Jellyfin's MediaStream.Index is global across every stream in a media
source, so index 0 is the video stream on virtually all files. We sent
AudioStreamIndex=0 as "the first audio track" on the HLS transcode URL,
the background audio-only handoff URL, the direct-play fallback URL and
the PlaybackInfo negotiation body — asking the server to use the video
stream as audio. Servers that honour it produce a picture with no sound;
only those that silently correct the index hid the bug, which is why it
surfaced as "some videos have no audio".
Omit the parameter unless a track was actually chosen, so the server
resolves the source's DefaultAudioStreamIndex. An explicit selection from
player_switch_audio_track still passes through unchanged. Dropped
outright from the static=true direct-play URL, which serves the original
file untouched.
dtourolle
db520c6551