## API

- reverse proxy (protects API keys)
	- download song (spotmate.online API)
		- /songs
	- fetch library (spotify.com API)
		- /
	- fetch playlist (spotify.com API)
	- nice-to: fetch playlist icon, song icon

	- register user: (username, service)
	- upload diagnostics
.

- do we abstract API from Spotify?
	- allows other services
	-
	- needs a user concept {user}.{service}
.

- do we cache the mp3 of the songs?
	- will we later use server-side processing of songs?
	- ideas about 50 ms centered gaussian-window, and 2048-point STFT
	- get features and train discriminator to find beats in song
	- actual beats where user stepped
	-
	- possibly we will need a time environment (spanning a musical bar?) as feature
	- cf. songs like "Disturbed - Rise" with strong complex drum pattern
.

- first draft:
	- constant (0-th order) BPM estimate of song - step pattern derived
	- adapt tempo only (not phase synchronized)
.