ffmpeg | branch: master | Gerion Entrup <gerion.ent...@flump.de> | Sun Jun 2 14:02:53 2024 +0200| [300df41c30c7767729e51be1d09cda02901f9b16] | committer: Michael Niedermayer
libavfilter/signature_lookup: fix jaccard distance Actually, the jaccard distance is defined as D = 1 - intersect / union. Additionally, the distance value is compared against a constant that must be between 0 and 1, which is not the case here. Both facts together has led to the fact, that the function always returned a matching course signature. To leave the constant intact and to avoid floating point computation, this commit multiplies with 1 << 16 making the constant effectively 9000 / (1<<16) =~ 0.14. Reported-by: Sachin Tilloo <sachin.til...@gmail.com> Reviewed-by: Sachin Tilloo <sachin.til...@gmail.com> Tested-by: Sachin Tilloo <sachin.til...@gmail.com> Signed-off-by: Michael Niedermayer <mich...@niedermayer.cc> > http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=300df41c30c7767729e51be1d09cda02901f9b16 --- libavfilter/signature_lookup.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/libavfilter/signature_lookup.c b/libavfilter/signature_lookup.c index a0ca818a9b..46602874de 100644 --- a/libavfilter/signature_lookup.c +++ b/libavfilter/signature_lookup.c @@ -127,9 +127,10 @@ static int get_jaccarddist(SignatureContext *sc, CoarseSignature *first, CoarseS { int jaccarddist, i, composdist = 0, cwthcount = 0; for (i = 0; i < 5; i++) { - if ((jaccarddist = intersection_word(first->data[i], second->data[i])) > 0) { + if ((jaccarddist = (1 << 16) * intersection_word(first->data[i], second->data[i])) > 0) { jaccarddist /= union_word(first->data[i], second->data[i]); } + jaccarddist = (1 << 16) - jaccarddist; if (jaccarddist >= sc->thworddist) { if (++cwthcount > 2) { /* more than half (5/2) of distances are too wide */ _______________________________________________ ffmpeg-cvslog mailing list ffmpeg-cvslog@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-cvslog To unsubscribe, visit link above, or email ffmpeg-cvslog-requ...@ffmpeg.org with subject "unsubscribe".
