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>

1 files changed, 87 insertions, 0 deletions

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 */