[FFmpeg-devel] [PATCH] mov: Evaluate the movie display matrix

Vittorio Giovara vittorio.giovara at gmail.com
Thu Oct 6 00:25:33 EEST 2016


This matrix needs to be applied after all others have (currently only
display matrix from trak), but cannot be handled in movie box, since
streams are not allocated yet.

So store it in main context and if not identity, apply it when appropriate,
handling the case when trak display matrix is identity and when it is not.

Signed-off-by: Vittorio Giovara <vittorio.giovara at gmail.com>
---
Please keep my in CC.
Vittorio

 libavformat/isom.h |  2 ++
 libavformat/mov.c  | 63 +++++++++++++++++++++++++++++++++++++++++++++---------
 2 files changed, 55 insertions(+), 10 deletions(-)

diff --git a/libavformat/isom.h b/libavformat/isom.h
index 2246fed..2aeb8fa 100644
--- a/libavformat/isom.h
+++ b/libavformat/isom.h
@@ -238,6 +238,8 @@ typedef struct MOVContext {
     uint8_t *decryption_key;
     int decryption_key_len;
     int enable_drefs;
+
+    int32_t movie_display_matrix[3][3]; ///< display matrix from mvhd
 } MOVContext;
 
 int ff_mp4_read_descr_len(AVIOContext *pb);
diff --git a/libavformat/mov.c b/libavformat/mov.c
index a15c8d1..26b332c 100644
--- a/libavformat/mov.c
+++ b/libavformat/mov.c
@@ -1211,6 +1211,7 @@ static int mov_read_mdhd(MOVContext *c, AVIOContext *pb, MOVAtom atom)
 
 static int mov_read_mvhd(MOVContext *c, AVIOContext *pb, MOVAtom atom)
 {
+    int i;
     int64_t creation_time;
     int version = avio_r8(pb); /* version */
     avio_rb24(pb); /* flags */
@@ -1238,7 +1239,12 @@ static int mov_read_mvhd(MOVContext *c, AVIOContext *pb, MOVAtom atom)
 
     avio_skip(pb, 10); /* reserved */
 
-    avio_skip(pb, 36); /* display matrix */
+    /* movie display matrix, store it in main context and use it later on */
+    for (i = 0; i < 3; i++) {
+        c->movie_display_matrix[i][0] = avio_rb32(pb); // 16.16 fixed point
+        c->movie_display_matrix[i][1] = avio_rb32(pb); // 16.16 fixed point
+        c->movie_display_matrix[i][2] = avio_rb32(pb); //  2.30 fixed point
+    }
 
     avio_rb32(pb); /* preview time */
     avio_rb32(pb); /* preview duration */
@@ -3798,9 +3804,24 @@ static int mov_read_meta(MOVContext *c, AVIOContext *pb, MOVAtom atom)
     return 0;
 }
 
+// return 0 when matrix is identity, 1 otherwise
+#define IS_MATRIX_FULL(matrix)       \
+    (matrix[0][0] != (1 << 16) ||    \
+     matrix[1][1] != (1 << 16) ||    \
+     matrix[2][2] != (1 << 30) ||    \
+     matrix[0][1] || matrix[0][2] || \
+     matrix[1][0] || matrix[1][2] || \
+     matrix[2][0] || matrix[2][1])
+
+// fixed point to double
+#define CONV_FP(x, sh) ((double) (x)) / (1 << sh)
+
+// double to fixed point
+#define CONV_DB(x, sh) (int32_t) ((x) * (1 << sh))
+
 static int mov_read_tkhd(MOVContext *c, AVIOContext *pb, MOVAtom atom)
 {
-    int i;
+    int i, j, e;
     int width;
     int height;
     int display_matrix[3][3];
@@ -3855,13 +3876,7 @@ static int mov_read_tkhd(MOVContext *c, AVIOContext *pb, MOVAtom atom)
 
     // save the matrix and add rotate metadata when it is not the default
     // identity
-    if (display_matrix[0][0] != (1 << 16) ||
-        display_matrix[1][1] != (1 << 16) ||
-        display_matrix[2][2] != (1 << 30) ||
-        display_matrix[0][1] || display_matrix[0][2] ||
-        display_matrix[1][0] || display_matrix[1][2] ||
-        display_matrix[2][0] || display_matrix[2][1]) {
-        int i, j;
+    if (IS_MATRIX_FULL(display_matrix)) {
         double rotate;
 
         av_freep(&sc->display_matrix);
@@ -3884,13 +3899,41 @@ static int mov_read_tkhd(MOVContext *c, AVIOContext *pb, MOVAtom atom)
         }
     }
 
+    // if movie display matrix is not identity, and if this is a video track
+    if (IS_MATRIX_FULL(c->movie_display_matrix) && width && height) {
+        // if trak display matrix was identity, just copy the movie one
+        if (!sc->display_matrix) {
+            sc->display_matrix = av_malloc(sizeof(int32_t) * 9);
+            if (!sc->display_matrix)
+                return AVERROR(ENOMEM);
+
+            for (i = 0; i < 3; i++)
+                for (j = 0; j < 3; j++)
+                    sc->display_matrix[i * 3 + j] = c->movie_display_matrix[i][j];
+        } else { // otherwise multiply the two and store the result
+            double val = 0;
+            for (i = 0; i < 3; i++) {
+                for (j = 0; j < 3; j++) {
+                    int sh = j == 2 ? 30 : 16;
+                    for (e = 0; e < 3; e++) {
+                        val += CONV_FP(display_matrix[i][e], sh) *
+                               CONV_FP(c->movie_display_matrix[e][j], sh);
+                    }
+                    sc->display_matrix[i * 3 + j] = CONV_DB(val, sh);
+                    val = 0;
+                }
+            }
+        }
+    }
+
     // transform the display width/height according to the matrix
     // to keep the same scale, use [width height 1<<16]
     if (width && height && sc->display_matrix) {
         double disp_transform[2];
 
         for (i = 0; i < 2; i++)
-            disp_transform[i] = hypot(display_matrix[i][0], display_matrix[i][1]);
+            disp_transform[i] = hypot(sc->display_matrix[i * 3],
+                                      sc->display_matrix[i * 3 + 1]);
 
         if (disp_transform[0] > 0       && disp_transform[1] > 0 &&
             disp_transform[0] < (1<<24) && disp_transform[1] < (1<<24) &&
-- 
2.10.0



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