[FFmpeg-cvslog] ffmpeg: take into account image flipping in the display matrix

[James Almer]

ffmpeg | branch: master | James Almer <jamrial at gmail.com> | Wed Sep  8 15:34:26 2021 -0300| [42fce6fffe2010a0d5eab454aa04813995f4222f] | committer: James Almer

ffmpeg: take into account image flipping in the display matrix

This covers only standard rotations.
Fixes part of ticket #6945.

Signed-off-by: James Almer <jamrial at gmail.com>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=42fce6fffe2010a0d5eab454aa04813995f4222f
---

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

diff --git a/fftools/ffmpeg_filter.c b/fftools/ffmpeg_filter.c
index a4c2de07da..da0d4faf54 100644
--- a/fftools/ffmpeg_filter.c
+++ b/fftools/ffmpeg_filter.c
@@ -765,18 +765,36 @@ static int configure_input_video_filter(FilterGraph *fg, InputFilter *ifilter,
         theta = get_rotation(displaymatrix);
 
         if (fabs(theta - 90) < 1.0) {
+            if (displaymatrix[3] > 0) {
+                ret = insert_filter(&last_filter, &pad_idx, "hflip", NULL);
+                if (ret < 0)
+                    return ret;
+            }
             ret = insert_filter(&last_filter, &pad_idx, "transpose", "clock");
         } else if (fabs(theta - 180) < 1.0) {
-            ret = insert_filter(&last_filter, &pad_idx, "hflip", NULL);
-            if (ret < 0)
-                return ret;
-            ret = insert_filter(&last_filter, &pad_idx, "vflip", NULL);
+            if (displaymatrix[0] < 0) {
+                ret = insert_filter(&last_filter, &pad_idx, "hflip", NULL);
+                if (ret < 0)
+                    return ret;
+            }
+            if (displaymatrix[4] < 0) {
+                ret = insert_filter(&last_filter, &pad_idx, "vflip", NULL);
+            }
         } else if (fabs(theta - 270) < 1.0) {
+            if (displaymatrix[3] < 0) {
+                ret = insert_filter(&last_filter, &pad_idx, "hflip", NULL);
+                if (ret < 0)
+                    return ret;
+            }
             ret = insert_filter(&last_filter, &pad_idx, "transpose", "cclock");
         } else if (fabs(theta) > 1.0) {
             char rotate_buf[64];
             snprintf(rotate_buf, sizeof(rotate_buf), "%f*PI/180", theta);
             ret = insert_filter(&last_filter, &pad_idx, "rotate", rotate_buf);
+        } else if (fabs(theta) < 1.0) {
+            if (displaymatrix && displaymatrix[4] < 0) {
+                ret = insert_filter(&last_filter, &pad_idx, "vflip", NULL);
+            }
         }
         if (ret < 0)
             return ret;