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vo_opengl: implement HDR (SMPTE ST2084) 

Currently, this relies on the user manually entering their display
brightness (since we have no way to detect this at runtime or from ICC
metadata). The default value of 250 was picked by looking at ~10 reviews
on tftcentral.co.uk and realizing they all come with around 250 cd/m^2
out of the box. (In addition, ITU-R Rec. BT.2022 supports this)

Since there is no metadata in FFmpeg to indicate usage of this TRC, the
only way to actually play HDR content currently is to set
``--vf=format=gamma=st2084``. (It could be guessed based on SEI, but
this is not implemented yet)

Incidentally, since SEI is ignored, it's currently assumed that all
content is scaled to 10,000 cd/m^2 (and hard-clipped where out of
range). I don't see this assumption changing much, though.

As an unfortunate consequence of the fact that we don't know the display
brightness, mixed with the fact that LittleCMS' parametric tone curves
are not flexible enough to support PQ, we have to build the 3DLUT
against gamma 2.2 if it's used. This might be a good thing, though,
consdering the PQ source space is probably not fantastic for
interpolation either way.

Partially addresses #2572.
This commit is contained in:
Niklas Haas 2016-05-15 20:16:12 +02:00
parent 965031ccd5
commit f81f486c68
7 changed files with 60 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
DOCS/man/vf.rst
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@ -310,6 +310,7 @@ Available filters are:
:gamma2.2: Pure power curve (gamma 2.2)
:gamma2.8: Pure power curve (gamma 2.8)
:prophoto: ProPhoto RGB (ROMM) curve
:st2084: SMPTE ST2084 (HDR) curve
``<stereo-in>``
Set the stereo mode the video is assumed to be encoded in. Takes the

8
DOCS/man/vo.rst
View File

@ -1052,6 +1052,14 @@ Available video output drivers are:
Pure power curve (gamma 2.8), also used for BT.470-BG
prophoto
ProPhoto RGB (ROMM)
st2084
SMPTE ST2084 (HDR) curve, PQ OETF
``target-brightness=<1..100000>``
Specifies the display's approximate brightness in cd/m^2. When playing
HDR content, video colors will be scaled and clipped to this
brightness. The default of 250 cd/m^2 corresponds to a typical consumer
display.
``icc-profile=<file>``
Load an ICC profile and use it to transform video RGB to screen output.

1
video/csputils.c
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@ -77,6 +77,7 @@ const struct m_opt_choice_alternatives mp_csp_trc_names[] = {
{"gamma2.2", MP_CSP_TRC_GAMMA22},
{"gamma2.8", MP_CSP_TRC_GAMMA28},
{"prophoto", MP_CSP_TRC_PRO_PHOTO},
{"st2084", MP_CSP_TRC_SMPTE_ST2084},
{0}
};

1
video/csputils.h
View File

@ -78,6 +78,7 @@ enum mp_csp_trc {
MP_CSP_TRC_GAMMA22,
MP_CSP_TRC_GAMMA28,
MP_CSP_TRC_PRO_PHOTO,
MP_CSP_TRC_SMPTE_ST2084,
MP_CSP_TRC_COUNT
};

