Fix ALSA hardware volume control being too sensitive#186
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maximmaxim345 merged 2 commits intomainfrom Mar 17, 2026
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…e curve Two changes to reduce excessive volume sensitivity: 1. ALSA volume: Add -M (mapped volume) flag to all amixer calls. Without this flag, amixer maps percentages linearly to the raw hardware range, which on DACs with wide dB ranges (e.g. HiFiBerry, USB interfaces) causes 90% to map to a much lower perceived loudness than expected. With -M, percentages map to perceptual loudness. 2. Software volume: Change the power curve from (v/100)^1.5 to linear (v/100). The protocol's delta-based group volume mechanism already adjusts player volumes proportionally, so the power curve compounds the reduction and makes low player volumes inaudible too quickly. https://claude.ai/code/session_01V1qvDy6hSsJtytm5PVeygU
The (v/100)^1.5 power curve is perceptually correct — restore it. The volume sensitivity issue is in the ALSA raw-percentage mapping, not the software volume path. https://claude.ai/code/session_01V1qvDy6hSsJtytm5PVeygU
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Pull request overview
Updates the ALSA volume backend to use amixer’s mapped-volume mode so that 0–100% volume values align with ALSA’s dB-mapped scaling, and adjusts tests to match the updated command invocations.
Changes:
- Add
-Mtoamixerinvocations used for playback capability probing, setting volume, and reading volume. - Update ALSA volume controller tests to assert the new
amixer -M ...argument order.
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.
| File | Description |
|---|---|
sendspin/alsa_volume.py |
Adds -M to amixer calls so volume set/get uses mapped percentage semantics. |
tests/test_alsa_volume.py |
Updates expected subprocess argument tuples to include -M for set/get flows. |
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Summary
-M(mapped volume) flag to allamixercalls in the ALSA volume controller-M,amixermaps percentages linearly to the raw hardware register range, which on DACs with wide dB ranges (e.g. HiFiBerry, USB interfaces) causes a given percentage to sound much quieter than expected-M, percentages use perceptual (dB-aware) mapping so that90%actually sounds like 90% loudness