Re: [PATCH] Implement Limited Video Range

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

On Mon, Nov 30, 2015 at 09:43:32AM +0100, Daniel Vetter wrote:
> On Mon, Nov 30, 2015 at 08:08:48AM +0100, Peter Frühberger wrote:
> > (Resent cause of moderation)
> > 
> > This implements a highly needed feature in a minimal non instructive way.
> > Consider a Limited Range display (like most TVs) where you want to watch a
> > decoded video. The TV is set to limited range and the intel driver also
> > uses full scaling Limited 16:235 mode, e.g. if you display the gray value
> > 16 - the driver will postprocess it to something like ~ 22.
> > 
> > The following happens currently in linux intel video world:
> > Video is decoded with e.g. vaapi, the decoded surface is either used via
> > EGL directly in Limited Range. Limited Range processing takes place and at
> > the end while rendering the intel driver will scale down the limited range
> > data again as it cannot distunguish of the data it gets when e.g. rendering
> > with OpenGL like we succesfully do in kodi.
> > 
> > Another use case is vaapi when using the old vaCopySurfaceGLX
> > (vaPutSurface) which would automatically use BT601 / BT709 matrix to
> > upscale the content without any dithering to Full Range RGB. Later on this
> > is scaled down again with the Limited 16:235 setting and output. Quality
> > degrades two times.
> > 
> > Users and applications widely used want to make sure that colors appear on
> > screen like they were processed after the last processing step. In video
> > case two use cases make sense:
> > 
> > a) scaling limited range to full range with dithering applied when you need
> > to output fullrange
> > b) already having limited range and outputting that without any further
> > touching by the driver
> > 
> > Use case a) is already possible. Usecase b) will be possible with the
> > attached patch. It is a possibility to get Limited Range on screen in
> > perfect quality in 2k15.
> > 
> > For the future a userspace api to provide info frames and so on in a
> > generic way should be considered but until we have this I bet we have 2
> > years to go. This solution also works on X11 (without wayland) and is
> > useful for existing applications.
> > 
> > Thanks much for consideration.
> > 
> > ---
> > From deaa9d730c08aefefe3671d073d93d970bb39a31 Mon Sep 17 00:00:00 2001
> > From: fritsch <peter.fruehberger@gmail.com>
> > Date: Sun, 29 Nov 2015 16:38:14 +0100
> > Subject: [PATCH] Intel: Implement Video Color Range
> > 
> > ---
> >  drivers/gpu/drm/i915/i915_drv.h      |  1 +
> >  drivers/gpu/drm/i915/intel_display.c |  4 ++--
> >  drivers/gpu/drm/i915/intel_drv.h     |  8 ++++++++
> >  drivers/gpu/drm/i915/intel_hdmi.c    | 17 +++++++++++++++--
> >  drivers/gpu/drm/i915/intel_modes.c   |  1 +
> >  5 files changed, 27 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/i915_drv.h
> > b/drivers/gpu/drm/i915/i915_drv.h
> > index 95bb27d..e453461 100644
> > --- a/drivers/gpu/drm/i915/i915_drv.h
> > +++ b/drivers/gpu/drm/i915/i915_drv.h
> > @@ -3449,6 +3449,7 @@ int intel_freq_opcode(struct drm_i915_private
> > *dev_priv, int val);
> >  #define INTEL_BROADCAST_RGB_AUTO 0
> >  #define INTEL_BROADCAST_RGB_FULL 1
> >  #define INTEL_BROADCAST_RGB_LIMITED 2
> > +#define INTEL_BROADCAST_RGB_VIDEO 3
> > 
> >  static inline uint32_t i915_vgacntrl_reg(struct drm_device *dev)
> >  {
> > diff --git a/drivers/gpu/drm/i915/intel_display.c
> > b/drivers/gpu/drm/i915/intel_display.c
> > index 71860f8..ea40d81 100644
> > --- a/drivers/gpu/drm/i915/intel_display.c
> > +++ b/drivers/gpu/drm/i915/intel_display.c
> > @@ -8605,7 +8605,7 @@ static void intel_set_pipe_csc(struct drm_crtc *crtc)
> >    * consideration.
> >    */
> > 
> > - if (intel_crtc->config->limited_color_range)
> > + if (intel_crtc->config->limited_color_range &&
> > !intel_crtc->config->video_color_range)
> >   coeff = ((235 - 16) * (1 << 12) / 255) & 0xff8; /* 0.xxx... */
> > 
> >   /*
> > @@ -8629,7 +8629,7 @@ static void intel_set_pipe_csc(struct drm_crtc *crtc)
> >   if (INTEL_INFO(dev)->gen > 6) {
> >   uint16_t postoff = 0;
> > 
> > - if (intel_crtc->config->limited_color_range)
> > + if (intel_crtc->config->limited_color_range &&
> > !intel_crtc->config->video_color_range)
> >   postoff = (16 * (1 << 12) / 255) & 0x1fff;
> > 
> >   I915_WRITE(PIPE_CSC_POSTOFF_HI(pipe), postoff);
> > diff --git a/drivers/gpu/drm/i915/intel_drv.h
> > b/drivers/gpu/drm/i915/intel_drv.h
> > index 0598932..6940243 100644
> > --- a/drivers/gpu/drm/i915/intel_drv.h
> > +++ b/drivers/gpu/drm/i915/intel_drv.h
> > @@ -372,6 +372,13 @@ struct intel_crtc_state {
> >    */
> >   bool limited_color_range;
> > 
> > + /*
> > +  *
> > +  * Use reduced/limited/broadcast rgb range without compressing.
> > +  *
> > +  */
> > + bool video_color_range;
> 
> I think the names and semantics are confusion, resulting in hard-to-read
> if conditions. What about:
> 
> 	bool limit_color_range; /* should we limit from full->16:235 in
> 	the encoder/csc? */

We might call this simply as "adjust_color_range" or something like
that. Then it would also work for the limited->full conversion if we
ever come up with some use case that would need such a thing. Althoguh
it does mean we'd have to check both flags when deciding how to program
the port/pipeconf range bit/pipe csc.

