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lavu/tx: add full-sized iMDCT transform flag

This commit is contained in:
Lynne 2021-04-10 03:55:37 +02:00
parent aa6c757d50
commit 0072a42388
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GPG Key ID: A2FEA5F03F034464
3 changed files with 42 additions and 2 deletions
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11
libavutil/tx.h
View File

@ -55,7 +55,8 @@ enum AVTXType {
* Stride must be a non-zero multiple of sizeof(float).
*
* NOTE: the inverse transform is half-length, meaning the output will not
* contain redundant data. This is what most codecs work with.
* contain redundant data. This is what most codecs work with. To do a full
* inverse transform, set the AV_TX_FULL_IMDCT flag on init.
*/
AV_TX_FLOAT_MDCT = 1,
@ -116,6 +117,14 @@ enum AVTXFlags {
* May be slower with certain transform types.
*/
AV_TX_UNALIGNED = 1ULL << 1,
/**
* Performs a full inverse MDCT rather than leaving out samples that can be
* derived through symmetry. Requires an output array of 'len' floats,
* rather than the usual 'len/2' floats.
* Ignored for all transforms but inverse MDCTs.
*/
AV_TX_FULL_IMDCT = 1ULL << 2,
};
/**

4
libavutil/tx_priv.h
View File

@ -121,6 +121,10 @@ struct AVTXContext {
int *pfatab; /* Input/Output mapping for compound transforms */
int *revtab; /* Input mapping for power of two transforms */
int *inplace_idx; /* Required indices to revtab for in-place transforms */
av_tx_fn top_tx; /* Used for computing transforms derived from other
* transforms, like full-length iMDCTs and RDFTs.
* NOTE: Do NOT use this to mix assembly with C code. */
};
/* Checks if type is an MDCT */

29
libavutil/tx_template.c
View File

@ -875,6 +875,24 @@ static void naive_mdct(AVTXContext *s, void *_dst, void *_src,
}
}
static void full_imdct_wrapper_fn(AVTXContext *s, void *_dst, void *_src,
ptrdiff_t stride)
{
int len = s->m*s->n*4;
int len2 = len >> 1;
int len4 = len >> 2;
FFTSample *dst = _dst;
s->top_tx(s, dst + len4, _src, stride);
stride /= sizeof(*dst);
for (int i = 0; i < len4; i++) {
dst[ i*stride] = -dst[(len2 - i - 1)*stride];
dst[(len - i - 1)*stride] = dst[(len2 + i + 0)*stride];
}
}
static int gen_mdct_exptab(AVTXContext *s, int len4, double scale)
{
const double theta = (scale < 0 ? len4 : 0) + 1.0/8.0;
@ -942,6 +960,10 @@ int TX_NAME(ff_tx_init_mdct_fft)(AVTXContext *s, av_tx_fn *tx,
if (is_mdct) {
s->scale = *((SCALE_TYPE *)scale);
*tx = inv ? naive_imdct : naive_mdct;
if (inv && (flags & AV_TX_FULL_IMDCT)) {
s->top_tx = *tx;
*tx = full_imdct_wrapper_fn;
}
}
return 0;
}
@ -990,8 +1012,13 @@ int TX_NAME(ff_tx_init_mdct_fft)(AVTXContext *s, av_tx_fn *tx,
init_cos_tabs(i);
}
if (is_mdct)
if (is_mdct) {
if (inv && (flags & AV_TX_FULL_IMDCT)) {
s->top_tx = *tx;
*tx = full_imdct_wrapper_fn;
}
return gen_mdct_exptab(s, n*m, *((SCALE_TYPE *)scale));
}
return 0;
}