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lavu/tx: add 2-point FFT transform 

By itself, this allows 6-point, 10-point and 30-point transforms.
When the 9-point transform is added it allows for 18-point FFT,
and also for a 36-point MDCT (used by MP3).
This commit is contained in:
Lynne 2020-02-25 06:49:26 +00:00
parent 9f494d1397
commit 2465fe1302
2 changed files with 19 additions and 11 deletions
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2
libavutil/tx.h
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@ -93,7 +93,7 @@ typedef void (*av_tx_fn)(AVTXContext *s, void *out, void *in, ptrdiff_t stride);
/**
* Initialize a transform context with the given configuration
* Currently power of two lengths from 4 to 131072 are supported, along with
* Currently power of two lengths from 2 to 131072 are supported, along with
* any length decomposable to a power of two and either 3, 5 or 15.
*
* @param ctx the context to allocate, will be NULL on error

28
libavutil/tx_template.c
View File

@ -286,6 +286,14 @@ static void fft##n(FFTComplex *z)\
pass(z,TX_NAME(ff_cos_##n),n4/2);\
}
static void fft2(FFTComplex *z)
{
FFTComplex tmp;
BF(tmp.re, z[0].re, z[0].re, z[1].re);
BF(tmp.im, z[0].im, z[0].im, z[1].im);
z[1] = tmp;
}
static void fft4(FFTComplex *z)
{
FFTSample t1, t2, t3, t4, t5, t6, t7, t8;
@ -347,8 +355,8 @@ DECL_FFT(65536,32768,16384)
DECL_FFT(131072,65536,32768)
static void (* const fft_dispatch[])(FFTComplex*) = {
fft4, fft8, fft16, fft32, fft64, fft128, fft256, fft512, fft1024,
fft2048, fft4096, fft8192, fft16384, fft32768, fft65536, fft131072
NULL, fft2, fft4, fft8, fft16, fft32, fft64, fft128, fft256, fft512,
fft1024, fft2048, fft4096, fft8192, fft16384, fft32768, fft65536, fft131072
};
#define DECL_COMP_FFT(N) \
@ -359,7 +367,7 @@ static void compound_fft_##N##xM(AVTXContext *s, void *_out, \
FFTComplex *in = _in; \
FFTComplex *out = _out; \
FFTComplex fft##N##in[N]; \
void (*fftp)(FFTComplex *z) = fft_dispatch[av_log2(m) - 2]; \
void (*fftp)(FFTComplex *z) = fft_dispatch[av_log2(m)]; \
\
for (int i = 0; i < m; i++) { \
for (int j = 0; j < N; j++) \
@ -383,7 +391,7 @@ static void monolithic_fft(AVTXContext *s, void *_out, void *_in,
{
FFTComplex *in = _in;
FFTComplex *out = _out;
int m = s->m, mb = av_log2(m) - 2;
int m = s->m, mb = av_log2(m);
for (int i = 0; i < m; i++)
out[s->revtab[i]] = in[i];
fft_dispatch[mb](out);
@ -398,7 +406,7 @@ static void compound_imdct_##N##xM(AVTXContext *s, void *_dst, void *_src, \
const int m = s->m, len8 = N*m >> 1; \
const int *in_map = s->pfatab, *out_map = in_map + N*m; \
const FFTSample *src = _src, *in1, *in2; \
void (*fftp)(FFTComplex *) = fft_dispatch[av_log2(m) - 2]; \
void (*fftp)(FFTComplex *) = fft_dispatch[av_log2(m)]; \
\
stride /= sizeof(*src); /* To convert it from bytes */ \
in1 = src; \
@ -439,7 +447,7 @@ static void compound_mdct_##N##xM(AVTXContext *s, void *_dst, void *_src, \
FFTComplex *exp = s->exptab, tmp, fft##N##in[N]; \
const int m = s->m, len4 = N*m, len3 = len4 * 3, len8 = len4 >> 1; \
const int *in_map = s->pfatab, *out_map = in_map + N*m; \
void (*fftp)(FFTComplex *) = fft_dispatch[av_log2(m) - 2]; \
void (*fftp)(FFTComplex *) = fft_dispatch[av_log2(m)]; \
\
stride /= sizeof(*dst); \
\
@ -485,7 +493,7 @@ static void monolithic_imdct(AVTXContext *s, void *_dst, void *_src,
FFTComplex *z = _dst, *exp = s->exptab;
const int m = s->m, len8 = m >> 1;
const FFTSample *src = _src, *in1, *in2;
void (*fftp)(FFTComplex *) = fft_dispatch[av_log2(m) - 2];
void (*fftp)(FFTComplex *) = fft_dispatch[av_log2(m)];
stride /= sizeof(*src);
in1 = src;
@ -514,7 +522,7 @@ static void monolithic_mdct(AVTXContext *s, void *_dst, void *_src,
FFTSample *src = _src, *dst = _dst;
FFTComplex *exp = s->exptab, tmp, *z = _dst;
const int m = s->m, len4 = m, len3 = len4 * 3, len8 = len4 >> 1;
void (*fftp)(FFTComplex *) = fft_dispatch[av_log2(m) - 2];
void (*fftp)(FFTComplex *) = fft_dispatch[av_log2(m)];
stride /= sizeof(*dst);
@ -567,7 +575,7 @@ int TX_NAME(ff_tx_init_mdct_fft)(AVTXContext *s, av_tx_fn *tx,
const void *scale, uint64_t flags)
{
const int is_mdct = ff_tx_type_is_mdct(type);
int err, n = 1, m = 1, max_ptwo = 1 << (FF_ARRAY_ELEMS(fft_dispatch) + 1);
int err, n = 1, m = 1, max_ptwo = 1 << (FF_ARRAY_ELEMS(fft_dispatch) - 1);
if (is_mdct)
len >>= 1;
@ -583,7 +591,7 @@ int TX_NAME(ff_tx_init_mdct_fft)(AVTXContext *s, av_tx_fn *tx,
#undef CHECK_FACTOR
/* len must be a power of two now */
if (!(len & (len - 1)) && len >= 4 && len <= max_ptwo) {
if (!(len & (len - 1)) && len >= 2 && len <= max_ptwo) {
m = len;
len = 1;
}