commit 84b05ac19a18fcc1bac5b7809820555006fb4156
author Rupert Swarbrick <rupert.swarbrick@argondesign.com> Fri Oct 27 18:10:53 2017 +0100
committer Yaowu Xu <yaowu@google.com> Mon Oct 30 16:33:26 2017 +0000
tree 4bcd8389a2cc357c05e4e8221ba88a696e65c10a
parent 118129679646239ea9c81a8f645e99692e18378b

Stop backward adaptation if EXT_TILE + cm->large_scale_tile

Backwards adaptation doesn't really make sense in this context,
because ext-tile means the decoder might not decode every tile in the
frame, in which case it can't work out how to adapt probabilities.

It turns out that the tests in the tree were passing when
SIMPLE_BWD_ADAPT was disabled because (presumably) all of them
happened to decode every tile, so backward adaptation worked as you'd
expect. With SIMPLE_BWD_ADAPT, there's some code in get_tile_buffers
to figure out which is the largest tile. This wasn't mirrored in
get_ls_tile_buffers, which caused the encoder and decoder to get out
of sync because they ended up with different CDFs. You also can't
easily fix things in get_ls_tile_buffers because that code is careful
not to calculate the size of tiles it doesn't need.

BUG=aomedia:917

Change-Id: Ia926692f86ca1466252108e09da3de590d45f048

av1/decoder/decodeframe.c

diff --git a/av1/decoder/decodeframe.c b/av1/decoder/decodeframe.c
index cd37088..7071e8c 100644
--- a/av1/decoder/decodeframe.c
+++ b/av1/decoder/decodeframe.c
@@ -3299,7 +3299,13 @@
                        " state");
   }
 
-  if (!cm->error_resilient_mode) {
+#if CONFIG_EXT_TILE
+  const int might_bwd_adapt =
+      !(cm->error_resilient_mode || cm->large_scale_tile);
+#else
+  const int might_bwd_adapt = !cm->error_resilient_mode;
+#endif  // CONFIG_EXT_TILE
+  if (might_bwd_adapt) {
     cm->refresh_frame_context = aom_rb_read_bit(rb)
                                     ? REFRESH_FRAME_CONTEXT_FORWARD
                                     : REFRESH_FRAME_CONTEXT_BACKWARD;

av1/encoder/bitstream.c

diff --git a/av1/encoder/bitstream.c b/av1/encoder/bitstream.c
index 884d27b..29458b2 100644
--- a/av1/encoder/bitstream.c
+++ b/av1/encoder/bitstream.c
@@ -4155,7 +4155,13 @@
   }
 #endif  // CONFIG_REFERENCE_BUFFER
 
-  if (!cm->error_resilient_mode) {
+#if CONFIG_EXT_TILE
+  const int might_bwd_adapt =
+      !(cm->error_resilient_mode || cm->large_scale_tile);
+#else
+  const int might_bwd_adapt = !cm->error_resilient_mode;
+#endif  // CONFIG_EXT_TILE
+  if (might_bwd_adapt) {
     aom_wb_write_bit(
         wb, cm->refresh_frame_context == REFRESH_FRAME_CONTEXT_FORWARD);
   }

av1/encoder/encoder.c

diff --git a/av1/encoder/encoder.c b/av1/encoder/encoder.c
index 19d8686..691d479 100644
--- a/av1/encoder/encoder.c
+++ b/av1/encoder/encoder.c
@@ -2480,6 +2480,11 @@
       (oxcf->error_resilient_mode || oxcf->frame_parallel_decoding_mode)
           ? REFRESH_FRAME_CONTEXT_FORWARD
           : REFRESH_FRAME_CONTEXT_BACKWARD;
+#if CONFIG_EXT_TILE
+  if (oxcf->large_scale_tile)
+    cm->refresh_frame_context = REFRESH_FRAME_CONTEXT_FORWARD;
+#endif  // CONFIG_EXT_TILE
+
 #if !CONFIG_NO_FRAME_CONTEXT_SIGNALING
   cm->reset_frame_context = RESET_FRAME_CONTEXT_NONE;
 #endif
@@ -5406,7 +5411,11 @@
       // Only reset the current context.
       cm->reset_frame_context = RESET_FRAME_CONTEXT_CURRENT;
     }
-#endif
+#if CONFIG_EXT_TILE
+    if (cpi->oxcf.large_scale_tile)
+      cm->refresh_frame_context = REFRESH_FRAME_CONTEXT_FORWARD;
+#endif  // CONFIG_EXT_TILE
+#endif  // !CONFIG_NO_FRAME_CONTEXT_SIGNALING
   }
   if (cpi->oxcf.mtu == 0) {
     cm->num_tg = cpi->oxcf.num_tile_groups;
@@ -6206,6 +6215,10 @@
       (oxcf->error_resilient_mode || oxcf->frame_parallel_decoding_mode)
           ? REFRESH_FRAME_CONTEXT_FORWARD
           : REFRESH_FRAME_CONTEXT_BACKWARD;
+#if CONFIG_EXT_TILE
+  if (oxcf->large_scale_tile)
+    cm->refresh_frame_context = REFRESH_FRAME_CONTEXT_FORWARD;
+#endif  // CONFIG_EXT_TILE
 
   cpi->refresh_last_frame = 1;
   cpi->refresh_golden_frame = 0;