wrapper: leading low hum to prime Discord (configurable MS/HZ/DB)

README.md

@@ -89,6 +89,10 @@ command environment (`VESKSLOP_TTS_VOX_CLEAN=1` omits the `\!wH1/\!wH0` stutter
 wrapper). Line-leading `/rate N` and `/pitch N` controls are also handled by the
 wrapper, so the WebUI does not need to implement them. See `docs/TTS-DESIGN.md`.
 
+A short low-level leading hum (80 ms, 75 Hz, -48 dBFS) primes Discord's audio pipeline
+so the first word is not gated; tune with `VESKSLOP_TTS_HUM_MS` (0 = off),
+`VESKSLOP_TTS_HUM_HZ`, and `VESKSLOP_TTS_HUM_DB`.
+
 ## Layout
 
 - `host/sapi4host.c` — host: voice select, pitch/speed, text -> WAV

docs/NOTES.md

@@ -66,6 +66,11 @@ without them.
   silence is retained, so it shapes silence, not speech. Measured head: first sample
   >30 at 22.6 ms, speech (>500) at 29.6 ms, natural ~15 ms attack; tail decays over
   ~18 ms. No click, no attenuation of the first word.
+- Leading hum (default on): 80 ms of 75 Hz at -48 dBFS peak before the engine padding,
+  to prime Discord's pipeline. Verified 75.0 Hz / -48.0 dBFS, speech onset ~110 ms,
+  final -18.6 LUFS / -3.0 dBFS, apply pass +~10 ms. `VESKSLOP_TTS_HUM_MS=0` disables and
+  reproduces the previous output byte-for-byte. Tuning: `_HUM_HZ` (30-200), `_HUM_DB`
+  (-80..-6; raise toward -36 if a client still gates the start).
 
 ## SAPI4 runtime engine discovery (`speech.dll`)
 

docs/TTS-DESIGN.md

@@ -234,6 +234,15 @@ record what the engine needs to interpret, add, or hide._
   Measured on a Keith Bell line: first sample >30 at 22.6 ms, speech (>500) at 29.6 ms,
   attack rising naturally over about 15 ms, tail decaying over about 18 ms. No click and
   no attenuation of the first word; Veskslop's 150 ms playback lead-in sits on top.
+- Leading hum (on by default): 80 ms of a 75 Hz sine at -48 dBFS peak is prepended
+  before the engine padding, to keep Discord's audio pipeline open so the first word is
+  not gated. Configurable: `VESKSLOP_TTS_HUM_MS` (0 disables), `_HUM_HZ` (30-200),
+  `_HUM_DB` (-80..-6). It sits about 45 dB under the speech peak; raise `_HUM_DB` toward
+  -36 if a client still gates the start, lower it for stealth. Generated in the same
+  ffmpeg pass (no extra process) and not part of the EBU measurement, so the documented
+  loudness/peak targets still hold. Measured: hum 75.0 Hz / -48.0 dBFS, speech onset at
+  about 110 ms, final -18.6 LUFS / -3.0 dBFS; `HUM_MS=0` reproduces the previous output
+  byte-for-byte.
 
 ### Voice IDs
 

setup/veskslop-tts.sh

@@ -20,6 +20,9 @@
 #                   VESKSLOP_TTS_WORD_GAP_MS  silence between words in ms (0-500)
 #                   VESKSLOP_TTS_VOX          1 = VOX prosody, NetTTS-style (Flextalk)
 #                   VESKSLOP_TTS_VOX_CLEAN    1 = VOX without the \!wH1/\!wH0 stutter
+#                   VESKSLOP_TTS_HUM_MS       leading low hum in ms, 0 = off (default 80)
+#                   VESKSLOP_TTS_HUM_HZ       hum frequency, 30-200 (default 75)
+#                   VESKSLOP_TTS_HUM_DB       hum peak level, -80..-6 (default -48)
 #
 # Output: 48 kHz mono s16le WAV, trimmed, faded, loudness-normalized.
 set -eu
@@ -52,6 +55,9 @@ WORDS=${VESKSLOP_TTS_WORDS:-0}
 WORD_GAP=${VESKSLOP_TTS_WORD_GAP_MS:-120}
 VOX=${VESKSLOP_TTS_VOX:-0}
 VOX_CLEAN=${VESKSLOP_TTS_VOX_CLEAN:-0}
+HUM_MS=${VESKSLOP_TTS_HUM_MS:-80}
+HUM_HZ=${VESKSLOP_TTS_HUM_HZ:-75}
+HUM_DB=${VESKSLOP_TTS_HUM_DB:--48}
 
