feat(streaming): per-account transcoding profiles

CHANGELOG.md

@@ -54,6 +54,16 @@ out first, whether or not it breaks a compile.
   release needs the `SIGNTOOL_PFX_BASE64` and `SIGNTOOL_PFX_PASSWORD` secrets:
   without them the archives stop before they build and nothing is published,
   though the image's build still runs.
+- **Transcoding profiles** (#403, [RFC-027](docs/rfcs/RFC-027-transcoding-profiles.md)):
+  an account can say once what an app that does not ask should get, as a default
+  and per Subsonic client name, in Settings › Playback or through
+  `/api/v2/transcoding-profiles`. A request naming a format or a bit rate is
+  answered as before, and so is every request of an account with no profile.
+  Under one, a Subsonic `stream` or a native stream that names neither may now be
+  transcoded, a source at or under the bit rate excepted. Stream tickets, and so
+  the web player, downloads and public shares keep the original. An app that seeks
+  by byte range may fail to seek in a transcode still being encoded; a row of
+  Original for it puts it right.
 - **The transcoding state in the web client's administration**: whether the
   server can transcode (without it, listeners get the original files only),
   the transcodes running against the global limit, the per-account limit and

docs/README.md

@@ -52,6 +52,7 @@ The design decisions, one per document. A `Status` line never changes; the
 | [RFC-024](rfcs/RFC-024-lyrics-stats-and-mixes.md) | LRCLIB lyrics, listening statistics, mixes and local similar songs |
 | [RFC-025](rfcs/RFC-025-smart-playlists-and-podcasts.md) | Smart playlists and podcasts |
 | [RFC-026](rfcs/RFC-026-no-jukebox.md) | No jukebox mode: why the server does not play on its own output |
+| [RFC-027](rfcs/RFC-027-transcoding-profiles.md) | Transcoding profiles: per account and Subsonic client name |
 
 ## Plans and analyses
 

docs/analyses/web-client-gap-analysis.md

@@ -15,10 +15,11 @@
 > decided against ([RFC-026](../rfcs/RFC-026-no-jukebox.md)). The client speaks
 > nine languages since #391 and #392, all but English fetched on demand (#393).
 > Every route of the "server knows, screen ignores" table is wired, the
-> transcoding state last (#404). Still open, as an issue: per-account
-> transcoding profiles (#403). **Amended 2026-11-01:** the web client follows
-> the library event stream since #405; the user journal (`/api/v2/sync/*`) is
-> still unread by it.
+> transcoding state last (#404). Transcoding profiles, the gap of degree, are
+> settled per account and per Subsonic client name
+> ([RFC-027](../rfcs/RFC-027-transcoding-profiles.md), #403). **Amended
+> 2026-11-01:** the web client follows the library event stream since #405; the
+> user journal (`/api/v2/sync/*`) is still unread by it.
 
 ## What was found
 
@@ -103,7 +104,11 @@ format or bitrate profile. And **translation**: 34 languages against two.
 > awaiting a native read (#406). Jukebox is #402, transcoding profiles #403.
 >
 > **State on 2026-11-02.** Jukebox is decided against, so the gap stays and is
-> deliberate ([RFC-026](../rfcs/RFC-026-no-jukebox.md)).
+> deliberate ([RFC-026](../rfcs/RFC-026-no-jukebox.md)). **Transcoding profiles
+> are no longer a gap** ([RFC-027](../rfcs/RFC-027-transcoding-profiles.md),
+> #403): an account sets a default and one row per Subsonic client name in
+> Settings › Playback, for clients that do not ask. It stays narrower than
+> Navidrome's on one point, deliberately: the web player keeps playing originals.
 
 ### What Navidrome does, the server already knows how to do, and the screen ignores
 

docs/compatibility/subsonic-compatibility.md

@@ -351,6 +351,35 @@ no podcast screen over Subsonic, so neither exercised the methods. Not
 recorded: whether a channel's and an episode's `coverArt` show through
 `getCoverArt`.
 
