[FFmpeg-cvslog] lavu/tx: add full-sized iMDCT transform flag
Lynne
git at videolan.org
Sat Apr 24 18:20:05 EEST 2021
ffmpeg | branch: master | Lynne <dev at lynne.ee> | Sat Apr 10 03:55:37 2021 +0200| [0072a4238817c18e31e1f59cf8ec9a30bdf42a5c] | committer: Lynne
lavu/tx: add full-sized iMDCT transform flag
> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=0072a4238817c18e31e1f59cf8ec9a30bdf42a5c
---
libavutil/tx.h | 11 ++++++++++-
libavutil/tx_priv.h | 4 ++++
libavutil/tx_template.c | 29 ++++++++++++++++++++++++++++-
3 files changed, 42 insertions(+), 2 deletions(-)
diff --git a/libavutil/tx.h b/libavutil/tx.h
index a3d70644e4..55173810ee 100644
--- a/libavutil/tx.h
+++ b/libavutil/tx.h
@@ -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,
};
/**
diff --git a/libavutil/tx_priv.h b/libavutil/tx_priv.h
index 0b40234355..1d4245e71b 100644
--- a/libavutil/tx_priv.h
+++ b/libavutil/tx_priv.h
@@ -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 */
diff --git a/libavutil/tx_template.c b/libavutil/tx_template.c
index b3532c1c5e..a68a84dcd5 100644
--- a/libavutil/tx_template.c
+++ b/libavutil/tx_template.c
@@ -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;
}
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