Use ffmpeg apng muxer for radar loop

ImageMagick on Arch lacks the APNG png-writer; magick was silently
producing single-frame PNGs. Switch to ffmpeg's concat demuxer +
apng muxer, which gives proper animated APNG with per-frame
durations (last frame still gets END_PAUSE).

Add ffmpeg to the pacman install list in setup.sh.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

2 files changed, 16 insertions, 8 deletions

diff --git a/radarFetch.sh b/radarFetch.sh
index 0dcc457..4ba302c 100755
--- a/radarFetch.sh
+++ b/radarFetch.sh
@@ -30,6 +30,7 @@ require_cmd() {
 }
 require_cmd curl
 require_cmd magick
+require_cmd ffmpeg
 
 mkdir -p "$TRANS_DIR" "$FRAMES_DIR" "$PLATES_DIR" "$OUT_DIR"
 
@@ -167,22 +168,29 @@ if [ "${#composited[@]}" -eq 0 ]; then
     exit 0
 fi
 
-# --- 6. Assemble APNG loop -----------------------------------------------
-# Per-frame delays: last frame gets END_PAUSE so the eye can rest on "now".
+# --- 6. Assemble APNG loop via ffmpeg concat demuxer ---------------------
+# ImageMagick's PNG writer on Arch lacks APNG support; ffmpeg's apng muxer
+# handles it. Per-frame durations: last frame gets END_PAUSE.
 mkdir -p "$PUBLISH_DIR"
 TMP_APNG="${OUT_DIR}/loop.apng.tmp"
+LIST_FILE="${OUT_DIR}/concat.txt"
 
-build_cmd=(magick -loop 0)
+: > "$LIST_FILE"
 last_idx=$(( ${#composited[@]} - 1 ))
 for i in "${!composited[@]}"; do
+    printf "file '%s'\n" "${composited[$i]}" >> "$LIST_FILE"
     if [ "$i" -eq "$last_idx" ]; then
-        build_cmd+=(-delay "$END_PAUSE" "${composited[$i]}")
+        printf "duration %s\n" "$(awk "BEGIN{print $END_PAUSE/100}")" >> "$LIST_FILE"
     else
-        build_cmd+=(-delay "$FRAME_DELAY" "${composited[$i]}")
+        printf "duration %s\n" "$(awk "BEGIN{print $FRAME_DELAY/100}")" >> "$LIST_FILE"
     fi
 done
-build_cmd+=("$TMP_APNG")
-"${build_cmd[@]}"
+# ffmpeg concat quirk: last file must be repeated without a duration line
+printf "file '%s'\n" "${composited[$last_idx]}" >> "$LIST_FILE"
+
+ffmpeg -y -hide_banner -loglevel error \
+    -f concat -safe 0 -i "$LIST_FILE" \
+    -plays 0 -f apng "$TMP_APNG"
 
 install -m 644 "$TMP_APNG" "$PUBLISH_PATH"
 rm -f "$TMP_APNG"
diff --git a/setup.sh b/setup.sh
index 363a6fc..ae182bd 100755
--- a/setup.sh
+++ b/setup.sh
@@ -16,7 +16,7 @@ OWNER=st33v
 # Packages
 # ---------------------------------------------------------------------------
 echo "==> Installing required packages..."
-pacman -Sy --needed --noconfirm curl imagemagick ghostscript nginx
+pacman -Sy --needed --noconfirm curl imagemagick ghostscript ffmpeg nginx
 
 # ---------------------------------------------------------------------------
 # Nginx conflict checks