Ogg changes

[Stephen Drake]

On Wed, 2007-11-14 at 15:00 +0000, Stephen Drake wrote:
> Hello all,
> 
> I'm not sure if everyone is aware of this, so I'll just put it out
> there.
> 
> There has been a shift in recommended file extensions and mime types for
> Ogg files over the last month and this will probably affect how we
> encode the screencasts for distribution (recording is unaffected). 

It appears that I missed the last two or three years of discussion on
the xiph.org mailing lists, so this is hardly new, though the updated
RFC does give it more traction.

> Basically the change is as follows
> 
> Video -> .ogv
> Audio -> .oga
> other -> .ogx
> 
> The current .ogg is rendered legacy/deprecated and will only be used for
> Vorbis I, i.e. existing music only files.
> 
> Now for the interesting part. It is recommended that the new files
> contain a skeleton structure to allow better use of multiple streams,
> seeking etc. So we can't just rename the files *.ogg -> *.ogv, for
> example.

Actually that's wrong, we can rename them to .ogv and they will be
acceptable. In fact there doesn't appear to be any great benefit to
using the skeleton format at the moment.

Perhaps it would be worth trialing annodex based streams with subtitles
at some point, but I'm struggling to find any examples of this in the
wild.

> This means we are going to have to decide how we intend to change the
> current encoding methods and also how we will handle the existing
> screencasts i.e. do we leave them be and just start afresh or go back
> and re-encode?

Regardless of any changes, I can't see the any media players that
currently play these files suddenly stop doing so. 

Still, it's nice to keep up with the recommendations of the development
team and that might be even easier as it looks like ffmpeg2theora has
been patched to name output files as .ogv by default. So maybe we can
just switch when that has been packaged up for release.

Due to the aggressive six month release schedule of Ubuntu, it's likely
that no-ones going to care about the earlier non-ogv screencast before
too long, especially if Ubuntu 8.04 (Hardy) does indeed sport a new
look.

> There is a wiki page on xiph.org detailing the changes,
> http://wiki.xiph.org/index.php/MIME_Types_and_File_Extensions
> 
> and I think this bug report is also worth reading,
> https://bugs.freedesktop.org/show_bug.cgi?id=12890
> 
> Thoughts?
> 
> Steve

Regards,

Steve