Fix -w volume script: shared helper, correct dB mapping, skip on power-off#1
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mr-manuel merged 1 commit intoMay 6, 2026
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Adds a -w <script> option that invokes an executable script whenever LMS sends a volume command (AUDG packet). The script receives a single integer argument 0-100 mapped from the LMS dB range (-72..0 dB) using the same linear scale that the ALSA mixer path already uses. When -w is active the internal software gain is held at unity (FIXED_ONE) so the script has full control over output level. The shared helper call_volume_script() is placed in output.c (always compiled) to avoid duplicating the mapping arithmetic across the ALSA, PortAudio and PulseAudio backends. On POSIX the script is launched asynchronously via a shell "&" so the audio thread is not blocked; on Windows "start /B" is used instead. -w is mutually exclusive with -V (ALSA hardware volume control).
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Following up on your comment in ralph-irving#258.
This fixes three issues in the current
-wimplementation and refactors the code to avoid duplication across backends.Changes
Shared helper in output.c — replaces the ~40-line inline block copy-pasted into
output_alsa.candoutput_pa.cwith a singlecall_volume_script()function. All three backends (ALSA, PortAudio, PulseAudio) call it with one line.Correct dB floor — the hardcoded
dB_min = -49.510895causedvol=0for any LMS volume at or below ~16%, as reported by allmazz in the PR comments. The fix mirrors the floor that ALSA's own mixer path uses:MINVOL_DB = 72, giving a -72..0 dB range mapped linearly to 0-100.Skip script on power-off —
call_volume_script()returns immediately whenoutput.state == OUTPUT_OFF. This prevents LMS's fade-to-off AUDG sequence from reaching the script and muting external hardware (e.g. a miniDSP whose master gain affects all inputs including sources other than squeezelite).Consistent async on all backends — PulseAudio previously ran the script synchronously (blocking the audio thread). Now all POSIX backends launch with
&; Windows usesstart /B.Man page —
-wdocumented indoc/squeezelite.1.