Hi all,
where would i find some references on how to include an image (cover art) in a ogg file, using a command line tool for linux (oggenc) ?

I need to know which size are allowed/suggested, which formats (jpg or png), etc.
Thanks for your help!

IIRC Ogg Vorbis spec does not explicitly support coverart embedding in the .ogg file.

That said, if you really want to embed a coverart, you can embed a Base64-encoded file into your own custom tag.

Okay, I suppose people are aware thatMP3Tag and Softpointer Audioshell both permit one to embed a jpg, but neither will detect what the other did. So, is it a waste of effort to attempt it with either?
I'm interested mainly because the Canola player for Nokia N800 seems to be able to display art -- it looks great with MP3s.

J. River Media Center (ver. 9 - 12) has used the Base64 system for years. It can convert a binary image to Base64 encoded text so that it can be placed in a Vorbis comment. JRMC can display embedded Ogg Vorbis cover art in its thumbnail views and visualizations. Softpointer has adopted this Base64 system too (Tag&Rename and AudioShell).

Florian's Mp3tag (http://www.mp3tag.de/en/) does not allow adding cover art to Vorbis comments (yet?). Perhaps you mean some other program with "MP3Tag".

I did mean Florian's project: I right-click on the CD pic at lower left, select image, and write tag to file. When one views the files in MP3Tag, the cover is displayed. This was with development builds e and f of this month.

I think that's because the Ogg spec implictly supports cover-art embedding, because you can mux any file in an .ogg file.

Exactly, but I don't know of anything that can mux a picture in.

I tested that before posting. The lower left corner display has a bug. It should not allow adding cover art because that feature is not available with Ogg Vorbis files. After adding an image the display shows it momentarily, but on next data refresh it is gone. In the "Extented Tags" window you can see the reality. The cover art options are disabled.

(Mp3tag v.2.37f)

Now when you say "mux"....

You can certainly produce valid Ogg streams with additional data muxed as another logical stream. But this will make most if not all Vorbis players reject the stream (they don't like non-Vorbis streams). Also, due to the lack of a specification of how to embed pictures there's no right or wrong. Don't expect Vorbis players to recognise something you've just made up.

You can certainly base64-encode a JPEG image and include it as a tag. It seems a wannabe-quasi-standard has already evolved. But since this isn't official either there's a slim chance that files with cover art embedded as base64-encoded tag can cause some players to behave in a weird fashion. For instance, if your player doesn't expect such really loooong ascii tags and likes to display all of'em by default you'll see a lot of garbage on your screen...

Though I personally don't like the 2nd solution (the comment packet is misused) it looks like the best approach which doesn't break too much.

Edit: Ogg Skeleton may be a way to describe a secondary stream (holding a picture) as album art in the distant future.

Cheers!
SG

Uhm... not so clear:
1. is there any tool to achieve this ?
2. which players are able to display the embedded pic, then ?