obu: don't output invisible but showable key frames more than once

From section 6.8.2 in the AV1 spec:

"It is a requirement of bitstream conformance that when show_existing_frame is
used to show a previous frame with RefFrameType[ frame_to_show_map_idx ] equal
to KEY_FRAME, that the frame is output via the show_existing_frame mechanism at
most once."

3 files changed, 9 insertions, 1 deletions

diff --git a/src/obu.c b/src/obu.c
index d0f8fcf..6d06a10 100644
--- a/src/obu.c
+++ b/src/obu.c
@@ -1558,7 +1558,7 @@ int dav1d_parse_obus(Dav1dContext *const c, Dav1dData *const in, const int globa
         if (c->frame_hdr->show_existing_frame) {
             if (!c->refs[c->frame_hdr->existing_frame_idx].p.p.data[0]) goto error;
             if (c->strict_std_compliance &&
-                !c->refs[c->frame_hdr->existing_frame_idx].p.p.frame_hdr->showable_frame)
+                !c->refs[c->frame_hdr->existing_frame_idx].p.showable)
             {
                 goto error;
             }
@@ -1613,6 +1613,7 @@ int dav1d_parse_obus(Dav1dContext *const c, Dav1dData *const in, const int globa
             }
             if (c->refs[c->frame_hdr->existing_frame_idx].p.p.frame_hdr->frame_type == DAV1D_FRAME_TYPE_KEY) {
                 const int r = c->frame_hdr->existing_frame_idx;
+                c->refs[r].p.showable = 0;
                 for (int i = 0; i < 8; i++) {
                     if (i == r) continue;
 
diff --git a/src/picture.c b/src/picture.c
index 7046ed1..544828f 100644
--- a/src/picture.c
+++ b/src/picture.c
@@ -202,6 +202,7 @@ int dav1d_thread_picture_alloc(Dav1dContext *const c, Dav1dFrameContext *const f
     c->frame_flags &= flags_mask;
 
     p->visible = f->frame_hdr->show_frame;
+    p->showable = f->frame_hdr->showable_frame;
     if (have_frame_mt) {
         atomic_init(&p->progress[0], 0);
         atomic_init(&p->progress[1], 0);
@@ -259,6 +260,7 @@ void dav1d_thread_picture_ref(Dav1dThreadPicture *const dst,
 {
     dav1d_picture_ref(&dst->p, &src->p);
     dst->visible = src->visible;
+    dst->showable = src->showable;
     dst->progress = src->progress;
     dst->flags = src->flags;
 }
@@ -268,6 +270,7 @@ void dav1d_thread_picture_move_ref(Dav1dThreadPicture *const dst,
 {
     dav1d_picture_move_ref(&dst->p, &src->p);
     dst->visible = src->visible;
+    dst->showable = src->showable;
     dst->progress = src->progress;
     dst->flags = src->flags;
     memset(src, 0, sizeof(*src));
diff --git a/src/picture.h b/src/picture.h
index 0e30d48..154c85a 100644
--- a/src/picture.h
+++ b/src/picture.h
@@ -52,6 +52,10 @@ enum PictureFlags {
 typedef struct Dav1dThreadPicture {
     Dav1dPicture p;
     int visible;
+    // This can be set for inter frames, non-key intra frames, or for invisible
+    // keyframes that have not yet been made visible using the show-existing-frame
+    // mechanism.
+    int showable;
     enum PictureFlags flags;
     // [0] block data (including segmentation map and motion vectors)
     // [1] pixel data