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alsa-lib 1.2.13⚓︎

alsa-lib is the userspace runtime library for ALSA. Besides libasound, the package also installs the shared ALSA configuration tree under /usr/share/alsa, which is essential for normal device discovery and PCM definitions on the target.

In the audio stack it is the common base for playback, capture, mixer access and AirPlay output.

Soft-float / FPU emulation⚓︎

Many FritzBox SoCs (e.g. GRX550 MIPS32) lack a hardware FPU. Floating-point
operations in audio processing (sample rate conversion, equalization) are
emulated in software, which overwhelms the CPU and causes stuttering.

The alsaequal ALSA equalizer plugin is disabled because it depends on heavy floating-point computation (IIR/EQ filtering via ladspa / caps) — software-emulated FPU makes it unusable.

By default, the build system sets:
- defaults.pcm.rate_converter linear (integer-only, no FPU, unacceptable audio quality)
- pcm.default pcm.plughw (bypasses ALSA mixer, uses hw-native rates)

Applications should be configured to use ALSA device hw:0,0 (direct
hardware access) instead of default (which may trigger resampling).

Rate converter quality notes⚓︎

The following rate converter plugins produce low audio quality and are
not recommended for music playback:

Plugin Alias / option Quality issue
linear --disable-resample in MPD Fastest but lowest quality; only 0th-order hold
lavcrate_faster ffmpeg soxr or lavc faster preset Heavy aliasing, audible artifacts
samplerate_order libsamplerate zero-order hold Same as linear, DC-like distortion
samplerate_linear libsamplerate linear interpolation Noticeable high-frequency roll-off and aliasing

For music, stick with hw:0,0 to avoid resampling entirely.

Also use an audio card supporting both native 44.1 and 48 kHz sampling frequencies (better with S16_LE and S24_3LE). A card only supporting 48000 Hz will require software resampling for 44100 Hz content.