lavc: Implement Dolby Vision RPU parsing

Based on a mixture of guesswork, partial documentation in patents, and
reverse engineering of real-world samples. Confirmed working for all the
samples I've thrown at it.

Contains some annoying machinery to persist these values in between
frames, which is needed in theory even though I've never actually seen a
sample that relies on it in practice. May or may not work.

Since the distinction matters greatly for parsing the color matrix
values, this includes a small helper function to guess the right profile
from the RPU itself in case the user has forgotten to forward the dovi
configuration record to the decoder. (Which in practice, only ffmpeg.c
and ffplay do..)

Notable omissions / deviations:
- CRC32 verification. This is based on the MPEG2 CRC32 type, which is
  similar to IEEE CRC32 but apparently different in subtle enough ways
  that I could not get it to pass verification no matter what parameters
  I fed to av_crc. It's possible the code needs some changes.
- Linear interpolation support. Nothing documents this (beyond its
  existence) and no samples use it, so impossible to implement.
- All of the extension metadata blocks, but these contain values that
  seem largely congruent with ST2094, HDR10, or other existing forms of
  side data, so I will defer parsing/attaching them to a future commit.
- The patent describes a mechanism for predicting coefficients from
  previous RPUs, but the bit for the flag whether to use the
  prediction deltas or signal entirely new coefficients does not seem to
  be present in actual RPUs, so we ignore this subsystem entirely.
- In the patent's spec, the NLQ subsystem also loops over
  num_nlq_pivots, but even in the patent the number is hard-coded to one
  iteration rather than signalled. So we only store one set of coefs.

Heavily influenced by https://github.com/quietvoid/dovi_tool
Documentation drawn from US Patent 10,701,399 B2 and ETSI GS CCM 001

Signed-off-by: Niklas Haas <git@haasn.dev>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

4 files changed, 539 insertions, 0 deletions

diff --git a/configure b/configure
index e16a5f34f6..34878117e7 100755
--- a/configure
+++ b/configure
@@ -2434,6 +2434,7 @@ CONFIG_EXTRA="
     cbs_vp9
     dirac_parse
     dnn
+    dovi_rpu
     dvprofile
     exif
     faandct
@@ -2706,6 +2707,7 @@ cbs_mpeg2_select="cbs"
 cbs_vp9_select="cbs"
 dct_select="rdft"
 dirac_parse_select="golomb"
+dovi_rpu_select="golomb"
 dnn_suggest="libtensorflow libopenvino"
 dnn_deps="avformat swscale"
 error_resilience_select="me_cmp"
diff --git a/libavcodec/Makefile b/libavcodec/Makefile
index 79c4275133..e048a1c377 100644
--- a/libavcodec/Makefile
+++ b/libavcodec/Makefile
@@ -77,6 +77,7 @@ OBJS-$(CONFIG_CBS_MPEG2)               += cbs_mpeg2.o
 OBJS-$(CONFIG_CBS_VP9)                 += cbs_vp9.o
 OBJS-$(CONFIG_CRYSTALHD)               += crystalhd.o
 OBJS-$(CONFIG_DCT)                     += dct.o dct32_fixed.o dct32_float.o
+OBJS-$(CONFIG_DOVI_RPU)                += dovi_rpu.o
 OBJS-$(CONFIG_ERROR_RESILIENCE)        += error_resilience.o
 OBJS-$(CONFIG_EXIF)                    += exif.o tiff_common.o
 OBJS-$(CONFIG_FAANDCT)                 += faandct.o
diff --git a/libavcodec/dovi_rpu.c b/libavcodec/dovi_rpu.c
new file mode 100644
index 0000000000..a87562c8a3
--- /dev/null
+++ b/libavcodec/dovi_rpu.c
@@ -0,0 +1,449 @@
+/*
+ * Dolby Vision RPU decoder
+ *
+ * Copyright (C) 2021 Jan Ekström
+ * Copyright (C) 2021 Niklas Haas
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "libavutil/buffer.h"
+
+#include "dovi_rpu.h"
+#include "golomb.h"
+#include "get_bits.h"
+
+enum {
+    RPU_COEFF_FIXED = 0,
+    RPU_COEFF_FLOAT = 1,
+};
+
+/**
+ * Private contents of vdr_ref.
