mov: add support for reading and writing the 'chan' tag

This implements reading the tag in the demuxer and adds support for writing it
in the muxer. Some example channel layout tables for muxing are included for
ac3, aac, and alac, but they are not utilized yet.

1 files changed, 26 insertions, 0 deletions

diff --git a/libavformat/movenc.c b/libavformat/movenc.c
index 5d770aa..897a204 100644
--- a/libavformat/movenc.c
+++ b/libavformat/movenc.c
@@ -37,6 +37,7 @@
 #include "libavutil/opt.h"
 #include "libavutil/dict.h"
 #include "rtpenc.h"
+#include "mov_chan.h"
 
 #undef NDEBUG
 #include <assert.h>
@@ -338,6 +339,31 @@ static int mov_write_ms_tag(AVIOContext *pb, MOVTrack *track)
     return updateSize(pb, pos);
 }
 
+static int mov_write_chan_tag(AVIOContext *pb, MOVTrack *track)
+{
+    uint32_t layout_tag, bitmap;
+    int64_t pos = avio_tell(pb);
+
+    layout_tag = ff_mov_get_channel_layout_tag(track->enc->codec_id,
+                                               track->enc->channel_layout,
+                                               &bitmap);
+    if (!layout_tag) {
+        av_log(track->enc, AV_LOG_WARNING, "not writing 'chan' tag due to "
+               "lack of channel information\n");
+        return 0;
+    }
+
+    avio_wb32(pb, 0);           // Size
+    ffio_wfourcc(pb, "chan");   // Type
+    avio_w8(pb, 0);             // Version
+    avio_wb24(pb, 0);           // Flags
+    avio_wb32(pb, layout_tag);  // mChannelLayoutTag
+    avio_wb32(pb, bitmap);      // mChannelBitmap
+    avio_wb32(pb, 0);           // mNumberChannelDescriptions
+
+    return updateSize(pb, pos);
+}
+
 static int mov_write_wave_tag(AVIOContext *pb, MOVTrack *track)
 {
     int64_t pos = avio_tell(pb);