[FFmpeg-cvslog] avformat/mov: support SpatialAudioBox ambisonic layouts with arbitrary channel mapping

[James Almer]

ffmpeg | branch: master | James Almer <jamrial at gmail.com> | Fri Apr 26 11:37:10 2024 -0300| [37c8d93e56955638983d48e04f08d767eae265e1] | committer: James Almer

avformat/mov: support SpatialAudioBox ambisonic layouts with arbitrary channel mapping

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

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=37c8d93e56955638983d48e04f08d767eae265e1
---

 libavformat/mov.c | 29 ++++++++++++++++++++++-------
 1 file changed, 22 insertions(+), 7 deletions(-)

diff --git a/libavformat/mov.c b/libavformat/mov.c
index ede25d3342..d99c971999 100644
--- a/libavformat/mov.c
+++ b/libavformat/mov.c
@@ -7925,7 +7925,8 @@ cleanup:
 static int mov_read_SA3D(MOVContext *c, AVIOContext *pb, MOVAtom atom)
 {
     AVStream *st;
-    int i, version, type;
+    AVChannelLayout ch_layout = { 0 };
+    int ret, i, version, type;
     int ambisonic_order, channel_order, normalization, channel_count;
 
     if (c->fc->nb_streams < 1)
@@ -7968,24 +7969,38 @@ static int mov_read_SA3D(MOVContext *c, AVIOContext *pb, MOVAtom atom)
     }
 
     channel_count = avio_rb32(pb);
-    if (ambisonic_order < 0 || channel_count != (ambisonic_order + 1LL) * (ambisonic_order + 1LL)) {
+    if (ambisonic_order < 0 || ambisonic_order > 31 ||
+        channel_count != (ambisonic_order + 1LL) * (ambisonic_order + 1LL)) {
         av_log(c->fc, AV_LOG_ERROR,
                "Invalid number of channels (%d / %d)\n",
                channel_count, ambisonic_order);
         return 0;
     }
 
+    ret = av_channel_layout_custom_init(&ch_layout, channel_count);
+    if (ret < 0)
+        return 0;
+
     for (i = 0; i < channel_count; i++) {
-        if (i != avio_rb32(pb)) {
-            av_log(c->fc, AV_LOG_WARNING,
-                   "Ambisonic channel reordering is not supported\n");
+        unsigned channel = avio_rb32(pb);
+
+        if (channel >= channel_count) {
+            av_log(c->fc, AV_LOG_ERROR, "Invalid channel index (%d / %d)\n",
+                   channel, ambisonic_order);
+            av_channel_layout_uninit(&ch_layout);
             return 0;
         }
+        ch_layout.u.map[i].id = AV_CHAN_AMBISONIC_BASE + channel;
+    }
+
+    ret = av_channel_layout_retype(&ch_layout, 0, AV_CHANNEL_LAYOUT_RETYPE_FLAG_CANONICAL);
+    if (ret < 0) {
+        av_channel_layout_uninit(&ch_layout);
+        return 0;
     }
 
     av_channel_layout_uninit(&st->codecpar->ch_layout);
-    st->codecpar->ch_layout.order = AV_CHANNEL_ORDER_AMBISONIC;
-    st->codecpar->ch_layout.nb_channels = channel_count;
+    st->codecpar->ch_layout = ch_layout;
 
     return 0;
 }