Chiebot-Mirror
/
FFmpeg
mirror of https://github.com/FFmpeg/FFmpeg.git
8
0
Fork 0
Code Issues Projects Releases Wiki Activity

lavu/tx: optimize and simplify inverse MDCTs

Browse Source 
Convert the input from a scatter to a gather instead,
which is faster and better for SIMD.
Also, add a pre-shuffled exptab version to avoid
gathering there at all. This doubles the exptab size,
but the speedup makes it worth it. In SIMD, the
exptab will likely be purged to a higher cache
anyway because of the FFT in the middle, and
the amount of loads stays identical.

For a 960-point inverse MDCT, the speedup is 10%.

This makes it possible to write sane and fast SIMD
versions of inverse MDCTs.
pull/388/head
Lynne 2 years ago
parent 412922cc6f
commit ae66a9db7b
No known key found for this signature in database
GPG Key ID: A2FEA5F03F034464
3 changed files with 45 additions and 20 deletions
Whitespace
Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL
Split View
Diff Options
Show Stats Download Patch File Download Diff File
  1. 4
      libavutil/tx.c
  2. 11
      libavutil/tx_priv.h
  3. 50
      libavutil/tx_template.c

4
libavutil/tx.c
Unescape View File

@ -44,7 +44,6 @@ int ff_tx_gen_compound_mapping(AVTXContext *s, int n, int m)
int *in_map, *out_map;
const int inv = s->inv;
const int len = n*m; /* Will not be equal to s->len for MDCTs */
const int mdct = TYPE_IS(MDCT, s->type);
int m_inv, n_inv;
/* Make sure the numbers are coprime */
@ -63,8 +62,7 @@ int ff_tx_gen_compound_mapping(AVTXContext *s, int n, int m)
/* Ruritanian map for input, CRT map for output, can be swapped */
for (int j = 0; j < m; j++) {
for (int i = 0; i < n; i++) {
/* Shifted by 1 to simplify MDCTs */
in_map[j*n + i] = ((i*m + j*n) % len) << mdct;
in_map[j*n + i] = (i*m + j*n) % len;
out_map[(i*m*m_inv + j*n*n_inv) % len] = i*m + j;
}
}

11
libavutil/tx_priv.h
Unescape View File

@ -297,10 +297,13 @@ void ff_tx_init_tabs_float (int len);
void ff_tx_init_tabs_double(int len);
void ff_tx_init_tabs_int32 (int len);
/* Typed init function to initialize an MDCT exptab in a context. */
int ff_tx_mdct_gen_exp_float (AVTXContext *s);
int ff_tx_mdct_gen_exp_double(AVTXContext *s);
int ff_tx_mdct_gen_exp_int32 (AVTXContext *s);
/* Typed init function to initialize an MDCT exptab in a context.
* If pre_tab is set, duplicates the entire table, with the first
* copy being shuffled according to pre_tab, and the second copy
* being the original. */
int ff_tx_mdct_gen_exp_float (AVTXContext *s, int *pre_tab);
int ff_tx_mdct_gen_exp_double(AVTXContext *s, int *pre_tab);
int ff_tx_mdct_gen_exp_int32 (AVTXContext *s, int *pre_tab);
/* Lists of codelets */
extern const FFTXCodelet * const ff_tx_codelet_list_float_c [];

