10 Commits
Author SHA1 Message Date
Emma ThorpeandClaude Opus 5 c63115f246 feat: level the mirror's volume with ReplayGain tags
Build and publish container / build (pull_request) Successful in 7m41s
Rockbox applies the offset a ReplayGain tag carries but has no loudness
analysis of its own, so an untagged mirror plays every album at whatever
level it was mastered to.

Albums are measured with rsgain once their tracks are in place, album gain
and track gain both, leaving the device to choose between them. An album is
re-measured as a whole whenever it gains, loses or replaces a track, because
album gain is a property of all of its tracks and one new track makes the
value stored on every sibling wrong.

rsgain runs with --preserve-mtimes. Staleness here is an mtime comparison
and tagging rewrites the file, so without it every levelled track would look
newer than its source and the next pass would re-encode the whole library.

Whether a file has already been levelled is decided by walking its ID3v2
frame headers and seeking over the bodies. Cover art is embedded in every
mirror file, so reading the tag whole would turn an idle pass into a full
read of the library.

A missing rsgain is reported and then left alone rather than failing the
pass: the mirror is still correct audio in the right place.

Two existing tests move with the change. ffprobe's csv writer renders the
ReplayGain side data as a trailing empty field, and a copied MP3 now differs
from its source in the container while carrying identical audio.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
2026-08-28 16:49:37 +01:00
Emma Thorpe ece79515c0 fix: cost the device prefix exactly rather than approximately
Build and publish container / build (pull_request) Successful in 3m54s
The budget subtracted the prefix length plus two, on the assumption of a
leading and a trailing slash. That is right for /Music and wrong for an empty
prefix, where there is only one slash -- losing a character at the card root,
which is exactly where the longest paths sit.

Computed from the prefix as it will actually appear instead: /Music/ costs
seven characters and gives a mirror-relative budget of 253, the root costs one
and gives 259.

Worth being exact about because the reverse error is worse. A checker
comparing mirror-relative paths against the flat 260 passes everything between
253 and 260, and those are precisely the paths closest to the edge.
2026-08-25 11:52:03 +01:00
Emma Thorpe 46435feebd fix: cut long names from the middle, not the end
Build and publish container / build (pull_request) Canceled after 1m18s
The shortening fitted the path and destroyed its meaning. Lidarr writes
"Artist - Album - 07 - Flamethrower.mp3" inside a directory already named for
that artist and album, so a long album title occurs three times in one path and
everything that distinguishes one track from another sits at the very end.
Cutting from the end removed precisely that:

  King Gizzard & the Lizard Wizard - PetroDragonic Apocalypse; or, Dawn of Eter~c526.mp3

All seven tracks on that record reduced to the same string bar the hash. The
path fitted; the result was seven files nobody could tell apart on the device,
which is a worse outcome than the failure it replaced.

Cut from the middle instead, giving two thirds of the remaining room to the
tail because the head is generally a restatement of the directory the file
already sits in:

  King Gizzard & the Lizard~c526~ginning of Merciless Damnation - 07 - Flamethrower.mp3

The eight real paths that prompted this are now regression tests: every track
on that album keeps its number and title, all seven names stay distinct, and
The Beatles' "The Long One" -- whose length is the title itself rather than a
repeated album name -- keeps both ends.
2026-08-25 11:50:42 +01:00
Emma Thorpe d5f67c6de5 feat: shorten paths that exceed the device's limit
Build and publish container / build (pull_request) Successful in 2m16s
Rockbox's MAX_PATH is 260, defined in firmware/include/fs_defines.h and used to
size the directory entry buffer in dir.h. It bounds the path as the device sees
it, so the directory the mirror is copied into spends part of the same budget;
--device-prefix accounts for that and defaults to /Music.

Over-budget paths are shortened from the deepest component outward. The track
name carries the least navigational value and the artist directory the most, so
the filename is cut first and the artist only if nothing else will serve. A
shortened component keeps its extension and gains four hex digits of the
original name: two long titles sharing a prefix cut to the same string
otherwise, and a silent collision between two tracks is a worse outcome than an
ugly filename.

The result is stable. The same source always yields the same shortened name, so
one pass does not rename what the last one wrote -- an unstable scheme would
churn the whole mirror every six hours. A path too deeply nested to fit without
reducing every component to nonsense is left alone and reported rather than
mangled.

Migration now tries more than one previous naming, because there is more than
one. A mirror already running with --fat32-safe holds sanitised but unshortened
paths, and matching only the original unsanitised name would have re-encoded
every one of them instead of moving it.

The checker gains the same two options, since it was measuring the
mirror-relative path against a limit that applies to the device-absolute one,
and so under-reported by the length of the destination directory.
2026-08-25 11:46:26 +01:00
Emma Thorpe 3f50577de6 fix: report renames honestly in a dry run
Build and publish container / build (pull_request) Successful in 1m38s
--dry-run described a FAT32 rename as an encode. process() skipped the rename
whenever dry_run was set, then found no file at the target and fell through to
the encode path, so a preview of enabling --fat32-safe announced a full
re-encode of every track whose name held a reserved character. The real run
moves those files in a moment. A preview that inverts the cost of the thing
being previewed is worse than no preview at all.

