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ffmpeg/libavfilter/scale.c
Kevin Mark 05feeeb813 libavfilter/scale: Populate ow/oh when using 0 as w/h 
The input width and height is known at parse time so there's no
reason ow/oh should not be usable when using 0 as the width or
height expression.

Previously in "scale=0:ow" ow would be set to "0" which works,
conveniently, as "scale=0:0" is perfectly valid input but this breaks
down when you do something like "scale=0:ow/4" which one could
reasonably expect to work as well, but does not as ow is 0 not the
real value.

This change handles the 0 case for w/h immediately so the ow/oh
variables work as expected. Consequently, the rest of the code does
not need to handle 0 input. w/h will always be > 0 or < 0.

The second explicit (int) cast ensures that ow/oh appear as integers
as a user might expect when dealing with pixel dimensions.

Signed-off-by: Kevin Mark <kmark937@gmail.com>
Signed-off-by: Ronald S. Bultje <rsbultje@gmail.com>
2017-06-19 14:27:52 -04:00

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/*
* Copyright (c) 2007 Bobby Bingham
*
* 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 <stdint.h>
#include "scale.h"
#include "libavutil/eval.h"
#include "libavutil/mathematics.h"
#include "libavutil/pixdesc.h"
static const char *const var_names[] = {
"PI",
"PHI",
"E",
"in_w", "iw",
"in_h", "ih",
"out_w", "ow",
"out_h", "oh",
"a",
"sar",
"dar",
"hsub",
"vsub",
"ohsub",
"ovsub",
NULL
};
enum var_name {
VAR_PI,
VAR_PHI,
VAR_E,
VAR_IN_W, VAR_IW,
VAR_IN_H, VAR_IH,
VAR_OUT_W, VAR_OW,
VAR_OUT_H, VAR_OH,
VAR_A,
VAR_SAR,
VAR_DAR,
VAR_HSUB,
VAR_VSUB,
VAR_OHSUB,
VAR_OVSUB,
VARS_NB
};
/**
* This must be kept in sync with var_names so that it is always a
* complete list of var_names with the scale2ref specific names
* appended. scale2ref values must appear in the order they appear
* in the var_name_scale2ref enum but also be below all of the
* non-scale2ref specific values.
*/
static const char *const var_names_scale2ref[] = {
"PI",
"PHI",
"E",
"in_w", "iw",
"in_h", "ih",
"out_w", "ow",
"out_h", "oh",
"a",
"sar",
"dar",
"hsub",
"vsub",
"ohsub",
"ovsub",
"main_w",
"main_h",
"main_a",
"main_sar",
"main_dar", "mdar",
"main_hsub",
"main_vsub",
NULL
};
enum var_name_scale2ref {
VAR_S2R_MAIN_W,
VAR_S2R_MAIN_H,
VAR_S2R_MAIN_A,
VAR_S2R_MAIN_SAR,
VAR_S2R_MAIN_DAR, VAR_S2R_MDAR,
VAR_S2R_MAIN_HSUB,
VAR_S2R_MAIN_VSUB,
VARS_S2R_NB
};
int ff_scale_eval_dimensions(void *log_ctx,
const char *w_expr, const char *h_expr,
AVFilterLink *inlink, AVFilterLink *outlink,
int *ret_w, int *ret_h)
{
const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(inlink->format);
const AVPixFmtDescriptor *out_desc = av_pix_fmt_desc_get(outlink->format);
const char *expr;
int w, h;
int factor_w, factor_h;
int eval_w, eval_h;
int ret;
const char scale2ref = outlink->src->nb_inputs == 2 && outlink->src->inputs[1] == inlink;
double var_values[VARS_NB + VARS_S2R_NB], res;
const AVPixFmtDescriptor *main_desc;
const AVFilterLink *main_link;
const char *const *names = scale2ref ? var_names_scale2ref : var_names;
if (scale2ref) {
