lavu/tx: remove special -1 inverted lookup mode

It was somewhat hacky and unnecessary.

libavutil/tx.c

@@ -213,7 +213,7 @@ int ff_tx_gen_split_radix_parity_revtab(AVTXContext *s, int len, int inv,
     if (len < basis)
         return AVERROR(EINVAL);
 
-    if (!(s->map = av_mallocz((inv_lookup == -1 ? 2 : 1)*len*sizeof(*s->map))))
+    if (!(s->map = av_mallocz(len*sizeof(*s->map))))
         return AVERROR(ENOMEM);
 
     av_assert0(!dual_stride || !(dual_stride & (dual_stride - 1)));
@@ -221,9 +221,6 @@ int ff_tx_gen_split_radix_parity_revtab(AVTXContext *s, int len, int inv,
 
     parity_revtab_generator(s->map, len, inv, 0, 0, 0, len,
                             basis, dual_stride, inv_lookup != 0);
-    if (inv_lookup == -1)
-        parity_revtab_generator(s->map + len, len, inv, 0, 0, 0, len,
-                                basis, dual_stride, 0);
 
     return 0;
 }

libavutil/tx_priv.h

@@ -290,8 +290,7 @@ int ff_tx_gen_ptwo_inplace_revtab_idx(AVTXContext *s);
  * If length is smaller than basis/2 this function will not do anything.
  *
  * If inv_lookup is set to 1, it will flip the lookup from out[map[i]] = src[i]
- * to out[i] = src[map[i]]. If set to -1, will generate 2 maps, the first one
- * flipped, the second one regular.
+ * to out[i] = src[map[i]].
  */
 int ff_tx_gen_split_radix_parity_revtab(AVTXContext *s, int len, int inv,
                                         int inv_lookup, int basis, int dual_stride);