50
libavutil/tx_template.c
Unescape View File

@ -948,7 +948,7 @@ static av_cold int TX_NAME(ff_tx_mdct_sr_init)(AVTXContext *s,
const void *scale)
{
int ret;
FFTXCodeletOptions sub_opts = { .invert_lookup = 0 };
FFTXCodeletOptions sub_opts = { .invert_lookup = inv };
s->scale_d = *((SCALE_TYPE *)scale);
s->scale_f = s->scale_d;
@ -961,9 +961,14 @@ static av_cold int TX_NAME(ff_tx_mdct_sr_init)(AVTXContext *s,
inv, scale)))
return ret;
if ((ret = TX_TAB(ff_tx_mdct_gen_exp)(s)))
if ((ret = TX_TAB(ff_tx_mdct_gen_exp)(s, inv ? s->sub->map : NULL)))
return ret;
/* Saves a multiply in a hot path. */
if (inv)
for (int i = 0; i < (s->len >> 1); i++)
s->sub->map[i] <<= 1;
return 0;
}
@ -1020,12 +1025,14 @@ static void TX_NAME(ff_tx_mdct_sr_inv)(AVTXContext *s, void *_dst, void *_src,
in2 = src + ((len2*2) - 1) * stride;
for (int i = 0; i < len2; i++) {
TXComplex tmp = { in2[-2*i*stride], in1[2*i*stride] };
CMUL3(z[sub_map[i]], tmp, exp[i]);
int k = sub_map[i];
TXComplex tmp = { in2[-k*stride], in1[k*stride] };
CMUL3(z[i], tmp, exp[i]);
}
s->fn[0](&s->sub[0], z, z, sizeof(TXComplex));
exp += len2;
for (int i = 0; i < len4; i++) {
const int i0 = len4 + i, i1 = len4 - i - 1;
TXComplex src1 = { z[i1].im, z[i1].re };
@ -1141,9 +1148,13 @@ static av_cold int TX_NAME(ff_tx_mdct_pfa_init)(AVTXContext *s,
if ((ret = ff_tx_gen_compound_mapping(s, cd->factors[0], sub_len)))
return ret;
if ((ret = TX_TAB(ff_tx_mdct_gen_exp)(s)))
if ((ret = TX_TAB(ff_tx_mdct_gen_exp)(s, inv ? s->map : NULL)))
return ret;
/* Saves multiplies in loops. */
for (int i = 0; i < len; i++)
s->map[i] <<= 1;
if (!(s->tmp = av_malloc(len*sizeof(*s->tmp))))
return AVERROR(ENOMEM);
@ -1160,6 +1171,7 @@ static void TX_NAME(ff_tx_mdct_pfa_##N##xM_inv)(AVTXContext *s, void *_dst, \
TXComplex *z = _dst, *exp = s->exp; \
const TXSample *src = _src, *in1, *in2; \
const int len4 = s->len >> 2; \
const int len2 = s->len >> 1; \
const int m = s->sub->len; \
const int *in_map = s->map, *out_map = in_map + N*m; \
const int *sub_map = s->sub->map; \
@ -1168,13 +1180,15 @@ static void TX_NAME(ff_tx_mdct_pfa_##N##xM_inv)(AVTXContext *s, void *_dst, \
in1 = src; \
in2 = src + ((N*m*2) - 1) * stride; \
\
for (int i = 0; i < m; i++) { \
for (int i = 0; i < len2; i += N) { \
for (int j = 0; j < N; j++) { \
const int k = in_map[i*N + j]; \
const int k = in_map[j]; \
TXComplex tmp = { in2[-k*stride], in1[k*stride] }; \
CMUL3(fft##N##in[j], tmp, exp[k >> 1]); \
CMUL3(fft##N##in[j], tmp, exp[j]); \
} \
fft##N(s->tmp + sub_map[i], fft##N##in, m); \
fft##N(s->tmp + *(sub_map++), fft##N##in, m); \
exp += N; \
in_map += N; \
} \
\
for (int i = 0; i < N; i++) \
@ -1405,22 +1419,32 @@ static const FFTXCodelet TX_NAME(ff_tx_rdft_c2r_def) = {
.prio = FF_TX_PRIO_BASE,
};
int TX_TAB(ff_tx_mdct_gen_exp)(AVTXContext *s)
int TX_TAB(ff_tx_mdct_gen_exp)(AVTXContext *s, int *pre_tab)
{
int off = 0;
int len4 = s->len >> 1;
double scale = s->scale_d;
const double theta = (scale < 0 ? len4 : 0) + 1.0/8.0;
size_t alloc = pre_tab ? 2*len4 : len4;
if (!(s->exp = av_malloc_array(len4, sizeof(*s->exp))))
if (!(s->exp = av_malloc_array(alloc, sizeof(*s->exp))))
return AVERROR(ENOMEM);
scale = sqrt(fabs(scale));
if (pre_tab)
off = len4;
for (int i = 0; i < len4; i++) {
const double alpha = M_PI_2 * (i + theta) / len4;
s->exp[i].re = RESCALE(cos(alpha) * scale);
s->exp[i].im = RESCALE(sin(alpha) * scale);
s->exp[off + i] = (TXComplex){ RESCALE(cos(alpha) * scale),
RESCALE(sin(alpha) * scale) };
}
if (pre_tab)
for (int i = 0; i < len4; i++)
s->exp[i] = s->exp[len4 + pre_tab[i]];
return 0;
}

Write Preview
Loading…
Cancel
Save