main_link = outlink->src->inputs[0];
main_desc = av_pix_fmt_desc_get(main_link->format);
}
var_values[VAR_PI] = M_PI;
var_values[VAR_PHI] = M_PHI;
var_values[VAR_E] = M_E;
var_values[VAR_IN_W] = var_values[VAR_IW] = inlink->w;
var_values[VAR_IN_H] = var_values[VAR_IH] = inlink->h;
var_values[VAR_OUT_W] = var_values[VAR_OW] = NAN;
var_values[VAR_OUT_H] = var_values[VAR_OH] = NAN;
var_values[VAR_A] = (double) inlink->w / inlink->h;
var_values[VAR_SAR] = inlink->sample_aspect_ratio.num ?
(double) inlink->sample_aspect_ratio.num / inlink->sample_aspect_ratio.den : 1;
var_values[VAR_DAR] = var_values[VAR_A] * var_values[VAR_SAR];
var_values[VAR_HSUB] = 1 << desc->log2_chroma_w;
var_values[VAR_VSUB] = 1 << desc->log2_chroma_h;
var_values[VAR_OHSUB] = 1 << out_desc->log2_chroma_w;
var_values[VAR_OVSUB] = 1 << out_desc->log2_chroma_h;
if (scale2ref) {
var_values[VARS_NB + VAR_S2R_MAIN_W] = main_link->w;
var_values[VARS_NB + VAR_S2R_MAIN_H] = main_link->h;
var_values[VARS_NB + VAR_S2R_MAIN_A] = (double) main_link->w / main_link->h;
var_values[VARS_NB + VAR_S2R_MAIN_SAR] = main_link->sample_aspect_ratio.num ?
(double) main_link->sample_aspect_ratio.num / main_link->sample_aspect_ratio.den : 1;
var_values[VARS_NB + VAR_S2R_MAIN_DAR] = var_values[VARS_NB + VAR_S2R_MDAR] =
var_values[VARS_NB + VAR_S2R_MAIN_A] * var_values[VARS_NB + VAR_S2R_MAIN_SAR];
var_values[VARS_NB + VAR_S2R_MAIN_HSUB] = 1 << main_desc->log2_chroma_w;
var_values[VARS_NB + VAR_S2R_MAIN_VSUB] = 1 << main_desc->log2_chroma_h;
}
/* evaluate width and height */
av_expr_parse_and_eval(&res, (expr = w_expr),
names, var_values,
NULL, NULL, NULL, NULL, NULL, 0, log_ctx);
eval_w = var_values[VAR_OUT_W] = var_values[VAR_OW] = (int) res == 0 ? inlink->w : (int) res;
if ((ret = av_expr_parse_and_eval(&res, (expr = h_expr),
names, var_values,
NULL, NULL, NULL, NULL, NULL, 0, log_ctx)) < 0)
goto fail;
eval_h = var_values[VAR_OUT_H] = var_values[VAR_OH] = (int) res == 0 ? inlink->h : (int) res;
/* evaluate again the width, as it may depend on the output height */
if ((ret = av_expr_parse_and_eval(&res, (expr = w_expr),
names, var_values,
NULL, NULL, NULL, NULL, NULL, 0, log_ctx)) < 0)
goto fail;
eval_w = (int) res == 0 ? inlink->w : (int) res;
w = eval_w;
h = eval_h;
/* Check if it is requested that the result has to be divisible by a some
* factor (w or h = -n with n being the factor). */
factor_w = 1;
factor_h = 1;
if (w < -1) {
factor_w = -w;
}
if (h < -1) {
factor_h = -h;
}
if (w < 0 && h < 0) {
w = inlink->w;
h = inlink->h;
}
/* Make sure that the result is divisible by the factor we determined
* earlier. If no factor was set, it is nothing will happen as the default
* factor is 1 */
if (w < 0)
w = av_rescale(h, inlink->w, inlink->h * factor_w) * factor_w;
if (h < 0)
h = av_rescale(w, inlink->h, inlink->w * factor_h) * factor_h;
*ret_w = w;
*ret_h = h;
return 0;
fail:
av_log(log_ctx, AV_LOG_ERROR,
"Error when evaluating the expression '%s'.\n"
"Maybe the expression for out_w:'%s' or for out_h:'%s' is self-referencing.\n",
expr, w_expr, h_expr);
return ret;
}
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