+## Deviation for RFC-027: a silent request may be transcoded
+
+An account may now set a transcoding profile
+([RFC-027](../rfcs/RFC-027-transcoding-profiles.md)), through the native API and
+Settings › Playback. The wire does not change: no parameter, method or field was
+added. What changes is the answer to one request, for an account that set one.
+
+- **A request that names neither a format nor a positive `maxBitRate`** may now be
+  answered with a transcode where it used to be answered with the original.
+  `maxBitRate=0` and an empty `format=` count as naming nothing. The
+  `Content-Type` says what was sent, as it always has.
+- **Every other request is answered as before**: `format=raw`, any format named,
+  one this server cannot produce included (see RFC-022 above), any positive
+  `maxBitRate`, and `download`.
+- **An account with no profile sees no change at all.** Neither does a source at or
+  under the profile's bit rate, which stays the original.
+- **A profile's transcode takes the ceilings' slots**, and past them is answered
+  `429`. A client preloading the next track may meet that where it used to receive
+  the original.
+
+**The limit.** A live transcode refuses a range past the first byte with `416`
+until the encode is whole in the cache. So a client that does not ask and seeks by
+byte range may fail to seek under a profile, where it worked on the original. An
+override of `raw` for that client's name (`c`) puts it back on the original, and
+Settings › Playback says so.
+
+**No client has been run against this.** This section does not say which clients
+are concerned, and the next campaign should find out.
+
 ## Correction: an unsynced lyrics line is an object in JSON
 
 Found on 2026-10-27, while preparing the third client campaign, before any

docs/guides/api-v2-guide.md

@@ -699,6 +699,40 @@ two are indistinguishable from the rows alone.
 
 See [RFC-007](../rfcs/RFC-007-library-event-stream.md) for the reasoning.
 
+### Transcoding profiles
+
+An account can say once what a client that does not ask should get
+([RFC-027](../rfcs/RFC-027-transcoding-profiles.md)).
+**A profile applies to `GET /api/v2/tracks/{id}/stream` and to Subsonic
+`stream`, when the request names neither a format nor a bit rate**, and to nothing
+else. Stream tickets, downloads and public shares keep the original, and a request
+that names something gets what it named.
+
+```bash
+# The account's default
+curl -X PUT "https://music.example.com/api/v2/transcoding-profiles" \
+  -H "Authorization: Bearer ACCESS_TOKEN" -H "Content-Type: application/json" \
+  -d '{"format": "opus", "bitrate": 128}'
+
+# One Subsonic client on the original, under the name it sends as `c`
+curl -X PUT "https://music.example.com/api/v2/transcoding-profiles" \
+  -H "Authorization: Bearer ACCESS_TOKEN" -H "Content-Type: application/json" \
+  -d '{"client": "Feishin", "format": "raw"}'
+```
+
+`PUT` replaces a whole row. `bitrate`, from 32 to 512, is a ceiling: a source at or
+under it stays the original, and one of unknown bit rate is encoded. Left out, it
+takes the format's default. `raw` is for a client's row only and takes no bit rate.
+An account holds at most 32 rows, and a 33rd answers `409`. `GET` answers the
+`profiles` and the `seen_clients`, the names this account's Subsonic clients have
+streamed with without asking since the server started.
+`DELETE /api/v2/transcoding-profiles?client=Feishin` removes a row, and without
+`client` the default; it answers `204` whether or not the row was there.
+
+A native client that names nothing and seeks by byte range will meet the `416` a
+live transcode gives past the first byte, under an account with a default. Name a
+format, `raw` included, if that is not what you want.
+
 ### When a transcode is refused
 
 Transcoding is bounded twice: once for the whole server and once per account.

docs/guides/subsonic-api-guide.md

@@ -220,6 +220,14 @@ Without an explicit format, `maxBitRate` is a ceiling: WaveFlow keeps the
 original when its known bitrate fits and otherwise transcodes to MP3. Original
 and completed cached responses support Range; live transcodes are chunked.
 
+A request that names neither a format nor a positive `maxBitRate` is what the
+account's transcoding profile applies to, if it set one
+([RFC-027](../rfcs/RFC-027-transcoding-profiles.md)): a row for this client's `c`,
+compared without ASCII case, or else the account's default. A source at or under
+the profile's bit rate stays the original. The `Content-Type` names what was sent.
+A client that seeks by byte range may fail to seek in a live transcode; a row of
+`raw` for its name keeps it on the original.
+
 ## Implemented methods
 
 Only the following methods are dispatched. Unknown methods answer HTTP `200`