lavc/vp9: fix reference frame dimensions check for SINGLE_REFERENCE mode

With the description in frame size with refs semantics (SPEC 7.2.5),
it is a requirement of bitstream conformance that for at least one
reference frame has the valid dimensions.

Modify the check to make sure the decoder works well in SINGLE_REFERENCE
mode that not all reference frames have valid dimensions.

Check and error out if invalid reference frame is used in inter_recon.

One of the failure case is a 480x272 inter frame (SINGLE_REFERENCE mode)
with following reference pool:

0.  960x544    LAST    valid
1. 1920x1088 GOLDEN  invalid, but not used in single reference mode
2. 1920x1088 ALTREF  invalid, but not used in single reference mode
3~7  ...     Unused

Identical logic in libvpx:
<https://github.com/webmproject/libvpx/blob/master/vp9/decoder/vp9_decodeframe.c#L736>

Signed-off-by: Linjie Fu <linjie.fu@intel.com>
Signed-off-by: Ronald S. Bultje <rsbultje@gmail.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/libavcodec/vp9dec.h b/libavcodec/vp9dec.h
index de02b146f0..e203666bb4 100644
--- a/libavcodec/vp9dec.h
+++ b/libavcodec/vp9dec.h
@@ -36,6 +36,8 @@
 #include "vp9dsp.h"
 #include "vp9shared.h"
 
+#define REF_INVALID_SCALE 0xFFFF
+
 enum MVJoint {
     MV_JOINT_ZERO,
     MV_JOINT_H,
@@ -221,6 +223,9 @@ struct VP9TileData {
     struct { int x, y; } min_mv, max_mv;
     int16_t *block_base, *block, *uvblock_base[2], *uvblock[2];
     uint8_t *eob_base, *uveob_base[2], *eob, *uveob[2];
+
+    // error message
+    int error_info;
 };
 
 void ff_vp9_fill_mv(VP9TileData *td, VP56mv *mv, int mode, int sb);