Hello everybody,

recently I've been working on a set of scripts for pre-generating thumbnails of 
video and picture files in a set of given directories. The idea is to be able 
to run thumbnail-generation in the background, per cron, per cmdline, not-in-X, 
not-using-nautilus, etc.

I've been reading a lot of documentation regarding this topic and I think I 
have come quite far in understanding all the details and requirements.

However I still need a little help (obviously...), but first, let me share my 
work with you...

Here is my three scripts:

batch_thumbnailer:
http://pastebin.com/Z0QNz0Eb

vids_thumbnailer:
http://pastebin.com/e4mQ4Lca

pics_thumbnailer:
http://pastebin.com/fd6yUUHM

batch_thumbnailer is the main scripts that calls vids+pics_thumbnailer, if in 
$PATH.

The syntax is: batch_thumbnailer [<dir> ...]

What it does is basically:

1. search the given directories (non-recursive) for files
2. determine the files mimetype and filter out all of type video/*, image/*
3. create a batch list for video files and process it with vids_thumbnailer
4. create a batch list for picture files and process it with pics_thumbnailer

The steps 3 and 4 are similar and can be broken down in sub-steps:
a. for each file, determine absolute path (file -> /path/to/file)
b. for each file, determine URI (/path/to/file -> file:///path/to/file)
c. for each URI, determine MD5 checksum (echo -n file:///path/to/file | md5sum 
| cut -c -32)
d. for each file, determine modification time (file.mtime = $(stat -c "%Y" 
file))
e. for each file, store a thumbnail under $HOME/.thumbnails/normal/$MD5.png 
with required metadata Thumb::URI := $URI and Thumb::MTime := file.mtime
(f.) if thumbnail generation has failed, move thumbnail to 
$HOME/.thumbnails/fail[/$0]/$MD5.png

The one place to start reading about thumbnails is probably:

[1] http://jens.triq.net/thumbnail-spec/

So that's that.

Now I've created a whole batch of thumbnails with my scripts, however my 
problem is that nautilus is still recreating every single media file when I 
change to it's directory. I notice this because obviously it takes some time to 
display the thumbnails and also the mtime of the thumbnail is updated when 
re-/overwritten.

My idea in the first place was to have the thumbnails created and then nautilus 
is just displaying them superfast, since they already exist. However, this is 
not the case.

I spent some time figuring out the differences between my thumbnails and 
nautilus thumbnails, but I cant really tell the differences nor explain the 
"overwriting/recreating" behavior of nautilus. What I have tried so far is, I 
noticed another optional tag in the pings "Software: GNOME::ThumbnailFactory" 
and recreated that in my scripts, ... still with no change. Nautilus seems to 
allways overwrite my thumbnails.

That makes me wanna stop any further work on my scripts, because I must first 
know what the real problem is or else I waste my time.

FYI, these are my thumbnailers in nautilus (gconf-editor -> 
/desktop/gnome/thumbnailers/...):
- im...@x-pict := /usr/bin/gm convert -size %s -resize %s +profile "*" %i[0] %o
- video@<any> := /usr/bin/ffmpegthumbnailer -s %s -c png -f -t 50%% -i %i -o %o

I would like to know in what way GNOME's thumbnail creation standard differs 
from the one described in [1] or whether nautilus/gnome stores 
extra-information elsewhere (outside $HOME/.thumbnails). My goal is the 
pre-create thumbnails in my scripts, that nautilus can actually use and 
instantly display, without re-creation/overwrites.

Thank you for all support, answers and feedback in advance,
it's all welcome.

Bye,
Pasxalis.



PS: I've been forwarded to nautilus-list@gnome.org from gnome-l...@gnome.org:
http://mail.gnome.org/archives/gnome-list/2010-October/msg00009.html


                                          
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