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FFmpeg/libavutil/tx.c
Lynne af94ab7c7c
lavu/tx: add an RDFT implementation 
RDFTs are full of conventions that vary between implementations.
What I've gone for here is what's most common between
both fftw, avcodec's rdft and what we use, the equivalent of
which is DFT_R2C for forward and IDFT_C2R for inverse. The
other 2 conventions (IDFT_R2C and DFT_C2R) were not used at
all in our code, and their names are also not appropriate.
If there's a use for either, we can easily add a flag which
would just flip the sign on one exptab.

For some unknown reason, possibly to allow reusing FFT's exp tables,
av_rdft's C2R output is 0.5x lower than what it should be to ensure
a proper back-and-forth conversion.
This code outputs its real samples at the correct level, which
matches FFTW's level, and allows the user to change the level
and insert arbitrary multiplies for free by setting the scale option.
2022-01-26 04:12:46 +01:00

656 lines
20 KiB
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/*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "cpu.h"
#include "qsort.h"
#include "bprint.h"
#include "tx_priv.h"
#define TYPE_IS(type, x) \
(((x) == AV_TX_FLOAT_ ## type) || \
((x) == AV_TX_DOUBLE_ ## type) || \
((x) == AV_TX_INT32_ ## type))
/* Calculates the modular multiplicative inverse */
static av_always_inline int mulinv(int n, int m)
{
n = n % m;
for (int x = 1; x < m; x++)
if (((n * x) % m) == 1)
return x;
av_assert0(0); /* Never reached */
return 0;
}
/* Guaranteed to work for any n, m where gcd(n, m) == 1 */
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 */
if (av_gcd(n, m) != 1)
return AVERROR(EINVAL);
m_inv = mulinv(m, n);
n_inv = mulinv(n, m);
if (!(s->map = av_malloc(2*len*sizeof(*s->map))))
return AVERROR(ENOMEM);
in_map = s->map;
out_map = s->map + len;
/* 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;
out_map[(i*m*m_inv + j*n*n_inv) % len] = i*m + j;
}
}
/* Change transform direction by reversing all ACs */
if (inv) {
for (int i = 0; i < m; i++) {
int *in = &in_map[i*n + 1]; /* Skip the DC */
for (int j = 0; j < ((n - 1) >> 1); j++)
FFSWAP(int, in[j], in[n - j - 2]);
}
}
/* Our 15-point transform is also a compound one, so embed its input map */
if (n == 15) {
for (int k = 0; k < m; k++) {
int tmp[15];
memcpy(tmp, &in_map[k*15], 15*sizeof(*tmp));
for (int i = 0; i < 5; i++) {
for (int j = 0; j < 3; j++)
in_map[k*15 + i*3 + j] = tmp[(i*3 + j*5) % 15];
}
}
}
return 0;
}
static inline int split_radix_permutation(int i, int len, int inv)
{
len >>= 1;
if (len <= 1)
return i & 1;
if (!(i & len))
return split_radix_permutation(i, len, inv) * 2;
len >>= 1;
return split_radix_permutation(i, len, inv) * 4 + 1 - 2*(!(i & len) ^ inv);
}
int ff_tx_gen_ptwo_revtab(AVTXContext *s, int invert_lookup)
{
int len = s->len;
if (!(s->map = av_malloc(len*sizeof(*s->map))))
return AVERROR(ENOMEM);
if (invert_lookup) {
for (int i = 0; i < s->len; i++)
s->map[i] = -split_radix_permutation(i, len, s->inv) & (len - 1);
} else {
for (int i = 0; i < s->len; i++)
s->map[-split_radix_permutation(i, len, s->inv) & (len - 1)] = i;
}
return 0;
}
int ff_tx_gen_ptwo_inplace_revtab_idx(AVTXContext *s)
