Hi Maxime,

W dniu 15.08.2022 o 10:37, Maxime Ripard pisze:

Hi,

On Fri, Jul 29, 2022 at 07:55:30PM +0200, Mateusz Kwiatkowski wrote:

quoted

Hi Maxime,

I think that declaring PAL-B and SECAM-B as the only supported 576i
norms is a bit random.

Starting with this patch, PAL-N should be supported as well, right?

Oh, sure. I forgot about it. My brain was too focused on the "standard PAL"
modes, which excludes PAL-N.

quoted

Norms B, D, G, H, I, K, K1 and L (for both PAL and SECAM) are
essentially identical if we're talking about baseband signals, AFAIK
they only differ when those are modulated as RF signals. I'm not sure
if there's a point to differentiating those (that's more about patch
05/35) unless we need to deal with some device that actually features
an RF modulator.

What I was aiming for is to have all the cases we have in all the
drivers covered so that we can make that property generic. i915
declares and uses all those variants:

https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/i915/display/intel_sdvo.c#L68

Especially since it's i915 and it's pretty much the standard as far as
the uAPI goes, I'd rather avoid any regression there.

OK, if there are already drivers that differentiate those, then it doesn't make
sense to introduce regressions. And yes, there is plenty of software already out
there that differentiate between those modes in the context of composite video.
It still doesn't make much sense from the engineering point of view, though.

quoted

But if we do want to have all those norms separate, then I'd say that
VC4 should declare support for all of those, and all should map to the
same VEC settings. Some users from e.g. the UK might think that they
won't get proper picture if PAL-I is not on the list of supported
norms. Same goes for e.g. SECAM-D/K in the former Soviet territories,
and so on.

I'd be open to it, but we can always extend vc4 to support those modes
later on. The work you did to make that easier should make it trivial.

Doing that in the future is OK as well. I just wanted to point out that
PAL-B/D/G/H/I/K/K1/L (and same for SECAM) is the same exact thing as far as
baseband composite video is concerned, so declaring only one of those as
supported is potentially misleading for anybody who is not aware of that fact.

Maxime

Best regards,
Mateusz Kwiatkowski

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