Steven Liu <l...@chinaffmpeg.org> 于2018年12月26日周三 下午4:15写道：
>
> Before patch:
> init nbits = 17, get 10000 samples, average cost: 16175 us
> After patch:
> init nbits = 17, get 10000 samples, average cost: 14989 us
>
> Signed-off-by: Steven Liu <l...@chinaffmpeg.org>
> ---
> libavcodec/fft_template.c | 46 +++++++++++++++++++++++++++++++++++-----------
> 1 file changed, 35 insertions(+), 11 deletions(-)
>
> diff --git a/libavcodec/fft_template.c b/libavcodec/fft_template.c
> index 762c014bc8..20a62e4290 100644
> --- a/libavcodec/fft_template.c
> +++ b/libavcodec/fft_template.c
> @@ -261,17 +261,41 @@ av_cold int ff_fft_init(FFTContext *s, int nbits, int
> inverse)
> if (s->fft_permutation == FF_FFT_PERM_AVX) {
> fft_perm_avx(s);
> } else {
> - for(i=0; i<n; i++) {
> - int k;
> - j = i;
> - if (s->fft_permutation == FF_FFT_PERM_SWAP_LSBS)
> - j = (j&~3) | ((j>>1)&1) | ((j<<1)&2);
> - k = -split_radix_permutation(i, n, s->inverse) & (n-1);
> - if (s->revtab)
> - s->revtab[k] = j;
> - if (s->revtab32)
> - s->revtab32[k] = j;
> - }
> +#define PROCESS_FFT_PERM_SWAP_LSBS(num) do {\
> + for(i = 0; i < n; i++) {\
> + int k;\
> + j = i;\
> + j = (j & ~3) | ((j >> 1) & 1) | ((j << 1) & 2);\
> + k = -split_radix_permutation(i, n, s->inverse) & (n - 1);\
> + s->revtab##num[k] = j;\
> + } \
> +} while(0);
> +
> +#define PROCESS_FFT_PERM_DEFAULT(num) do {\
> + for(i = 0; i < n; i++) {\
> + int k;\
> + j = i;\
> + k = -split_radix_permutation(i, n, s->inverse) & (n - 1);\
> + s->revtab##num[k] = j;\
> + } \
> +} while(0);
> +
> +#define SPLIT_RADIX_PERMUTATION(num) do { \
> + if (s->fft_permutation == FF_FFT_PERM_SWAP_LSBS) {\
> + PROCESS_FFT_PERM_SWAP_LSBS(num) \
> + } else {\
> + PROCESS_FFT_PERM_DEFAULT(num) \
> + }\
> +} while(0);
> +
> + if (s->revtab)
> + SPLIT_RADIX_PERMUTATION()
> + if (s->revtab32)
> + SPLIT_RADIX_PERMUTATION(32)
> +
> +#undef PROCESS_FFT_PERM_DEFAULT
> +#undef PROCESS_FFT_PERM_SWAP_LSBS
> +#undef SPLIT_RADIX_PERMUTATION
> }
>
> return 0;
> --
> 2.15.2 (Apple Git-101.1)
>
>
>
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ping
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