diff --git a/Changelog b/Changelog
index 53c89cd349..90da1856e3 100644
--- a/Changelog
+++ b/Changelog
@@ -5,6 +5,7 @@ version <next>
 
 - HNM version 4 demuxer and video decoder
 - Live HDS muxer
+- setsar/setdar filters now support variables in ratio expressions
 
 
 version 2.1:
diff --git a/doc/filters.texi b/doc/filters.texi
index 57679cca5c..7f07848e65 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -6970,6 +6970,31 @@ Default value is @code{100}.
 
 @end table
 
+The parameter @var{sar} is an expression containing
+the following constants:
+
+@table @option
+@item E, PI, PHI
+the corresponding mathematical approximated values for e
+(euler number), pi (greek PI), phi (golden ratio)
+
+@item w, h
+the input width and height
+
+@item a
+same as @var{w} / @var{h}
+
+@item sar
+input sample aspect ratio
+
+@item dar
+input display aspect ratio, it is the same as (@var{w} / @var{h}) * @var{sar}
+
+@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
+
 @subsection Examples
 
 @itemize
diff --git a/libavfilter/vf_aspect.c b/libavfilter/vf_aspect.c
index f926ea97b1..eaece16afe 100644
--- a/libavfilter/vf_aspect.c
+++ b/libavfilter/vf_aspect.c
@@ -30,11 +30,38 @@
 #include "libavutil/mathematics.h"
 #include "libavutil/opt.h"
 #include "libavutil/parseutils.h"
+#include "libavutil/pixdesc.h"
 
 #include "avfilter.h"
 #include "internal.h"
 #include "video.h"
 
+static const char *const var_names[] = {
+    "PI",
+    "PHI",
+    "E",
+    "w",
+    "h",
+    "a", "dar",
+    "sar",
+    "hsub",
+    "vsub",
+    NULL
+};
+
+enum var_name {
+    VAR_PI,
+    VAR_PHI,
+    VAR_E,
+    VAR_W,
+    VAR_H,
+    VAR_A, VAR_DAR,
+    VAR_SAR,
+    VAR_HSUB,
+    VAR_VSUB,
+    VARS_NB
+};
+
 typedef struct {
     const AVClass *class;
     AVRational dar;
@@ -43,7 +70,7 @@ typedef struct {
 #if FF_API_OLD_FILTER_OPTS
     float aspect_den;
 #endif
-    char *ratio_str;
+    char *ratio_expr;
 } AspectContext;
 
 static av_cold int init(AVFilterContext *ctx)
@@ -52,28 +79,20 @@ static av_cold int init(AVFilterContext *ctx)
     int ret;
 
 #if FF_API_OLD_FILTER_OPTS
-    if (s->ratio_str && s->aspect_den > 0) {
+    if (s->ratio_expr && s->aspect_den > 0) {
         double num;
         av_log(ctx, AV_LOG_WARNING,
                "num:den syntax is deprecated, please use num/den or named options instead\n");
-        ret = av_expr_parse_and_eval(&num, s->ratio_str, NULL, NULL,
+        ret = av_expr_parse_and_eval(&num, s->ratio_expr, NULL, NULL,
                                      NULL, NULL, NULL, NULL, NULL, 0, ctx);
         if (ret < 0) {
-            av_log(ctx, AV_LOG_ERROR, "Unable to parse ratio numerator \"%s\"\n", s->ratio_str);
+            av_log(ctx, AV_LOG_ERROR, "Unable to parse ratio numerator \"%s\"\n", s->ratio_expr);
             return AVERROR(EINVAL);
         }
         s->sar = s->dar = av_d2q(num / s->aspect_den, s->max);
-    } else
-#endif
-    if (s->ratio_str) {
-        ret = av_parse_ratio(&s->sar, s->ratio_str, s->max, 0, ctx);
-        if (ret < 0 || s->sar.num < 0 || s->sar.den <= 0) {
-            av_log(ctx, AV_LOG_ERROR,
-                   "Invalid string '%s' for aspect ratio\n", s->ratio_str);
-            return AVERROR(EINVAL);
-        }
-        s->dar = s->sar;
     }
+#endif
+
     return 0;
 }
 
@@ -97,6 +116,48 @@ static inline void compute_dar(AVRational *dar, AVRational sar, int w, int h)
     }
 }
 