Prune compounded it. With nothing renamed, the pre-sanitisation files are still
on disk, and they were reported as orphans due for deletion -- so the same dry
run claimed the library would be re-encoded and the originals thrown away,
neither of which is true.

Renames are now their own outcome: reported as "would rename" in a dry run,
counted separately from encodes in the pass summary, and excluded from the
orphan list when a dry run leaves them in place.
2026-08-25 11:34:42 +01:00
Emma Thorpe 3141f7ca87 feat: name the mirror so a FAT32 device will take it, and copy album art
Build and publish container / build (pull_request) Successful in 2m18s
Two changes for playing the mirror on a Rockbox iPod, where the device is FAT32
and Rockbox reads a plain directory tree rather than a database.

--fat32-safe names mirror files acceptably: the reserved characters and control
characters become underscores, trailing dots and spaces are stripped because
FAT eats them silently and the name then round-trips as a different one, and a
component left empty becomes an underscore. Names differing only in case are
detected as collisions, since two files here are one file there and the second
would silently overwrite the first. "Kick Out the Epic Motherf**ker" is a real
example from a real library, and without this it simply never arrives.

Off by default. It renames files, and that should be a decision rather than a
surprise on somebody's next pass.

Turning it on does not re-encode anything. Every track whose name held a
reserved character changes path, and encoding those again would be hours of
work producing files that already exist byte for byte, so the run moves them
instead and logs each one. Prune then finds nothing left behind.

Album art is now also copied into the mirror as cover.jpg beside the tracks.
Rockbox searches the filesystem for art -- cover.jpg, folder.jpg and the rest,
in the track's directory or its parent -- and that search never looks at the
picture embedded in the tag, so a mirror that only embeds art displays none of
it on the device. Embedding continues for the Apple firmware; both are now
satisfied. A cover whose tracks have all been pruned is removed too, or its
directory would never look empty and never go.

Adds tools/check_fat32.py, which reports unacceptable paths before a copy
rather than during one: rsync reports them too, but scattered through fifty
thousand files where they are easy to lose. It exits non-zero so it can gate a
script.

The README documents the rsync invocation, including why --modify-window=2 is
required against FAT and why Rhythmbox must be kept out of the transfer --
rb_ipod_helpers_is_ipod() reads access-protocols from media-player-info and
returns true on the USB id alone, without looking at the filesystem, so
removing iPod_Control changes nothing.
2026-08-25 10:29:55 +01:00
Emma Thorpe e9852e6c86 fix: keep the mirror readable under a umask that masks the owner's read bit
Build and publish container / build (pull_request) Successful in 15m16s
The umask handling added for group access cleared only the group bits and left
owner and other to the environment. A container whose umask carries 0400 then
produces mirror directories of mode 0300: writable and enterable, unreadable to
the very run that created them, and unreadable to anything serving the share.

Clear the owner read and execute bits from the umask as well. The `other` bits
stay where the environment puts them, because whether the mirror is
world-readable is a real policy question; being able to read a directory the
process itself just created is not.

Files were never exposed to this: mkstemp sets 0600 outright and copy2 takes
the source file's mode, both ignoring the umask.
2026-08-24 13:21:07 +01:00
Emma Thorpe a1382185a7 fix: copy through a temporary file so a cut-short copy is not kept
Build and publish container / build (pull_request) Successful in 6m57s
Copies of already-MP3 sources were written straight to their destination while
encodes went via a temporary file and a rename. A copy interrupted by a full
disk, a killed container or an I/O error therefore left a truncated MP3 in the
mirror -- and because shutil.copy2 reproduces the source's mtime along with its
bytes, staleness detection would read that fragment as up to date and never
replace it. The damage is silent and permanent until someone plays the track.

Give copy the same temporary-file-and-rename path encode already uses, so the
destination either has the whole file or has nothing.
2026-08-24 11:36:08 +01:00
Emma Thorpe 100671da99 fix: make everything written into the mirror group-readable
The mirror is written by one account and read by another -- an SMB share, or
whatever else serves it -- but nothing here produced a group-readable file.
Encodes go through `tempfile.mkstemp`, which creates 0600 regardless of the
umask and keeps that mode through the rename into place, so every encoded
track landed unreadable. Copies of existing MP3s inherit the mode of a source
file in a library this tool does not own, which may be no better.

Add the group-read bit explicitly: to the temporary file before it is renamed,
so a mirror file is never visible without it, and to a copy once it has landed.
Directories are handled by clearing the group bits from the process umask
rather than chmod'ing each one, since a file the group cannot reach is no more
useful than one it cannot read. Only the group bits are touched; the world bits
and ownership stay with the umask as before.