 case "$VOICE" in
     sam)            ENGVOICE="Sam" ;;
@@ -377,7 +383,29 @@ else
 fi
 
 TMPOUT="$TMP/out.wav"
-if ! "$MICROSLOP_FFMPEG" -hide_banner -nostats -y -i "$RAW" -af "$PRE,volume=${GAIN}dB" \
+# Leading hum: a quiet low tone in the pre-speech padding, to prime Discord's
+# audio pipeline so the first syllable is not gated. Level/frequency/duration
+# are configurable; 0 ms disables it.
+case "$HUM_MS" in *[!0-9]*|"") HUM_MS=80 ;; esac
+[ "$HUM_MS" -gt 2000 ] && HUM_MS=2000
+case "$HUM_HZ" in *[!0-9.]*|"") HUM_HZ=75 ;; esac
+case "$HUM_DB" in *[!0-9.-]*|""|"."|"-") HUM_DB=-48 ;; esac
+if [ "$HUM_MS" -gt 0 ]; then
+    HUM_S=$(awk -v ms="$HUM_MS" 'BEGIN{printf "%.3f", ms/1000}')
+    HUM_HZ=$(awk -v v="$HUM_HZ" 'BEGIN{ if (v<30) v=30; if (v>200) v=200; printf "%.1f", v }')
+    HUM_DB=$(awk -v v="$HUM_DB" 'BEGIN{ if (v>-6) v=-6; if (v<-80) v=-80; printf "%.1f", v }')
+    HUM_AMP=$(awk -v db="$HUM_DB" 'BEGIN{printf "%.6f", 10^(db/20)}')
+    HUM_FADE=$(awk -v s="$HUM_S" 'BEGIN{ f=s/4; if (f>0.02) f=0.02; if (f<0.005) f=0.005; printf "%.3f", f }')
+    HUM_FADE_OUT=$(awk -v s="$HUM_S" -v f="$HUM_FADE" 'BEGIN{printf "%.3f", s-f}')
+    if ! "$MICROSLOP_FFMPEG" -hide_banner -nostats -y \
+            -f lavfi -i "aevalsrc=exprs='$HUM_AMP*sin(2*PI*$HUM_HZ*t)':s=48000:d=$HUM_S" \
+            -i "$RAW" \
+            -filter_complex "[0:a]afade=t=in:st=0:d=$HUM_FADE,afade=t=out:st=$HUM_FADE_OUT:d=$HUM_FADE,aformat=sample_fmts=s16:channel_layouts=mono:sample_rates=48000[h];[1:a]$PRE,volume=${GAIN}dB,aresample=48000,aformat=sample_fmts=s16:channel_layouts=mono[a];[h][a]concat=n=2:v=0:a=1[out]" \
+            -map "[out]" -c:a pcm_s16le "$TMPOUT" >/dev/null 2>"$TMP/ff"; then
+        head -c 400 "$TMP/ff" >&2
+        exit 1
+    fi
+elif ! "$MICROSLOP_FFMPEG" -hide_banner -nostats -y -i "$RAW" -af "$PRE,volume=${GAIN}dB" \
         -ar 48000 -ac 1 -c:a pcm_s16le "$TMPOUT" >/dev/null 2>"$TMP/ff"; then
     head -c 400 "$TMP/ff" >&2
     exit 1