Re: Thumbnailing service project; opinions, suggestions?

[Philip Van Hoof <spam pvanhoof be>]

On Mon, 2009-10-19 at 16:20 +0100, Rob Taylor wrote:

> We already have a thumbnailing service that is only just now starting to
> be used. A complete reimplementation of soemthing existing will not be a
> very useful thing. I also suggest that 13weeks for your entire plan is
> very over optimistic. I would suggest a better option would be to do a
> library with optimised thumbnailing routines. This would also be very
> useful for existng projects and probably result in you code being used
> in a number of situations.

> To add complexity you could also branch out
> into making thumbnail clips for videos. If you write up such a plan
> completely, i think you'd find it's more than enough work for a 13 week
> project.

Agree that a video thumbnailer would be very useful. However, we're
already developing (/ hopefully this week finishing) a video thumbnailer
that implements the 'specialized thumbnailer' spec (spec is available on
the page that Mark mentioned).

http://live.gnome.org/ThumbnailerSpec

Code can be found here (again, this week it'll receive some improve-
ments). This will likely also be the video thumbnailer that will make
thumbnails for videos on Harmattan devices.

http://maemo.gitorious.org/maemo-af/maemo-video-thumbnailer

A *very* useful thumbnailer for Maemo Harmattan would be a PDF one that
doesn't link with gdkpixbuf.

At the Maemo conference in Amsterdam I spoke with one of the KOffice
guys. He told me that there's some interest in making thumbnailers for
all of the formats that KOffice supports. Probably using Qt C++.

We're doing all this thumbnailing stuff in the open, you can find
feature branches for Tumbler's integration into Harmattan here:

http://maemo.gitorious.org/maemo-af/tumbler

Among the branches you'll find work that removes usage of GdkPixbuf. The
reason for that is that on Harmattan all GdkPixbuf usage is being
replaced with libquill. You can find the libquill project here:

http://maemo.gitorious.org/maemo-image-editor

That libquill library still depends on qtimagefilter which might be hard
for some people to get (there's an opensource release of it somewhere,
but it ain't easy to get this stuff installed). This week will the
libquill people work on refactoring-away this dependency (they told me).

(Quill is a different project, I wont go further into it)

You can find upstream Tumbler at the XFCE project. We're trying very
hard to ensure that each feature and change introduced for Maemo
Harmattan goes into the upstream project. Jannis Pohlmann is the XFCE
developer responsible for the upstream Tumbler project.

http://git.xfce.org/apps/tumbler/

Key features (on Maemo Harmattan, most/all are in upstream too):

o. Two schedulers each having their own queue: Background and
   foreground. The background one is set to SCHED_IDLE and uses
   IOPRIO_CLASS_IDLE for I/O priorities.
o. DBus signals are emitted with dbus_message_set_destination to avoid
   DBus traffic waking up processes needlessly
o. Ready and Error in case of foreground are emitted immediately
o. Ready and Error in case of background are emitted in group
o. Unqueue also cancels I/O operations
o. The mount-pre-unmount cancels I/O operations in case I/O takes place
   on the device being unmounted
o. Abstracted cache (makes it possible to implement your own thumbnail
   cache, although we probably wont use this on Maemo)
o. In Maemo we store JPEG instead of PNG (PNG is ~ braindead for this,
   as often are thumbnails in PNG of a JPEG larger and slower to load as
   the original JPEG)
o. The libquill library for rescaling large images rapidly
o. We'll ship with a specialized video thumbnailer that uses GStreamer
o. etc


-- 
Philip Van Hoof, freelance software developer
home: me at pvanhoof dot be 
gnome: pvanhoof at gnome dot org 
http://pvanhoof.be/blog
http://codeminded.be