+static int get_aspect_ratio(AVFilterLink *inlink, AVRational *aspect_ratio)
+{
+    AVFilterContext *ctx = inlink->dst;
+    AspectContext *s = inlink->dst->priv;
+    const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(inlink->format);
+    double var_values[VARS_NB], res;
+    int ret;
+
+    var_values[VAR_PI]    = M_PI;
+    var_values[VAR_PHI]   = M_PHI;
+    var_values[VAR_E]     = M_E;
+    var_values[VAR_W]     = inlink->w;
+    var_values[VAR_H]     = inlink->h;
+    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;
+
+    /* evaluate new aspect ratio*/
+    ret = av_expr_parse_and_eval(&res, s->ratio_expr,
+                                      var_names, var_values,
+                                      NULL, NULL, NULL, NULL, NULL, 0, ctx);
+    if (ret < 0) {
+        ret = av_parse_ratio(aspect_ratio, s->ratio_expr, s->max, 0, ctx);
+    } else
+        *aspect_ratio = av_d2q(res, s->max);
+
+    if (ret < 0) {
+        av_log(ctx, AV_LOG_ERROR,
+               "Error when evaluating the expression '%s'\n", s->ratio_expr);
+        return ret;
+    }
+    if (aspect_ratio->num < 0 || aspect_ratio->den <= 0) {
+        av_log(ctx, AV_LOG_ERROR,
+                "Invalid string '%s' for aspect ratio\n", s->ratio_expr);
+        return AVERROR(EINVAL);
+    }
+    return 0;
+}
+
 #if CONFIG_SETDAR_FILTER
 
 static int setdar_config_props(AVFilterLink *inlink)
@@ -105,6 +166,16 @@ static int setdar_config_props(AVFilterLink *inlink)
     AVRational dar;
     AVRational old_dar;
     AVRational old_sar = inlink->sample_aspect_ratio;
+    int ret;
+
+#if FF_API_OLD_FILTER_OPTS
+    if (!(s->ratio_expr && s->aspect_den > 0)) {
+#endif
+    if ((ret = get_aspect_ratio(inlink, &s->dar)))
+        return ret;
+#if FF_API_OLD_FILTER_OPTS
+    }
+#endif
 
     if (s->dar.num && s->dar.den) {
         av_reduce(&s->sar.num, &s->sar.den,
@@ -126,9 +197,9 @@ static int setdar_config_props(AVFilterLink *inlink)
 }
 
 static const AVOption setdar_options[] = {
-    { "dar",   "set display aspect ratio", OFFSET(ratio_str), AV_OPT_TYPE_STRING, {.str="0"}, .flags=FLAGS },
-    { "ratio", "set display aspect ratio", OFFSET(ratio_str), AV_OPT_TYPE_STRING, {.str="0"}, .flags=FLAGS },
-    { "r",     "set display aspect ratio", OFFSET(ratio_str), AV_OPT_TYPE_STRING, {.str="0"}, .flags=FLAGS },
+    { "dar",   "set display aspect ratio", OFFSET(ratio_expr), AV_OPT_TYPE_STRING, { .str = "0" }, .flags = FLAGS },
+    { "ratio", "set display aspect ratio", OFFSET(ratio_expr), AV_OPT_TYPE_STRING, { .str = "0" }, .flags = FLAGS },
+    { "r",     "set display aspect ratio", OFFSET(ratio_expr), AV_OPT_TYPE_STRING, { .str = "0" }, .flags = FLAGS },
 #if FF_API_OLD_FILTER_OPTS
     { "dar_den", NULL, OFFSET(aspect_den), AV_OPT_TYPE_FLOAT, { .dbl = 0 }, 0, FLT_MAX, FLAGS },
 #endif
@@ -175,6 +246,16 @@ static int setsar_config_props(AVFilterLink *inlink)
     AspectContext *s = inlink->dst->priv;
     AVRational old_sar = inlink->sample_aspect_ratio;
     AVRational old_dar, dar;
+    int ret;
+
+#if FF_API_OLD_FILTER_OPTS
+    if (!(s->ratio_expr && s->aspect_den > 0)) {
+#endif
+    if ((ret = get_aspect_ratio(inlink, &s->sar)))
+        return ret;
+#if FF_API_OLD_FILTER_OPTS
+    }
+#endif
 
     inlink->sample_aspect_ratio = s->sar;
 
@@ -188,9 +269,9 @@ static int setsar_config_props(AVFilterLink *inlink)
 }
 
 static const AVOption setsar_options[] = {
-    { "sar",   "set sample (pixel) aspect ratio", OFFSET(ratio_str), AV_OPT_TYPE_STRING, {.str="0"}, .flags=FLAGS },
-    { "ratio", "set sample (pixel) aspect ratio", OFFSET(ratio_str), AV_OPT_TYPE_STRING, {.str="0"}, .flags=FLAGS },
-    { "r",     "set sample (pixel) aspect ratio", OFFSET(ratio_str), AV_OPT_TYPE_STRING, {.str="0"}, .flags=FLAGS },
+    { "sar",   "set sample (pixel) aspect ratio", OFFSET(ratio_expr), AV_OPT_TYPE_STRING, { .str = "0" }, .flags = FLAGS },
+    { "ratio", "set sample (pixel) aspect ratio", OFFSET(ratio_expr), AV_OPT_TYPE_STRING, { .str = "0" }, .flags = FLAGS },
+    { "r",     "set sample (pixel) aspect ratio", OFFSET(ratio_expr), AV_OPT_TYPE_STRING, { .str = "0" }, .flags = FLAGS },
 #if FF_API_OLD_FILTER_OPTS
     { "sar_den", NULL, OFFSET(aspect_den), AV_OPT_TYPE_FLOAT, { .dbl = 0 }, 0, FLT_MAX, FLAGS },
 #endif