Function audio_forces_transcode 

pub fn audio_forces_transcode(streams: &[(Option<&str>, bool)]) -> bool

Decide whether we must transcode regardless of what the server negotiated, given the source’s audio streams as (codec, is_default) in source order.

Advertising a narrow profile (video_audio_codecs) is necessary but not sufficient: Jellyfin 10.11.5 enforces a DirectPlayProfile’s container and video codec but ignores its audio codec — an E-AC-3 track is offered for direct play even when the profile lists only AAC, and neither a VideoAudio CodecProfile nor MaxAudioChannels changes that. So the client cannot delegate this decision; it knows what its own renderer can decode and must apply that itself.

The track that matters is the one the server will actually serve (see served_audio_codec). An unknown codec is left alone — forcing a transcode on a guess would burn server CPU for files that play.

TRACES: UR-004 | DR-149 | UT-148