lib: don't buffer an extra frame when there's a single spatial layer

3 files changed, 8 insertions, 6 deletions

diff --git a/src/internal.h b/src/internal.h
index b42b316..55710bf 100644
--- a/src/internal.h
+++ b/src/internal.h
@@ -189,6 +189,7 @@ struct Dav1dContext {
     int operating_point;
     unsigned operating_point_idc;
     int all_layers;
+    int max_spatial_id;
     unsigned frame_size_limit;
     int strict_std_compliance;
     int output_invisible_frames;
diff --git a/src/lib.c b/src/lib.c
index f851f2d..c42d2c6 100644
--- a/src/lib.c
+++ b/src/lib.c
@@ -322,7 +322,8 @@ static int output_image(Dav1dContext *const c, Dav1dPicture *const out)
 {
     int res = 0;
 
-    Dav1dThreadPicture *const in = c->all_layers ? &c->out : &c->cache;
+    Dav1dThreadPicture *const in = c->all_layers || !c->max_spatial_id
+                                   ? &c->out : &c->cache;
     if (!c->apply_grain || !has_grain(&in->p)) {
         dav1d_picture_move_ref(out, &in->p);
         dav1d_thread_picture_unref(in);
@@ -332,18 +333,16 @@ static int output_image(Dav1dContext *const c, Dav1dPicture *const out)
     res = dav1d_apply_grain(c, out, &in->p);
     dav1d_thread_picture_unref(in);
 end:
-    if (!c->all_layers && c->out.p.data[0]) {
+    if (!c->all_layers && c->max_spatial_id && c->out.p.data[0]) {
         dav1d_thread_picture_move_ref(in, &c->out);
     }
     return res;
 }
 
 static int output_picture_ready(Dav1dContext *const c, const int drain) {
-    if (!c->all_layers) {
+    if (!c->all_layers && c->max_spatial_id) {
         if (c->out.p.data[0] && c->cache.p.data[0]) {
-            const unsigned spatial_mask = c->operating_point_idc >> 8;
-            const int max_spatial_id = spatial_mask ? ulog2(spatial_mask) : 0;
-            if (max_spatial_id == c->cache.p.frame_hdr->spatial_id ||
+            if (c->max_spatial_id == c->cache.p.frame_hdr->spatial_id ||
                 c->out.flags & PICTURE_FLAG_NEW_TEMPORAL_UNIT)
                 return 1;
             dav1d_thread_picture_unref(&c->cache);
diff --git a/src/obu.c b/src/obu.c
index e3d6671..b02da32 100644
--- a/src/obu.c
+++ b/src/obu.c
@@ -138,6 +138,8 @@ static int parse_seq_hdr(Dav1dContext *const c, GetBits *const gb,
         const int op_idx =
             c->operating_point < hdr->num_operating_points ? c->operating_point : 0;
         c->operating_point_idc = hdr->operating_points[op_idx].idc;
+        const unsigned spatial_mask = c->operating_point_idc >> 8;
+        c->max_spatial_id = spatial_mask ? ulog2(spatial_mask) : 0;
 #if DEBUG_SEQ_HDR
         printf("SEQHDR: post-operating-points: off=%u\n",
                dav1d_get_bits_pos(gb) - init_bit_pos);