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Enable ALSA software resampling for hw: devices 

Use snd_pcm_hw_params_set_rate_resample(1) to enable ALSA's rate plugin,
which provides software resampling even with hw: device interface.

This fixes audio distortion when HDMI sources output non-48kHz rates
(e.g., 44.1kHz from SBCs). ALSA now automatically resamples any input
rate to the configured 48kHz that Opus expects.

The rate plugin is available because ALSA is compiled with
--with-pcm-plugins=rate in install_audio_deps.sh
This commit is contained in:
Alex P 2025-11-21 00:28:35 +02:00
parent 3cd5bdd16c
commit 3ed663b4d1
1 changed files with 4 additions and 14 deletions
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18
internal/audio/c/audio.c
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@ -376,21 +376,11 @@ static int configure_alsa_device(snd_pcm_t *handle, const char *device_name, uin
err = snd_pcm_hw_params_set_channels(handle, params, num_channels);
if (err < 0) return err;
// Force exact rate for Opus compatibility (ALSA resamples if hardware differs)
err = snd_pcm_hw_params_set_rate_resample(handle, params, 1);
if (err < 0) return err;
err = snd_pcm_hw_params_set_rate(handle, params, sample_rate, 0);
if (err < 0) {
fprintf(stderr, "WARNING: %s: Failed to set %u Hz: %s, falling back to nearest\n",
device_name, sample_rate, snd_strerror(err));
fflush(stderr);
unsigned int actual_rate = sample_rate;
err = snd_pcm_hw_params_set_rate_near(handle, params, &actual_rate, 0);
if (err < 0) return err;
fprintf(stderr, "WARNING: %s: Using %u Hz (Opus may fail if non-standard)\n",
device_name, actual_rate);
fflush(stderr);
}
if (err < 0) return err;
uint16_t actual_frame_size = frame_size;