lavc/decode: merge stereo3d information from decoder with packet side data

The HEVC decoder will start setting stereoscopic view position (left or
right) based on 3D Reference Displays Info SEI message in future
commits. This information should be merged with container-derived
stereo3D side data.

libavcodec/decode.c

@@ -37,6 +37,7 @@
 #include "libavutil/internal.h"
 #include "libavutil/mastering_display_metadata.h"
 #include "libavutil/mem.h"
+#include "libavutil/stereo3d.h"
 
 #include "avcodec.h"
 #include "avcodec_internal.h"
@@ -1423,6 +1424,42 @@ const AVPacketSideData *ff_get_coded_side_data(const AVCodecContext *avctx,
     return packet_side_data_get(avctx->coded_side_data, avctx->nb_coded_side_data, type);
 }
 
+static int side_data_stereo3d_merge(AVFrameSideData *sd_frame,
+                                    const AVPacketSideData *sd_pkt)
+{
+    const AVStereo3D *src;
+    AVStereo3D       *dst;
+    int ret;
+
+    ret = av_buffer_make_writable(&sd_frame->buf);
+    if (ret < 0)
+        return ret;
+    sd_frame->data = sd_frame->buf->data;
+
+    dst = (      AVStereo3D*)sd_frame->data;
+    src = (const AVStereo3D*)sd_pkt->data;
+
+    if (dst->type == AV_STEREO3D_UNSPEC)
+        dst->type = src->type;
+
+    if (dst->view == AV_STEREO3D_VIEW_UNSPEC)
+        dst->view = src->view;
+
+    if (dst->primary_eye == AV_PRIMARY_EYE_NONE)
+        dst->primary_eye = src->primary_eye;
+
+    if (!dst->baseline)
+        dst->baseline = src->baseline;
+
+    if (!dst->horizontal_disparity_adjustment.num)
+        dst->horizontal_disparity_adjustment = src->horizontal_disparity_adjustment;
+
+    if (!dst->horizontal_field_of_view.num)
+        dst->horizontal_field_of_view = src->horizontal_field_of_view;
+
+    return 0;
+}
+
 static int side_data_map(AVFrame *dst,
                          const AVPacketSideData *sd_src, int nb_sd_src,
                          const SideDataMap *map)
@@ -1439,8 +1476,15 @@ static int side_data_map(AVFrame *dst,
             continue;
 
         sd_frame = av_frame_get_side_data(dst, type_frame);
-        if (sd_frame)
+        if (sd_frame) {
+            if (type_frame == AV_FRAME_DATA_STEREO3D) {
+                int ret = side_data_stereo3d_merge(sd_frame, sd_pkt);
+                if (ret < 0)
+                    return ret;
+            }
+
             continue;
+        }
 
         sd_frame = av_frame_new_side_data(dst, type_frame, sd_pkt->size);
         if (!sd_frame)