Volume is set to 100% at start op play of mp3 file when replay_gain_handler is set to mixer

[janui]

Volume is set to 100% at start op play of mp3 file when replay_gain_handler is set to mixer

[MaxKellermann]

The volume should not be changed

No, this is wrong. A mp3 file should not play at the same volume level as the previous song - this would imply that a mp3 song will play at different volume levels, depending on which song precedes it.

If you rely solely on the volume adjustments in the MP3 header, that's fine - but from MPD's perspective, that's a song without ReplayGain information, and that's correct.

Maybe what you need to do is configure a replaygain_missing_preamp. Unfortunately, the guy who submitted this feature many years ago didn't document it. I'll add documentation for it to the user manual, and that will resolve your issue.

[janui]

Dear Max,

Thanks for your answer. However, your answer still does not explain why the MPD volume level jumps from its preset level to 100% when a mp3 file is played.

MPD seems to be forgetting its reference volume level. It appears that when replay_gain_handler is set to mixer and replay_gain is enabled MPD assumes that volume control is disabled (or set at 100%).
This is not consistent with the processing of replay_gain when replay_gain_handler is not set. In this case the preset volume level is maintained.