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Re: libextractor - key-value pairs and mime types
From: |
Christian Grothoff |
Subject: |
Re: libextractor - key-value pairs and mime types |
Date: |
Tue, 8 Feb 2022 18:00:39 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 |
On 2/8/22 2:38 PM, madmurphy wrote:
> Got it! I agree about your solution for the duplicate mime types.
>
> but until that is done, a key-value pair type would at least be
> better than 'unknown'.
>
> “Unknown” can continue to exist as an identifier for other cases, just
> not the key-value ones :)
Yes, of course. That's what I meant, too.
> Also I forgot to mention a third point:
>
> 3. Add an |EXTRACTOR_METATYPE_NO_METATYPE = -1| to |enum
> EXTRACTOR_MetaType| (more or less like |NULL| if that was a pointer).
> Without a |EXTRACTOR_METATYPE_NO_METATYPE| a programmer is forced to
> save the |have_metatype| information in another variable. The fact that
> it is a negative number is not a problem, because as the name suggests,
> /it is not a metatype/.
Are you sure that EXTRACTOR_METATYPE_RESERVED (0) is not good enough
here? We usually use it to terminate lists, but as far as I see, it
should be what you think of as NO_METATYPE. But if there is a use-case
RESERVED doens't cover, I'm not categorically against introducing a -1
value.
Patches welcome ;-).
-Christian
> P.S. Sorry for picking the wrong mailing list!
>
>
> On Tue, Feb 8, 2022 at 9:57 AM Christian Grothoff <grothoff@gnunet.org
> <mailto:grothoff@gnunet.org>> wrote:
>
> Hi madmurphy,
>
> The 'correct' place for GNU libextractor discussions would be
>
> https://lists.gnu.org/mailman/listinfo/libextractor
>
> Alas, with my libextractor maintainer hat on, I would say this:
>
> On 2/7/22 10:01 PM, madmurphy wrote:
> > Hi again, GNUnet people.
> >
> > Is this the place where to discuss about libextractor? I have two
> points.
> >
> > #1 I often see something interesting. Key-value pairs are
> categorized as
> > |EXTRACTOR_METATYPE_UNKNOWN|:
> >
> > unknown: chroma-format=4:2:0
> > unknown: bit-depth-chroma=8
> > unknown: colorimetry=bt709
> > unknown: stream-format=avc
> > unknown: stream-format=raw
> > unknown: bit-depth-luma=8
> > unknown: base-profile=lc
> > unknown: mpegversion=4
> > unknown: profile=high
> > unknown: alignment=au
> > unknown: parsed=true
> > unknown: framed=true
> > unknown: variant=iso
> > unknown: profile=lc
> > unknown: level=4.1
> >
> > But one point is that they are often numerous, and another point
> is that
> > that of a key-value type is a really interesting metatype to have (and
> > is not really “unknown”, since the key is self-explanatory). Would it
> > not make sense to add an |EXTRACTOR_METATYPE_KEY_VALUE_PAIR| to
> the list
> > of MetaTypes?
>
> We could do that. Sometimes I think it would be better to add new
> specific LE types for some of the above, but until that is done, a
> key-value pair type would at least be better than 'unknown'.
>
> > ...
> >
> > /* generic attributes */
> > EXTRACTOR_METATYPE_UNKNOWN = 45,
> > EXTRACTOR_METATYPE_DESCRIPTION = 46,
> > EXTRACTOR_METATYPE_COPYRIGHT = 47,
> > EXTRACTOR_METATYPE_RIGHTS = 48,
> > EXTRACTOR_METATYPE_KEYWORDS = 49,
> > EXTRACTOR_METATYPE_ABSTRACT = 50,
> > EXTRACTOR_METATYPE_SUMMARY = 51,
> > EXTRACTOR_METATYPE_SUBJECT = 52,
> > EXTRACTOR_METATYPE_CREATOR = 53,
> > EXTRACTOR_METATYPE_FORMAT = 54,
> > EXTRACTOR_METATYPE_FORMAT_VERSION = 55,
> > *EXTRACTOR_METATYPE_KEY_VALUE_PAIR* = XXX,
> >
> > ...