{
int *src_map, out_map_idx = 0, len = s->len;
if (!s->sub || !s->sub->map)
return AVERROR(EINVAL);
if (!(s->map = av_mallocz(len*sizeof(*s->map))))
return AVERROR(ENOMEM);
src_map = s->sub->map;
/* The first coefficient is always already in-place */
for (int src = 1; src < s->len; src++) {
int dst = src_map[src];
int found = 0;
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 < out_map_idx; j++) {
if (dst == s->map[j]) {
found = 1;
break;
}
}
dst = src_map[dst];
} while (dst != src && !found);
if (!found)
s->map[out_map_idx++] = src;
}
s->map[out_map_idx++] = 0;
return 0;
}
static void parity_revtab_generator(int *revtab, int n, int inv, int offset,
int is_dual, int dual_high, int len,
int basis, int dual_stride, int inv_lookup)
{
len >>= 1;
if (len <= basis) {
int k1, k2, stride, even_idx, odd_idx;
is_dual = is_dual && dual_stride;
dual_high = is_dual & dual_high;
stride = is_dual ? FFMIN(dual_stride, len) : 0;
even_idx = offset + dual_high*(stride - 2*len);
odd_idx = even_idx + len + (is_dual && !dual_high)*len + dual_high*len;
for (int i = 0; i < len; i++) {
k1 = -split_radix_permutation(offset + i*2 + 0, n, inv) & (n - 1);
k2 = -split_radix_permutation(offset + i*2 + 1, n, inv) & (n - 1);
if (inv_lookup) {
revtab[even_idx++] = k1;
revtab[odd_idx++] = k2;
} else {
revtab[k1] = even_idx++;
revtab[k2] = odd_idx++;
}
if (stride && !((i + 1) % stride)) {
even_idx += stride;
odd_idx += stride;
}
}
return;
}
parity_revtab_generator(revtab, n, inv, offset,
0, 0, len >> 0, basis, dual_stride, inv_lookup);
parity_revtab_generator(revtab, n, inv, offset + (len >> 0),
1, 0, len >> 1, basis, dual_stride, inv_lookup);
parity_revtab_generator(revtab, n, inv, offset + (len >> 0) + (len >> 1),
1, 1, len >> 1, basis, dual_stride, inv_lookup);
}
int ff_tx_gen_split_radix_parity_revtab(AVTXContext *s, int invert_lookup,
int basis, int dual_stride)
{
int len = s->len;
int inv = s->inv;
if (!(s->map = av_mallocz(len*sizeof(*s->map))))
return AVERROR(ENOMEM);
basis >>= 1;
if (len < basis)
return AVERROR(EINVAL);
av_assert0(!dual_stride || !(dual_stride & (dual_stride - 1)));
av_assert0(dual_stride <= basis);
parity_revtab_generator(s->map, len, inv, 0, 0, 0, len,
basis, dual_stride, invert_lookup);
return 0;
}
static void reset_ctx(AVTXContext *s)
{
if (!s)
return;
if (s->sub)
for (int i = 0; i < s->nb_sub; i++)
reset_ctx(&s->sub[i]);
if (s->cd_self->uninit)
s->cd_self->uninit(s);
av_freep(&s->sub);
av_freep(&s->map);
av_freep(&s->exp);
av_freep(&s->tmp);
memset(s, 0, sizeof(*s));
}
av_cold void av_tx_uninit(AVTXContext **ctx)
{
if (!(*ctx))
return;
reset_ctx(*ctx);
av_freep(ctx);
}
static av_cold int ff_tx_null_init(AVTXContext *s, const FFTXCodelet *cd,
uint64_t flags, FFTXCodeletOptions *opts,
int len, int inv, const void *scale)
{
/* Can only handle one sample+type to one sample+type transforms */
if (TYPE_IS(MDCT, s->type) || TYPE_IS(RDFT, s->type))
return AVERROR(EINVAL);
return 0;
}
/* Null transform when the length is 1 */
static void ff_tx_null(AVTXContext *s, void *_out, void *_in, ptrdiff_t stride)
{
memcpy(_out, _in, stride);
}
static const FFTXCodelet ff_tx_null_def = {
.name = "null",
.function = ff_tx_null,
.type = TX_TYPE_ANY,
