allow dynamic metadata updates (from named pipe / fifo)

[Björn]

Summary of the bug:

I try to find a solution to update metadata in a generated HLS live audio stream dynamicaly.

I came up with this idea:

mkfifo /tmp/metadata.fifo

ffmpeg -i ​http://some.icecast.url:8000/broadcast -f ffmetadata -i /tmp/metadata.fifo -map_metadata 1 ...

echo "artist=Test" >> /tmp/metadata.fifo

but that doesn't work out beecho "artist=bla2fsa" >> /tmp/metadata.fifocause ffmpeg doesn't seem to read the names pipe after new data arrived there. Otherwise it would be a great solution to allow dynamic metadata updates. Do you see a way to allow ffmpeg to read from the fifo continouisly?

How to reproduce:

% ffmpeg -i input ... output

ffmpeg version 6.0.1 Copyright (c) 2000-2023 the FFmpeg developers
  built with gcc 12 (Debian 12.2.0-14)