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I'm running a fresh Debian sid / KDE with Pulseaudio and the VLC/Phonon backend (default).

When I play a (16 bits) mp3 file with most of my players (VLC/cVLC, SMplayer, Juk, etc), the Pulseaudio manager paman states a f32l (32 bits) stream. The sink itself is 16 bits.

When I play the same file with mplayer in xterm, the stream is in the correct sample type (16 bits). Same with Spotify.

VLC throws a mysterious

mpgatofixed32 audio converter debug: mpga->f32l

But I can't dig useful information from it. Nothing relates to this in VLC configuration.

I suspect the VLC Phonon backend, but it has no kind of configuration. I tried with the Gstreamer backend but no luck.

I've checked /usr/bin/start-pulseaudio-kde but nothing related. I've greped fl32 and float32 in ~ and /etc but nothing.

My /etc/pulse/daemon.conf has

default-sample-format = s16le

Output of /etc/asound.conf :

pcm.!default {
  type pulse
}
ctl.!default {
  type pulse
}
defaults.pcm.dmix.!rate 44100
defaults.pcm.!rate_converter "samplerate_best"

But it's the same with or without it.

Does it come from the mp3 codecs ? Is it possible to configure them ? It's hard to find information on playback configuration.

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I finally got more details with a

lsof -c vlc 

which pointed me to

/usr/lib/vlc/plugins/audio_filter/libmpgatofixed32_plugin.so 

which seems to stupidly convert everything to 32 bits. Erasing the plugin makes the playback in 16 bits again.

Just so you know sampletypes above 16 bits are not only useless (no one can hear it) but also harmful, see : http://people.xiph.org/~xiphmont/demo/neil-young.html

I just don't understand why this is the default behavior.

SMPlayer is still impacted though, pretty sure it uses the same kind of plugin.

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