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Liked songs — the device ⇄ PC contract

Added 2026-08-20 alongside the PC-side likesync tool (repo: Sony sync).

Cinder has had liked songs since 2026-07-27 (cinder_liked.conf + the Now Playing heart + the Library's "Liked songs" row). What it did not have is a way for a like to arrive from the PC, which is what a sync needs — the device is the only participant that cannot reach the network, so every path between it, Last.fm and MusicBee has to be a file.

The three files

path direction format written by
/contents/cinder_liked.conf — one MediaStore object_id per line Cinder (the real store)
/contents/cinder_loved.tsv device → PC artist \t title, # header Cinder, on every liked change
/contents/cinder_liked_import.tsv PC → device artist \t title, # artist… header likesync

Object ids are rebuilt whenever the MTP database is, so they cannot cross the USB cable — hence the two TSVs. /contents is the volume Windows mounts, so all three are readable and editable by hand over USB-MSC, which matters for a list the owner curated by hand and cannot otherwise back up.

What Cinder does with the import

player/cinder-ffi/src/likes.rs, called from cinder_db_open right after the library is built:

  1. read /contents/cinder_liked_import.tsv; absent → nothing happens (the normal boot);
  2. no # artist header → ignore and leave it in place (it is not ours);
  3. resolve each row against the library just built — artist+title normalised the same way the PC normalises (case, curly punctuation, feat. credits, re-issue suffixes such as - Remastered 2009 / (2021 Mix)), then by primary artist, then by album artist (a featured-artist track is tagged to the guest: Cleo Sol — Woman on a Little Simz album);
  4. rows present but nothing resolved → ignore and leave it in place, so the next boot retries (that shape means the library had not loaded, not that the list is empty);
  5. otherwise replace the liked set with the resolved ids, rewrite cinder_liked.conf and the cinder_loved.tsv export, and rename the import to …​.tsv.done.

Replace, not merge, because the import is the merged whole list, not a delta — a track missing from it was deliberately unliked somewhere, and merging would make an unlike impossible to express. An empty file with the header therefore means "everything was unliked" and is honoured; the PC writes it atomically, so a zero-row file cannot be a torn write.

The rename is the signal back to the PC: while the file exists, likesync treats the device as additive-only, because its export still shows the pre-push list. A Cinder build without this feature never renames it, so an un-updated device keeps working — it just never gains hearts from the PC, and likesync says so.

What is NOT here

  • No network on the device. There is no WiFi on an NW-A55, and track.love cannot be expressed in an Audioscrobbler/1.1 log either: its rating column is L = Listened / S = Skipped, which is not a love. That is why loves need their own file rather than riding the scrobbler log.
  • No liked-songs playlist written by the device. likesync writes /contents/MUSIC/Liked Songs.m3u8 per volume, which Sony's indexer picks up like any other playlist, so it plays without a firmware change.

Tests

cargo test -p cinder-ffi likes:: — 11 cases: the re-issue folding, live/remix staying distinct, the featured-artist and primary-artist fallbacks, junk lines, the missing header, the unresolved refusal, the empty-clear, and the rename.