Replace scaling byte with explicit display size

If the intended display size is different than the size the frame is
coded at, then send that size explicitly in the bitstream. Adds a new
bit to the frame header to indicate whether the extra size fields
are present.

Change-Id: I525c66f22d207efaf1e5f903c6a2a91b80245854

1 files changed, 15 insertions, 8 deletions

diff --git a/vp9/decoder/vp9_decodframe.c b/vp9/decoder/vp9_decodframe.c
index b53e419b5..c61c11225 100644
--- a/vp9/decoder/vp9_decodframe.c
+++ b/vp9/decoder/vp9_decodframe.c
@@ -1275,12 +1275,13 @@ int vp9_decode_frame(VP9D_COMP *pbi, const unsigned char **p_data_end) {
   if (data_end - data < 3) {
     vpx_internal_error(&pc->error, VPX_CODEC_CORRUPT_FRAME, "Truncated packet");
   } else {
+    int scaling_active;
     pc->last_frame_type = pc->frame_type;
     pc->frame_type = (FRAME_TYPE)(data[0] & 1);
     pc->version = (data[0] >> 1) & 7;
     pc->show_frame = (data[0] >> 4) & 1;
-    first_partition_length_in_bytes =
-      (data[0] | (data[1] << 8) | (data[2] << 16)) >> 5;
+    scaling_active = (data[0] >> 5) & 1;
+    first_partition_length_in_bytes = data[1] | (data[2] << 8);
 
     if (!read_is_valid(data, first_partition_length_in_bytes, data_end))
       vpx_internal_error(&pc->error, VPX_CODEC_CORRUPT_FRAME,
@@ -1310,14 +1311,20 @@ int vp9_decode_frame(VP9D_COMP *pbi, const unsigned char **p_data_end) {
        * if we have enough data. Otherwise we will end up with the wrong
        * size.
        */
-      if (data + 5 < data_end) {
-        pc->Width  = read_le16(data);
+      if (scaling_active && data + 4 < data_end) {
+        pc->display_width = read_le16(data + 0);
+        pc->display_height = read_le16(data + 2);
+        data += 4;
+      }
+      if (data + 4 < data_end) {
+        pc->Width = read_le16(data + 0);
         pc->Height = read_le16(data + 2);
-
-        pc->horiz_scale = data[4] >> 4;
-        pc->vert_scale  = data[4] & 0x0F;
+        data += 4;
+      }
+      if (!scaling_active) {
+        pc->display_width = pc->Width;
+        pc->display_height = pc->Height;
       }
-      data += 5;
 
       if (width != pc->Width || height != pc->Height) {
         if (pc->Width <= 0) {