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FFmpeg/libavfilter/scale_eval.h
Tristan Schmelcher 179830108d
avfilter/scale_eval: Reduce rounding error.
When force_original_aspect_ratio and force_divisible_by are both
used, dimensions are now rounded to the nearest allowed multiple of
force_divisible_by rather than first rounding to the nearest integer and
then rounding in a static direction. This results in less distortion of
the aspect ratio.

Reviewed-by: Thierry Foucu <tfoucu@google.com>
Signed-off-by: Tristan Schmelcher <tschmelcher@google.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
2022-09-27 00:07:43 +02:00

50 lines
1.8 KiB
C

/*
* 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 AVFILTER_SCALE_EVAL_H
#define AVFILTER_SCALE_EVAL_H
#include "avfilter.h"
/**
* Parse and evaluate string expressions for width and height. Upon success,
* ff_scale_adjust_dimensions must be called with evaluated width and height
* to obtain actual target dimensions.
*
* Returns 0 upon success, negative value if one of the expressions could
* not be parsed or if NaN was the result of their evaluation.
*/
int ff_scale_eval_dimensions(void *ctx,
const char *w_expr, const char *h_expr,
AVFilterLink *inlink, AVFilterLink *outlink,
int *ret_w, int *ret_h);
/**
* Transform evaluated width and height obtained from ff_scale_eval_dimensions
* into actual target width and height for scaling. Adjustment can occur if one
* or both of the evaluated values are of the form '-n' or if
* force_original_aspect_ratio is set. force_divisible_by is used only when
* force_original_aspect_ratio is set and must be at least 1.
*
* Returns 0.
*/
int ff_scale_adjust_dimensions(AVFilterLink *inlink,
int *ret_w, int *ret_h,
int force_original_aspect_ratio, int force_divisible_by);
#endif