.flags = AV_TX_UNALIGNED | FF_TX_ALIGNED |
FF_TX_OUT_OF_PLACE | AV_TX_INPLACE,
.factors[0] = TX_FACTOR_ANY,
.min_len = 1,
.max_len = 1,
.init = ff_tx_null_init,
.cpu_flags = FF_TX_CPU_FLAGS_ALL,
.prio = FF_TX_PRIO_MAX,
};
static const FFTXCodelet * const ff_tx_null_list[] = {
&ff_tx_null_def,
NULL,
};
static void print_flags(AVBPrint *bp, uint64_t f)
{
int prev = 0;
const char *sep = ", ";
av_bprintf(bp, "flags: [");
if ((f & FF_TX_ALIGNED) && ++prev)
av_bprintf(bp, "aligned");
if ((f & AV_TX_UNALIGNED) && ++prev)
av_bprintf(bp, "%sunaligned", prev > 1 ? sep : "");
if ((f & AV_TX_INPLACE) && ++prev)
av_bprintf(bp, "%sinplace", prev > 1 ? sep : "");
if ((f & FF_TX_OUT_OF_PLACE) && ++prev)
av_bprintf(bp, "%sout_of_place", prev > 1 ? sep : "");
if ((f & FF_TX_FORWARD_ONLY) && ++prev)
av_bprintf(bp, "%sfwd_only", prev > 1 ? sep : "");
if ((f & FF_TX_INVERSE_ONLY) && ++prev)
av_bprintf(bp, "%sinv_only", prev > 1 ? sep : "");
if ((f & FF_TX_PRESHUFFLE) && ++prev)
av_bprintf(bp, "%spreshuf", prev > 1 ? sep : "");
if ((f & AV_TX_FULL_IMDCT) && ++prev)
av_bprintf(bp, "%simdct_full", prev > 1 ? sep : "");
av_bprintf(bp, "]");
}
static void print_type(AVBPrint *bp, enum AVTXType type)
{
av_bprintf(bp, "%s",
type == TX_TYPE_ANY ? "any" :
type == AV_TX_FLOAT_FFT ? "fft_float" :
type == AV_TX_FLOAT_MDCT ? "mdct_float" :
type == AV_TX_FLOAT_RDFT ? "rdft_float" :
type == AV_TX_DOUBLE_FFT ? "fft_double" :
type == AV_TX_DOUBLE_MDCT ? "mdct_double" :
type == AV_TX_DOUBLE_RDFT ? "rdft_double" :
type == AV_TX_INT32_FFT ? "fft_int32" :
type == AV_TX_INT32_MDCT ? "mdct_int32" :
type == AV_TX_INT32_RDFT ? "rdft_int32" :
"unknown");
}
static void print_cd_info(const FFTXCodelet *cd, int prio, int print_prio)
{
AVBPrint bp = { 0 };
av_bprint_init(&bp, 0, AV_BPRINT_SIZE_AUTOMATIC);
av_bprintf(&bp, "%s - type: ", cd->name);
print_type(&bp, cd->type);
av_bprintf(&bp, ", len: ");
if (cd->min_len != cd->max_len)
av_bprintf(&bp, "[%i, ", cd->min_len);
if (cd->max_len == TX_LEN_UNLIMITED)
av_bprintf(&bp, "∞");
else
av_bprintf(&bp, "%i", cd->max_len);
av_bprintf(&bp, "%s, factors: [", cd->min_len != cd->max_len ? "]" : "");
for (int i = 0; i < TX_MAX_SUB; i++) {
if (i && cd->factors[i])
av_bprintf(&bp, ", ");
if (cd->factors[i] == TX_FACTOR_ANY)
av_bprintf(&bp, "any");
else if (cd->factors[i])
av_bprintf(&bp, "%i", cd->factors[i]);
else
break;
}
av_bprintf(&bp, "], ");
print_flags(&bp, cd->flags);
if (print_prio)
av_bprintf(&bp, ", prio: %i", prio);
av_log(NULL, AV_LOG_VERBOSE, "%s\n", bp.str);
}
typedef struct TXCodeletMatch {
const FFTXCodelet *cd;
int prio;
} TXCodeletMatch;
static int cmp_matches(TXCodeletMatch *a, TXCodeletMatch *b)
{
return FFDIFFSIGN(b->prio, a->prio);
}
/* We want all factors to completely cover the length */
static inline int check_cd_factors(const FFTXCodelet *cd, int len)
{
int all_flag = 0;
for (int i = 0; i < TX_MAX_SUB; i++) {
int factor = cd->factors[i];
/* Conditions satisfied */
if (len == 1)
return 1;
/* No more factors */
if (!factor) {
break;
} else if (factor == TX_FACTOR_ANY) {
all_flag = 1;
continue;
}
if (factor == 2) { /* Fast path */
int bits_2 = ff_ctz(len);
if (!bits_2)
return 0; /* Factor not supported */
len >>= bits_2;
