* [FFmpeg-devel] [PATCH 1/2] avcodec/ffv1enc: replace 3 double precision log2() by 1 single precision log2() @ 2025-03-30 15:00 Michael Niedermayer 2025-03-30 15:00 ` [FFmpeg-devel] [PATCH 2/2] avcodec/ffv1enc: replace the remaining log2() by magic Michael Niedermayer 2025-04-02 21:21 ` [FFmpeg-devel] [PATCH 1/2] avcodec/ffv1enc: replace 3 double precision log2() by 1 single precision log2() Michael Niedermayer 0 siblings, 2 replies; 3+ messages in thread From: Michael Niedermayer @ 2025-03-30 15:00 UTC (permalink / raw) To: FFmpeg development discussions and patches This makes the remap finding heuristic much faster Signed-off-by: Michael Niedermayer <michael@niedermayer.cc> --- libavcodec/ffv1enc.c | 16 +++++++++++----- 1 file changed, 11 insertions(+), 5 deletions(-) diff --git a/libavcodec/ffv1enc.c b/libavcodec/ffv1enc.c index a09b31218db..2a188ade776 100644 --- a/libavcodec/ffv1enc.c +++ b/libavcodec/ffv1enc.c @@ -1390,7 +1390,7 @@ static void encode_float32_remap(FFV1Context *f, FFV1SliceContext *sc, int last_mul_index = -1; int mul_count = 1 << log2_mul_count; - score_sum[log2_mul_count] += log2_mul_count; + score_sum[log2_mul_count] += log2_mul_count * log2_mul_count; for (int i= 0; i<pixel_num; i++) { int64_t val = sc->unit[p][i].val; int mul_index = (val + 1LL)*mul_count >> 32; @@ -1414,11 +1414,17 @@ static void encode_float32_remap(FFV1Context *f, FFV1SliceContext *sc, } cost = FFMAX((delta + mul/2) / mul, 1); - score_tab[si] += log2(cost); - if (mul > 1) - score_tab[si] += log2(fabs(delta - cost*mul)+1) * (1 + (mul_count > 1)); + float score = 1; + if (mul > 1) { + score *= (fabs(delta - cost*mul)+1); + if (mul_count > 1) + score *= score; + } + score *= cost; + score *= score; if (mul_index != last_mul_index) - score_tab[si] += 0.5*log2(mul); + score *= mul; + score_tab[si] += log2f(score); } } last_val = val; -- 2.49.0 _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe". ^ permalink raw reply [flat|nested] 3+ messages in thread
* [FFmpeg-devel] [PATCH 2/2] avcodec/ffv1enc: replace the remaining log2() by magic 2025-03-30 15:00 [FFmpeg-devel] [PATCH 1/2] avcodec/ffv1enc: replace 3 double precision log2() by 1 single precision log2() Michael Niedermayer @ 2025-03-30 15:00 ` Michael Niedermayer 2025-04-02 21:21 ` [FFmpeg-devel] [PATCH 1/2] avcodec/ffv1enc: replace 3 double precision log2() by 1 single precision log2() Michael Niedermayer 1 sibling, 0 replies; 3+ messages in thread From: Michael Niedermayer @ 2025-03-30 15:00 UTC (permalink / raw) To: FFmpeg development discussions and patches big secret, reading a float as the corresponding integer is a good approximation of log2() for numbers not too close to 1.0. At the same time it maintains strict monotonicity this reduces run time from 19sec to 17sec for the slowest of my testcases (with default remap_optimizer 3) Compression is about the same: -rw-r----- 1 michael michael 497603370 Mar 30 15:23 float-303503-fixed-40-optim-3-1log2F.nut -rw-r----- 1 michael michael 497603374 Mar 28 11:27 float-303503-fixed-40-optim-3b.nut -rw-r----- 1 michael michael 549938852 Mar 28 11:27 float-303503-float16-40-optim-3b.nut -rw-r----- 1 michael michael 549938857 Mar 30 15:23 float-303503-float16-40-optim-3-1log2F.nut -rw-r----- 1 michael michael 1150827841 Mar 28 11:28 float-303503-float-40-optim-3b.nut -rw-r----- 1 michael michael 1150832913 Mar 30 15:22 float-303503-float-40-optim-3ref-log2F2.nut Signed-off-by: Michael Niedermayer <michael@niedermayer.cc> --- libavcodec/ffv1enc.