codecparsers: vc1: fix bitplanes decoding.

Fix decoding of DIFF2 or NORM2 bitplanes with an odd number of macroblocks.
In particular, account for the first bit that was already parsed so that to
avoid a buffer overflow after all pairs are parsed.

This fixes SA00040.vc1 conformance test.

https://bugzilla.gnome.org/show_bug.cgi?id=692312

Signed-off-by: Gwenole Beauchesne <gwenole.beauchesne@intel.com>

diff --git a/gst-libs/gst/codecparsers/gstvc1parser.c b/gst-libs/gst/codecparsers/gstvc1parser.c
index 0cc1230f5bc066a47a24e0a8eac870bd56d4d38f..19b88a4348273efeae5e63cb6055bdc6fc15843b 100644 (file)
--- a/gst-libs/gst/codecparsers/gstvc1parser.c
+++ b/gst-libs/gst/codecparsers/gstvc1parser.c
@@ -435,7 +435,7 @@ bitplane_decoding (GstBitReader * br, guint8 * data,
   const guint height = seqhdr->mb_height;
   const guint stride = seqhdr->mb_stride;
   guint imode, invert, invert_mask;
-  guint x, y, v;
+  guint x, y, v, o;
   guint8 *pdata = data;
 
   *is_raw = FALSE;
@@ -464,7 +464,8 @@ bitplane_decoding (GstBitReader * br, guint8 * data,
       GST_DEBUG ("Parsing IMODE_DIFF2 or IMODE_NORM2 biplane");
 
       x = 0;
-      if ((height * width) & 1) {
+      o = (height * width) & 1;
+      if (o) {
         GET_BITS (br, 1, &v);
         if (pdata) {
           *pdata++ = (v ^ invert_mask) & 1;
@@ -475,7 +476,7 @@ bitplane_decoding (GstBitReader * br, guint8 * data,
         }
       }
 
-      for (y = 0; y < height * width; y += 2) {
+      for (y = o; y < height * width; y += 2) {
         if (!decode_vlc (br, &v, vc1_norm2_vlc_table,
                 G_N_ELEMENTS (vc1_norm2_vlc_table)))
           goto failed;