+ */
+typedef struct DOVIVdrRef {
+    AVDOVIDataMapping mapping;
+    AVDOVIColorMetadata color;
+} DOVIVdrRef;
+
+void ff_dovi_ctx_unref(DOVIContext *s)
+{
+    for (int i = 0; i < FF_ARRAY_ELEMS(s->vdr_ref); i++)
+        av_buffer_unref(&s->vdr_ref[i]);
+
+    *s = (DOVIContext) {
+        .logctx = s->logctx,
+    };
+}
+
+void ff_dovi_ctx_flush(DOVIContext *s)
+{
+    for (int i = 0; i < FF_ARRAY_ELEMS(s->vdr_ref); i++)
+        av_buffer_unref(&s->vdr_ref[i]);
+
+    *s = (DOVIContext) {
+        .logctx = s->logctx,
+        .dv_profile = s->dv_profile,
+    };
+}
+
+int ff_dovi_ctx_replace(DOVIContext *s, const DOVIContext *s0)
+{
+    int ret;
+    s->logctx = s0->logctx;
+    s->mapping = s0->mapping;
+    s->color = s0->color;
+    s->dv_profile = s0->dv_profile;
+    for (int i = 0; i < DOVI_MAX_DM_ID; i++) {
+        if ((ret = av_buffer_replace(&s->vdr_ref[i], s0->vdr_ref[i])) < 0)
+            goto fail;
+    }
+
+    return 0;
+
+fail:
+    ff_dovi_ctx_unref(s);
+    return ret;
+}
+
+void ff_dovi_update_cfg(DOVIContext *s, const AVDOVIDecoderConfigurationRecord *cfg)
+{
+    if (!cfg)
+        return;
+
+    s->dv_profile = cfg->dv_profile;
+}
+
+int ff_dovi_attach_side_data(DOVIContext *s, AVFrame *frame)
+{
+    AVFrameSideData *sd;
+    AVBufferRef *buf;
+    AVDOVIMetadata *dovi;
+    size_t dovi_size;
+
+    if (!s->mapping || !s->color)
+        return 0; /* incomplete dovi metadata */
+
+    dovi = av_dovi_metadata_alloc(&dovi_size);
+    if (!dovi)
+        return AVERROR(ENOMEM);
+
+    buf = av_buffer_create((uint8_t *) dovi, dovi_size, NULL, NULL, 0);
+    if (!buf) {
+        av_free(dovi);
+        return AVERROR(ENOMEM);
+    }
+
+    sd = av_frame_new_side_data_from_buf(frame, AV_FRAME_DATA_DOVI_METADATA, buf);
+    if (!sd) {
+        av_buffer_unref(&buf);
+        return AVERROR(ENOMEM);
+    }
+
+    /* Copy only the parts of these structs known to us at compiler-time. */
+#define COPY(t, a, b, last) memcpy(a, b, offsetof(t, last) + sizeof((b)->last))
+    COPY(AVDOVIRpuDataHeader, av_dovi_get_header(dovi), &s->header, disable_residual_flag);
+    COPY(AVDOVIDataMapping, av_dovi_get_mapping(dovi), s->mapping, nlq[2].linear_deadzone_threshold);
+    COPY(AVDOVIColorMetadata, av_dovi_get_color(dovi), s->color, source_diagonal);
+    return 0;
+}
+
+static int guess_profile(const AVDOVIRpuDataHeader *hdr)
+{
+    switch (hdr->vdr_rpu_profile) {
+    case 0:
+        if (hdr->bl_video_full_range_flag)
+            return 5;
+        break;
+    case 1:
+        if (hdr->el_spatial_resampling_filter_flag && !hdr->disable_residual_flag) {
+            if (hdr->vdr_bit_depth == 12) {
+                return 7;
+            } else {
+                return 4;
+            }
+        } else {
+            return 8;
+        }
+    }
+
+    return 0; /* unknown */
+}
+
+static inline uint64_t get_ue_coef(GetBitContext *gb, const AVDOVIRpuDataHeader *hdr)
+{
+    uint64_t ipart;
+    union { uint32_t u32; float f32; } fpart;
+
+    switch (hdr->coef_data_type) {
+    case RPU_COEFF_FIXED:
+        ipart = get_ue_golomb_long(gb);
+        fpart.u32 = get_bits_long(gb, hdr->coef_log2_denom);
