Git Inbox Mirror of the ffmpeg-devel mailing list - see https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
 help / color / mirror / Atom feed
From: Gerion Entrup <gerion.entrup@flump.de>
To: FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org>
Subject: Re: [FFmpeg-devel] [PATCH 1/2] libavfilter/signature_lookup: fix possible division by zero
Date: Fri, 24 May 2024 12:33:11 +0200
Message-ID: <2453178.Mh6RI2rZIc@falbala> (raw)
In-Reply-To: <20240507174628.GF6420@pb2>


[-- Attachment #1.1: Type: text/plain, Size: 1329 bytes --]

Am Dienstag, 7. Mai 2024, 19:46:28 MESZ schrieb Michael Niedermayer:
> On Mon, May 06, 2024 at 12:30:39AM +0200, Gerion Entrup wrote:
> > ---
> >  libavfilter/signature_lookup.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/libavfilter/signature_lookup.c b/libavfilter/signature_lookup.c
> > index a0ca818a9b..b39a3e225b 100644
> > --- a/libavfilter/signature_lookup.c
> > +++ b/libavfilter/signature_lookup.c
> > @@ -128,7 +128,7 @@ 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) {
> > -            jaccarddist /= union_word(first->data[i], second->data[i]);
> > +            jaccarddist /= FFMAX(union_word(first->data[i], second->data[i]), 1);
> >          }
> 
> for which input data does this cause a division by 0 ?

Sorry for the late answer. I missed your mail somehow.
union_word counts the amount of one bits that are created when you are "or"ing
the course signatures. So, when the underlying videos are so different that all
bits of the created signatures are different, the "or"-operator will always
return 0 and so also its sum (I have not tested this).

Gerion


[-- Attachment #1.2: This is a digitally signed message part. --]
[-- Type: application/pgp-signature, Size: 659 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".

  reply	other threads:[~2024-05-24 10:33 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-05-05 22:30 Gerion Entrup
2024-05-05 22:30 ` [FFmpeg-devel] [PATCH 2/2] libavfilter/signature_lookup: fix jaccard distance Gerion Entrup
2024-05-07 17:46 ` [FFmpeg-devel] [PATCH 1/2] libavfilter/signature_lookup: fix possible division by zero Michael Niedermayer
2024-05-24 10:33   ` Gerion Entrup [this message]
2024-05-24 21:03     ` Michael Niedermayer
2024-05-26 15:08       ` Gerion Entrup
2024-05-26 17:26         ` Michael Niedermayer

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=2453178.Mh6RI2rZIc@falbala \
    --to=gerion.entrup@flump.de \
    --cc=ffmpeg-devel@ffmpeg.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Git Inbox Mirror of the ffmpeg-devel mailing list - see https://ffmpeg.org/mailman/listinfo/ffmpeg-devel

This inbox may be cloned and mirrored by anyone:

	git clone --mirror https://master.gitmailbox.com/ffmpegdev/0 ffmpegdev/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 ffmpegdev ffmpegdev/ https://master.gitmailbox.com/ffmpegdev \
		ffmpegdev@gitmailbox.com
	public-inbox-index ffmpegdev

Example config snippet for mirrors.


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git