Re: [PATCH] Remove illogical/bogus "Automatic" mode from "Broadcast RGB" property

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Mon, Apr 13, 2015 at 03:13:12PM +0100, Damien Lespiau wrote:
> On Wed, Apr 08, 2015 at 07:18:06PM +0800, Tom Yan wrote:
> > https://bugzilla.kernel.org/show_bug.cgi?id=94921
> > 
> > As mentioned in the above bug report, switching output color range
> > "Automatically" according to current mode does not make sense in
> > computer use case.
> 
> Current code seems correct to me after re-reading CEA-861-E again. However can
> we do better? Maybe! From the spec:
> 
> "The QS (AVI Q support) bit of byte 3 allows a display to declare that it
> supports the reception of either type of quantization range for any video
> format, under the direction of InfoFrame Q data (see Section 6.4 for
> information concerning bits Q1 and Q0). This allows a source to override the
> default quantization range for any video format.  If the sink declares a
> selectable RGB Quantization Range (QS=1) then it shall expect limited range
> pixel values if it receives Q=1 and it shall expect full range pixel values if
> it receives Q=2 (see section 6.4). For other values of Q, the sink shall expect
> pixel values with the default range for the transmitted video format."
> 
> So, for sinks that support it, we could default to sending the full
> range picture and overriding the quantization bit in the AVI infoframe.
> 
> You could you try to run edid-decode [1] on your sink EDID to check if
> it supports overriding the quantization level (I added decoding the VCDB
> a while back).
> 
> Ville, what do you think?

Sure, if you can actually find a display that supports the Q bit.
I've not seen one yet :( They should have just made it mandatory,
otherwise I fear it's never going to catch on.

-- 
Ville Syrjälä
Intel OTC
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