26
video/out/opengl/video.c
View File

@ -320,6 +320,7 @@ const struct gl_video_opts gl_video_opts_def = {
.gamma = 1.0f,
.prescale_passes = 1,
.prescale_downscaling_threshold = 2.0f,
.target_brightness = 250,
};
const struct gl_video_opts gl_video_opts_hq_def = {
@ -348,6 +349,7 @@ const struct gl_video_opts gl_video_opts_hq_def = {
.deband = 1,
.prescale_passes = 1,
.prescale_downscaling_threshold = 2.0f,
.target_brightness = 250,
};
static int validate_scaler_opt(struct mp_log *log, const m_option_t *opt,
@ -376,6 +378,7 @@ const struct m_sub_options gl_video_conf = {
OPT_FLAG("gamma-auto", gamma_auto, 0),
OPT_CHOICE_C("target-prim", target_prim, 0, mp_csp_prim_names),
OPT_CHOICE_C("target-trc", target_trc, 0, mp_csp_trc_names),
OPT_INTRANGE("target-brightness", target_brightness, 0, 1, 100000),
OPT_FLAG("pbo", pbo, 0),
SCALER_OPTS("scale", SCALER_SCALE),
SCALER_OPTS("dscale", SCALER_DSCALE),
@ -2202,7 +2205,8 @@ static void pass_scale_main(struct gl_video *p)
// Adapts the colors from the given color space to the display device's native
// gamut.
static void pass_colormanage(struct gl_video *p, enum mp_csp_prim prim_src,
static void pass_colormanage(struct gl_video *p, bool display_scaled,
enum mp_csp_prim prim_src,
enum mp_csp_trc trc_src)
{
GLSLF("// color management\n");
@ -2214,6 +2218,13 @@ static void pass_colormanage(struct gl_video *p, enum mp_csp_prim prim_src,
enum mp_csp_prim prim_orig = p->image_params.primaries;
enum mp_csp_trc trc_orig = p->image_params.gamma;
// One exception: SMPTE ST.2084 is not implemented by LittleCMS
// for technical limitation reasons, so we use a gamma 2.2 input curve
// here instead. We could pick any value we want here, the difference
// is just coding efficiency.
if (trc_orig == MP_CSP_TRC_SMPTE_ST2084)
trc_orig = MP_CSP_TRC_GAMMA22;
if (gl_video_get_lut3d(p, prim_orig, trc_orig)) {
prim_dst = prim_orig;
trc_dst = trc_orig;
@ -2237,6 +2248,15 @@ static void pass_colormanage(struct gl_video *p, enum mp_csp_prim prim_src,
if (need_gamma)
pass_linearize(p->sc, trc_src);
// For HDR, the assumption of reference brightness = display brightness
// is discontinued. Instead, we have to rescale the brightness to match
// the display (and clip out-of-range values)
if (p->image_params.gamma == MP_CSP_TRC_SMPTE_ST2084 && !display_scaled) {
int reference_brightness = 10000; // As per SMPTE ST.2084
GLSLF("color.rgb = clamp(%f * color.rgb, 0.0, 1.0);\n",
(float)reference_brightness / p->opts.target_brightness);
}
// Adapt to the right colorspace if necessary
if (prim_src != prim_dst) {
struct mp_csp_primaries csp_src = mp_get_csp_primaries(prim_src),
@ -2391,7 +2411,7 @@ static void pass_draw_osd(struct gl_video *p, int draw_flags, double pts,
}
// Subtitle color management, they're assumed to be sRGB by default
if (cms)
pass_colormanage(p, MP_CSP_PRIM_BT_709, MP_CSP_TRC_SRGB);
pass_colormanage(p, true, MP_CSP_PRIM_BT_709, MP_CSP_TRC_SRGB);
gl_sc_set_vao(p->sc, mpgl_osd_get_vao(p->osd));
gl_sc_gen_shader_and_reset(p->sc);
mpgl_osd_draw_part(p->osd, vp_w, vp_h, n);
@ -2514,7 +2534,7 @@ static void pass_draw_to_screen(struct gl_video *p, int fbo)
GLSL(color.rgb = pow(color.rgb, vec3(user_gamma));)
}
pass_colormanage(p, p->image_params.primaries,
pass_colormanage(p, false, p->image_params.primaries,
p->use_linear ? MP_CSP_TRC_LINEAR : p->image_params.gamma);
// Draw checkerboard pattern to indicate transparency

1
video/out/opengl/video.h
View File

@ -111,6 +111,7 @@ struct gl_video_opts {
int gamma_auto;
int target_prim;
int target_trc;
int target_brightness;
int linear_scaling;
int correct_downscaling;
int sigmoid_upscaling;

25
video/out/opengl/video_shaders.c
View File

@ -220,6 +220,13 @@ void pass_sample_oversample(struct gl_shader_cache *sc, struct scaler *scaler,
GLSLF("}\n");
}
// Common constants for SMPTE ST.2084 (HDR)
static const float HDR_M1 = 2610./4096 * 1./4,
HDR_M2 = 2523./4096 * 128,
HDR_C1 = 3424./4096,
HDR_C2 = 2413./4096 * 32,
HDR_C3 = 2392./4096 * 32;
// Linearize (expand), given a TRC as input
void pass_linearize(struct gl_shader_cache *sc, enum mp_csp_trc trc)
{
@ -251,6 +258,15 @@ void pass_linearize(struct gl_shader_cache *sc, enum mp_csp_trc trc)
pow(color.rgb, vec3(1.8)),
lessThan(vec3(0.03125), color.rgb));)
break;
case MP_CSP_TRC_SMPTE_ST2084:
GLSLF("color.rgb = pow(color.rgb, vec3(1.0/%f));\n", HDR_M2);
GLSLF("color.rgb = max(color.rgb - vec3(%f), vec3(0.0)) \n"
" / (vec3(%f) - vec3(%f) * color.rgb);\n",
HDR_C1, HDR_C2, HDR_C3);
GLSLF("color.rgb = pow(color.rgb, vec3(1.0/%f));\n", HDR_M1);
break;
default:
abort();
}
}
@ -285,6 +301,15 @@ void pass_delinearize(struct gl_shader_cache *sc, enum mp_csp_trc trc)
pow(color.rgb, vec3(1.0/1.8)),
lessThanEqual(vec3(0.001953), color.rgb));)
break;
case MP_CSP_TRC_SMPTE_ST2084:
GLSLF("color.rgb = pow(color.rgb, vec3(%f));\n", HDR_M1);
GLSLF("color.rgb = (vec3(%f) + vec3(%f) * color.rgb) \n"
" / (vec3(1.0) + vec3(%f) * color.rgb);\n",
HDR_C1, HDR_C2, HDR_C3);
GLSLF("color.rgb = pow(color.rgb, vec3(%f));\n", HDR_M2);
break;
default:
abort();
}
}