Matthias Blankertz
5013e2359d
Add documentation of playlist database schema in DEVELOP.md. Add settings for persist and shuffle to BTreeDB. Implement the different persist modes. Shuffle will be implemented in a followup commit. Signed-off-by: Matthias Blankertz <matthias@blankertz.org>
2.5 KiB
Developer notes
How to setup python environment for mypy and pytest
cd software
python -m venv test-venv
. test-venv/bin/activate
pip install -r tests/requirements.txt
pip install -U micropython-rp2-pico_w-stubs --target typings
'database' schema for btree db
Playlist storage
The playlist data is stored in the btree database in a hierarchical schema. The hierarchy levels are separated by the '/' character. Currently, the schema is as follows: The top level for a playlist is the 'tag' id encoded as a hexadecimal string. Beneath this, the 'playlist' key contains the elements in the playlist. The keys used for the playlist entries should be decimal integers, prefixed with sufficient zeros such that they are in the correct order when sorted lexicographically. All keys must have the same width. When writing a playlist using the playlistdb module, the keys are 00000, 00001, etc. by default.
Playlist modes
The 'playlistshuffle' key located under the 'tag' key can be 'no' or 'yes' and specifies whether the playlist is in shuffle mode. Should this key be absent the default value is 'no'.
The 'playlistpersist' key located under the 'tag' key can be 'no', 'track' or 'offset'. Should this key be absent the default value is 'track'.
- When it is 'no', the playlist position is not saved when playback stops. If shuffle mode is active, the shuffle random seed is also not saved.
- When it is 'track', the currently playing track is saved when playback stops. If shuffle mode is active, the shuffle random seed is also saved. Should playback reach the last track (in shuffle mode: the last track in the permutated order), the saved position is reset and playback is stopped. The next time the playlist is started it will start from the first track and with a new shuffle seed if applicable.
- When it is 'offset', the operation is basically the same as in 'track' mode. The difference is that the offset in the currently playing track is also saved and playback will resume at that position.
The 'playlistpos' key located under the 'tag' key stores the key of the current playlist entry. The 'playlistshuffleseed' key stores the random seed used to shuffle the playlist. The 'playlistposoffset' key stores the offset in the current playlist entry.
Example
For example, a playlist with two entries 'a.mp3' and 'b.mp3' for a tag with the id '00aa11bb22' would be stored in the following key/value pairs in the btree db:
- 00aa11bb22/playlist/00000: a.mp3
- 00aa11bb22/playlist/00001: b.mp3
- 00aa11bb22/playlistpos: 00000