add a script

scripts/mkv-to-webm

@@ -0,0 +1,21 @@
+#!/usr/bin/env bash
+
+F="${1:?need arg1 to be set to input .mkv}"
+OUT="${1%.mkv}.webm"
+LOGBASE="${OUT}.passlog"
+
+# Pass 1: video only, stats only
+ffmpeg -y \
+  -i "$F" \
+  -map 0:v:0 \
+  -c:v libsvtav1 -preset 5 -crf 30 -g 240 -pix_fmt yuv420p \
+  -an -pass 1 -passlogfile "$LOGBASE" -f webm /dev/null
+
+# Pass 2: video + copy Opus audio
+ffmpeg \
+  -i "$F" \
+  -map 0:v:0 -map 0:a:0 \
+  -c:v libsvtav1 -preset 5 -crf 30 -g 240 -pix_fmt yuv420p \
+  -c:a copy \
+  -pass 2 -passlogfile "$LOGBASE" \
+  "$OUT"