Encoding: H.265 final montages, slow preset, sunrise retention

- sky-cam.conf: add ENCODE_PRESET=slow (applied to all encodes);
  split CRF_MONTAGE (intermediates, H.264) from CRF_MONTAGE_FINAL=22
  (archive montage, H.265); add SUNRISE_RETENTION_DAYS=10; improve
  CAPTURE_INTERVAL comment with storage/density table
- montage-mvt.sh: steps 1+2 use preset; step 3 final switches to
  libx265 + CRF_MONTAGE_FINAL + -tag:v hvc1 for broad compatibility
- 4-seasons.sh: both encode steps use ENCODE_PRESET
- daily_sunrise_video.sh: all encode steps use ENCODE_PRESET; rolling
  retention deletes sunrise videos older than SUNRISE_RETENTION_DAYS

https://claude.ai/code/session_01C4jbd3waXG3eKZYbGUjLUQ

sky-cam.conf

@@ -217,20 +217,28 @@ SUNRISE_TARGET_SECS=10
 SUNRISE_OVERLAY_ENABLED=true
 # Opacity of the sunrise-time text (0.0 = invisible, 1.0 = fully opaque).
 SUNRISE_OVERLAY_OPACITY=0.45
+# Delete daily sunrise videos older than this many days (rolling window).
+# Set 0 to keep forever.
+SUNRISE_RETENTION_DAYS=10
 
 # ── Video encoding quality ────────────────────────────────────────────────────
 # FFmpeg CRF: lower = higher quality / larger files.  Typical range 18–30.
 #   18 ≈ visually lossless     23 = ffmpeg default     28 = smaller/lower
-# Different scripts use different defaults by design — intermediate/draft
-# encodings use a higher CRF (smaller files, quality less critical), while
-# final "polished" outputs use a lower CRF for better quality.
-# Each is independent — changing one does NOT change the others.
+# H.265 (libx265) CRF is not directly comparable — H.265 CRF 22 ≈ H.264 CRF 26
+# in visual quality but ~40-50% smaller file.  Final montages use H.265;
+# intermediates (deleted after use) stay H.264.
 #
-CRF_SUNRISE=28        # daily_sunrise_video.sh   — daily Mattermost upload
-CRF_SEASONS_RAW=28    # 4-seasons.sh             — raw concat before speed-adjust
-CRF_SEASONS_FINAL=26  # 4-seasons.sh             — final daily clip (goes into montage)
-CRF_MONTAGE=26        # montage-mvt.sh           — concat and speed-adjust and final
-AUDIO_BITRATE=192k    # montage-mvt.sh           — music track on movement montages
+# ENCODE_PRESET: slow = better compression, same CRF quality, ~2× encode time.
+# Use 'medium' on slower machines, 'slow' or 'slower' on fast ones.
+# All encodes run at night so 'slow' is the right default.
+#
+CRF_SUNRISE=28           # daily_sunrise_video.sh   — daily Mattermost upload (H.264)
+CRF_SEASONS_RAW=28       # 4-seasons.sh             — raw concat before speed-adjust (H.264)
+CRF_SEASONS_FINAL=26     # 4-seasons.sh             — final daily clip (goes into montage) (H.264)
+CRF_MONTAGE=28           # montage-mvt.sh           — intermediate concat + sped steps (H.264)
+CRF_MONTAGE_FINAL=22     # montage-mvt.sh           — final archive montage (H.265)
+ENCODE_PRESET=slow       # ffmpeg preset for all encodes (slow/medium/fast)
+AUDIO_BITRATE=192k       # montage-mvt.sh           — music track on movement montages
 
 # ── Montage attribution overlay ───────────────────────────────────────────────
 # A translucent bar across the top of each movement montage, naming the
@@ -254,12 +262,15 @@ MONTAGE_ATTR_FADE=1    # attribution fade-in and fade-out length (seconds)
 # CAM_RTSP_<cam> goes in .env (see bottom of this file), not here.
 
 # Seconds between captured frames (applies to all cameras).
-# 10 = one frame every 10 s → 8640 frames/day → good timelapse density.
+# Lower = smoother timelapse + larger storage footprint:
+#   10 s →  8,640 frames/day ~2.5 GB/day     (default, good balance)
+#    5 s → 17,280 frames/day ~5 GB/day        (smoother motion)
+#    2 s → 43,200 frames/day ~12 GB/day       (very smooth, high storage)
+# CAPTURE_STALE_SECS should always be at least 2× CAPTURE_INTERVAL.
 CAPTURE_INTERVAL=10
 
 # Seconds without a new frame before the watchdog sends a stall notification.
-# Should be at least 2× CAPTURE_INTERVAL.  A recovery notification fires
-# automatically when frames start arriving again.
+# A recovery notification fires automatically when capture resumes.
 CAPTURE_STALE_SECS=30
 
 # ── Sunrise audio capture ──────────────────────────────────────────────────────