Rockbox open source high quality audio player as a Music Player Daemon
mpris
rockbox
mpd
libadwaita
audio
rust
zig
deno
Increase PCM normalizer target and gain range
Set TARGET_RMS to 0.35 (-9 dBFS) for a louder, punchier target and
expand MAX_GAIN/MIN_GAIN to +20/-20 dB to better handle very quiet or
very loud material. Tweak RMS and gain attack/release constants to
reduce pumping while remaining responsive. Warm-start rms_estimate at
0.1 so initial chunks are boosted instead of over-corrected.
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firmware/pcm_normalizer.c
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firmware/pcm_normalizer.c
···
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* Very slow: prevents the "pumping" artefact during pauses
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* or quiet passages between tracks.
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*
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* MAX_GAIN Hard upper bound on the boost, +12 dB.
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* MAX_GAIN Hard upper bound on the boost, +18 dB.
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* Prevents amplifying near-silence to noise.
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*
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* MIN_GAIN Hard lower bound, -12 dB.
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* MIN_GAIN Hard lower bound, -18 dB.
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* Prevents crushing content that is louder than target.
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*
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* GATE_THRESH RMS below this level → chunk is silence; neither the RMS
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* estimate nor the gain are updated. -60 dBFS ≈ 0.001.
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* ──────────────────────────────────────────────────────────────────────────── */
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#define TARGET_RMS 0.0708f
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#define RMS_ATTACK 0.3f
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#define RMS_RELEASE 0.997f
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#define GAIN_ATTACK 0.3f
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#define GAIN_RELEASE 0.9995f
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#define MAX_GAIN 4.0f
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#define MIN_GAIN 0.25f
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#define TARGET_RMS 0.35f /* -9 dBFS — loud, punchy target */
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#define RMS_ATTACK 0.3f /* fast: track loud transients in ~2-3 chunks */
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#define RMS_RELEASE 0.99f /* ~7 s to settle on a quieter signal */
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#define GAIN_ATTACK 0.3f /* reduce gain quickly to prevent clipping */
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#define GAIN_RELEASE 0.98f /* ~3 s to raise gain — feels responsive without pumping */
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#define MAX_GAIN 10.0f /* +20 dB — handles very quiet classical / ambient */
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#define MIN_GAIN 0.1f /* -20 dB */
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#define GATE_THRESH 0.001f
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static bool normalizer_enabled = false;
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static float gain = 1.0f;
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static float rms_estimate = TARGET_RMS; /* warm-start avoids over-correction on first chunk */
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static float rms_estimate = 0.1f; /* warm-start below target → gain > 1 from the first chunk */
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void pcm_normalizer_enable(bool enable)
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{
···
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/* Reset state on each fresh enable so a stale gain from a previous
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* session doesn't immediately blast or mute the first chunk. */
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gain = 1.0f;
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rms_estimate = TARGET_RMS;
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rms_estimate = 0.1f;
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}
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normalizer_enabled = enable;
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}