fix slice header checking

Originally committed as revision 19303 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/cavsdec.c

@@ -441,7 +441,7 @@ static inline int check_for_slice(AVSContext *h) {
     align = (-get_bits_count(gb)) & 7;
     /* check for stuffing byte */
     if(!align && (show_bits(gb,8) == 0x80))
-        get_bits(gb,8);
+        align = 8;
     if((show_bits_long(gb,24+align) & 0xFFFFFF) == 0x000001) {
         skip_bits_long(gb,24+align);
         h->stc = get_bits(gb,8);