Issue description:
Hi there,
First of all thanks for this awesome piece of software!
I use mutagen to write SYLT frames in MP3 files, e.g. with tags.add(SYLT(encoding=Encoding.UTF8, type=1, format=2, text=res)).
UTF8 is coded as 0x03: mutagen/mutagen/id3/_specs.py at main · quodlibet/mutagen · GitHub
The spec confirms that 0x03 holds for UTF-8: id3v2.4.0-structure - ID3.org
$03 UTF-8 [UTF-8] encoded Unicode [UNICODE]. Terminated with $00.
exiftool shows that the first byte of the frame is indeed 0x03:
| SynLyrics (SubDirectory) -->
| - Tag 'SYLT' (1089 bytes):
| 0000: 03 58 58 58 02 01 00 20 50 61 73 20 64 75 20 63 [.XXX... Pas du c]
| 0010: 6f 75 72 61 67 65 20 63 27 65 73 74 20 64 27 6c [ourage c'est d'l]
| 0020: 27 69 6e 63 6f 6e 73 63 69 65 6e 74 00 00 00 36 ['inconscient...6]
| 0030: d6 20 4e 61 75 66 72 61 67 65 20 76 6f 6c 6f 6e [. Naufrage volon]
| 0040: 74 61 69 72 65 2c 20 6e 6f 69 65 20 6d 65 73 20 [taire, noie mes ]
| [snip 1009 bytes]
Not sure how to interpret the above part saying the encoding must end with 0x00, but the specs for the header of SYLT frames confirms it holds on one byte:
<Header for 'Synchronised lyrics/text', ID: "SYLT">
Text encoding $xx
Language $xx xx xx
Time stamp format $xx
Content type $xx
Content descriptor <text string according to encoding> $00 (00)
Other programs such as go-sylt are able to correctly read the lyrics.
The relevant logs on the app are:
2025-11-14 04:36:14.540 Error/MusicPlayer: Error parsing SYLT binary frame
java.lang.IllegalArgumentException: Unsupported text encoding: 3
at js.n.l0(r8-map-id-962fb70ab25dee31aa1ef7b5088ee9356fda45aec6e9ff453b2a8a1c8b437840:26)
at hi.a.invoke(r8-map-id-962fb70ab25dee31aa1ef7b5088ee9356fda45aec6e9ff453b2a8a1c8b437840:455)
at ni.d.n(r8-map-id-962fb70ab25dee31aa1ef7b5088ee9356fda45aec6e9ff453b2a8a1c8b437840:68)
at p5.o.invoke(r8-map-id-962fb70ab25dee31aa1ef7b5088ee9356fda45aec6e9ff453b2a8a1c8b437840:89)
at i5.k.run(r8-map-id-962fb70ab25dee31aa1ef7b5088ee9356fda45aec6e9ff453b2a8a1c8b437840:40)
at i5.o.b(r8-map-id-962fb70ab25dee31aa1ef7b5088ee9356fda45aec6e9ff453b2a8a1c8b437840:72)
at p5.y.K(r8-map-id-962fb70ab25dee31aa1ef7b5088ee9356fda45aec6e9ff453b2a8a1c8b437840:156)
at a6.g0.run(r8-map-id-962fb70ab25dee31aa1ef7b5088ee9356fda45aec6e9ff453b2a8a1c8b437840:504)
at android.os.Handler.handleCallback(Handler.java:942)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loopOnce(Looper.java:201)
at android.os.Looper.loop(Looper.java:288)
at android.os.HandlerThread.run(HandlerThread.java:67)
I uploaded the MP3 and the debug log file with a description set as this issue’s name.
Thanks in advance for your help 
Logs:
Upload description: Unsupported encoding for synced lyrics added with mutagen
Additional information:
Reproduction steps:
Media provider:
Subsonic
Screenshots:
