diff --git a/libavcodec/dct-test.c b/libavcodec/dct-test.c
index a531c88569..fed5ff282d 100644
--- a/libavcodec/dct-test.c
+++ b/libavcodec/dct-test.c
@@ -42,6 +42,7 @@
 #include "dct.h"
 #include "idctdsp.h"
 #include "simple_idct.h"
+#include "xvididct.h"
 #include "aandcttab.h"
 #include "faandct.h"
 #include "faanidct.h"
@@ -62,11 +63,14 @@ static const struct algo fdct_tab[4] = {
     { "IJG-LLM-INT", ff_jpeg_fdct_islow_8, FF_IDCT_PERM_NONE },
 };
 
-static const struct algo idct_tab[4] = {
+static const struct algo idct_tab[] = {
     { "FAANI",       ff_faanidct,          FF_IDCT_PERM_NONE },
     { "REF-DBL",     ff_ref_idct,          FF_IDCT_PERM_NONE },
     { "INT",         ff_j_rev_dct,         FF_IDCT_PERM_LIBMPEG2 },
     { "SIMPLE-C",    ff_simple_idct_8,     FF_IDCT_PERM_NONE },
+#if CONFIG_MPEG4_DECODER
+    { "XVID",        ff_xvid_idct,         FF_IDCT_PERM_NONE, 0, 1 },
+#endif /* CONFIG_MPEG4_DECODER */
 };
 
 #if ARCH_ARM
diff --git a/libavcodec/x86/xvididct_init.c b/libavcodec/x86/xvididct_init.c
index ce5f240aee..e4f7345795 100644
--- a/libavcodec/x86/xvididct_init.c
+++ b/libavcodec/x86/xvididct_init.c
@@ -26,10 +26,16 @@
 #include "idctdsp.h"
 #include "xvididct.h"
 
-av_cold void ff_xvid_idct_init_x86(IDCTDSPContext *c)
+av_cold void ff_xvid_idct_init_x86(IDCTDSPContext *c, AVCodecContext *avctx,
+                                   unsigned high_bit_depth)
 {
     int cpu_flags = av_get_cpu_flags();
 
+    if (high_bit_depth ||
+        !(avctx->idct_algo == FF_IDCT_AUTO ||
+          avctx->idct_algo == FF_IDCT_XVID))
+        return;
+
     if (INLINE_MMX(cpu_flags)) {
         c->idct_put  = ff_xvid_idct_mmx_put;
         c->idct_add  = ff_xvid_idct_mmx_add;
diff --git a/libavcodec/xvididct.c b/libavcodec/xvididct.c
index 0562fdbb63..ca89703233 100644
--- a/libavcodec/xvididct.c
+++ b/libavcodec/xvididct.c
@@ -1,4 +1,8 @@
 /*
+ * Xvid MPEG-4 IDCT
+ *
+ * Copyright (C) 2006-2011 Xvid Solutions GmbH
+ *
  * This file is part of Libav.
  *
  * Libav is free software; you can redistribute it and/or
@@ -16,23 +20,331 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
+/**
+ * @file
+ * Walken IDCT
+ * Alternative IDCT implementation for decoding compatibility.
+ *
+ * @author Skal
+ * @note This C version is not the original IDCT, but a modified one that
+ *       yields the same error profile as the MMX/MMXEXT/SSE2 versions.
+ */
+
 #include "config.h"
 #include "libavutil/attributes.h"
 #include "avcodec.h"
 #include "idctdsp.h"
 #include "xvididct.h"
 
