From 7fc4c184630043587ace5b44ef70ccf70c7409fe Mon Sep 17 00:00:00 2001
From: Lars Kiesow <lkiesow@uos.de>
Date: Sat, 25 Jan 2014 14:40:48 +0100
Subject: [PATCH 1/4] Factors for scale filter

---
 libavfilter/vf_scale.c | 26 ++++++++++++++++++++++----
 1 file changed, 22 insertions(+), 4 deletions(-)

diff --git a/libavfilter/vf_scale.c b/libavfilter/vf_scale.c
index 2e692cff5b..bda536df91 100644
--- a/libavfilter/vf_scale.c
+++ b/libavfilter/vf_scale.c
@@ -270,11 +270,20 @@ static int config_props(AVFilterLink *outlink)
     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);
+    /* 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). After we got the factor,
+     * we set w/h back to -1 so that the automatic scaling is done. */
+    int factor_w = 1;
+    int factor_h = 1;
+    if (w < -1) {
+        factor_w = -w;
+        w = -1;
     }
+    if (h < -1) {
+        factor_h = -h;
+        h = -1;
+    }
+
     if (w == -1 && h == -1)
         scale->w = scale->h = 0;
 
@@ -287,6 +296,15 @@ static int config_props(AVFilterLink *outlink)
     if (h == -1)
         h = av_rescale(w, inlink->h, inlink->w);
 
+    /* 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 */
+    w = (w / factor_w) * factor_w;
+    h = (h / factor_h) * factor_h;
+
+
+    /* Note that force_original_aspect_ratio may overwrite the previous set
+     * dimensions so that it is not divisible by the set factors anymore. */
     if (scale->force_original_aspect_ratio) {
         int tmp_w = av_rescale(h, inlink->w, inlink->h);
         int tmp_h = av_rescale(w, inlink->h, inlink->w);

From e395f8de5ac682d8c99673d431ad7c0575bf2a7e Mon Sep 17 00:00:00 2001
From: Lars Kiesow <lkiesow@uos.de>
Date: Sat, 25 Jan 2014 15:00:02 +0100
Subject: [PATCH 2/4] Fixed factor for scale filter

---
 libavfilter/vf_scale.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/libavfilter/vf_scale.c b/libavfilter/vf_scale.c
index bda536df91..2ea55ef441 100644
--- a/libavfilter/vf_scale.c
+++ b/libavfilter/vf_scale.c
@@ -236,6 +236,7 @@ static int config_props(AVFilterLink *outlink)
     double var_values[VARS_NB], res;
     char *expr;
     int ret;
+    int factor_w, factor_h;
 
     var_values[VAR_IN_W]  = var_values[VAR_IW] = inlink->w;
     var_values[VAR_IN_H]  = var_values[VAR_IH] = inlink->h;
@@ -273,15 +274,17 @@ static int config_props(AVFilterLink *outlink)
     /* 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). After we got the factor,
      * we set w/h back to -1 so that the automatic scaling is done. */
-    int factor_w = 1;
-    int factor_h = 1;
+    factor_w = 1;
+    factor_h = 1;
     if (w < -1) {
         factor_w = -w;
         w = -1;
+        scale->w = -1;
     }
     if (h < -1) {
         factor_h = -h;
         h = -1;
+        scale->h = -1;
     }
 
     if (w == -1 && h == -1)
@@ -302,7 +305,6 @@ static int config_props(AVFilterLink *outlink)
     w = (w / factor_w) * factor_w;
     h = (h / factor_h) * factor_h;
 
-
     /* Note that force_original_aspect_ratio may overwrite the previous set
      * dimensions so that it is not divisible by the set factors anymore. */
     if (scale->force_original_aspect_ratio) {

From 69b1d1d99bc5384d4ca305aa76e246a06c5b98b5 Mon Sep 17 00:00:00 2001
From: Lars Kiesow <lkiesow@uos.de>
Date: Sat, 25 Jan 2014 15:02:15 +0100
Subject: [PATCH 3/4] Documentation for scale filter factor

---
 libavfilter/vf_scale.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/libavfilter/vf_scale.c b/libavfilter/vf_scale.c
index 2ea55ef441..945ed121dd 100644
--- a/libavfilter/vf_scale.c
+++ b/libavfilter/vf_scale.c
@@ -81,6 +81,7 @@ typedef struct {
      * New dimensions. Special values are:
      *   0 = original width/height
      *  -1 = keep original aspect
+     *  -N = try to keep aspect but make sure it is divisible by N
      */
     int w, h;
     char *size_str;

From c49b0360966da9cdbdbafd0ce926269e777bc774 Mon Sep 17 00:00:00 2001
From: Lars Kiesow <lkiesow@uos.de>
Date: Sat, 25 Jan 2014 15:34:23 +0100
Subject: [PATCH 4/4] Documentation for scale filter factor

---
 doc/filters.texi | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/doc/filters.texi b/doc/filters.texi
index 9e67db4888..28e7a24af9 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -6911,6 +6911,11 @@ maintains the aspect ratio of the input image, calculated from the
 other specified dimension. If both of them are -1, the input size is
 used
 
+If one of the values is -n with n > 1, the scale filter will also use a value
+that maintains the aspect ratio of the input image, calculated from the other
+specified dimension. After that it will, however, make sure that the calculated
+dimension is divisible by n and adjust the value if necessary.
+
 See below for the list of accepted constants for use in the dimension
 expression.