Hi All,
I would like to ask a question on several “+1”s in VPFE user guide, SPRU977a.
On page 129, Table 61, for HORZ_INFO field NPH:
Number of pixels, horizontal. Sets number of horizontal pixels that are output to SDRAM = NPH + 1. This bit field is latched by VD.
So for BT.656 data which has 720 active samples and occupies 1440 bytes (due to 4:2:2 YUV), do I need to set NPH to 1439? This seems pretty weird to me simply because this is somehow awkward and odd here.
And on page 128, Table 59, fields of register HD_VD_WID:
|
Field |
Value |
Description |
|
HDW |
0-FFFh |
Width of HD sync pulse, if output. HDW + 1 pixel clocks.
|
|
VDW |
0-FFFh |
Width of VD sync pulse, if output. VDW + 1 lines.
|
How should I understand these two “+1”s here? If I am setting HDW to 0, will the width of HD sync pulse be 0+1 =1 (is it in periods of clock signals? Half period or full period?)? The same question applies to VDW: if I am setting VDW to 0, will the width of VD sync pulse be 0+1=1 (unit?)?
My guess is that this relates to 0-based indexing/counting which is common in computer science/engineering. In view of this, the question on HDW and VDW seems less disturbing. But still if NPH in the first question needs to be set to 1439, the number of bytes per line minus one, I still find it quite strange a rule here.
I would appreciate anyone who could give his opinion.
Sincerely,
Zheng
