe that the WSS value is really a 14-bit
number with other information besides just aspect ratio. Aspect ratio is contained in the
lower 4 bits, and the table below covers only those bits.
WSS value Aspect ratio Picture placement Active lines
0+8=8 4:3 Full 576
1+0=1 14:9 Letterbox centre 504
2+0=2 14:9 Letterbox top 504
3+8=11 16:9 Letterbox centre 430
4+0=4 16:9 Letterbox top 430
5+8=13 >16:9 Letterbox deeper than 16:9 undefined
6+8=14 14:9 Full- height 4:3, framed to be “14:9-safe” 576
7+0=7 16:9 Full-height 16:9 (anamorphic) 576
Note
the occasional “+8” in the first column above. It stems from the fourth aspect ratio bit,
a parity bit over the first three.
4.3.2 De-glitcher
The de-glitcher corrects timing errors within a single video line. The de-glitcher has a 2048
samples buffer. When the first signal is present, we call it the “initial phase signal”, data is
taken from the centre of this buffer. If the timing reference of the video signal changes,