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scale: make the filter parametric

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Make the filter accept parametric expressions for the output video
size.

Signed-off-by: Stefano Sabatini <stefano.sabatini-lala@poste.it>
Signed-off-by: Anton Khirnov <anton@khirnov.net>
pull/2/head
Stefano Sabatini 14 years ago committed by Anton Khirnov
parent b137bf7df3
commit 68e23c083a
2 changed files with 139 additions and 14 deletions
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  1. 60
      doc/filters.texi
  2. 93
      libavfilter/vf_scale.c

60
doc/filters.texi
Unescape View File

@ -772,13 +772,33 @@ can be used to test the monowhite pixel format descriptor definition.
Scale the input video to @var{width}:@var{height} and/or convert the image format.
For example the command:
The parameters @var{width} and @var{height} are expressions containing
the following constants:
@example
./ffmpeg -i in.avi -vf "scale=200:100" out.avi
@end example
@table @option
@item E, PI, PHI
the corresponding mathematical approximated values for e
(euler number), pi (greek PI), phi (golden ratio)
@item in_w, in_h
the input width and heigth
@item iw, ih
same as @var{in_w} and @var{in_h}
@item out_w, out_h
the output (cropped) width and heigth
@item ow, oh
same as @var{out_w} and @var{out_h}
will scale the input video to a size of 200x100.
@item a
input display aspect ratio, same as @var{iw} / @var{ih}
@item hsub, vsub
horizontal and vertical chroma subsample values. For example for the
pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
@end table
If the input image format is different from the format requested by
the next filter, the scale filter will convert the input to the
@ -793,6 +813,36 @@ ratio of the input image.
The default value of @var{width} and @var{height} is 0.
Some examples follow:
@example
# scale the input video to a size of 200x100.
scale=200:100
# scale the input to 2x
scale=2*iw:2*ih
# the above is the same as
scale=2*in_w:2*in_h
# scale the input to half size
scale=iw/2:ih/2
# increase the width, and set the height to the same size
scale=3/2*iw:ow
# seek for Greek harmony
scale=iw:1/PHI*iw
scale=ih*PHI:ih
# increase the height, and set the width to 3/2 of the height
scale=3/2*oh:3/5*ih
# increase the size, but make the size a multiple of the chroma
scale="trunc(3/2*iw/hsub)*hsub:trunc(3/2*ih/vsub)*vsub"
# increase the width to a maximum of 500 pixels, keep the same input aspect ratio
scale='min(500\, iw*3/2):-1'
@end example
@anchor{setdar}
@section setdar

93
libavfilter/vf_scale.c
Unescape View File

@ -24,9 +24,39 @@
*/
#include "avfilter.h"
#include "libavutil/avstring.h"
#include "libavutil/eval.h"
#include "libavutil/pixdesc.h"
#include "libswscale/swscale.h"
static const char *var_names[] = {
"PI",
"PHI",
"E",
"in_w", "iw",
"in_h", "ih",
"out_w", "ow",
"out_h", "oh",
"a",
"hsub",
"vsub",
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_HSUB,
VAR_VSUB,
VARS_NB
};
typedef struct {
struct SwsContext *sws; ///< software scaler context
@ -41,6 +71,9 @@ typedef struct {
int hsub, vsub; ///< chroma subsampling
int slice_y; ///< top of current output slice
int input_is_pal; ///< set to 1 if the input format is paletted
char w_expr[256]; ///< width expression string
char h_expr[256]; ///< height expression string
} ScaleContext;
static av_cold int init(AVFilterContext *ctx, const char *args, void *opaque)
@ -48,21 +81,16 @@ static av_cold int init(AVFilterContext *ctx, const char *args, void *opaque)
ScaleContext *scale = ctx->priv;
const char *p;
av_strlcpy(scale->w_expr, "iw", sizeof(scale->w_expr));
av_strlcpy(scale->h_expr, "ih", sizeof(scale->h_expr));
scale->flags = SWS_BILINEAR;
if (args) {
sscanf(args, "%d:%d", &scale->w, &scale->h);
sscanf(args, "%255[^:]:%255[^:]", scale->w_expr, scale->h_expr);
p = strstr(args,"flags=");
if (p) scale->flags = strtoul(p+6, NULL, 0);
}
/* sanity check params */
if (scale->w < -1 || scale->h < -1) {
av_log(ctx, AV_LOG_ERROR, "Size values less than -1 are not acceptable.\n");
return AVERROR(EINVAL);
}
if (scale->w == -1 && scale->h == -1)
scale->w = scale->h = 0;
return 0;
}
@ -109,6 +137,48 @@ static int config_props(AVFilterLink *outlink)
AVFilterLink *inlink = outlink->src->inputs[0];
ScaleContext *scale = ctx->priv;
int64_t w, h;
double var_values[VARS_NB], res;
char *expr;
int ret;
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] = (float) inlink->w / inlink->h;
var_values[VAR_HSUB] = 1<<av_pix_fmt_descriptors[inlink->format].log2_chroma_w;
var_values[VAR_VSUB] = 1<<av_pix_fmt_descriptors[inlink->format].log2_chroma_h;
/* evaluate width and height */
av_expr_parse_and_eval(&res, (expr = scale->w_expr),
var_names, var_values,
NULL, NULL, NULL, NULL, NULL, 0, ctx);
scale->w = var_values[VAR_OUT_W] = var_values[VAR_OW] = res;
if ((ret = av_expr_parse_and_eval(&res, (expr = scale->h_expr),
var_names, var_values,
NULL, NULL, NULL, NULL, NULL, 0, ctx)) < 0)
goto fail;
scale->h = var_values[VAR_OUT_H] = var_values[VAR_OH] = res;
/* evaluate again the width, as it may depend on the output height */
if ((ret = av_expr_parse_and_eval(&res, (expr = scale->w_expr),
var_names, var_values,
NULL, NULL, NULL, NULL, NULL, 0, ctx)) < 0)
goto fail;
scale->w = res;
w = scale->w;
h = scale->h;
/* sanity check params */
if (w < -1 || h < -1) {
av_log(ctx, AV_LOG_ERROR, "Size values less than -1 are not acceptable.\n");
return AVERROR(EINVAL);
}
if (w == -1 && h == -1)
scale->w = scale->h = 0;
if (!(w = scale->w))
w = inlink->w;
@ -142,6 +212,11 @@ static int config_props(AVFilterLink *outlink)
return AVERROR(EINVAL);
return 0;
fail:
av_log(NULL, AV_LOG_ERROR,
"Error when evaluating the expression '%s'\n", expr);
return ret;
}
static void start_frame(AVFilterLink *link, AVFilterBufferRef *picref)

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