ogg dev - Apr 2007 - AW: embedded pictures in vorbis comments?

Hi,

I think we can start by defining an official field name at
www.xiph.org/vorbis/doc/v-comment.html which is used as a file system link to an
existing image file. I suggest the field name to be "PICTURE".

What is ogg MNG? Is it a container format for PNG files which should be embedded
in OGG files?
If I understand correctly, the picture would be placed in a different logical
stream inside the ogg file. The question is how many players or taggers are
going to support this. For example, I saw that WinAmp (version 5.32) can't
tag multiplexed ogg vorbis files correctly (it ruined a ogg vorbis + theora file
so that only the music could be played afterwards, but not the video any more).
My .NET tagging library can handle it correctly now by the way ;-)

Cheers,
Mathias


----- Urspr?ngliche Mail ----
Von: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
An: Mathias Kunter <mathiaskunter@yahoo.de>
CC: ogg-dev@xiph.org
Gesendet: Samstag, den 28. April 2007, 03:31:13 Uhr
Betreff: Re: [ogg-dev] embedded pictures in vorbis comments?

Hi Mathias,

The solution you are suggesting won't work because it will not only
"not work" in existing players, but probably break them completely,
such that the audio file that you are trying to improve will not play.
It is better that files which add functionality to an existing format
will continue to be played by players which only understand the old
format.

There are some existing, conformant ways of associating image data
with Ogg files. You could enter a URL into the vorbiscomment header to
get a link to album art. Or use XSPF playlists for this. Or use
Annodex and CMML with images on chapters. All of which only deal with
links to external pictures.

But I've read the thread on the album art, and people would like to
see the pictures embedded in the stream, so let's address this.

Currently, I believe, there is no fully functioning implementation for
this at Xiph, however Ogg MNG would be the way to do this using PNG
and MNG images. Or Ogg Spots for all non-animated image types. There
is an existing implementation of Ogg MNG.

If you are really keen, why don't you start programming on Ogg MNG and
integration with Ogg Vorbis? It would be most welcomed here!

Cheers,
Silvia.


On 4/23/07, Mathias Kunter <mathiaskunter@yahoo.de>
wrote:
> Hello,
>
> I'd like to ask about the possibility of embedding pictures like an
album cover artwork into a vorbis comment header. Since the data in a comment
string after the separating "=" has a defined length, this could
theoretically also be binary picture data. For example
>
> "PICTURE=[...any binary data...]"
>
> It only would be a problem for existing software which isn't aware of
this and which would try to display the binary data as text...
>
>
> Mathias
>
>
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On Sat, Apr 28, 2007 at 11:09:03AM +0000, Mathias Kunter wrote:
> I think we can start by defining an official field name at
www.xiph.org/vorbis/doc/v-comment.html which is used as a file system link to an
existing image file. I suggest the field name to be "PICTURE".
That's fine. Note that FLAC imports some other fields, like media-type 
and "picture type", an enumeration of semantic categories, from the 
id3v2 spec for it's picture metadata block.
> What is ogg MNG? Is it a container format for PNG files which should be
embedded in OGG files?
MNG is a superset of PNG and JPEG. There's a general proposal for using 
it as the standard for embedding PNG, JPEG, mJPEG, lossless video, 
DVD-style graphical overlays, station-id bugs, etc. in Ogg streams. 

  http://libpng.org/pub/mng/
  http://wiki.xiph.org/OggMNG

OggSpots was a simpler proposal to embed single or sequences of PNG or 
jpeg images without the MNG wrapper.
> If I understand correctly, the picture would be placed in a different
logical stream inside the ogg file. The question is how many players or taggers
are going to support this. For example, I saw that WinAmp (version 5.32)
can't tag multiplexed ogg vorbis files correctly (it ruined a ogg vorbis +
theora file so that only the music could be played afterwards, but not the video
any more). My .NET tagging library can handle it correctly now by the way ;-)
Yes, the picture would be placed in a separate logical stream, with an 
OggSkeleton header marking its intended use. Nothing supports that yet,
but nothing supports the vorbis-comment extension either, so that's not
really an argument.

More seriously, the Ogg Vorbis spec says that decoders are allowed to 
reject multiplexed streams, so such files may not work with a lot of
current audio software and embedded players. (Video players work fine.)
So while the multiplexed image stream is what we should do, it probably 
makes sense to support a vorbiscomment option as well as the freedesktop 
directory-icon pseudo-standard for albums. :(

 -r