Properly detect XvMC capabilities.

modules/video_output/x11/xcommon.c

@@ -426,7 +426,7 @@ int E_(Activate) ( vlc_object_t *p_this )
     msg_Dbg(p_vout, "Deinterlace = %d", p_vout->p_sys->xvmc_deinterlace_method);
     msg_Dbg(p_vout, "Crop = %d", p_vout->p_sys->xvmc_crop_style);
 
-    if( !checkXvMCCap( p_vout ) )
+    if( checkXvMCCap( p_vout ) == VLC_EGENERIC )
     {
         msg_Err( p_vout, "no XVMC capability found" );
         E_(Deactivate)( p_vout );

modules/video_output/x11/xvmc.c

@@ -754,16 +754,18 @@ int checkXvMCCap( vout_thread_t *p_vout )
                                       curCap->type_id,
                                       curCap->max_width,
                                       curCap->max_height,
-                                      XVMC_DIRECT, &c) )
+                                      XVMC_DIRECT, &c ) )
     {
+        msg_Dbg( p_vout, "using direct XVMC rendering context" );
         p_vout->p_sys->context_flags = XVMC_DIRECT;
     }
     else if( Success == XvMCCreateContext( p_vout->p_sys->p_display, i_xvport,
                                            curCap->type_id,
                                            curCap->max_width,
                                            curCap->max_height,
-                                           0, &c) )
+                                           0, &c ) )
     {
+        msg_Dbg( p_vout, "using default XVMC rendering context" );
         p_vout->p_sys->context_flags = 0;
     }
     else