Fix visual glitch with XvMC, caused by wrong idct permutation.

In the past XvMC forced simple_idct since
it was using FF_IDCT_PERM_NONE.
However now we have SIMD variants of simple_idct that
are using FF_IDCT_PERM_TRANSPOSE and if they are selected
XvMC would get coefficients in the wrong order.

The patch creates new FF_IDCT_NONE that
is used only for this kind of hardware decoding
and that fallbacks to the old C only simple idct.
Signed-off-by: Ivan Kalvachev <ikalvachev@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/avcodec.h

@@ -3146,6 +3146,7 @@ typedef struct AVCodecContext {
 #if FF_API_ARCH_ALPHA
 #define FF_IDCT_SIMPLEALPHA   23
 #endif
+#define FF_IDCT_NONE          24 /* Used by XvMC to extract IDCT coefficients with FF_IDCT_PERM_NONE */
 #define FF_IDCT_SIMPLEAUTO    128
 
     /**

libavcodec/idctdsp.c

@@ -279,6 +279,7 @@ av_cold void ff_idctdsp_init(IDCTDSPContext *c, AVCodecContext *avctx)
                 c->perm_type = FF_IDCT_PERM_NONE;
 #endif /* CONFIG_FAANIDCT */
             } else { // accurate/default
+                /* Be sure FF_IDCT_NONE will select this one, since it uses FF_IDCT_PERM_NONE */
                 c->idct_put  = ff_simple_idct_put_8;
                 c->idct_add  = ff_simple_idct_add_8;
                 c->idct      = ff_simple_idct_8;

libavcodec/mpeg12dec.c

@@ -1217,7 +1217,7 @@ static void setup_hwaccel_for_pixfmt(AVCodecContext *avctx)
 #endif
         )
         if (avctx->idct_algo == FF_IDCT_AUTO)
-            avctx->idct_algo = FF_IDCT_SIMPLE;
+            avctx->idct_algo = FF_IDCT_NONE;
 
     if (avctx->hwaccel && avctx->pix_fmt == AV_PIX_FMT_XVMC) {
         Mpeg1Context *s1 = avctx->priv_data;