+        return (ipart << hdr->coef_log2_denom) + fpart.u32;
+
+    case RPU_COEFF_FLOAT:
+        fpart.u32 = get_bits_long(gb, 32);
+        return fpart.f32 * (1 << hdr->coef_log2_denom);
+    }
+
+    return 0; /* unreachable */
+}
+
+static inline int64_t get_se_coef(GetBitContext *gb, const AVDOVIRpuDataHeader *hdr)
+{
+    int64_t ipart;
+    union { uint32_t u32; float f32; } fpart;
+
+    switch (hdr->coef_data_type) {
+    case RPU_COEFF_FIXED:
+        ipart = get_se_golomb_long(gb);
+        fpart.u32 = get_bits_long(gb, hdr->coef_log2_denom);
+        return (ipart << hdr->coef_log2_denom) + fpart.u32;
+
+    case RPU_COEFF_FLOAT:
+        fpart.u32 = get_bits_long(gb, 32);
+        return fpart.f32 * (1 << hdr->coef_log2_denom);
+    }
+
+    return 0; /* unreachable */
+}
+
+#define VALIDATE(VAR, MIN, MAX)                                                 \
+    do {                                                                        \
+        if (VAR < MIN || VAR > MAX) {                                           \
+            av_log(s->logctx, AV_LOG_ERROR, "RPU validation failed: "           \
+                   #MIN" <= "#VAR" = %d <= "#MAX"\n", (int) VAR);               \
+            goto fail;                                                          \
+        }                                                                       \
+    } while (0)
+
+int ff_dovi_rpu_parse(DOVIContext *s, const uint8_t *rpu, size_t rpu_size)
+{
+    AVDOVIRpuDataHeader *hdr = &s->header;
+    GetBitContext *gb = &(GetBitContext){0};
+    DOVIVdrRef *vdr;
+    int ret;
+
+    uint8_t nal_prefix;
+    uint8_t rpu_type;
+    uint8_t vdr_seq_info_present;
+    uint8_t vdr_dm_metadata_present;
+    uint8_t use_prev_vdr_rpu;
+    uint8_t use_nlq;
+    uint8_t profile;
+    if ((ret = init_get_bits8(gb, rpu, rpu_size)) < 0)
+        return ret;
+
+    /* RPU header, common values */
+    nal_prefix = get_bits(gb, 8);
+    VALIDATE(nal_prefix, 25, 25);
+    rpu_type = get_bits(gb, 6);
+    if (rpu_type != 2) {
+        av_log(s->logctx, AV_LOG_WARNING, "Unrecognized RPU type "
+               "%"PRIu8", ignoring\n", rpu_type);
+        return 0;
+    }
+
+    hdr->rpu_type = rpu_type;
+    hdr->rpu_format = get_bits(gb, 11);
+
+    /* Values specific to RPU type 2 */
+    hdr->vdr_rpu_profile = get_bits(gb, 4);
+    hdr->vdr_rpu_level = get_bits(gb, 4);
+
+    vdr_seq_info_present = get_bits1(gb);
+    if (vdr_seq_info_present) {
+        hdr->chroma_resampling_explicit_filter_flag = get_bits1(gb);
+        hdr->coef_data_type = get_bits(gb, 2);
+        VALIDATE(hdr->coef_data_type, RPU_COEFF_FIXED, RPU_COEFF_FLOAT);
+        switch (hdr->coef_data_type) {
+        case RPU_COEFF_FIXED:
+            hdr->coef_log2_denom = get_ue_golomb(gb);
+            VALIDATE(hdr->coef_log2_denom, 13, 32);
+            break;
+        case RPU_COEFF_FLOAT:
+            hdr->coef_log2_denom = 32; /* arbitrary, choose maximum precision */
+            break;
+        }
+
+        hdr->vdr_rpu_normalized_idc = get_bits(gb, 2);
+        hdr->bl_video_full_range_flag = get_bits1(gb);
+
