It seems there is still a endian bug with Xv:
playing movies requesting a YV12 colorspace show wrong colors (usually green people). It's the same for both xv ports.

For me (NV34 on ppc), it can be fixed  by applying the following patch:

--- nv_video.c~ 2008-01-21 11:33:53.000000000 +0900
+++ nv_video.c  2008-01-21 19:02:27.000000000 +0900
@@ -689,11 +689,7 @@
                        }
                if (e)  {
                        unsigned short *vud = (unsigned short *) vuvud;
-#if X_BYTE_ORDER == X_BIG_ENDIAN
-                       *vud = (vs[0]<<8) | (us[0] << 0);
-#else
                        *vud = vs[0] | (us[0]<<8);
-#endif
                        }
                dst += dstPitch ;
                src1 += srcPitch2;