> 
> 	bool limited_color_range_output; /* set the infoframe or not? */
> 
> Names aren't great yet I think, coffee's not yet working ;-)
> 
> Thanks, Daniel
> 
> > +
> >   /* DP has a bunch of special case unfortunately, so mark the pipe
> >    * accordingly. */
> >   bool has_dp_encoder;
> > @@ -682,6 +689,7 @@ struct intel_hdmi {
> >   int ddc_bus;
> >   bool limited_color_range;
> >   bool color_range_auto;
> > + bool color_range_video;
> >   bool has_hdmi_sink;
> >   bool has_audio;
> >   enum hdmi_force_audio force_audio;
> > diff --git a/drivers/gpu/drm/i915/intel_hdmi.c
> > b/drivers/gpu/drm/i915/intel_hdmi.c
> > index 9eafa19..dc78760 100644
> > --- a/drivers/gpu/drm/i915/intel_hdmi.c
> > +++ b/drivers/gpu/drm/i915/intel_hdmi.c
> > @@ -464,7 +464,8 @@ static void intel_hdmi_set_avi_infoframe(struct
> > drm_encoder *encoder,
> >   }
> > 
> >   if (intel_hdmi->rgb_quant_range_selectable) {
> > - if (intel_crtc->config->limited_color_range)
> > + if (intel_crtc->config->limited_color_range ||
> > +     intel_crtc->config->video_color_range)
> >   frame.avi.quantization_range =
> >   HDMI_QUANTIZATION_RANGE_LIMITED;
> >   else
> > @@ -1266,6 +1267,8 @@ bool intel_hdmi_compute_config(struct intel_encoder
> > *encoder,
> >   pipe_config->limited_color_range =
> >   intel_hdmi->limited_color_range;
> >   }
> > + if (intel_hdmi->color_range_video)
> > +               pipe_config->video_color_range = true;
> > 
> >   if (adjusted_mode->flags & DRM_MODE_FLAG_DBLCLK) {
> >   pipe_config->pixel_multiplier = 2;
> > @@ -1485,25 +1488,35 @@ intel_hdmi_set_property(struct drm_connector
> > *connector,
> >   if (property == dev_priv->broadcast_rgb_property) {
> >   bool old_auto = intel_hdmi->color_range_auto;
> >   bool old_range = intel_hdmi->limited_color_range;
> > + bool old_range_video = intel_hdmi->color_range_video;
> > 
> >   switch (val) {
> >   case INTEL_BROADCAST_RGB_AUTO:
> >   intel_hdmi->color_range_auto = true;
> > + intel_hdmi->color_range_video = false;
> >   break;
> >   case INTEL_BROADCAST_RGB_FULL:
> >   intel_hdmi->color_range_auto = false;
> >   intel_hdmi->limited_color_range = false;
> > + intel_hdmi->color_range_video = false;
> >   break;
> >   case INTEL_BROADCAST_RGB_LIMITED:
> >   intel_hdmi->color_range_auto = false;
> >   intel_hdmi->limited_color_range = true;
> > + intel_hdmi->color_range_video = false;
> > + break;
> > + case INTEL_BROADCAST_RGB_VIDEO:
> > +                        intel_hdmi->color_range_auto = false;
> > +                        intel_hdmi->limited_color_range = true;
> > +                        intel_hdmi->color_range_video = true;
> >   break;
> >   default:
> >   return -EINVAL;
> >   }
> > 
> >   if (old_auto == intel_hdmi->color_range_auto &&
> > -     old_range == intel_hdmi->limited_color_range)
> > +     old_range == intel_hdmi->limited_color_range &&
> > +     old_range_video == intel_hdmi->color_range_video)
> >   return 0;
> > 
> >   goto done;
> > diff --git a/drivers/gpu/drm/i915/intel_modes.c
> > b/drivers/gpu/drm/i915/intel_modes.c
> > index 38a4c8c..c49681a 100644
> > --- a/drivers/gpu/drm/i915/intel_modes.c
> > +++ b/drivers/gpu/drm/i915/intel_modes.c
> > @@ -103,6 +103,7 @@ static const struct drm_prop_enum_list
> > broadcast_rgb_names[] = {
> >   { INTEL_BROADCAST_RGB_AUTO, "Automatic" },
> >   { INTEL_BROADCAST_RGB_FULL, "Full" },
> >   { INTEL_BROADCAST_RGB_LIMITED, "Limited 16:235" },
> > + { INTEL_BROADCAST_RGB_VIDEO, "Video 16:235 pass-through" },
> >  };
> > 
> >  void
> > -- 
> > 2.5.0
> 
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx@lists.freedesktop.org
> > http://lists.freedesktop.org/mailman/listinfo/intel-gfx
> 
> 
> -- 
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/intel-gfx

-- 
Ville Syrjälä
Intel OTC
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