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dmedia - The Distributed Media Library
======================================
dmedia is simple distributed media library. Media files are given a globally
unique ID based on their content-hash. Meta-data is stored in CouchDB.
Meta-data for a large number of media files can be available locally (meta-data
is small). Actual media files can be loaded on-demand from peers or cloud when
not available locally (media files are big). Goals are to make synchronization
super easy, and to lay groundwork for a distributed content creation workflow.
Work on dmedia is coordinated through Launchpad. For the latest code, to file a
bug, or to otherwise get involved, see the dmedia project in Launchpad:
https://launchpad.net/dmedia
Although it didn't start as such, dmedia has become a foundational component for
the Novacut distributed video editor. To learn more, see:
http://novacut.com/
https://launchpad.net/novacut
https://launchpad.net/~novacut-community
Use and installation
====================
You can run the `dmedia` script directly from the source tree without any build
or installation step. This is the quickest way to try dmedia. You can run the
`dmedia` script from the source tree like this:
./dmedia /media/EOS_DIGITAL jpg cr2
That will recursively import all JPG and CR2 files from your memory card mounted
at "/media/EOS_DIGITAL".
To install dmedia system-wide, run this:
sudo python setup.py install
Then you can run the `dmedia` script from any location like this:
dmedia /media/EOS_DIGITAL jpg cr2
You can also install dmedia locally for your user only like this:
python setup.py install --user
This will install dmedia in ~/.local/. To run the dmedia script, you will have
to ensure that ~/.local/bin is in your path. To do this, add the following in
your ~/.profile:
# Also add .local/bin if it exists
if [ -d "$HOME/.local/bin" ] ; then
PATH="$HOME/.local/bin:$PATH"
fi
You will have to logout and login for the change to take effect.
Testing the dmedia script
=========================
dmedia is at an early state still, but the functionality it has so far should
be quite stable.
The `dmedia` script will eventually be turned into a VCS-style script with
several commands. For now it has a single function, to recursively import media
files from a directory. At this point, it's a quick-and-dirty demo of how media
files might be stored and how their meta-data might be stored.
For example, say we scan all the JPG images in the '/usr/share/backgrounds'
directory:
dmedia /usr/share/backgrounds jpg
Media files are uniquely ID'ed by their base32-encoded sha1 content-hash. In
the above example, the 'Life_by_Paco_Espinoza.jpg' file happens to have a sha1
content-hash of '6BRRXCGRM2GKVPTREJPGRNGUR2GF2L4K'. As such, this file
will be stored at:
~/.dmedia/6B/RRXCGRM2GKVPTREJPGRNGUR2GF2L4K.jpg
Meta-data for the media files is stored in CouchCB using desktop-couch. Each
media file has its own document. The sha1 content-hash is used as the document
'_id'. For example, the 'Life_by_Paco_Espinoza.jpg' file has a document that
looks like this:
{
"_id": "6BRRXCGRM2GKVPTREJPGRNGUR2GF2L4K",
"_rev": "1-c19ea015eb53ede147d63d55f3967d13",
"name": "Life_by_Paco_Espinoza.jpg",
"record_type": "http://example.com/dmedia",
"bytes": 360889,
"height": 1500,
"shutter": "1/400",
"width": 2000,
"ext": "jpg",
"camera": "DSC-H5",
"iso": 125,
"focal_length": "6.0 mm",
"mtime": 1284394022,
"aperture": 4
}
All media files will have the following fields:
bytes - File size in bytes
mtime - Value of path.getmtime() at time of import
name - The path.basename() part of the original source file
ext - The extension of the original source file, normalized to lower-case
Additional fields depend upon the type of media file. For example, image and
video files will always have 'width' and 'height', whereas video and audio files
will always have a 'duration'.
You can browse through the dmedia database using a standard web-browser, like
this:
firefox ~/.local/share/desktop-couch/couchdb.html
Note that the sha1 hash is only being used as a stop-gap. dmedia will use the
Skein hash after its final constant tweaks are made. See:
http://blog.novacut.com/2010/09/how-about-that-skein-hash.html
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