float16 is a sign bit followed by "positive is larger" exponent and mantisse
that way the up direction changes between negative and positive numbers
flipping the exponent and mantisse for positive numbers gives a compression
gain of 0.5% for both RCT and noRCT modes using the
ACES_OT_VWG_SampleFrames testset
Sponsored-by: Sovereign Tech Fund
Signed-off-by: Michael Niedermayer <mich...@niedermayer.cc>
---
libavcodec/ffv1dec_template.c | 10 ++++++++++
libavcodec/ffv1enc_template.c | 11 +++++++++++
2 files changed, 21 insertions(+)
diff --git a/libavcodec/ffv1dec_template.c b/libavcodec/ffv1dec_template.c
index e983d1ba648..0be17b54bbb 100644
--- a/libavcodec/ffv1dec_template.c
+++ b/libavcodec/ffv1dec_template.c
@@ -185,6 +185,16 @@ static int RENAME(decode_rgb_frame)(FFV1Context *f,
FFV1SliceContext *sc,
b += g;
r += g;
}
+ if (f->flt) {
+ if (!(r&0x8000))
+ r ^= 0x7FFF;
+ if (!(g&0x8000))
+ g ^= 0x7FFF;
+ if (!(b&0x8000))
+ b ^= 0x7FFF;
+ if (transparency && !(a&0x8000))
+ a ^= 0x7FFF;
+ }
if (lbd)
*((uint32_t*)(src[0] + x*4 + stride[0]*y)) = b +
((unsigned)g<<8) + ((unsigned)r<<16) + ((unsigned)a<<24);
diff --git a/libavcodec/ffv1enc_template.c b/libavcodec/ffv1enc_template.c
index bc14926ab95..4d20cb93627 100644
--- a/libavcodec/ffv1enc_template.c
+++ b/libavcodec/ffv1enc_template.c
@@ -180,6 +180,17 @@ static int RENAME(encode_rgb_frame)(FFV1Context *f,
FFV1SliceContext *sc,
r = *((const uint16_t *)(src[2] + x*2 + stride[2]*y));
}
+ if (f->flt) {
+ if (!(r&0x8000))
+ r ^= 0x7FFF;
+ if (!(g&0x8000))
+ g ^= 0x7FFF;
+ if (!(b&0x8000))
+ b ^= 0x7FFF;
+ if (transparency && !(a&0x8000))
+ a ^= 0x7FFF;
+ }
+
if (sc->slice_coding_mode != 1) {
b -= g;
r -= g;
--
2.48.1
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