+#define ROW_SHIFT 11
+#define COL_SHIFT  6
+
+// #define FIX(x)   (int)((x) * (1 << ROW_SHIFT))
+#define RND0 65536 // 1 << (COL_SHIFT + ROW_SHIFT - 1);
+#define RND1 3597  // FIX (1.75683487303);
+#define RND2 2260  // FIX (1.10355339059);
+#define RND3 1203  // FIX (0.587788325588);
+#define RND4 0
+#define RND5 120   // FIX (0.058658283817);
+#define RND6 512   // FIX (0.25);
+#define RND7 512   // FIX (0.25);
+
+static const int TAB04[] = { 22725, 21407, 19266, 16384, 12873,  8867, 4520 };
+static const int TAB17[] = { 31521, 29692, 26722, 22725, 17855, 12299, 6270 };
+static const int TAB26[] = { 29692, 27969, 25172, 21407, 16819, 11585, 5906 };
+static const int TAB35[] = { 26722, 25172, 22654, 19266, 15137, 10426, 5315 };
+
+static int idct_row(short *in, const int *const tab, int rnd)
+{
+    const int c1 = tab[0];
+    const int c2 = tab[1];
+    const int c3 = tab[2];
+    const int c4 = tab[3];
+    const int c5 = tab[4];
+    const int c6 = tab[5];
+    const int c7 = tab[6];
+
+    const int right = in[5] | in[6] | in[7];
+    const int left  = in[1] | in[2] | in[3];
+    if (!(right | in[4])) {
+        const int k = c4 * in[0] + rnd;
+        if (left) {
+            const int a0 = k + c2 * in[2];
+            const int a1 = k + c6 * in[2];
+            const int a2 = k - c6 * in[2];
+            const int a3 = k - c2 * in[2];
+
+            const int b0 = c1 * in[1] + c3 * in[3];
+            const int b1 = c3 * in[1] - c7 * in[3];
+            const int b2 = c5 * in[1] - c1 * in[3];
+            const int b3 = c7 * in[1] - c5 * in[3];
+
+            in[0] = (a0 + b0) >> ROW_SHIFT;
+            in[1] = (a1 + b1) >> ROW_SHIFT;
+            in[2] = (a2 + b2) >> ROW_SHIFT;
+            in[3] = (a3 + b3) >> ROW_SHIFT;
+            in[4] = (a3 - b3) >> ROW_SHIFT;
+            in[5] = (a2 - b2) >> ROW_SHIFT;
+            in[6] = (a1 - b1) >> ROW_SHIFT;
+            in[7] = (a0 - b0) >> ROW_SHIFT;
+        } else {
+            const int a0 = k >> ROW_SHIFT;
+            if (a0) {
+                in[0] =
+                in[1] =
+                in[2] =
+                in[3] =
+                in[4] =
+                in[5] =
+                in[6] =
+                in[7] = a0;
+            } else
+                return 0;
+        }
+    } else if (!(left | right)) {
+        const int a0 = (rnd + c4 * (in[0] + in[4])) >> ROW_SHIFT;
+        const int a1 = (rnd + c4 * (in[0] - in[4])) >> ROW_SHIFT;
+
+        in[0] = a0;
+        in[3] = a0;
+        in[4] = a0;
+        in[7] = a0;
+        in[1] = a1;
+        in[2] = a1;
+        in[5] = a1;
+        in[6] = a1;
+    } else {
+        const int k  = c4 * in[0] + rnd;
+        const int a0 = k + c2 * in[2] + c4 * in[4] + c6 * in[6];
+        const int a1 = k + c6 * in[2] - c4 * in[4] - c2 * in[6];
+        const int a2 = k - c6 * in[2] - c4 * in[4] + c2 * in[6];
+        const int a3 = k - c2 * in[2] + c4 * in[4] - c6 * in[6];
+
+        const int b0 = c1 * in[1] + c3 * in[3] + c5 * in[5] + c7 * in[7];
