Re: How to read artwork bitmaps embedded in MP3 files as "image"-Tag

[Benoît Minisini <benoit.minisini@xxxxxxxxxxxxxxxx>]

Le 10/03/2026 à 13:18, Claus Dietrich a écrit :
> Am 10.03.26 um 02:44 schrieb Benoît Minisini:
> > I added in the last commit support for GStreamer "sample"
> > objects, through a new 'MediaSample' class.
> >
> > The image tag returns such an object, that includes the image
> > contents (returned by the 'Data' property), and some metadata
> > (returned by the 'Info' property).
> >
> > That metadata is returned as a collection of collections. The
> > contents of these collections can be anything.
> >
> > In the case of the mp3 I used for testing (not yours), I get that:
> >
> > {"image/jpeg":{"width":400,"height":400,"sof-marker":2}}
> >
> > It seems to mean that the image is a JPEG, so you have to use the 
> > 'Image.FromString()' method to transform the sample data into an
> > Image object.
> >
> > Try it and tell me if you have any problem.
>
> Hi Benoît!
>
> Thanks a lot for your attention in this matter.
>
> It works for the image tag, but it doesn't allow to access the
> TagList- Data any longer. The TagList-Collection now always returns
> an object instead of a string. So my demo app is now crashing at
>
> TextArea1.text &= TagList[sTag]
>
> These tag Strings are certainly used in most Gambas media
> applications out there.
>
> This is what I did:
>
> Public Sub PipeEvents_Tag(TagList As MediaTagList)
>
> For Each sTag As String In Taglist.Tags If sTag = "image" Then Print
> "Info: "; TagList[sTag].Info Print "Type: ";
> TypeOf(TagList[sTag].Info) Print "Size: "; TagList[sTag].Size 
> PictureBox1.Image = Image.FromString(TagList[sTag].Data) else 
> 'TextArea1.text &= TagList[sTag]     '<--- OUT-COMMENTED BECAUSE THE
> APP IS NOW CRASHING HERE Endif Next
>
> End
>
> I hope you have an idea to get this backwards compatible with
> existing code out there (in best case). If not (which would be OK
> for me) ... how about new Text Property in the MediaSample class?
> Deliver any text via the Data Property of the new MediaSample-Class?

It's backward compatible: it was never said that a tag is only a string.
A tag can be any datatype.

I can eventually make an automatic conversion of MediaSample to string,
but what for?

> In case of an image tag, the Info-property in my case returns 
> "(Collection 0x58fd8b0c2918)" and a test showed that this data type
> is 16. So it seems that we have a new data type in Gambas -
> correct?

Of course not. TypeOf() returns 'gb.Object' (= 16) to tells you that the
value contains an object.

The documentation of TypeOf(): https://gambaswiki.org/wiki/lang/typeof

> I would have expected a String under the title "Info". As the info- 
> property is supposed to be a collection of collections - how could
> this object be enumerated - and would there be any use by doing
> this? I am further wondering why (and how) you got "{"image/jpeg": 
> {"width":400,"height":400,"sof-marker":2}}" in your project.

It's the JSON corresponding to the collection. How do you want me to
print the contents of a collection inside a mail otherwise?

You enumerate the contents of the Info property as you like. I can just
guarantee that it is a collection of collections. The contents inside
the child collections can be anything.

There is no way to know what exactly is inside the Data property of a
MediaSample. Apparently the key of the first collection seems to be a
mimetype, but I think it's purely a convention of the GStreamer plugin
that decodes the MP3. Another plugin may use a totally different way of
communicating the contents of the metadata associated with the decoded file.

Good luck with that!

--
Benoît Minisini.