diff options
Diffstat (limited to 'libavutil/tx.c')
| -rw-r--r-- | libavutil/tx.c | 17 |
1 files changed, 16 insertions, 1 deletions
diff --git a/libavutil/tx.c b/libavutil/tx.c index 1161df3285..05d4de30cc 100644 --- a/libavutil/tx.c +++ b/libavutil/tx.c @@ -30,7 +30,7 @@ int ff_tx_type_is_mdct(enum AVTXType type) } } -/* Calculates the modular multiplicative inverse, not fast, replace */ +/* Calculates the modular multiplicative inverse */ static av_always_inline int mulinv(int n, int m) { n = n % m; @@ -91,6 +91,17 @@ int ff_tx_gen_compound_mapping(AVTXContext *s) return 0; } +static inline int split_radix_permutation(int i, int m, int inverse) +{ + m >>= 1; + if (m <= 1) + return i & 1; + if (!(i & m)) + return (split_radix_permutation(i, m, inverse) << 1); + m >>= 1; + return (split_radix_permutation(i, m, inverse) << 2) + 1 - 2*(!(i & m) ^ inverse); +} + int ff_tx_gen_ptwo_revtab(AVTXContext *s, int invert_lookup) { const int m = s->m, inv = s->inv; @@ -117,6 +128,7 @@ int ff_tx_gen_ptwo_inplace_revtab_idx(AVTXContext *s) if (!(s->inplace_idx = av_malloc(s->m*sizeof(*s->inplace_idx)))) return AVERROR(ENOMEM); + /* The first coefficient is always already in-place */ for (int src = 1; src < s->m; src++) { int dst = s->revtab[src]; int found = 0; @@ -124,6 +136,9 @@ int ff_tx_gen_ptwo_inplace_revtab_idx(AVTXContext *s) if (dst <= src) continue; + /* This just checks if a closed loop has been encountered before, + * and if so, skips it, since to fully permute a loop we must only + * enter it once. */ do { for (int j = 0; j < nb_inplace_idx; j++) { if (dst == s->inplace_idx[j]) { |