+        const int b1 = c3 * in[1] - c7 * in[3] - c1 * in[5] - c5 * in[7];
+        const int b2 = c5 * in[1] - c1 * in[3] + c7 * in[5] + c3 * in[7];
+        const int b3 = c7 * in[1] - c5 * in[3] + c3 * in[5] - c1 * in[7];
+
+        in[0] = (a0 + b0) >> ROW_SHIFT;
+        in[1] = (a1 + b1) >> ROW_SHIFT;
+        in[2] = (a2 + b2) >> ROW_SHIFT;
+        in[3] = (a3 + b3) >> ROW_SHIFT;
+        in[4] = (a3 - b3) >> ROW_SHIFT;
+        in[5] = (a2 - b2) >> ROW_SHIFT;
+        in[6] = (a1 - b1) >> ROW_SHIFT;
+        in[7] = (a0 - b0) >> ROW_SHIFT;
+    }
+    return 1;
+}
+
+#define TAN1  0x32EC
+#define TAN2  0x6A0A
+#define TAN3  0xAB0E
+#define SQRT2 0x5A82
+
+#define MULT(c, x, n)  (((c) * (x)) >> (n))
+// 12b version => #define MULT(c,x, n)  ((((c) >> 3) * (x)) >> ((n) - 3))
+// 12b zero-testing version:
+
+#define BUTTERFLY(a, b, tmp)     \
+    (tmp) = (a) + (b);           \
+    (b)   = (a) - (b);           \
+    (a)   = (tmp)
+
+#define LOAD_BUTTERFLY(m1, m2, a, b, tmp, s)   \
+    (m1) = (s)[(a)] + (s)[(b)];                \
+    (m2) = (s)[(a)] - (s)[(b)]
+
+static void idct_col_8(short *const in)
+{
+    int mm0, mm1, mm2, mm3, mm4, mm5, mm6, mm7, spill;
+
+    // odd
+
+    mm4 = (int) in[7 * 8];
+    mm5 = (int) in[5 * 8];
+    mm6 = (int) in[3 * 8];
+    mm7 = (int) in[1 * 8];
+
+    mm0 = MULT(TAN1, mm4, 16) + mm7;
+    mm1 = MULT(TAN1, mm7, 16) - mm4;
+    mm2 = MULT(TAN3, mm5, 16) + mm6;
+    mm3 = MULT(TAN3, mm6, 16) - mm5;
+
+    mm7 = mm0 + mm2;
+    mm4 = mm1 - mm3;
+    mm0 = mm0 - mm2;
+    mm1 = mm1 + mm3;
+    mm6 = mm0 + mm1;
+    mm5 = mm0 - mm1;
+    mm5 = 2 * MULT(SQRT2, mm5, 16); // 2*sqrt2
+    mm6 = 2 * MULT(SQRT2, mm6, 16); // Watch out: precision loss but done to match
+                                    // the pmulhw used in MMX/MMXEXT/SSE2 versions
+
+    // even
+
+    mm1 = (int) in[2 * 8];
+    mm2 = (int) in[6 * 8];
+    mm3 = MULT(TAN2, mm2, 16) + mm1;
+    mm2 = MULT(TAN2, mm1, 16) - mm2;
+
+    LOAD_BUTTERFLY(mm0, mm1, 0 * 8, 4 * 8, spill, in);
+
+    BUTTERFLY(mm0, mm3, spill);
+    BUTTERFLY(mm0, mm7, spill);
+    in[8 * 0] = (int16_t) (mm0 >> COL_SHIFT);
+    in[8 * 7] = (int16_t) (mm7 >> COL_SHIFT);
+    BUTTERFLY(mm3, mm4, mm0);
+    in[8 * 3] = (int16_t) (mm3 >> COL_SHIFT);
+    in[8 * 4] = (int16_t) (mm4 >> COL_SHIFT);
+
+    BUTTERFLY(mm1, mm2, mm0);
+    BUTTERFLY(mm1, mm6, mm0);
+    in[8 * 1] = (int16_t) (mm1 >> COL_SHIFT);
+    in[8 * 6] = (int16_t) (mm6 >> COL_SHIFT);
+    BUTTERFLY(mm2, mm5, mm0);
+    in[8 * 2] = (int16_t) (mm2 >> COL_SHIFT);
+    in[8 * 5] = (int16_t) (mm5 >> COL_SHIFT);
+}
+
+static void idct_col_4(short *const in)
+{
+    int mm0, mm1, mm2, mm3, mm4, mm5, mm6, mm7, spill;
+
+    // odd
+
+    mm0 = (int) in[1 * 8];
+    mm2 = (int) in[3 * 8];
+
+    mm1 = MULT(TAN1, mm0, 16);
+    mm3 = MULT(TAN3, mm2, 16);
+
+    mm7 = mm0 + mm2;
+    mm4 = mm1 - mm3;
+    mm0 = mm0 - mm2;
+    mm1 = mm1 + mm3;
+    mm6 = mm0 + mm1;
+    mm5 = mm0 - mm1;
