>I understand that the lowest "legal" Y' value is 16. I assume it comes
>right off my camera in the range 16-235? But the libdv and kino
Yep -- off the camera in 16-235 range.
>documentation led me to believe that to get the same brightness on a
>computer monitor as I would get playing back from my camera to the TV,
>I would need another 16 added on. From the libdv README:
>
> NTSC Setup/Pedestal
> ===================
> The decoder's add_ntsc_setup option should only be used
> by North American NTSC users when viewing the video on your computer
> monitor. It should never be used when transcoding, image processing,
> or rendering.
That doesn't make any sense. I mean, the logic just isn't logical.
If 16 is black for transcoding and image processing, it should be black
for the display, too.
>I'm talking about the libdv option add_ntsc_setup, which adds 16 to
>Y'. Since it shifts Y' I don't think any software should do it by
>default, and I spent a while tracking down why different programs'
>output had different brightness levels. yuvcorrect -M STAT is handy
>for that. It all traces back to add_ntsc_setup in libdv.
>
> "Yes, setup, please." It's a question of how the analog signal is
> interpreted; it's all the same once it is digital (thankfully).
>
>So, to be clear: I want Y' values between 16-235 everywhere, in
>whatever digital format?
The answer is Yes; 16 == Black in digital video.
I went and checked out the histograms from yuvcorrect like you suggested,
and, lo and behold, smil2yuv *is* adding an additional 16 to the luma.
(i.e. the smallest Y' value I see in the output is ~32...)
That 'add_ntsc_setup' doesn't make any sense to me whatsoever; I get the
impression that someone jumped to a wrong conclusion when they read some
specification.
And it is certainly a bug in smil2yuv to have that turned on; even following
their own explanation, it shouldn't be on for transcoding.
Have you asked about this on the libdv or kino lists? I'm curious to see
what kind of reasoning those guys give when pressed for a better explanation.
(And if *I* am wrong, I want to be corrected!)
"I know this so I point at Q-tip
and he states 'Black is Black'"
-De La Soul, "Me, Myself, and I"
-matt m.
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