Monorepo for Aesthetic.Computer
aesthetic.computer
native: inject ±1 LSB dither to prevent SOF silence-detect amp shutdown
The SOF DSP's internal silence detector powers down the SSP1 BE DAI
after ~20-40s of all-zero frames, which drops MAX98360A sdmode to 0
(speaker amp off, never comes back). sysfs power/control override
failed on this platform ("Could not set runtime-PM: …/power/control").
Inject ±1 LSB alternating dither into every otherwise-zero sample.
At S16_LE this is -96 dBFS — utterly inaudible even at max volume —
but it keeps non-zero data flowing through the PGA/DAI so the
pipeline stays active and the amp stays powered.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
+12
+12
fedac/native/src/audio.c
+12
fedac/native/src/audio.c
···
1489
1489
buffer[i * 2] = (int16_t)(mix_l * 26000);
1490
1490
buffer[i * 2 + 1] = (int16_t)(mix_r * 26000);
1491
1491
1492
+
/* DAPM keepalive: inject ±1 LSB dither when the buffer
1493
+
* would otherwise be pure zeros. SOF DSP's internal
1494
+
* silence detector powers down the SSP1 BE DAI after
1495
+
* ~20-40s of all-zero frames, which drops MAX98360A
1496
+
* sdmode to 0 (speaker amp off). ±1 at 16-bit S16_LE
1497
+
* is -96 dBFS — utterly inaudible, but keeps the
1498
+
* pipeline alive and the amp powered. */
1499
+
if (buffer[i * 2] == 0 && buffer[i * 2 + 1] == 0) {
1500
+
buffer[i * 2] = (i & 1) ? 1 : -1;
1501
+
buffer[i * 2 + 1] = (i & 1) ? -1 : 1;
1502
+
}
1503
+
1492
1504
// HDMI audio: 1-pole low-pass filter + downsample
1493
1505
// (volume already applied above to mix_l/mix_r)
1494
1506
if (audio->hdmi_pcm) {