[FFmpeg-devel] [PATCH] avformat/movenc: Write auxi box for animated AVIF with alpha

[Vignesh Venkatasubramanian <vigneshv-at-google.com@ffmpeg.org>]

According to the HEIF specification (ISO/IEC 23008-12) Section
7.5.3.1, tracks with handler_type 'auxv' must contain a 'auxi' box
in its SampleEntry to notify the nature of the auxiliary track to the
decoder.

The content is the same as the 'auxC' box. So parameterize and re-use
the existing function.

Signed-off-by: Vignesh Venkatasubramanian <vigneshv@google.com>
---
 libavformat/movenc.c | 27 +++++++++++++++------------
 1 file changed, 15 insertions(+), 12 deletions(-)

diff --git a/libavformat/movenc.c b/libavformat/movenc.c
index c8b2e141cb..754f95912a 100644
--- a/libavformat/movenc.c
+++ b/libavformat/movenc.c
@@ -2179,6 +2179,16 @@ static int mov_write_ccst_tag(AVIOContext *pb)
     return update_size(pb, pos);
 }
 
+static int mov_write_aux_tag(AVIOContext *pb, const char *aux_type)
+{
+    int64_t pos = avio_tell(pb);
+    avio_wb32(pb, 0); /* size */
+    ffio_wfourcc(pb, aux_type);
+    avio_wb32(pb, 0); /* Version & flags */
+    avio_write(pb, "urn:mpeg:mpegB:cicp:systems:auxiliary:alpha\0", 44);
+    return update_size(pb, pos);
+}
+
 static int mov_write_video_tag(AVFormatContext *s, AVIOContext *pb, MOVMuxContext *mov, MOVTrack *track)
 {
     int ret = AVERROR_BUG;
@@ -2363,8 +2373,11 @@ static int mov_write_video_tag(AVFormatContext *s, AVIOContext *pb, MOVMuxContex
     if (avid)
         avio_wb32(pb, 0);
 
-    if (track->mode == MODE_AVIF)
+    if (track->mode == MODE_AVIF) {
         mov_write_ccst_tag(pb);
+        if (s->nb_streams > 0 && track == &mov->tracks[1])
+            mov_write_aux_tag(pb, "auxi");
+    }
 
     return update_size(pb, pos);
 }
@@ -3044,16 +3057,6 @@ static int mov_write_pixi_tag(AVIOContext *pb, MOVMuxContext *mov, AVFormatConte
     return update_size(pb, pos);
 }
 
-static int mov_write_auxC_tag(AVIOContext *pb)
-{
-    int64_t pos = avio_tell(pb);
-    avio_wb32(pb, 0); /* size */
-    ffio_wfourcc(pb, "auxC");
-    avio_wb32(pb, 0); /* Version & flags */
-    avio_write(pb, "urn:mpeg:mpegB:cicp:systems:auxiliary:alpha\0", 44);
-    return update_size(pb, pos);
-}
-
 static int mov_write_ipco_tag(AVIOContext *pb, MOVMuxContext *mov, AVFormatContext *s)
 {
     int64_t pos = avio_tell(pb);
@@ -3066,7 +3069,7 @@ static int mov_write_ipco_tag(AVIOContext *pb, MOVMuxContext *mov, AVFormatConte
         if (!i)
             mov_write_colr_tag(pb, &mov->tracks[0], 0);
         else
-            mov_write_auxC_tag(pb);
+            mov_write_aux_tag(pb, "auxC");
     }
     return update_size(pb, pos);
 }
-- 
2.37.3.968.ga6b4b080e4-goog

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