Keep the TTS echo at unity gain so the level drives the repeats

microslopsam/docs/TTS-DESIGN.md

@@ -665,7 +665,7 @@ Inputs: `{out}`, `{text_file}`, optional positional voice/speed/pitch/expression
 | --- | --- |
 | `VESKSLOP_TTS_PROFILE` | `pitch:27:...`/`key=value,...` overrides; the wrapper writes the full profile (defaults + overrides) to the Wine registry with `wine reg import` before every synthesis. |
 | `VESKSLOP_TTS_HIGHPASS` | High-pass Hz, 40-400 (default 40). |
-| `VESKSLOP_TTS_ECHO` | Mono echo 0-100 (`aecho`), default 0. |
+| `VESKSLOP_TTS_ECHO` | Mono echo 0-100 (`aecho`), default 0. The echo is mixed under the dry voice, so the voice level does not change. |
 | `VESKSLOP_TTS_WORDS` / `VESKSLOP_TTS_WORD_GAP_MS` | Word-by-word synthesis with silence gaps (Flextalk only). |
 
 Placeholders `{profile}`, `{highpass}`, `{echo}`, `{words}`, `{word_gap_ms}` mirror the env vars.

microslopsam/setup/veskslop-tts.sh

@@ -17,7 +17,8 @@
 #                   VESKSLOP_TTS_HIGHPASS     high-pass Hz (40-400, default 40)
 #                   VESKSLOP_TTS_ECHO         mono echo amount 0-100 (default 0)
 #                   VESKSLOP_TTS_ECHO_DELAY_MS  echo delay 10-400 (default 60)
-#                   VESKSLOP_TTS_ECHO_LEVEL   echo output gain 0-0.95 (default 0.85)
+#                   VESKSLOP_TTS_ECHO_LEVEL   echo repeat level 0-0.95, relative to the
+#                                             dry voice (default 0.85)
 #                   VESKSLOP_TTS_CRUNCH       off | hl90 | hl90hq | telephone | adpcm | crush
 #                                             (1990s lossy character, applied last)
 #                   VESKSLOP_TTS_CRUNCH_BITS  1-16, overrides the preset bit depth
@@ -495,9 +496,18 @@ ECHO_LEVEL=$(awk -v v="$ECHO_LEVEL" 'BEGIN{ if (v<0) v=0; if (v>0.95) v=0.95; pr
 
 SIL="silenceremove=start_periods=1:start_duration=0.05:start_silence=0.03:start_threshold=-50dB"
 PRE="highpass=f=$HIGHPASS,$SIL,afade=t=in:st=0:d=0.008,areverse,$SIL,afade=t=in:st=0:d=0.008,areverse"
+# aecho's in_gain/out_gain scale the dry signal as well, so a low ECHO_LEVEL used to
+# quiet the whole line (and the streaming path, which skips the loudness measurement,
+# had nothing to make it up). Keep both gains at unity and let the repeats' decay carry
+# the level; the limiter absorbs the summed peaks.
 if [ "$ECHO" -gt 0 ]; then
-    DECAY=$(awk -v e="$ECHO" 'BEGIN{printf "%.2f", 0.2 + e * 0.006}')
-    PRE="$PRE,aecho=0.8:${ECHO_LEVEL}:${ECHO_DELAY}:${DECAY}"
+    DECAY=$(awk -v e="$ECHO" -v l="$ECHO_LEVEL" 'BEGIN{
+        d = (0.2 + e * 0.006) * (l / 0.85);
+        if (d < 0.02) d = 0.02;
+        if (d > 0.95) d = 0.95;
+        printf "%.2f", d
+    }')
+    PRE="$PRE,aecho=1:1:${ECHO_DELAY}:${DECAY},alimiter=limit=0.98:level=disabled"
 fi
 
 # Compression stage ("crunch"): the lossy 1990s codec character, built as its own