} else {
int res = len % factor;
if (res)
return 0; /* Factor not supported */
while (!res) {
len /= factor;
res = len % factor;
}
}
}
return all_flag || (len == 1);
}
av_cold int ff_tx_init_subtx(AVTXContext *s, enum AVTXType type,
uint64_t flags, FFTXCodeletOptions *opts,
int len, int inv, const void *scale)
{
int ret = 0;
AVTXContext *sub = NULL;
TXCodeletMatch *cd_tmp, *cd_matches = NULL;
unsigned int cd_matches_size = 0;
int nb_cd_matches = 0;
AVBPrint bp = { 0 };
/* Array of all compiled codelet lists. Order is irrelevant. */
const FFTXCodelet * const * const codelet_list[] = {
ff_tx_codelet_list_float_c,
ff_tx_codelet_list_double_c,
ff_tx_codelet_list_int32_c,
ff_tx_null_list,
#if ARCH_X86
ff_tx_codelet_list_float_x86,
#endif
};
int codelet_list_num = FF_ARRAY_ELEMS(codelet_list);
/* We still accept functions marked with SLOW, even if the CPU is
* marked with the same flag, but we give them lower priority. */
const int cpu_flags = av_get_cpu_flags();
const int slow_mask = AV_CPU_FLAG_SSE2SLOW | AV_CPU_FLAG_SSE3SLOW |
AV_CPU_FLAG_ATOM | AV_CPU_FLAG_SSSE3SLOW |
AV_CPU_FLAG_AVXSLOW | AV_CPU_FLAG_SLOW_GATHER;
/* Flags the transform wants */
uint64_t req_flags = flags;
/* Unaligned codelets are compatible with the aligned flag */
if (req_flags & FF_TX_ALIGNED)
req_flags |= AV_TX_UNALIGNED;
/* If either flag is set, both are okay, so don't check for an exact match */
if ((req_flags & AV_TX_INPLACE) && (req_flags & FF_TX_OUT_OF_PLACE))
req_flags &= ~(AV_TX_INPLACE | FF_TX_OUT_OF_PLACE);
if ((req_flags & FF_TX_ALIGNED) && (req_flags & AV_TX_UNALIGNED))
req_flags &= ~(FF_TX_ALIGNED | AV_TX_UNALIGNED);
/* Flags the codelet may require to be present */
uint64_t inv_req_mask = AV_TX_FULL_IMDCT | FF_TX_PRESHUFFLE;
/* Loop through all codelets in all codelet lists to find matches
* to the requirements */
while (codelet_list_num--) {
const FFTXCodelet * const * list = codelet_list[codelet_list_num];
const FFTXCodelet *cd = NULL;
while ((cd = *list++)) {
int max_factor = 0;
/* Check if the type matches */
if (cd->type != TX_TYPE_ANY && type != cd->type)
continue;
/* Check direction for non-orthogonal codelets */
if (((cd->flags & FF_TX_FORWARD_ONLY) && inv) ||
((cd->flags & (FF_TX_INVERSE_ONLY | AV_TX_FULL_IMDCT)) && !inv))
continue;
/* Check if the requested flags match from both sides */
if (((req_flags & cd->flags) != (req_flags)) ||
((inv_req_mask & cd->flags) != (req_flags & inv_req_mask)))
continue;
/* Check if length is supported */
if ((len < cd->min_len) || (cd->max_len != -1 && (len > cd->max_len)))
continue;
/* Check if the CPU supports the required ISA */
if (!(!cd->cpu_flags || (cpu_flags & (cd->cpu_flags & ~slow_mask))))
continue;
/* Check for factors */
if (!check_cd_factors(cd, len))
continue;
/* Realloc array and append */
cd_tmp = av_fast_realloc(cd_matches, &cd_matches_size,
sizeof(*cd_tmp) * (nb_cd_matches + 1));
if (!cd_tmp) {
av_free(cd_matches);
return AVERROR(ENOMEM);
}
cd_matches = cd_tmp;
cd_matches[nb_cd_matches].cd = cd;
cd_matches[nb_cd_matches].prio = cd->prio;
/* If the CPU has a SLOW flag, and the instruction is also flagged
* as being slow for such, reduce its priority */
if ((cpu_flags & cd->cpu_flags) & slow_mask)