Mirror files written before this are repaired on the next pass. Their mtimes
are correct, so no other part of the pass would revisit them, and topping up
the mode costs a stat rather than a re-encode.
2026-08-24 11:36:08 +01:00
lyrathorpeandEmma Thorpe d4ccff3b75 feat: mirror a lossless library to MP3 for iPod sync (#1)
Build and publish container / build (push) Failing after 51s
## What

A path-for-path MP3 mirror of a lossless library. FLAC in, MP3 out, same relative layout, tags and cover art carried across. Already-MP3 sources are copied rather than re-encoded. Mirror files whose source has gone are deleted, along with any directory they emptied. The source library is never written to — mounted read-only in the compose file, and never opened for writing in code.

| Situation                        | Action                               |
| -------------------------------- | ------------------------------------ |
| No mirror file                   | encode                               |
| Source modified since the mirror | re-encode (a Lidarr quality upgrade) |
| Mirror up to date                | skip                                 |
| Source is already MP3            | copy verbatim                        |
| Source gone                      | delete, prune empty dirs             |

## Design notes

- **No database.** Freshness is mtime: an encode is stamped with its source's mtime, so a file is stale exactly when the two differ. Lidarr owns the library; a second tool with its own index would only fall out of step with it. This is also why it is not beets.
- **Atomic writes.** Encode to a temp file, rename into place. An interrupted run cannot leave a truncated MP3 that the next run treats as finished.
- **A lock file** in the mirror root stops two passes overlapping.
- **Refuses a mirror inside the source tree**, which would otherwise recurse.
- `--subdir` never prunes: a partial pass cannot distinguish an orphan from a file outside its scope.

## Shipping

- Python package with a `music-mirror` console script, no runtime dependencies beyond ffmpeg.
- `Dockerfile` plus `compose.yaml` as a TrueNAS Scale Custom App: source dataset read-only, mirror dataset writable, `MUSIC_MIRROR_INTERVAL=6h`.
- CI runs the tests **inside the image**, against the ffmpeg that ships, on every pull request, and on merge publishes multi-arch (amd64 + arm64) to this Gitea's registry using the `PACKAGES_SECRET` repository secret. Versioning follows the same conventional-commit scheme as `legacy-email-proxy`, including writing the released version back into `pyproject.toml` so the packaging metadata cannot drift behind the tag.

## Behaviour under Lidarr

| Lidarr does this                        | The mirror does this                                                             |
| --------------------------------------- | -------------------------------------------------------------------------------- |
| Replaces a file with a better rip        | Re-encodes in place; same path in, same path out, so no duplicate                 |
| Upgrades MP3 to FLAC                     | Both map to the same `.mp3` mirror path, so the old one is overwritten            |
| Renames a track, album or artist folder  | Old path pruned, new path encoded — correct, though it re-encodes rather than moving |
| Deletes an album or artist               | Every orphaned mirror file goes, and the directories they emptied with them        |

Three defects were found and fixed while writing those tests, each verified to
fail against the previous code:

- Pruning probed the source tree for a mirror file's original name, lowercase
  extensions only. A `.FLAC` source was never found, so its mirror file was
  deleted as an orphan and rebuilt on the next pass, for ever. Pruning now works
  from the set of paths the pass actually accounted for.
- Two sources could claim one mirror path — `01 Song.flac` beside a leftover
  `01 Song.mp3`. Both encoded to the same destination and each pass found the
  loser stale. The better format now wins, ties break on path.
- The source mtime was read after encoding rather than before, so a file still
  being written when the pass reached it could be stamped current while holding
  truncated audio.

## Why there is no flake

The deployment target is a container. A flake here would sit on no path between
the source and the NAS, and `nix flake check` would test against nixpkgs' ffmpeg
while the artefact ships Debian's — precisely the layer these tests exercise. It
was removed in favour of running the suite inside the image. The sibling
`legacy-email-proxy` keeps its flake because there the flake *is* the deployment
mechanism.

## Verification

- 21 tests, all real ffmpeg round-trips: layout, tag survival, MP3 output, skip-when-current, re-encode-on-change, orphan pruning, empty-dir removal, `--no-prune`, MP3 passthrough, `--dry-run`, `--subdir`, external cover art embedding, both refusal paths, and the Lidarr lifecycle cases below.
- The suite also runs in the multi-stage Docker `test` stage: 21 passed. The published `runtime` stage carries neither the tests nor pytest, verified by inspecting the image.
- Container built and run locally against a sample library: correct output path, Cyrillic tags intact.
- The release step was extracted from the workflow and run against a scratch repository: it commits and tags when the version changes, and skips the commit but still tags when `pyproject.toml` already carries it.
- **Not tested against the real library** — the first run there should be `--dry-run`.

## Follow-ups, not in this PR

- Lidarr imports are picked up on the next scheduled pass rather than instantly. A webhook trigger is the obvious next step if six hours feels slow.
- `PACKAGES_SECRET` must exist as a repository secret before the first merge, or the login step fails.

---------

Co-authored-by: Emma Thorpe <emma.thorpe@citrix.com>
Reviewed-on: #1
2026-08-21 15:30:58 +01:00