avformat, ffmpeg: deprecate old rotation API

The old "API" that signaled rotation as a metadata value has been
replaced by DISPLAYMATRIX side data quite a while ago.

There is no reason to make muxers/demuxers/API users support both. In
addition, the metadata API is dangerous, as user tags could "leak" into
it, creating unintended features or bugs.

ffmpeg CLI has to be updated to use the new API. In particular, we must
not allow to leak the "rotate" tag into the muxer. Some muxers will
catch this properly (like mov), but others (like mkv) can add it as
generic tag. Note applications, which use libavformat and assume the
old rotate API, will interpret such "rotate" user tags as rotate
metadata (which it is not), and incorrectly rotate the video.

The ffmpeg/ffplay tools drop the use of the old API for muxing and
demuxing, as all muxers/demuxers support the new API. This will mean
that the tools will not mistakenly interpret per-track "rotate" user
tags as rotate metadata. It will _not_ be treated as regression.

Unfortunately, hacks have been added, that allow the user to override
rotation by setting metadata explicitly, e.g. via

  -metadata:s:v:0 rotate=0

See references to trac #4560. fate-filter-meta-4560-rotate0 tests this.
It's easier to adjust the hack for supporting it than arguing for its
removal, so ffmpeg CLI now explicitly catches this case, and essentially
replaces the "rotate" value with a display matrix side data. (It would
be easier for both user and implementation to create an explicit option
for rotation.)

When the code under FF_API_OLD_ROTATE_API is disabled, one FATE
reference file has to be updated (because "rotate" is not exported
anymore).

Tested-by: Michael Niedermayer <michael@niedermayer.cc>
Reviewed-by: Michael Niedermayer <michael@niedermayer.cc>

3 files changed, 10 insertions, 1 deletions

diff --git a/libavformat/mov.c b/libavformat/mov.c
index 2fce5a6..4034ca5 100644
--- a/libavformat/mov.c
+++ b/libavformat/mov.c
@@ -4027,6 +4027,7 @@ static int mov_read_tkhd(MOVContext *c, AVIOContext *pb, MOVAtom atom)
             for (j = 0; j < 3; j++)
                 sc->display_matrix[i * 3 + j] = res_display_matrix[i][j];
 
+#if FF_API_OLD_ROTATE_API
         rotate = av_display_rotation_get(sc->display_matrix);
         if (!isnan(rotate)) {
             char rotate_buf[64];
@@ -4036,6 +4037,7 @@ static int mov_read_tkhd(MOVContext *c, AVIOContext *pb, MOVAtom atom)
             snprintf(rotate_buf, sizeof(rotate_buf), "%g", rotate);
             av_dict_set(&st->metadata, "rotate", rotate_buf, 0);
         }
+#endif
     }
 
     // transform the display width/height according to the matrix
diff --git a/libavformat/movenc.c b/libavformat/movenc.c
index 11b2670..3b4e3b5 100644
--- a/libavformat/movenc.c
+++ b/libavformat/movenc.c
@@ -2496,19 +2496,23 @@ static int mov_write_tkhd_tag(AVIOContext *pb, MOVMuxContext *mov,
     avio_wb16(pb, 0); /* reserved */
 
     /* Matrix structure */
+#if FF_API_OLD_ROTATE_API
     if (st && st->metadata) {
         AVDictionaryEntry *rot = av_dict_get(st->metadata, "rotate", NULL, 0);
         rotation = (rot && rot->value) ? atoi(rot->value) : 0;
     }
+#endif
     if (display_matrix) {
         for (i = 0; i < 9; i++)
             avio_wb32(pb, display_matrix[i]);
+#if FF_API_OLD_ROTATE_API
     } else if (rotation == 90) {
         write_matrix(pb,  0,  1, -1,  0, track->par->height, 0);
     } else if (rotation == 180) {
         write_matrix(pb, -1,  0,  0, -1, track->par->width, track->par->height);
     } else if (rotation == 270) {
         write_matrix(pb,  0, -1,  1,  0, 0, track->par->width);
+#endif
     } else {
         write_matrix(pb,  1,  0,  0,  1, 0, 0);
     }
diff --git a/libavformat/version.h b/libavformat/version.h
index dd4c680..ba2b912 100644
--- a/libavformat/version.h
+++ b/libavformat/version.h
@@ -32,7 +32,7 @@
 // Major bumping may affect Ticket5467, 5421, 5451(compatibility with Chromium)
 // Also please add any ticket numbers that you believe might be affected here
 #define LIBAVFORMAT_VERSION_MAJOR  57
-#define LIBAVFORMAT_VERSION_MINOR  67
+#define LIBAVFORMAT_VERSION_MINOR  68
 #define LIBAVFORMAT_VERSION_MICRO 100
 
 #define LIBAVFORMAT_VERSION_INT AV_VERSION_INT(LIBAVFORMAT_VERSION_MAJOR, \
@@ -94,6 +94,9 @@
 #ifndef FF_API_LAVF_KEEPSIDE_FLAG
 #define FF_API_LAVF_KEEPSIDE_FLAG       (LIBAVFORMAT_VERSION_MAJOR < 58)
 #endif
+#ifndef FF_API_OLD_ROTATE_API
+#define FF_API_OLD_ROTATE_API           (LIBAVFORMAT_VERSION_MAJOR < 58)
+#endif
 
 
 #ifndef FF_API_R_FRAME_RATE