From c63beb4581bcd3140e122b7a7c5b4a53ae35ec29 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Tomas=20H=C3=A4rdin?= Date: Fri, 3 Feb 2023 14:00:38 +0100 Subject: [PATCH 2/2] lavfi/vf_colorspace: Add SMPTE ST 2084 support MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Also adds inits and onits options for specifying what 28672 means in terms of nits (cd/m²). --- doc/filters.texi | 30 ++++++++++++++++++++++++++++ libavfilter/vf_colorspace.c | 39 +++++++++++++++++++++++++++++++++++-- 2 files changed, 67 insertions(+), 2 deletions(-) diff --git a/doc/filters.texi b/doc/filters.texi index 3a54c68f3e..26d9dfe54b 100644 --- a/doc/filters.texi +++ b/doc/filters.texi @@ -9839,6 +9839,10 @@ BT.2020 for 10-bits content @item bt2020-12 BT.2020 for 12-bits content +@anchor{smpte2084} +@item smpte2084 +SMPTE ST 2084 (perceptual quantizer) used by BT.2100. See @ref{inits} and @ref{onits}. + @end table @anchor{primaries} @@ -9980,6 +9984,32 @@ Override input transfer characteristics. Same accepted values as @ref{trc}. @item irange Override input color range. Same accepted values as @ref{range}. +@anchor{inits} +@item inits +Required when input trc is @ref{smpte2084}. +Specifies what the peak intermediate level should correspond to in nits (cd/m²). +Perceptually dequantized values get scaled and clipped so that the range [0,inits] fits in the filter's internal psuedo-restricted 15-bit format. +For inits < 10000 this corresponds to clipping of values outside the [0,inits]³ RGB cube. +For inits = 10000 values are not clipped, but values in the lower range will get truncated to zero due to the internal format's limited range. + +With BT.2100 input basic usage is: +@example +colorspace=bt709:inits=100 +@end example +which clips HDR to SDR in BT.709 colorspace. + +A more advanced use case is as follows: +@example +colorspace=bt709:inits=10000:trc=linear:format=yuv444p16,tonemap=hable:peak=0.01 +@end example +which with BT.2100 input performs very basic tonemapping. + +@anchor{onits} +@item onits +Used in combination with @ref{smpte2084}, defaults to 10000. +Similar to @ref{inits} but in reverse. +Specifies how to treat the peak intermediate level in nits (cd/m²) prior to perceptual quantization (PQ) as per SMPTE ST 2084. + @end table The filter converts the transfer characteristics, color space and color diff --git a/libavfilter/vf_colorspace.c b/libavfilter/vf_colorspace.c index 1e1ab5fb34..996c5f4e25 100644 --- a/libavfilter/vf_colorspace.c +++ b/libavfilter/vf_colorspace.c @@ -118,6 +118,7 @@ typedef struct ColorSpaceContext { enum AVColorTransferCharacteristic in_trc, out_trc, user_trc, user_itrc; enum AVColorPrimaries in_prm, out_prm, user_prm, user_iprm; enum AVPixelFormat in_format, user_format; + double user_inits, user_onits; int fast_mode; enum DitherMode dither; enum WhitepointAdaptation wp_adapt; @@ -173,6 +174,7 @@ static const struct TransferCharacteristics transfer_characteristics[AVCOL_TRC_N [AVCOL_TRC_IEC61966_2_4] = { 1.099, 0.018, 0.45, 4.5 }, [AVCOL_TRC_BT2020_10] = { 1.099, 0.018, 0.45, 4.5 }, [AVCOL_TRC_BT2020_12] = { 1.0993, 0.0181, 0.45, 4.5 }, + [AVCOL_TRC_SMPTE2084] = { 1.0, 0, 0, 0 }, // fake entry, actual TRC uses entirely separate formula }; static const struct