> >
> > #2 I often see that files get tagged with multiple mime types
> according
> > to libextractor:
> >
> > mimetype: video/quicktime
> > mimetype: video/x-h264
> > mimetype: audio/mpeg
> > mimetype: video/mp4
>
> That is because different plugins (using different methods/libraries)
> disagree on the 'correct' mime-type. Ideally, we'd identify which plugin
> gets it wrong (and why), and unify the mime-types.
>
> > But that never reflects the reality, since files should have only one
> > mime type (or at most, multiple mime types that mean the same thing).
> > But then I see what happens with file names: there is only one
> > |EXTRACTOR_METATYPE_GNUNET_ORIGINAL_FILENAME|, but there can be many
> > |EXTRACTOR_METATYPE_FILENAME|s (in the case of archives, for example):
> >
> > EXTRACTOR_METATYPE_FILENAME = 2,
> > ...
> > EXTRACTOR_METATYPE_GNUNET_ORIGINAL_FILENAME = 180,
> >
> > Would it not make sense to do something similar for mime types?
> Only one
> > “original mime type”, and an infinity of secondary mime types…?
> >
> > EXTRACTOR_METATYPE_MIMETYPE = 1,
> > ...
> > *EXTRACTOR_METATYPE_GNUNET_ORIGINAL_MIMETYPE* = XXX,
>
> I guess it depends. If this is for archives where files _inside_ the
> archive are given mime-types, then a different metatype makes sense
> (ditto for FILENAME: here we probably could have two types, one for the
> 'archive' and one for the 'contents'). But if the different mime-types
> are all about the 'original' file, then we should rather figure out
> which plugin gets it wrong. As for the "_GNUNET_" in the
> "_GNUNET_ORIGINAL_FILENAME" there, IIRC this again different because
> that is NOT a metatype used by GNU libextractor, but one that GNUnet
> itself generates and puts with the 'rest ' of the metadata.
>
> > So, two simple proposals:
> >
> > 1. Create |EXTRACTOR_METATYPE_KEY_VALUE_PAIR|
> > 2. Create |EXTRACTOR_METATYPE_GNUNET_ORIGINAL_MIMETYPE|
> >
> > What do you think? Does it make sense?
>
> It should definitively not be "GNUNET_ORIGINAL_MIMETYPE", and the real
> question is what is the origin of the different mime-types. If this is
> from an archive, maybe we should introduce
>
> EXTRACTOR_MIMETYPE_ARCHIVE_CONTENT_FILENAME
> EXTRACTOR_MIMETYPE_ARCHIVE_CONTENT_MIMETYPE
>
> and reserve
>
> EXTRACTOR_MIMETYPE_FILENAME
> EXTRACTOR_MIMETYPE_MIMETYPE
>
> for the top-level file. But AFAIK that won't solve your mime-type issue,
> which should really be resolved by going over the plugins and finding
> out why and where they disagree and picking the 'right' answer.
>
> My 2 cents
>
> Christian
>
- libextractor - key-value pairs and mime types, madmurphy, 2022/02/07
- Re: libextractor - key-value pairs and mime types, Christian Grothoff, 2022/02/08
- Re: libextractor - key-value pairs and mime types, madmurphy, 2022/02/08
- Re: libextractor - key-value pairs and mime types, madmurphy, 2022/02/08
- Re: libextractor - key-value pairs and mime types, madmurphy, 2022/02/08
- Re: libextractor - key-value pairs and mime types, madmurphy, 2022/02/08
- Re: libextractor - key-value pairs and mime types, Christian Grothoff, 2022/02/08
- Re: libextractor - key-value pairs and mime types, madmurphy, 2022/02/08
- Re: libextractor - key-value pairs and mime types,
Christian Grothoff <=