[FFmpeg-devel] [PATCH 5/6] avformat/movenc: write ChannelLayout box for PCM

[Zhao Zhili <quinkblack@foxmail.com>]

From: Zhao Zhili <zhilizhao@tencent.com>

Signed-off-by: Zhao Zhili <zhilizhao@tencent.com>
---
 libavformat/movenc.c | 44 +++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 43 insertions(+), 1 deletion(-)

diff --git a/libavformat/movenc.c b/libavformat/movenc.c
index 99b93c1d5b..2b84ed1afa 100644
--- a/libavformat/movenc.c
+++ b/libavformat/movenc.c
@@ -1203,6 +1203,43 @@ static int is_mp4_pcm_codec(enum AVCodecID codec)
     return 0;
 }
 
+static int mov_write_chnl_tag(AVFormatContext *s, AVIOContext *pb, MOVTrack *track)
+{
+    int64_t pos = avio_tell(pb);
+    int layout = 0;
+    int ret;
+    uint8_t speaker_pos[64] = { };
+
+    ret = ff_mov_get_channel_config_from_layout(&track->par->ch_layout, &layout);
+    if (ret || !layout) {
+        layout = 0;
+        ret = ff_mov_get_channel_positions_from_layout(&track->par->ch_layout,
+                speaker_pos, FF_ARRAY_ELEMS(speaker_pos));
+        if (ret) {
+            char buf[128] = {};
+
+            av_channel_layout_describe(&track->par->ch_layout, buf, sizeof(buf));
+            av_log(s, AV_LOG_WARNING, "unsupported channel layout %s, skip 'chnl'\n", buf);
+            return 0;
+        }
+    }
+
+    avio_wb32(pb, 0); /* size */
+    ffio_wfourcc(pb, "chnl");
+    avio_wb32(pb, 0); /* version & flags */
+
+    avio_w8(pb, 1); /* stream_structure */
+    avio_w8(pb, layout);
+    if (layout) {
+        avio_wb64(pb, 0);
+    } else {
+        for (int i = 0; i < track->par->ch_layout.nb_channels; i++)
+            avio_w8(pb, speaker_pos[i]);
+    }
+
+    return update_size(pb, pos);
+}
+
 static int mov_write_pcmc_tag(AVFormatContext *s, AVIOContext *pb, MOVTrack *track)
 {
     int64_t pos = avio_tell(pb);
@@ -1353,8 +1390,13 @@ static int mov_write_audio_tag(AVFormatContext *s, AVIOContext *pb, MOVMuxContex
         ret = mov_write_dmlp_tag(s, pb, track);
     else if (track->vos_len > 0)
         ret = mov_write_glbl_tag(pb, track);
-    else if (track->mode == MODE_MP4 && is_mp4_pcm_codec(track->par->codec_id))
+    else if (track->mode == MODE_MP4 && is_mp4_pcm_codec(track->par->codec_id)) {
+        if (track->par->ch_layout.nb_channels > 1)
+            ret = mov_write_chnl_tag(s, pb, track);
+        if (ret < 0)
+            return ret;
         ret = mov_write_pcmc_tag(s, pb, track);
+    }
 
     if (ret < 0)
         return ret;
-- 
2.25.1

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