@@ -71,6 +71,13 @@ enum var_name {

     VARS_NB

 };

+enum EvalMode {

+    EVAL_MODE_INIT,

+    EVAL_MODE_FRAME,

+    EVAL_MODE_NB

+};

+

+

 typedef struct ScaleContext {

     const AVClass *class;

     struct SwsContext *sws;     ///< software scaler context

@@ -112,6 +119,9 @@ typedef struct ScaleContext {

     int force_original_aspect_ratio;

     int nb_slices;

+

+    int eval_mode;              ///< expression evaluation mode

+

 } ScaleContext;

 AVFilter ff_vf_scale2ref;

@@ -494,17 +504,25 @@ static int filter_frame(AVFilterLink *link, AVFrame *in)

     if(   in->width  != link->w

        || in->height != link->h

-       || in->format != link->format) {

+       || in->format != link->format

+       || in->sample_aspect_ratio.den != link->sample_aspect_ratio.den || in->sample_aspect_ratio.num != link->sample_aspect_ratio.num) {

         int ret;

-        snprintf(buf, sizeof(buf)-1, "%d", outlink->w);

-        av_opt_set(scale, "w", buf, 0);

-        snprintf(buf, sizeof(buf)-1, "%d", outlink->h);

-        av_opt_set(scale, "h", buf, 0);

+

+        if (scale->eval_mode == EVAL_MODE_INIT) {

+            snprintf(buf, sizeof(buf)-1, "%d", outlink->w);

+            av_opt_set(scale, "w", buf, 0);

+            snprintf(buf, sizeof(buf)-1, "%d", outlink->h);

+            av_opt_set(scale, "h", buf, 0);

+        }

         link->dst->inputs[0]->format = in->format;

         link->dst->inputs[0]->w      = in->width;

         link->dst->inputs[0]->h      = in->height;

+        link->dst->inputs[0]->sample_aspect_ratio.den = in->sample_aspect_ratio.den;

+        link->dst->inputs[0]->sample_aspect_ratio.num = in->sample_aspect_ratio.num;

+

+

         if ((ret = config_props(outlink)) < 0)

             return ret;

     }

@@ -665,6 +683,9 @@ static const AVOption scale_options[] = {

     { "param0", "Scaler param 0",             OFFSET(param[0]),  AV_OPT_TYPE_DOUBLE, { .dbl = SWS_PARAM_DEFAULT  }, INT_MIN, INT_MAX, FLAGS },

     { "param1", "Scaler param 1",             OFFSET(param[1]),  AV_OPT_TYPE_DOUBLE, { .dbl = SWS_PARAM_DEFAULT  }, INT_MIN, INT_MAX, FLAGS },

     { "nb_slices", "set the number of slices (debug purpose only)", OFFSET(nb_slices), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, INT_MAX, FLAGS },

+    { "eval", "specify when to evaluate expressions", OFFSET(eval_mode), AV_OPT_TYPE_INT, {.i64 = EVAL_MODE_INIT}, 0, EVAL_MODE_NB-1, FLAGS, "eval" },

+         { "init",  "eval expressions once during initialization", 0, AV_OPT_TYPE_CONST, {.i64=EVAL_MODE_INIT},  .flags = FLAGS, .unit = "eval" },

+         { "frame", "eval expressions during initialization and per-frame", 0, AV_OPT_TYPE_CONST, {.i64=EVAL_MODE_FRAME}, .flags = FLAGS, .unit = "eval" },

     { NULL }

 };