Videos that require to be rotate and flipped ignore the flip

So you mean transposed and anti-transposed orientation don't work correctly? At least those are involutive (unlike quarter rotations), so they can't be mistaken for one another.

Yes this is my understanding as well.

In addition exit 4 is not well applied. Which is flip vertically, or « flip horizontally and 180 rotation »

changed the description

(sorry for editing/changing the ORIENTATION_ summary by accident - I drag-clicked my mouse while hovering over the list. I tried to restore the original ordering :/)

A few findings:

78ef0fd1

seems to have added "flip" detection to the 4.0 branch (master) in fact, when i comment out the surrounding code in libmp4.c any kind of rotation detection is disabled on the 3.0 branch.

I tried to backport the patch (manually by doing it line by line) and I think this makes sense.

I think this patch should do it:

Patch draft

diff --git a/modules/demux/mp4/essetup.c b/modules/demux/mp4/essetup.c
index 19b5ff16fc..05d892d57d 100644
--- a/modules/demux/mp4/essetup.c
+++ b/modules/demux/mp4/essetup.c
@@ -275,16 +275,32 @@ int SetupVideoES( demux_t *p_demux, mp4_track_t *p_track, MP4_Box_t *p_sample )
     p_track->fmt.video.i_visible_height = p_track->fmt.video.i_height;
 
     /* Rotation */
-    switch( (int)p_track->f_rotation ) {
-        case 90:
+    msg_Err(p_demux, "f_rotation: %" PRId32, (int)p_track->f_rotation);
+    msg_Err(p_demux, "i_flip: %" PRId32, p_track->i_flip);
+    if ( (int)p_track->f_rotation == 90 ) {
+        if ( p_track->i_flip ) {
+            p_track->fmt.video.orientation = ORIENT_TRANSPOSED;
+        } else {
             p_track->fmt.video.orientation = ORIENT_ROTATED_90;
-            break;
-        case 180:
+        }
+    } else if ( (int)p_track->f_rotation == 180 ) {
+        if ( p_track->i_flip ) {
+            p_track->fmt.video.orientation = ORIENT_VFLIPPED;
+        } else {
             p_track->fmt.video.orientation = ORIENT_ROTATED_180;
-            break;
-        case 270:
+        }
+    } else if ( (int)p_track->f_rotation == 270 ) {
+        if ( p_track->i_flip) {
+            p_track->fmt.video.orientation = ORIENT_ANTI_TRANSPOSED;
+        } else {
             p_track->fmt.video.orientation = ORIENT_ROTATED_270;
-            break;
+        }
+    } else {
+        if ( p_track->i_flip ) {
+            p_track->fmt.video.orientation = ORIENT_HFLIPPED;
+        } else {
+            p_track->fmt.video.orientation = ORIENT_NORMAL;
+        }
     }
 
     /* Set 360 video mode */
diff --git a/modules/demux/mp4/libmp4.c b/modules/demux/mp4/libmp4.c
index cf9eeadf42..5e778f44bd 100644
--- a/modules/demux/mp4/libmp4.c
+++ b/modules/demux/mp4/libmp4.c
@@ -1232,6 +1232,20 @@ static int MP4_ReadBox_tkhd(  stream_t *p_stream, MP4_Box_t *p_box )
     scale[1] = sqrt(conv_fx(matrix[1]) * conv_fx(matrix[1]) +
                     conv_fx(matrix[4]) * conv_fx(matrix[4]));
 
+    int64_t det = (int64_t)matrix[0] * matrix[4] - (int64_t)matrix[1] * matrix[3];
+    if (det < 0) {
+        /* If determinant is negative copy the matrix and flip it horizontally. */
+        const int flip[] = { -1, 1, 1 };
+        for (int j = 0; j < 9; j++)
+            matrix[j] *= flip[j % 3];
+        p_box->data.p_tkhd->i_flip = 1;
+    } else {
+        p_box->data.p_tkhd->i_flip = 0;
+    }
+    msg_Err(p_stream, "det : %" PRId32, det);
+    msg_Err(p_stream, "p_tkhd->i_flip: %" PRId32, p_box->data.p_tkhd->i_flip);
+
+
     if( likely(scale[0] > 0 && scale[1] > 0) )
     {
         rotation = atan2(conv_fx(matrix[1]) / scale[1],
diff --git a/modules/demux/mp4/libmp4.h b/modules/demux/mp4/libmp4.h
index bfab16515f..fa7394ae4b 100644
--- a/modules/demux/mp4/libmp4.h
+++ b/modules/demux/mp4/libmp4.h
@@ -509,6 +509,7 @@ typedef struct MP4_Box_data_tkhd_s
     int32_t  i_width;
     int32_t  i_height;
     float    f_rotation;
+    int32_t  i_flip;
 
 } MP4_Box_data_tkhd_t;
 
diff --git a/modules/demux/mp4/mp4.c b/modules/demux/mp4/mp4.c
index a5178d860f..908890183b 100644
--- a/modules/demux/mp4/mp4.c
+++ b/modules/demux/mp4/mp4.c
@@ -3367,6 +3367,7 @@ static void MP4_TrackSetup( demux_t *p_demux, mp4_track_t *p_track,
     p_track->i_width = BOXDATA(p_tkhd)->i_width / BLOCK16x16;
     p_track->i_height = BOXDATA(p_tkhd)->i_height / BLOCK16x16;
     p_track->f_rotation = BOXDATA(p_tkhd)->f_rotation;
+    p_track->i_flip = BOXDATA(p_tkhd)->i_flip;
 
     /* FIXME: unhandled box: tref */
 
diff --git a/modules/demux/mp4/mp4.h b/modules/demux/mp4/mp4.h
index b7c6cdf3d7..d2855246a3 100644
--- a/modules/demux/mp4/mp4.h
+++ b/modules/demux/mp4/mp4.h
@@ -99,6 +99,7 @@ typedef struct
     int i_width;
     int i_height;
     float f_rotation;
+    int i_flip;
 
     /* more internal data */
     uint32_t        i_timescale;    /* time scale for this track only */

If such a patch would be acceptable, I would love to be able to get it merged into the 3.0.x branch in addition to the master branch.

Please let me know the best way to proceed.

I also need to tripple check the EXIF5 and EXIF7 orientations. I mostly just got "something to be different" and didn't really triple check it.

changed the description

mentioned in merge request !7113 (closed)

mentioned in merge request !7115 (closed)

As mentioned in !7115 (closed) I actually got to the point to confirm that this was in fact fixed in the master branch with 78ef0fd1

Thank you for your time. a backport would be greatly appreciated!

mentioned in merge request !7116

Videos that require to be rotate and flipped ignore the flip

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