+        if ((hdr->rpu_format & 0x700) == 0) {
+            int bl_bit_depth_minus8 = get_ue_golomb_31(gb);
+            int el_bit_depth_minus8 = get_ue_golomb_31(gb);
+            int vdr_bit_depth_minus8 = get_ue_golomb_31(gb);
+            VALIDATE(bl_bit_depth_minus8, 0, 8);
+            VALIDATE(el_bit_depth_minus8, 0, 8);
+            VALIDATE(vdr_bit_depth_minus8, 0, 8);
+            hdr->bl_bit_depth = bl_bit_depth_minus8 + 8;
+            hdr->el_bit_depth = el_bit_depth_minus8 + 8;
+            hdr->vdr_bit_depth = vdr_bit_depth_minus8 + 8;
+            hdr->spatial_resampling_filter_flag = get_bits1(gb);
+            skip_bits(gb, 3); /* reserved_zero_3bits */
+            hdr->el_spatial_resampling_filter_flag = get_bits1(gb);
+            hdr->disable_residual_flag = get_bits1(gb);
+        }
+    }
+
+    if (!hdr->bl_bit_depth) {
+        av_log(s->logctx, AV_LOG_ERROR, "Missing RPU VDR sequence info?\n");
+        goto fail;
+    }
+
+    vdr_dm_metadata_present = get_bits1(gb);
+    use_prev_vdr_rpu = get_bits1(gb);
+    use_nlq = (hdr->rpu_format & 0x700) == 0 && !hdr->disable_residual_flag;
+
+    profile = s->dv_profile ? s->dv_profile : guess_profile(hdr);
+    if (profile == 5 && use_nlq) {
+        av_log(s->logctx, AV_LOG_ERROR, "Profile 5 RPUs should not use NLQ\n");
+        goto fail;
+    }
+
+    if (use_prev_vdr_rpu) {
+        int prev_vdr_rpu_id = get_ue_golomb_31(gb);
+        VALIDATE(prev_vdr_rpu_id, 0, DOVI_MAX_DM_ID);
+        if (!s->vdr_ref[prev_vdr_rpu_id]) {
+            av_log(s->logctx, AV_LOG_ERROR, "Unknown previous RPU ID: %u\n",
+                   prev_vdr_rpu_id);
+            goto fail;
+        }
+        vdr = (DOVIVdrRef *) s->vdr_ref[prev_vdr_rpu_id]->data;
+        s->mapping = &vdr->mapping;
+    } else {
+        int vdr_rpu_id = get_ue_golomb_31(gb);
+        VALIDATE(vdr_rpu_id, 0, DOVI_MAX_DM_ID);
+        if (!s->vdr_ref[vdr_rpu_id]) {
+            s->vdr_ref[vdr_rpu_id] = av_buffer_allocz(sizeof(DOVIVdrRef));
+            if (!s->vdr_ref[vdr_rpu_id])
+                return AVERROR(ENOMEM);
+        }
+
+        vdr = (DOVIVdrRef *) s->vdr_ref[vdr_rpu_id]->data;
+        s->mapping = &vdr->mapping;
+
+        vdr->mapping.vdr_rpu_id = vdr_rpu_id;
+        vdr->mapping.mapping_color_space = get_ue_golomb_31(gb);
+        vdr->mapping.mapping_chroma_format_idc = get_ue_golomb_31(gb);
+
+        for (int c = 0; c < 3; c++) {
+            AVDOVIReshapingCurve *curve = &vdr->mapping.curves[c];
+            int num_pivots_minus_2 = get_ue_golomb_31(gb);
+            int pivot = 0;
+
+            VALIDATE(num_pivots_minus_2, 0, AV_DOVI_MAX_PIECES - 1);
+            curve->num_pivots = num_pivots_minus_2 + 2;
+            for (int i = 0; i < curve->num_pivots; i++) {
+                pivot += get_bits(gb, hdr->bl_bit_depth);
+                curve->pivots[i] = av_clip_uint16(pivot);
+            }
+        }
+
+        if (use_nlq) {
+            vdr->mapping.nlq_method_idc = get_bits(gb, 3);
+            /**
+             * The patent mentions another legal value, NLQ_MU_LAW, but it's
+             * not documented anywhere how to parse or apply that type of NLQ.
