Peppy: guard the meter against native DSD (temporary, until alsa-lib is fixed)#779
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Peppy: guard the meter against native DSD (temporary, until alsa-lib is fixed)#779Gjuju wants to merge 1 commit into
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…s fixed) Since the softvol control binds to the hardware mixer element, the Peppy chain is transparent on hardware-volume DACs. Correct - but it exposes a latent alsa-lib defect: the meter's s16 scope has no DSD conversion and aborts the caller (pcm_meter.c:1222), killing MPD whenever Peppy is enabled with a DSD-capable DAC, hardware volume, dop "no" and a DSD file. Before that fix the stray softvol refused DSD by accident, so MPD always converted upstream and the bug never fired. Restore that behaviour deliberately: a unity route above the meter only negotiates linear PCM, so native DSD is refused and MPD falls back to dsd2pcm. Unity gain, no control created, bit-transparent for PCM, DoP markers pass unharmed. Remove when a meter-fixed alsa-lib ships. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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Since #769 the Peppy chain is transparent on hardware-volume DACs — which is correct, but exposes a latent alsa-lib defect: type meter's s16 scope has no DSD conversion and aborts the caller (pcm_meter.c:1222), killing MPD on Peppy + DSD-capable DAC + hardware volume + dop "no" + a DSD file. Before #769 the stray softvol refused DSD by accident, so MPD always converted and the bug never fired.
This adds a unity route above the meter that restores exactly that behaviour, deliberately: native DSD is refused at negotiation, MPD falls back to dsd2pcm, the meter reads PCM. Unity gain, no control created (no double attenuation), bit-transparent for PCM, and DoP passes unharmed (markers verified intact below the route). Transparent to users — nothing to enable.
Validated on a fresh Pi 3B (stock 10.3.1 develop, stock alsa-lib/peppy-alsa): the crash config plays S32_LE @352800 with live needles, 0 aborts; DoP unaffected.
Temporary by design: revert when a meter-fixed alsa-lib ships (moode-player/pkgbuild#24, or upstream alsa-project/alsa-lib#516/#517 reaching a base OS). Existing installs would need the postinstall to lay the updated file.