+    mm6 = 2 * MULT(SQRT2, mm6, 16); // 2*sqrt2
+    mm5 = 2 * MULT(SQRT2, mm5, 16);
+
+    // even
+
+    mm0 = mm1 = (int) in[0 * 8];
+    mm3 = (int) in[2 * 8];
+    mm2 = MULT(TAN2, mm3, 16);
+
+    BUTTERFLY(mm0, mm3, spill);
+    BUTTERFLY(mm0, mm7, spill);
+    in[8 * 0] = (int16_t) (mm0 >> COL_SHIFT);
+    in[8 * 7] = (int16_t) (mm7 >> COL_SHIFT);
+    BUTTERFLY(mm3, mm4, mm0);
+    in[8 * 3] = (int16_t) (mm3 >> COL_SHIFT);
+    in[8 * 4] = (int16_t) (mm4 >> COL_SHIFT);
+
+    BUTTERFLY(mm1, mm2, mm0);
+    BUTTERFLY(mm1, mm6, mm0);
+    in[8 * 1] = (int16_t) (mm1 >> COL_SHIFT);
+    in[8 * 6] = (int16_t) (mm6 >> COL_SHIFT);
+    BUTTERFLY(mm2, mm5, mm0);
+    in[8 * 2] = (int16_t) (mm2 >> COL_SHIFT);
+    in[8 * 5] = (int16_t) (mm5 >> COL_SHIFT);
+}
+
+static void idct_col_3(short *const in)
+{
+    int mm0, mm1, mm2, mm3, mm4, mm5, mm6, mm7, spill;
+
+    // odd
+
+    mm7 = (int) in[1 * 8];
+    mm4 = MULT(TAN1, mm7, 16);
+
+    mm6 = mm7 + mm4;
+    mm5 = mm7 - mm4;
+    mm6 = 2 * MULT(SQRT2, mm6, 16); // 2*sqrt2
+    mm5 = 2 * MULT(SQRT2, mm5, 16);
+
+    // even
+
+    mm0 = mm1 = (int) in[0 * 8];
+    mm3 = (int) in[2 * 8];
+    mm2 = MULT(TAN2, mm3, 16);
+
+    BUTTERFLY(mm0, mm3, spill);
+    BUTTERFLY(mm0, mm7, spill);
+    in[8 * 0] = (int16_t) (mm0 >> COL_SHIFT);
+    in[8 * 7] = (int16_t) (mm7 >> COL_SHIFT);
+    BUTTERFLY(mm3, mm4, mm0);
+    in[8 * 3] = (int16_t) (mm3 >> COL_SHIFT);
+    in[8 * 4] = (int16_t) (mm4 >> COL_SHIFT);
+
+    BUTTERFLY(mm1, mm2, mm0);
+    BUTTERFLY(mm1, mm6, mm0);
+    in[8 * 1] = (int16_t) (mm1 >> COL_SHIFT);
+    in[8 * 6] = (int16_t) (mm6 >> COL_SHIFT);
+    BUTTERFLY(mm2, mm5, mm0);
+    in[8 * 2] = (int16_t) (mm2 >> COL_SHIFT);
+    in[8 * 5] = (int16_t) (mm5 >> COL_SHIFT);
+}
+
+void ff_xvid_idct(int16_t *const in)
+{
+    int i, rows = 0x07;
+
+    idct_row(in + 0 * 8, TAB04, RND0);
+    idct_row(in + 1 * 8, TAB17, RND1);
+    idct_row(in + 2 * 8, TAB26, RND2);
+    if (idct_row(in + 3 * 8, TAB35, RND3))
+        rows |= 0x08;
+    if (idct_row(in + 4 * 8, TAB04, RND4))
+        rows |= 0x10;
+    if (idct_row(in + 5 * 8, TAB35, RND5))
+        rows |= 0x20;
+    if (idct_row(in + 6 * 8, TAB26, RND6))
+        rows |= 0x40;
+    if (idct_row(in + 7 * 8, TAB17, RND7))
+        rows |= 0x80;
+
+    if (rows & 0xF0) {
+        for (i = 0; i < 8; i++)
+            idct_col_8(in + i);
+    } else if (rows & 0x08) {
+        for (i = 0; i < 8; i++)
+            idct_col_4(in + i);
+    } else {
+        for (i = 0; i < 8; i++)
+            idct_col_3(in + i);
+    }
+}
+
+static void xvid_idct_put(uint8_t *dest, int line_size, int16_t *block)
+{
+    ff_xvid_idct(block);
+    ff_put_pixels_clamped(block, dest, line_size);
+}
+
+static void xvid_idct_add(uint8_t *dest, int line_size, int16_t *block)
+{
+    ff_xvid_idct(block);
+    ff_add_pixels_clamped(block, dest, line_size);
+}
+
 av_cold void ff_xvid_idct_init(IDCTDSPContext *c, AVCodecContext *avctx)
 {
     const unsigned high_bit_depth = avctx->bits_per_raw_sample > 8;
 
