[FFmpeg-devel] [PATCH] scale: make the filter parametric
Stefano Sabatini
stefano.sabatini-lala at poste.it
Wed Mar 30 22:42:12 CEST 2011
Make the filter accept parametric expressions for the output video
size.
---
doc/filters.texi | 62 +++++++++++++++++++++++++++++---
libavfilter/vf_scale.c | 93 +++++++++++++++++++++++++++++++++++++++++++-----
2 files changed, 141 insertions(+), 14 deletions(-)
diff --git a/doc/filters.texi b/doc/filters.texi
index 80f6fb0..92e2f82 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -984,13 +984,33 @@ 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:
- at example
-./ffmpeg -i in.avi -vf "scale=200:100" out.avi
- at end example
+ at table @option
+ at item E, PI, PHI
+the corresponding mathematical approximated values for e
+(euler number), pi (greek PI), phi (golden ratio)
+
+ at item in_w, in_h
+the input width and heigth
+
+ at item iw, ih
+same as @var{in_w} and @var{in_h}
-will scale the input video to a size of 200x100.
+ at item out_w, out_h
+the output (cropped) width and heigth
+
+ at item ow, oh
+same as @var{out_w} and @var{out_h}
+
+ at item a
+input display aspect ratio, same as @var{iw} / @var{ih}
+
+ at item hsub, vsub
+horizontal and vertical chroma subsample values. For example for the
+pixel format "yuv420p" @var{hsub} is 1 and @var{vsub} is 2.
+ at 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
@@ -1005,6 +1025,38 @@ ratio of the input image.
The default value of @var{width} and @var{height} is 0.
+Some examples follow:
+ at 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
+# subsample sizes, note that quoting and \-escaping is required since
+# "," is a filtergraph special character
+scale="round(3/2*iw\, hsub):round(3/2*ih\, vsub)"
+
+# increase the width up to 500 pixels, keep the same input aspect ratio
+scale='min(500, iw*3/2):-1'
+ at end example
+
@anchor{setdar}
@section setdar
diff --git a/libavfilter/vf_scale.c b/libavfilter/vf_scale.c
index b1f1ba5..42a00af 100644
--- a/libavfilter/vf_scale.c
+++ b/libavfilter/vf_scale.c
@@ -24,10 +24,40 @@
*/
#include "avfilter.h"
+#include "libavutil/avstring.h"
+#include "libavutil/eval.h"
#include "libavutil/pixdesc.h"
#include "libavutil/avassert.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
struct SwsContext *isws[2]; ///< software scaler context for interlaced material
@@ -44,6 +74,9 @@ typedef struct {
int slice_y; ///< top of current output slice
int input_is_pal; ///< set to 1 if the input format is paletted
int interlaced;
+
+ 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)
@@ -51,9 +84,12 @@ 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);
if(strstr(args,"interl=1")){
@@ -62,14 +98,6 @@ static av_cold int init(AVFilterContext *ctx, const char *args, void *opaque)
scale->interlaced=-1;
}
- /* 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;
}
@@ -118,6 +146,48 @@ 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] = 2<<av_pix_fmt_descriptors[inlink->format].log2_chroma_w;
+ var_values[VAR_VSUB] = 2<<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_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_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;
@@ -157,6 +227,11 @@ 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)
--
1.7.2.3
More information about the ffmpeg-devel
mailing list