[iFixRobots]

Voice notes sent from Beeper to LINE arrive on the other side but can't be played.

Beeper Android and Desktop record voice notes as Ogg/Opus, and the bridge uploads whatever bytes it gets as a LINE audio message. LINE audio is m4a or mp3 (the Messaging API audio message accepts only those, and audio from LINE clients is m4a, which is why inbound audio is bridged as audio/mp4). In Letter Sealing chats the file is end-to-end encrypted, so LINE can't transcode it either. A 130 s Android voice note:

"msg_content_type":3,"msg_metadata":{"AUDLEN":"130634","DURATION":"130634",...,"FILE_SIZE":"961774",...,"SID":"ema"

That's the Ogg file as sent (~59 kbps Opus).

Audio that isn't already m4a or mp3 now goes through ffmpeg to AAC in m4a before upload, the same way mautrix/meta (to-whatsapp.go) and mautrix/signal convert voice notes for networks that don't take Opus. A 130 s Opus clip converts in about 1.5 s. iOS voice notes (already m4a) and mp3 files are sent untouched.

	Before	After
Android/Desktop voice note	Ogg/Opus, won't play in LINE	AAC m4a
iOS voice note, mp3 file	unchanged	unchanged

Before / after: not run yet. It needs two LINE accounts: send a voice note from Beeper Android to a LINE account and play it in the LINE app, on main and on this branch.

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[indent]

Issues

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1 issue already resolved

• Audio files with embedded cover art (e.g. FLAC) get a video stream in the converted m4a because the ffmpeg args lack -vn. Add -vn to the output args so only audio is kept. (fixed by commit 9e42b56)
  _{Found by Indent Review Agent}

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Full results

Indent Review Agent

• Summary: No issues found
• Last ran on commit: 9e42b565
• Latest result

  {
    "summary": "No issues found",
    "findings": []
  }