[FFmpeg-devel] [PATCH v9 4/6] lavc: Implement Dolby Vision RPU parsing
Andreas Rheinhardt
andreas.rheinhardt at outlook.com
Sun Jan 2 06:18:27 EET 2022
Niklas Haas:
> From: Niklas Haas <git at haasn.dev>
>
> 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 does
> not seem to be implemented in lavu. (And I don't care enough to do so)
> - 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 at haasn.dev>
> ---
> configure | 2 +
> libavcodec/Makefile | 1 +
> libavcodec/dovi_rpu.c | 430 ++++++++++++++++++++++++++++++++++++++++++
> libavcodec/dovi_rpu.h | 71 +++++++
> 4 files changed, 504 insertions(+)
> create mode 100644 libavcodec/dovi_rpu.c
> create mode 100644 libavcodec/dovi_rpu.h
>
> diff --git a/configure b/configure
> index 0ccd3bda11..68658a847f 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 fb90ecea84..7364c7a91f 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..fc2e1fb2a1
> --- /dev/null
> +++ b/libavcodec/dovi_rpu.c
> @@ -0,0 +1,430 @@
> +/*
> + * 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]);
> +
> + /* Preserve the user-provided fields explicitly, reset everything else */
> + *s = (DOVIContext) {
> + .logctx = s->logctx,
> + .config = s->config,
> + };
> +}
> +
> +int ff_dovi_ctx_replace(DOVIContext *s, const DOVIContext *s0)
> +{
> + int ret;
> + s->logctx = s0->logctx;
> + s->config = s0->config;
> + s->mapping = s0->mapping;
> + s->color = s0->color;
> + 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;
> +}
> +
> +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);
> + }
> +
> + memcpy(av_dovi_get_header(dovi), &s->header, sizeof(s->header));
> + memcpy(av_dovi_get_mapping(dovi), s->mapping, sizeof(*s->mapping));
> + memcpy(av_dovi_get_color(dovi), s->color, sizeof(*s->color));
These are potentially problematic due to trailing padding in the
structures. This trailing padding might become valid fields in newer
versions of this structure. E.g. av_dovi_metadata_alloc() might
intentionally set the default values of these new fields to invalid
values. Yet lavc (with the old structure) sees them as padding, allowing
the compiler to trash these values on every write to these structures.
More likely though is that they will never be touched at all and
therefore retain their default (zero) initialization. Which might
conflict with the default value of these fields.
This can be fixed by only copying everything up to and including the
last field that we know of for every of these structures. This will
unfortunately increase the maintainence burden a bit.
> + 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;
Here and in get_se_coef below the f32 member of the union is not used
with RPU_COEFF_FIXED, so using the union seems unnecessary. It is also
slightly confusing, because upon seeing this and seeing that the union
is used with RPU_COEFF_FIXED, I expect it to be used for type-punning.
> +
> + case RPU_COEFF_FLOAT:
> + fpart.u32 = get_bits_long(gb, 32);
> + return fpart.f32 * (1 << hdr->coef_log2_denom);
You could just use av_int2float() here instead of adding the union yourself.
> + }
> +
> + 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)
Notice that rpu_size is converted to int before init_get_bits8() is
called. (It is not problematic with the use in 6/6 because the size has
already been checked in this case.)
> + return ret;
> +
More information about the ffmpeg-devel
mailing list