cd_matches[nb_cd_matches].prio -= 64;
/* Prioritize aligned-only codelets */
if ((cd->flags & FF_TX_ALIGNED) && !(cd->flags & AV_TX_UNALIGNED))
cd_matches[nb_cd_matches].prio += 64;
/* Codelets for specific lengths are generally faster */
if ((len == cd->min_len) && (len == cd->max_len))
cd_matches[nb_cd_matches].prio += 64;
/* Forward-only or inverse-only transforms are generally better */
if ((cd->flags & (FF_TX_FORWARD_ONLY | FF_TX_INVERSE_ONLY)))
cd_matches[nb_cd_matches].prio += 64;
/* Larger factors are generally better */
for (int i = 0; i < TX_MAX_SUB; i++)
max_factor = FFMAX(cd->factors[i], max_factor);
if (max_factor)
cd_matches[nb_cd_matches].prio += 16*max_factor;
nb_cd_matches++;
}
}
/* No matches found */
if (!nb_cd_matches)
return AVERROR(ENOSYS);
/* Sort the list */
AV_QSORT(cd_matches, nb_cd_matches, TXCodeletMatch, cmp_matches);
/* Print debugging info */
av_bprint_init(&bp, 0, AV_BPRINT_SIZE_AUTOMATIC);
av_bprintf(&bp, "For transform of length %i, %s, ", len,
inv ? "inverse" : "forward");
print_type(&bp, type);
av_bprintf(&bp, ", ");
print_flags(&bp, flags);
av_bprintf(&bp, ", found %i matches:", nb_cd_matches);
av_log(NULL, AV_LOG_VERBOSE, "%s\n", bp.str);
for (int i = 0; i < nb_cd_matches; i++) {
av_log(NULL, AV_LOG_VERBOSE, " %i: ", i + 1);
print_cd_info(cd_matches[i].cd, cd_matches[i].prio, 1);
}
if (!s->sub)
s->sub = sub = av_mallocz(TX_MAX_SUB*sizeof(*sub));
/* Attempt to initialize each */
for (int i = 0; i < nb_cd_matches; i++) {
const FFTXCodelet *cd = cd_matches[i].cd;
AVTXContext *sctx = &s->sub[s->nb_sub];
sctx->len = len;
sctx->inv = inv;
sctx->type = type;
sctx->flags = flags;
sctx->cd_self = cd;
s->fn[s->nb_sub] = cd->function;
s->cd[s->nb_sub] = cd;
ret = 0;
if (cd->init)
ret = cd->init(sctx, cd, flags, opts, len, inv, scale);
if (ret >= 0) {
s->nb_sub++;
goto end;
}
s->fn[s->nb_sub] = NULL;
s->cd[s->nb_sub] = NULL;
reset_ctx(sctx);
if (ret == AVERROR(ENOMEM))
break;
}
av_free(sub);
if (ret >= 0)
ret = AVERROR(ENOSYS);
end:
av_free(cd_matches);
return ret;
}
static void print_tx_structure(AVTXContext *s, int depth)
{
const FFTXCodelet *cd = s->cd_self;
for (int i = 0; i <= depth; i++)
av_log(NULL, AV_LOG_VERBOSE, " ");
print_cd_info(cd, cd->prio, 0);
for (int i = 0; i < s->nb_sub; i++)
print_tx_structure(&s->sub[i], depth + 1);
}
av_cold int av_tx_init(AVTXContext **ctx, av_tx_fn *tx, enum AVTXType type,
int inv, int len, const void *scale, uint64_t flags)
{
int ret;
AVTXContext tmp = { 0 };
const double default_scale_d = 1.0;
const float default_scale_f = 1.0f;
if (!len || type >= AV_TX_NB || !ctx || !tx)
return AVERROR(EINVAL);
if (!(flags & AV_TX_UNALIGNED))
flags |= FF_TX_ALIGNED;
if (!(flags & AV_TX_INPLACE))
flags |= FF_TX_OUT_OF_PLACE;
if (!scale && ((type == AV_TX_FLOAT_MDCT) || (type == AV_TX_INT32_MDCT)))
scale = &default_scale_f;
else if (!scale && (type == AV_TX_DOUBLE_MDCT))
scale = &default_scale_d;
ret = ff_tx_init_subtx(&tmp, type, flags, NULL, len, inv, scale);
if (ret < 0)
return ret;
*ctx = &tmp.sub[0];
*tx = tmp.fn[0];
av_log(NULL, AV_LOG_VERBOSE, "Transform tree:\n");
print_tx_structure(*ctx, 0);
return ret;
}
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