TransferCharacteristics * @@ -197,6 +199,9 @@ static int fill_gamma_table(ColorSpaceContext *s) double in_ialpha = 1.0 / in_alpha, in_igamma = 1.0 / in_gamma, in_idelta = 1.0 / in_delta; double out_alpha = s->out_txchr->alpha, out_beta = s->out_txchr->beta; double out_gamma = s->out_txchr->gamma, out_delta = s->out_txchr->delta; + double m1 = 1305.0/8192, m2 = 2523.0/32, c2 = 2413.0/128, c3 = 2392.0/128, c1 = c3 - c2 + 1; + double im1 = 1.0 / m1, im2 = 1.0 / m2; + double iscale = 10000.0 / s->user_inits, ioscale = s->user_onits / 10000.0; s->lin_lut = av_malloc(sizeof(*s->lin_lut) * 32768 * 2); if (!s->lin_lut) @@ -206,7 +211,15 @@ static int fill_gamma_table(ColorSpaceContext *s) double v = (n - 2048.0) / 28672.0, d, l; // delinearize - if (v <= -out_beta) { + if (s->out_trc == AVCOL_TRC_SMPTE2084) { + // see BT.2100-2 + if (v >= 0) { + double vm1 = pow(v * ioscale, m1); + d = pow((c1 + c2 * vm1)/(1 + c3 * vm1), m2); + } else { + d = 0; + } + } else if (v <= -out_beta) { d = -out_alpha * pow(-v, out_gamma) + (out_alpha - 1.0); } else if (v < out_beta) { d = out_delta * v; @@ -216,7 +229,19 @@ static int fill_gamma_table(ColorSpaceContext *s) s->delin_lut[n] = av_clip_int16(lrint(d * 28672.0)); // linearize - if (v <= -in_beta * in_delta) { + if (s->in_trc == AVCOL_TRC_SMPTE2084) { + // see BT.2100-2 + if (v >= 0) { + double vim2 = pow(v, im2); + // for inits < 10000 this will tonemap by clipping in RGB + // for inits = 10000 this makes unclipped linear values accessible when trc=linear + // note that precision will be lost in the lower end of PQ values, for example with + // 12-bit PQ and 16-bit output the first 422 values all get truncated to zero + l = iscale * pow((vim2 - c1 > 0 ? vim2 - c1 : 0) / (c2 - c3 * vim2), im1); + } else { + l = 0; + } + } else if (v <= -in_beta * in_delta) { l = -pow((1.0 - in_alpha - v) * in_ialpha, in_igamma); } else if (v < in_beta * in_delta) { l = v * in_idelta; @@ -514,6 +539,11 @@ static int create_filtergraph(AVFilterContext *ctx, } } + if (s->in_trc == AVCOL_TRC_SMPTE2084 && s->user_inits <= 0) { + av_log(ctx, AV_LOG_ERROR, "smpte2084 requires inits\n"); + return AVERROR(EINVAL); + } + if (!s->out_txchr) { av_freep(&s->lin_lut); s->out_trc = out->color_trc; @@ -956,6 +986,7 @@ static const AVOption colorspace_options[] = { ENUM("iec61966-2-4", AVCOL_TRC_IEC61966_2_4, "trc"), ENUM("bt2020-10", AVCOL_TRC_BT2020_10, "trc"), ENUM("bt2020-12", AVCOL_TRC_BT2020_12, "trc"), + ENUM("smpte2084", AVCOL_TRC_SMPTE2084, "trc"), { "format", "Output pixel format", OFFSET(user_format), AV_OPT_TYPE_INT, { .i64 = AV_PIX_FMT_NONE }, @@ -1008,6 +1039,10 @@ static const AVOption colorspace_options[] = { { "itrc", "Input transfer characteristics", OFFSET(user_itrc), AV_OPT_TYPE_INT, { .i64 = AVCOL_TRC_UNSPECIFIED }, AVCOL_TRC_RESERVED0, AVCOL_TRC_NB - 1, FLAGS, "trc" }, + { "inits", "Input nits. Specifies how PQ (SMPTE ST 2084) values are to be mapped to intermediate/output linear RGB", + OFFSET(user_inits), AV_OPT_TYPE_DOUBLE, {.dbl = 0}, 0, 10000, FLAGS }, + { "onits", "Output nits. Specifies how input/intermediate linear RGB is scaled for output PQ (SMPTE ST 2084) values", + OFFSET(user_onits), AV_OPT_TYPE_DOUBLE, {.dbl = 10000}, 1, 10000, FLAGS }, { NULL } }; -- 2.30.2