On 18/01/2025 14:00, Michael Niedermayer wrote:
This performs a tiny bit better than not using it but it is incompatible with the RCT which gives a bigger gainSponsored-by: Sovereign Tech Fund Signed-off-by: Michael Niedermayer <mich...@niedermayer.cc> --- libavcodec/ffv1.h | 20 ++++++++++++++++++++ libavcodec/ffv1enc_template.c | 33 ++++++++++++++++++++++++--------- 2 files changed, 44 insertions(+), 9 deletions(-) diff --git a/libavcodec/ffv1.h b/libavcodec/ffv1.h index 2c2df154037..84a443613df 100644 --- a/libavcodec/ffv1.h +++ b/libavcodec/ffv1.h @@ -196,6 +196,26 @@ static av_always_inline int fold(int diff, int bits) return diff; }+// We treat infinite as a big number, 0 as a small non 0 number, this is close enough, we ignore denormal numbers+static av_always_inline int64_t f2i(uint16_t f) +{ + int s = -(f>>15); + int64_t v = (1024L + (f & 1023)) << ((f & 0x7C00) >> 10); + return (v + s) ^ s; +} + +//undo above +static av_always_inline uint16_t i2f(int64_t v) +{ + int s = v>>63; + int e; + v = (v + s) ^ s; + + e = av_log2(v>>10); + + return (s&32768) + (e<<10) + ((v + (1U<<e)/2) >> e) - 1024; +} + static inline void update_vlc_state(VlcState *const state, const int v) { int drift = state->drift; diff --git a/libavcodec/ffv1enc_template.c b/libavcodec/ffv1enc_template.c index bc14926ab95..12d519320c0 100644 --- a/libavcodec/ffv1enc_template.c +++ b/libavcodec/ffv1enc_template.c @@ -64,7 +64,13 @@ RENAME(encode_line)(FFV1Context *f, FFV1SliceContext *sc,context = RENAME(get_context)(f->quant_tables[p->quant_table_index],sample[0] + x, sample[1] + x, sample[2] + x); - diff = sample[0][x] - RENAME(predict)(sample[0] + x, sample[1] + x); + + int64_t L = f2i(sample[0][x-1]); + int64_t T = f2i(sample[1][x]); + int64_t LT = f2i(sample[1][x-1]); + + diff = sample[0][x] - mid_pred(i2f(L), i2f(L + T - LT), i2f(T)); +// diff = sample[0][x] - RENAME(predict)(sample[0] + x, sample[1] + x);if (context < 0) {context = -context; @@ -147,7 +153,16 @@ static int RENAME(encode_rgb_frame)(FFV1Context *f, FFV1SliceContext *sc,memset(RENAME(sc->sample_buffer), 0, ring_size * MAX_PLANES *(w + 6) * sizeof(*RENAME(sc->sample_buffer))); - + if(0){ + int v; + for (v = 0; v<65536; v++) { + int64_t i = f2i(v); + int v2 = i2f(i); + if (v != v2) + av_log(0,0, "D %X %X %LX\n", v, v2, i); + av_assert0(v2 == v); + } + } for (y = 0; y < h; y++) { for (i = 0; i < ring_size; i++) for (p = 0; p < MAX_PLANES; p++) @@ -180,13 +195,13 @@ static int RENAME(encode_rgb_frame)(FFV1Context *f, FFV1SliceContext *sc, r = *((const uint16_t *)(src[2] + x*2 + stride[2]*y)); }- if (sc->slice_coding_mode != 1) {- b -= g; - r -= g; - g += (b * sc->slice_rct_by_coef + r * sc->slice_rct_ry_coef) >> 2; - b += offset; - r += offset; - } +// if (sc->slice_coding_mode != 1) { +// b -= g; +// r -= g; +// g += (b * sc->slice_rct_by_coef + r * sc->slice_rct_ry_coef) >> 2; +// b += offset; +// r += offset; +// }sample[0][0][x] = g;sample[1][0][x] = b;
I think using prediction independently on both exponent and mantissa, and coding the two via different contexts would be better, not to mention it would avoid the f2i hacks.
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