-    if (high_bit_depth ||
-        !(avctx->idct_algo == FF_IDCT_AUTO ||
-          avctx->idct_algo == FF_IDCT_XVID))
-        return;
+    if (!high_bit_depth &&
+        (avctx->idct_algo == FF_IDCT_AUTO ||
+         avctx->idct_algo == FF_IDCT_XVID)) {
+        c->idct_put  = xvid_idct_put;
+        c->idct_add  = xvid_idct_add;
+        c->idct      = ff_xvid_idct;
+        c->perm_type = FF_IDCT_PERM_NONE;
+    }
 
     if (ARCH_X86)
-        ff_xvid_idct_init_x86(c);
+        ff_xvid_idct_init_x86(c, avctx, high_bit_depth);
 
     ff_init_scantable_permutation(c->idct_permutation, c->perm_type);
 }
diff --git a/libavcodec/xvididct.h b/libavcodec/xvididct.h
index e6cc69a57f..499f8190fc 100644
--- a/libavcodec/xvididct.h
+++ b/libavcodec/xvididct.h
@@ -19,11 +19,16 @@
 #ifndef AVCODEC_XVIDIDCT_H
 #define AVCODEC_XVIDIDCT_H
 
+#include <stdint.h>
+
 #include "avcodec.h"
 #include "idctdsp.h"
 
+void ff_xvid_idct(int16_t *const in);
+
 void ff_xvid_idct_init(IDCTDSPContext *c, AVCodecContext *avctx);
 
-void ff_xvid_idct_init_x86(IDCTDSPContext *c);
+void ff_xvid_idct_init_x86(IDCTDSPContext *c, AVCodecContext *avctx,
+                           unsigned high_bit_depth);
 
 #endif /* AVCODEC_XVIDIDCT_H */
diff --git a/tests/fate/xvid.mak b/tests/fate/xvid.mak
index 68f01b5827..877b2a100b 100644
--- a/tests/fate/xvid.mak
+++ b/tests/fate/xvid.mak
@@ -1,8 +1,7 @@
 fate-xvid-custom-matrix: CMD = framemd5 -flags +bitexact -idct simple  -i $(TARGET_SAMPLES)/mpeg4/xvid_vlc_trac7411.h263
-fate-xvid-idctmmx:       CMD = framemd5 -flags +bitexact -cpuflags all -i $(TARGET_SAMPLES)/mpeg4/xvid_vlc_trac7411.h263
+fate-xvid-idct:          CMD = framemd5 -flags +bitexact -cpuflags all -i $(TARGET_SAMPLES)/mpeg4/xvid_vlc_trac7411.h263
 
-FATE_XVID-$(call DEMDEC, M4V, MPEG4) += fate-xvid-custom-matrix
-FATE_XVID-$(filter $(HAVE_MMX_INLINE), $(call DEMDEC, M4V, MPEG4)) += fate-xvid-idctmmx
+FATE_XVID-$(call DEMDEC, M4V, MPEG4) += fate-xvid-custom-matrix fate-xvid-idct
 
 FATE_SAMPLES_AVCONV += $(FATE_XVID-yes)
 
diff --git a/tests/ref/fate/xvid-idctmmx b/tests/ref/fate/xvid-idct
similarity index 100%
rename from tests/ref/fate/xvid-idctmmx
rename to tests/ref/fate/xvid-idct