[ogg-dev] Album art - requirements

Ralph Giles giles at xiph.org
Mon Oct 13 17:02:35 PDT 2008

On 13-Oct-08, at 2:10 PM, Silvia Pfeiffer wrote:

> is coverart a header-type content or a time-aligned type content?

Well, it's collection-level metadata, so it doesn't belong in files  
at all. :)

> It was my impression that it is mostly header-type content, i.e.  
> concerns the full file rather than segments of it.

It makes sense to reference it per-chain-segment in an Ogg context.

> Therefore, embedding it into any of the time-aligned streams (Kate,  
> CMML, OggMNG) doesn't make much sense to me.
> It should be in a header.

When I've suggested OggMNG (or rather OggJNG and OggPNG) for cover  
art in the past it was in that sense that it be a 'header only'  
stream, the way skeleton is.

I'd suggest defining an album-art reference in the skeleton fishhead  
that points to such a stream. We have the OggMNG spec for embedding  
png and jpeg images already, and svg could use a similar embedding to  
what we already do with cmml. But if it is in fact header only, it  
might be reasonable to put just anything in there, including JFIF and  
PDF. As usual it comes down to what people are willing to support.

We need the vorbiscomment option because the spec allows audio  
players to reject non-degenerate streams. So for audio .ogg files  
this is the only option. I don't think this is a good mechanism  
for .oga or .ogv files.

Note that either way this makes for an even bigger bitrate spike when  
streaming, so we probably want the ability to use an external  
reference for that. And make icecast covert on the fly...


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