+             */
+            VALIDATE(vdr->mapping.nlq_method_idc, 0, AV_DOVI_NLQ_LINEAR_DZ);
+        } else {
+            vdr->mapping.nlq_method_idc = AV_DOVI_NLQ_NONE;
+        }
+
+        vdr->mapping.num_x_partitions = get_ue_golomb_long(gb) + 1;
+        vdr->mapping.num_y_partitions = get_ue_golomb_long(gb) + 1;
+        /* End of rpu_data_header(), start of vdr_rpu_data_payload() */
+
+        for (int c = 0; c < 3; c++) {
+            AVDOVIReshapingCurve *curve = &vdr->mapping.curves[c];
+            for (int i = 0; i < curve->num_pivots - 1; i++) {
+                int mapping_idc = get_ue_golomb_31(gb);
+                VALIDATE(mapping_idc, 0, 1);
+                curve->mapping_idc[i] = mapping_idc;
+                switch (mapping_idc) {
+                case AV_DOVI_MAPPING_POLYNOMIAL: {
+                    int poly_order_minus1 = get_ue_golomb_31(gb);
+                    VALIDATE(poly_order_minus1, 0, 1);
+                    curve->poly_order[i] = poly_order_minus1 + 1;
+                    if (poly_order_minus1 == 0) {
+                        int linear_interp_flag = get_bits1(gb);
+                        if (linear_interp_flag) {
+                            /* lack of documentation/samples */
+                            avpriv_request_sample(s->logctx, "Dolby Vision "
+                                                  "linear interpolation");
+                            ff_dovi_ctx_unref(s);
+                            return AVERROR_PATCHWELCOME;
+                        }
+                    }
+                    for (int k = 0; k <= curve->poly_order[i]; k++)
+                        curve->poly_coef[i][k] = get_se_coef(gb, hdr);
+                    break;
+                }
+                case AV_DOVI_MAPPING_MMR: {
+                    int mmr_order_minus1 = get_bits(gb, 2);
+                    VALIDATE(mmr_order_minus1, 0, 2);
+                    curve->mmr_order[i] = mmr_order_minus1 + 1;
+                    curve->mmr_constant[i] = get_se_coef(gb, hdr);
+                    for (int j = 0; j < curve->mmr_order[i]; j++) {
+                        for (int k = 0; k < 7; k++)
+                            curve->mmr_coef[i][j][k] = get_se_coef(gb, hdr);
+                    }
+                    break;
+                }
+                }
+            }
+        }
+
+        if (use_nlq) {
+            for (int c = 0; c < 3; c++) {
+                AVDOVINLQParams *nlq = &vdr->mapping.nlq[c];
+                nlq->nlq_offset = get_bits(gb, hdr->el_bit_depth);
+                nlq->vdr_in_max = get_ue_coef(gb, hdr);
+                switch (vdr->mapping.nlq_method_idc) {
+                case AV_DOVI_NLQ_LINEAR_DZ:
+                    nlq->linear_deadzone_slope = get_ue_coef(gb, hdr);
+                    nlq->linear_deadzone_threshold = get_ue_coef(gb, hdr);
+                    break;
+                }
+            }
+        }
+    }
+
+    if (vdr_dm_metadata_present) {
+        AVDOVIColorMetadata *color;
+        int affected_dm_id = get_ue_golomb_31(gb);
+        int current_dm_id = get_ue_golomb_31(gb);
+        VALIDATE(affected_dm_id, 0, DOVI_MAX_DM_ID);
+        VALIDATE(current_dm_id, 0, DOVI_MAX_DM_ID);
+        if (!s->vdr_ref[affected_dm_id]) {
+            s->vdr_ref[affected_dm_id] = av_buffer_allocz(sizeof(DOVIVdrRef));
+            if (!s->vdr_ref[affected_dm_id])
+                return AVERROR(ENOMEM);
+        }
+
+        if (!s->vdr_ref[current_dm_id]) {
+            av_log(s->logctx, AV_LOG_ERROR, "Unknown previous RPU DM ID: %u\n",
+                   current_dm_id);
+            goto fail;
+        }
+
+        /* Update current pointer based on current_dm_id */
+        vdr = (DOVIVdrRef *) s->vdr_ref[current_dm_id]->data;
+        s->color = &vdr->color;
+
