# Using digital media masters

Master files -
either original sources or as close as possible -
are precious and should be carefully tracked.

Digital media files -
e.g. photos, videos, music -
are often large and binary encoded,
which poses special challenges for their tracking.


## Git-annex

Digital media masters are tracked with git and git-annex.

Git is a version control system -
a repository for historic versions of file contents of a folder.
Git-annex is an extension to git,
better handling large files.


### Paths

You are recommended to use path suffix "annex"
for media master projects.
Examples:

  * ~/public_annex/home-videos
  * ~/private_annex/friends-snoring
  * ~/shared_annex_family/xmas_photos


## Create

To turn a folder into a git repository
(see also alternative of (cloning)[#Clone] an existing project),
go into the folder,
and initialize its git and git-annex databases:

	git init
	git annex init --version=7

To use git-annex only for large files (git for smaller ones),
add e.g. the following to file `.gitattributes`:

	* annex.largefiles=((largerthan=100kb)and(not(mimetype=text/*)))
	*.svg annex.largefiles=nothing

Finally (save)[#Save] all content:

	git add -A
	git commit -m "Initial commit"


## Status

To check status of metadata, use git:

	git status

To check status of file content storage, use git-annex:

	git annex info


## Save

To "take a snapshot" of one of more files
for git-annex archival,
first mark which files are involved
and then archive their (changes to) content:

	git annex add foo bar
	git annex add baz
	git commit -m "Update foo bar, and add baz."

Alternatively you can update (but not add)
in one go:

	git commit -m "Update foo bar." foo bar


## Clone

To collaborate on a shared git repository,
first create a local clone from the shared location,
and tell git-annex to use it:

	git clone git://[[!template id=githost]]/example
	git annex init --version=7

Then from time to time syncronize:

	git annex sync --content --all

Alternatively (e.g. on slow/expensive network),
syncronize only metadata and only with nearest clones:

	git annex sync --fast


### Publish

To publish a git repository initially created locally,
first create a new empty git and git annex publicly,
then tell your local git where its new origin will be,
and finally push your local git and git annex into its new public location:

	ssh [[!template id=githost]] git init --bare --shared /srv/git/[[!template id=githost]]/example.git
	ssh [[!template id=githost]] GIT_DIR=/srv/git/[[!template id=githost]]/example.git git annex init
	git remote add origin [[!template id=githost]]:/srv/git/[[!template id=githost]]/example.git
	git push --set-upstream origin master
	git annex sync --content --all


## Split

Splitting media files is format-specific.

Many audio formats can be split
with the package shntool and appropriate helper tools,
e.g. like this for a FLAC file with CUE file for splicing hints:

	shnsplit -o flac -f CUE_FILE.cue FLAC_FILE.flac

For many other formats, including video content,
splitting can be done using the [copy] parameter to FFMpeg,
e.g. like this:

	ffmpeg -i INFILE -ss 15 -t 60 -acodec copy -vcodec copy OUTFILE

[copy]: https://ffmpeg.org/ffmpeg.html#Stream-copy
  "FFMpeg copy parameter"


## References

* [media-master][Source of this document]

[media-master]: <https://source.redpill.dk/media-master>.
  "Digital media master material"