feat(audio): CS43198 音量按 DS1039 数据手册定档 — 感知平方锥度映射(dB衰减=(1-pct)²×96dB, pct=0→真静音255)四路统一; SPEC_REF 补数据手册事实(PCM_VOLUME_A/B=0x0B/0x0C,DSD独立音量); DSD 模式记入 AUDIOD_DESIGN §13 后期规划。audiod 47/47 PASS

patch_v2/meow_audiod/meow_audiod.c

@@ -553,9 +553,10 @@ static int amixer_get(int numid, int card)
 
 static void dac_vol_set(int pct)
 {
-    int dac = 255 - pct * 255 / 100;   /* CS43198 寄存器=衰减量(0=最响 255=静音)，用户 pct 越大越响 → 反转映射 */
-    if (dac < 0) dac = 0;
-    if (dac > 255) dac = 255;
+    int t = 100 - pct, dac;
+	if (pct <= 0) dac = 255;                    /* 真静音（DS1039：255=-127.5dB） */
+	else dac = t * t * 192 / 10000;             /* 感知平方锥度：dB 衰减=(1-pct)^2×96dB */
+	if (dac > 255) dac = 255; if (dac < 0) dac = 0;  /* CS43198=衰减量(0最响255静音)+平方锥度(听感线性) */
     amixer_set(1, dac, 1);
     amixer_set(2, dac, 1);
     logmsg("DAC vol -> %d%% (L/R=%d)", pct, dac);