+        /* Update values of affected_dm_id */
+        vdr = (DOVIVdrRef *) s->vdr_ref[affected_dm_id]->data;
+        color = &vdr->color;
+        color->dm_metadata_id = affected_dm_id;
+        color->scene_refresh_flag = get_ue_golomb_31(gb);
+        for (int i = 0; i < 9; i++)
+            color->ycc_to_rgb_matrix[i] = av_make_q(get_sbits(gb, 16), 1 << 13);
+        for (int i = 0; i < 3; i++) {
+            int denom = profile == 4 ? (1 << 30) : (1 << 28);
+            unsigned offset = get_bits_long(gb, 32);
+            if (offset > INT_MAX) {
+                /* Ensure the result fits inside AVRational */
+                offset >>= 1;
+                denom >>= 1;
+            }
+            color->ycc_to_rgb_offset[i] = av_make_q(offset, denom);
+        }
+        for (int i = 0; i < 9; i++)
+            color->rgb_to_lms_matrix[i] = av_make_q(get_sbits(gb, 16), 1 << 14);
+
+        color->signal_eotf = get_bits(gb, 16);
+        color->signal_eotf_param0 = get_bits(gb, 16);
+        color->signal_eotf_param1 = get_bits(gb, 16);
+        color->signal_eotf_param2 = get_bits_long(gb, 32);
+        color->signal_bit_depth = get_bits(gb, 5);
+        VALIDATE(color->signal_bit_depth, 8, 16);
+        color->signal_color_space = get_bits(gb, 2);
+        color->signal_chroma_format = get_bits(gb, 2);
+        color->signal_full_range_flag = get_bits(gb, 2);
+        color->source_min_pq = get_bits(gb, 12);
+        color->source_max_pq = get_bits(gb, 12);
+        color->source_diagonal = get_bits(gb, 10);
+    }
+
+    /* FIXME: verify CRC32, requires implementation of AV_CRC_32_MPEG_2 */
+    return 0;
+
+fail:
+    ff_dovi_ctx_unref(s); /* don't leak potentially invalid state */
+    return AVERROR(EINVAL);
+}
diff --git a/libavcodec/dovi_rpu.h b/libavcodec/dovi_rpu.h
new file mode 100644
index 0000000000..f6ca5bbbc5
--- /dev/null
+++ b/libavcodec/dovi_rpu.h
@@ -0,0 +1,87 @@
+/*
+ * Dolby Vision RPU decoder
+ *
+ * Copyright (C) 2021 Jan Ekström
+ * Copyright (C) 2021 Niklas Haas
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef AVCODEC_DOVI_RPU_H
+#define AVCODEC_DOVI_RPU_H
+
+#include "libavutil/dovi_meta.h"
+#include "libavutil/frame.h"
+
+#define DOVI_MAX_DM_ID 15
+typedef struct DOVIContext {
+    void *logctx;
+
+    /**
+     * Currently active RPU data header, updates on every dovi_rpu_parse().
+     */
+    AVDOVIRpuDataHeader header;
+
+    /**
+     * Currently active data mappings, or NULL. Points into memory owned by the
+     * corresponding rpu/vdr_ref, which becomes invalid on the next call to
+     * dovi_rpu_parse.
+     */
+    const AVDOVIDataMapping *mapping;
+    const AVDOVIColorMetadata *color;
+
+    /**
+     * Private fields internal to dovi_rpu.c
+     */
+    AVBufferRef *vdr_ref[DOVI_MAX_DM_ID+1];
+    uint8_t dv_profile;
+
+} DOVIContext;
+
+int ff_dovi_ctx_replace(DOVIContext *s, const DOVIContext *s0);
+
+/**
+ * Completely reset a DOVIContext, preserving only logctx.
+ */
+void ff_dovi_ctx_unref(DOVIContext *s);
+
+/**
+ * Partially reset the internal state. Resets per-frame state while preserving
+ * fields parsed from the configuration record.
+ */
+void ff_dovi_ctx_flush(DOVIContext *s);
+
+/**
+ * Read the contents of an AVDOVIDecoderConfigurationRecord (usually provided
+ * by stream side data) and update internal state accordingly.
+ */
+void ff_dovi_update_cfg(DOVIContext *s, const AVDOVIDecoderConfigurationRecord *cfg);
+
+/**
+ * Parse the contents of a Dovi RPU NAL and update the parsed values in the
+ * DOVIContext struct.
+ *
+ * Returns 0 or an error code.
+ */
+int ff_dovi_rpu_parse(DOVIContext *s, const uint8_t *rpu, size_t rpu_size);
+
+/**
+ * Attach the decoded AVDOVIMetadata as side data to an AVFrame.
+ */
+int ff_dovi_attach_side_data(DOVIContext *s, AVFrame *frame);
+
+#endif /* AVCODEC_DOVI_RPU_H */