linux-kernel - Re: [PATCH v10 18/19] drm/vc4: vec: Add support for more analog TV standards

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Message-ID: <20221117171401.3ogenv6g5nszufmm@houat>
Date:   Thu, 17 Nov 2022 18:14:01 +0100
From:   Maxime Ripard <maxime@...no.tech>
To:     Mauro Carvalho Chehab <mauro.chehab@...ux.intel.com>
Cc:     Samuel Holland <samuel@...lland.org>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Ben Skeggs <bskeggs@...hat.com>, Chen-Yu Tsai <wens@...e.org>,
        David Airlie <airlied@...ux.ie>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
        Emma Anholt <emma@...olt.net>,
        Karol Herbst <kherbst@...hat.com>,
        Lyude Paul <lyude@...hat.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Daniel Vetter <daniel@...ll.ch>,
        Dom Cobley <dom@...pberrypi.com>,
        Dave Stevenson <dave.stevenson@...pberrypi.com>,
        Phil Elwell <phil@...pberrypi.com>,
        nouveau@...ts.freedesktop.org, intel-gfx@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        Mateusz Kwiatkowski <kfyatek+publicgit@...il.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Noralf Trønnes <noralf@...nnes.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        linux-sunxi@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v10 18/19] drm/vc4: vec: Add support for more analog TV
 standards

On Thu, Nov 17, 2022 at 04:49:28PM +0100, Mauro Carvalho Chehab wrote:
> On Thu, 17 Nov 2022 10:29:01 +0100
> Maxime Ripard <maxime@...no.tech> wrote:
> 
> > From: Mateusz Kwiatkowski <kfyatek+publicgit@...il.com>
> > 
> > Add support for the following composite output modes (all of them are
> > somewhat more obscure than the previously defined ones):
> > 
> > - NTSC_443 - NTSC-style signal with the chroma subcarrier shifted to
> >   4.43361875 MHz (the PAL subcarrier frequency). Never used for
> >   broadcasting, but sometimes used as a hack to play NTSC content in PAL
> >   regions (e.g. on VCRs).
> 
> > - PAL_N - PAL with alternative chroma subcarrier frequency,
> >   3.58205625 MHz. Used as a broadcast standard in Argentina, Paraguay
> >   and Uruguay to fit 576i50 with colour in 6 MHz channel raster.
> 
> That's not right. Argentina uses a different standard than Paraguay and
> Uruguai.
> 
> See, there are two variants of PAL/N. The original one and PAL/N' - also
> called PAL/NC or PAL/CN (Combination N). Some of the timings are 
> different on /NC variant.
> 
> As far as I'm aware, PAL/Nc is used in Argentina, while
> PAL/N is used in Paraguai and Uruguai, but I may be wrong on that,
> as it has been a long time since had to touch on this.
> 
> > - PAL60 - 480i60 signal with PAL-style color at normal European PAL
> >   frequency. Another non-standard, non-broadcast mode, used in similar
> >   contexts as NTSC_443. Some displays support one but not the other.
> 
> > - SECAM - French frequency-modulated analog color standard; also have
> >   been broadcast in Eastern Europe and various parts of Africa and Asia.
> >   Uses the same 576i50 timings as PAL.
> 
> This is also wrong. just like PAL, there are several variants of SECAM,
> one used in France, and a different one in France overseas and on
> previous France colonies in Africa and Asia. Eastern Europe also used
> different variants of SECAM.

And that's fine? Everything I did is supposed to be easy to extend if
and when needed, so if someone has some interest in providing support
for more standards, they are very welcome to do so.

I won't do it in this series though.

Maxime

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