[FFmpeg-devel] [PATCH] vf_spp: only assign function pointers if permutation matches expectations.

[Ronald S. Bultje]

---
 libavfilter/x86/vf_spp.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/libavfilter/x86/vf_spp.c b/libavfilter/x86/vf_spp.c
index 45a9eb0..8e3c820 100644
--- a/libavfilter/x86/vf_spp.c
+++ b/libavfilter/x86/vf_spp.c
@@ -217,6 +217,17 @@ static void store_slice_mmx(uint8_t *dst, const int16_t *src,
 
 #endif /* HAVE_MMX_INLINE */
 
+static const uint8_t simple_mmx_permutation[64] = {
+    0x00, 0x08, 0x04, 0x09, 0x01, 0x0C, 0x05, 0x0D,
+    0x10, 0x18, 0x14, 0x19, 0x11, 0x1C, 0x15, 0x1D,
+    0x20, 0x28, 0x24, 0x29, 0x21, 0x2C, 0x25, 0x2D,
+    0x12, 0x1A, 0x16, 0x1B, 0x13, 0x1E, 0x17, 0x1F,
+    0x02, 0x0A, 0x06, 0x0B, 0x03, 0x0E, 0x07, 0x0F,
+    0x30, 0x38, 0x34, 0x39, 0x31, 0x3C, 0x35, 0x3D,
+    0x22, 0x2A, 0x26, 0x2B, 0x23, 0x2E, 0x27, 0x2F,
+    0x32, 0x3A, 0x36, 0x3B, 0x33, 0x3E, 0x37, 0x3F,
+};
+
 av_cold void ff_spp_init_x86(SPPContext *s)
 {
 #if HAVE_MMX_INLINE
@@ -226,7 +237,9 @@ av_cold void ff_spp_init_x86(SPPContext *s)
         int64_t bps;
         s->store_slice = store_slice_mmx;
         av_opt_get_int(s->dct, "bits_per_sample", 0, &bps);
-        if (bps <= 8) {
+        if (bps <= 8 &&
+            !memcmp(s->dct->idct_permutation, simple_mmx_permutation,
+                    sizeof(simple_mmx_permutation))) {
             switch (s->mode) {
             case 0: s->requantize = hardthresh_mmx; break;
             case 1: s->requantize = softthresh_mmx; break;
-- 
2.8.1