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/libavcodec/ffv1enc.c b/libavcodec/ffv1enc.c index 2a188ade776..a09ab300389 100644 --- a/libavcodec/ffv1enc.c +++ b/libavcodec/ffv1enc.c @@ -1375,6 +1375,7 @@ static void encode_float32_remap(FFV1Context *f, FFV1SliceContext *sc, const int log2_mul_step = ((int[]){ 1, 8, 1, 1, 1, 1})[f->remap_optimizer]; const int bruteforce_count = ((int[]){ 0, 0, 0, 1, 1, 1})[f->remap_optimizer]; const int stair_mode = ((int[]){ 0, 0, 0, 1, 0, 0})[f->remap_optimizer]; + const int magic_log2 = ((int[]){ 1, 1, 1, 1, 0, 0})[f->remap_optimizer]; av_assert0 (pixel_num <= 65536); @@ -1390,7 +1391,9 @@ static void encode_float32_remap(FFV1Context *f, FFV1SliceContext *sc, int last_mul_index = -1; int mul_count = 1 << log2_mul_count; - score_sum[log2_mul_count] += log2_mul_count * log2_mul_count; + score_sum[log2_mul_count] = 2 * log2_mul_count; + if (magic_log2) + score_sum[log2_mul_count] = av_float2int((float)mul_count * mul_count); for (int i= 0; i<pixel_num; i++) { int64_t val = sc->unit[p][i].val; int mul_index = (val + 1LL)*mul_count >> 32; @@ -1424,7 +1427,10 @@ static void encode_float32_remap(FFV1Context *f, FFV1SliceContext *sc, score *= score; if (mul_index != last_mul_index) score *= mul; - score_tab[si] += log2f(score); + if (magic_log2) { + score_tab[si] += av_float2int(score); + } else + score_tab[si] += log2f(score); } } last_val = val; -- 2.49.0 _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe". ^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [FFmpeg-devel] [PATCH 1/2] avcodec/ffv1enc: replace 3 double precision log2() by 1 single precision log2() 2025-03-30 15:00 [FFmpeg-devel] [PATCH 1/2] avcodec/ffv1enc: replace 3 double precision log2() by 1 single precision log2() Michael Niedermayer 2025-03-30 15:00 ` [FFmpeg-devel] [PATCH 2/2] avcodec/ffv1enc: replace the remaining log2() by magic Michael Niedermayer @ 2025-04-02 21:21 ` Michael Niedermayer 1 sibling, 0 replies; 3+ messages in thread From: Michael Niedermayer @ 2025-04-02 21:21 UTC (permalink / raw) To: FFmpeg development discussions and patches [-- Attachment #1.1: Type: text/plain, Size: 506 bytes --] On Sun, Mar 30, 2025 at 05:00:22PM +0200, Michael Niedermayer wrote: > This makes the remap finding heuristic much faster > > Signed-off-by: Michael Niedermayer <michael@niedermayer.cc> > --- > libavcodec/ffv1enc.c | 16 +++++++++++----- > 1 file changed, 11 insertions(+), 5 deletions(-) will apply patchset [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB The greatest way to live with honor in this world is to be what we pretend to be. -- Socrates [-- Attachment #1.2: signature.asc --] [-- Type: application/pgp-signature, Size: 195 bytes --] [-- Attachment #2: Type: text/plain, Size: 251 bytes --] _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe". ^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2025-04-02 21:21 UTC | newest] Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2025-03-30 15:00 [FFmpeg-devel] [PATCH 1/2] avcodec/ffv1enc: replace 3 double precision log2() by 1 single precision log2() Michael Niedermayer 2025-03-30 15:00 ` [FFmpeg-devel] [PATCH 2/2] avcodec/ffv1enc: replace the remaining log2() by magic Michael Niedermayer 2025-04-02 21:21 ` [FFmpeg-devel] [PATCH 1/2] avcodec/ffv1enc: replace 3 double precision log2() by 1 single precision log2() Michael Niedermayer
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