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FFmpeg/libavcodec/h274.h
Niklas Haas 6bc29a6b57 avcodec/h274: add film grain synthesis routine
This could arguably also be a vf, but I decided to put it here since
decoders are technically required to apply film grain during the output
step, and I would rather want to avoid requiring users insert the
correct film grain synthesis filter on their own.

The code, while in C, is written in a way that unrolls/vectorizes fairly
well under -O3, and is reasonably cache friendly. On my CPU, a single
thread pushes about 400 FPS at 1080p.

Apart from hand-written assembly, one possible avenue of improvement
would be to change the access order to compute the grain row-by-row
rather than in 8x8 blocks. This requires some redundant PRNG calls, but
would make the algorithm more cache-oblivious.

The implementation has been written to the wording of SMPTE RDD 5-2006
as faithfully as I can manage. However, apart from passing a visual
inspection, no guarantee of correctness can be made due to the lack of
any publicly available reference implementation against which to
compare it.

Signed-off-by: Niklas Haas <git@haasn.dev>
Signed-off-by: James Almer <jamrial@gmail.com>
2021-08-24 09:58:52 -03:00

53 lines
1.8 KiB
C

/*
* H.274 film grain synthesis
* Copyright (c) 2021 Niklas Haas <ffmpeg@haasn.xyz>
*
* 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
*/
/**
* @file
* H.274 film grain synthesis.
* @author Niklas Haas <ffmpeg@haasn.xyz>
*/
#ifndef AVCODEC_H274_H
#define AVCODEC_H274_H
#include <libavutil/film_grain_params.h>
// Must be initialized to {0} prior to first usage
typedef struct H274FilmGrainDatabase {
// Database of film grain patterns, lazily computed as-needed
int8_t db[13 /* h */][13 /* v */][64][64];
uint16_t residency[13 /* h */]; // bit field of v
// Temporary buffer for slice generation
int16_t slice_tmp[64][64];
} H274FilmGrainDatabase;
// Synthesizes film grain on top of `in` and stores the result to `out`. `out`
// must already have been allocated and set to the same size and format as
// `in`.
//
// Returns a negative error code on error, such as invalid params.
int ff_h274_apply_film_grain(AVFrame *out, const AVFrame *in,
H274FilmGrainDatabase *db,
const AVFilmGrainParams *params);
#endif /* AVCODEC_H274_H */