[FFmpeg-devel] [PATCH v3] lavfi/delogo: take SAR into account

[Jean Delvare]

When interpolating, weights are based on relative distances, which
assume square pixels. If a non-1:1 sample aspect ratio is used, it
should be taken into account when comparing distances, because the
human eye and brain care about the picture as it is displayed, not
stored.

Signed-off-by: Jean Delvare <khali at linux-fr.org>
---
Changes since v2:
 * Adjusted the subject.
 * Don't use non-portable "? :" construct.
 * Alter sar.den in place.
 * Alter sar.den in the caller rather than in apply_delogo(), so we
   only do it once per frame.

 libavfilter/vf_delogo.c |   20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

--- ffmpeg.orig/libavfilter/vf_delogo.c	2013-06-28 09:41:50.291495611 +0200
+++ ffmpeg/libavfilter/vf_delogo.c	2013-06-28 10:45:42.496634606 +0200
@@ -56,7 +56,7 @@
  */
 static void apply_delogo(uint8_t *dst, int dst_linesize,
                          uint8_t *src, int src_linesize,
-                         int w, int h,
+                         int w, int h, AVRational sar,
                          int logo_x, int logo_y, int logo_w, int logo_h,
                          int band, int show, int direct)
 {
@@ -93,11 +93,11 @@ static void apply_delogo(uint8_t *dst, i
              xdst = dst+logo_x1+1,
              xsrc = src+logo_x1+1; x < logo_x2-1; x++, xdst++, xsrc++) {
 
-            /* Weighted interpolation based on relative distances */
-            weightl = (uint64_t)              (logo_x2-1-x) * (y-logo_y1) * (logo_y2-1-y);
-            weightr = (uint64_t)(x-logo_x1)                 * (y-logo_y1) * (logo_y2-1-y);
-            weightt = (uint64_t)(x-logo_x1) * (logo_x2-1-x)               * (logo_y2-1-y);
-            weightb = (uint64_t)(x-logo_x1) * (logo_x2-1-x) * (y-logo_y1);
+            /* Weighted interpolation based on relative distances, taking SAR into account */
+            weightl = (uint64_t)              (logo_x2-1-x) * (y-logo_y1) * (logo_y2-1-y) * sar.den;
+            weightr = (uint64_t)(x-logo_x1)                 * (y-logo_y1) * (logo_y2-1-y) * sar.den;
+            weightt = (uint64_t)(x-logo_x1) * (logo_x2-1-x)               * (logo_y2-1-y) * sar.num;
+            weightb = (uint64_t)(x-logo_x1) * (logo_x2-1-x) * (y-logo_y1)                 * sar.num;
 
             interp =
                 (topleft[src_linesize*(y-logo_y  -yclipt)]   +
@@ -217,6 +217,7 @@ static int filter_frame(AVFilterLink *in
     int vsub0 = desc->log2_chroma_h;
     int direct = 0;
     int plane;
+    AVRational sar;
 
     if (av_frame_is_writable(in)) {
         direct = 1;
@@ -231,6 +232,11 @@ static int filter_frame(AVFilterLink *in
         av_frame_copy_props(out, in);
     }
 
+    sar = in->sample_aspect_ratio;
+    /* Assume square pixels if SAR is unknown */
+    if (!sar.num)
+        sar.num = sar.den = 1;
+
     for (plane = 0; plane < 4 && in->data[plane]; plane++) {
         int hsub = plane == 1 || plane == 2 ? hsub0 : 0;
         int vsub = plane == 1 || plane == 2 ? vsub0 : 0;
@@ -239,7 +245,7 @@ static int filter_frame(AVFilterLink *in
                      in ->data[plane], in ->linesize[plane],
                      FF_CEIL_RSHIFT(inlink->w, hsub),
                      FF_CEIL_RSHIFT(inlink->h, vsub),
-                     s->x>>hsub, s->y>>vsub,
+                     sar, s->x>>hsub, s->y>>vsub,
                      FF_CEIL_RSHIFT(s->w, hsub),
                      FF_CEIL_RSHIFT(s->h, vsub),
                      s->band>>FFMIN(hsub, vsub),


-- 
Jean Delvare