#!/bin/bash
# Condense IP cam recording to motion segments using scene score time series
# Usage: ipcam-condense.sh input.mkv [threshold_mult] [gap_frames]
# threshold_mult: multiplier above median scene score (default 2)
# gap_frames: bridge gaps narrower than this many frames (default 10)
IN="$1"
MULT="${2:-3}"
GAPF="${3:-10}"
PAD=1
OUT="${IN%.*}_condensed.mkv"
TMP=$(mktemp -d)
trap "rm -rf $TMP" EXIT

# pass 1: extract scene score for every frame (~15s decode, no encode)
ffmpeg -i "$IN" -vf "select='gte(scene\,0)',metadata=print:file=$TMP/meta.txt" -an -f null /dev/null 2>/dev/null

# parse into timestamp,score pairs
grep -E 'pts_time|scene_score' "$TMP/meta.txt" | paste - - \
  | sed 's/.*pts_time://;s/\s*lavfi.scene_score=/,/' > "$TMP/scores.csv"

NFRAMES=$(wc -l < "$TMP/scores.csv")
if [ "$NFRAMES" -eq 0 ]; then
  echo "no frames in $IN"
  exit 1
fi

DUR=$(ffprobe -v error -show_entries format=duration -of csv=p=0 "$IN")
FPS=$(ffprobe -v error -select_streams v:0 -show_entries stream=r_frame_rate -of csv=p=0 "$IN")
# FPS is a fraction like 25/1
FPS_N=$(echo "$FPS" | cut -d/ -f1)
FPS_D=$(echo "$FPS" | cut -d/ -f2)

# pass 2: threshold, cluster, bridge gaps
awk -F, -v mult="$MULT" -v gapf="$GAPF" -v pad="$PAD" -v dur="$DUR" \
    -v fps_n="$FPS_N" -v fps_d="$FPS_D" '
NR == FNR {
  raw[NR] = $2 + 0
  times[NR] = $1 + 0
  next
}
FNR == 1 {
  n = NR - 1
  # convolution blur: moving average over kernel_r*2+1 frames
  kernel_r = int(fps_n / fps_d / 2)
  if (kernel_r < 1) kernel_r = 1
  for (i = 1; i <= n; i++) {
    sum = 0; cnt = 0
    lo = i - kernel_r; if (lo < 1) lo = 1
    hi = i + kernel_r; if (hi > n) hi = n
    for (j = lo; j <= hi; j++) { sum += raw[j]; cnt++ }
    scores[i] = sum / cnt
  }
  for (i = 1; i <= n; i++) ss[i] = scores[i]
  asort(ss)
  median = ss[int(n/2)]
  thresh = median * mult
  gap_sec = gapf * fps_d / fps_n
  printf "frames=%d blur=%d median=%.6f thresh=%.6f gap=%.2fs\n", n, kernel_r*2+1, median, thresh, gap_sec > "/dev/stderr"
}
{
  idx = FNR
  t = times[idx]
  sc = scores[idx]
  if (sc < thresh) next

  if (nc == 0 || t - ce[nc] > gap_sec) {
    nc++
    cs[nc] = t; ce[nc] = t
  } else {
    ce[nc] = t
  }
}
END {
  if (nc == 0) { print "no motion detected" > "/dev/stderr"; exit 1 }

  # apply padding and clamp
  kept = 0
  for (i = 1; i <= nc; i++) {
    s = cs[i] - pad; if (s < 0) s = 0
    e = ce[i] + pad; if (e > dur+0) e = dur+0
    kept++
    sh=int(s/3600); sm=int((s-sh*3600)/60); ss2=s-sh*3600-sm*60
    eh=int(e/3600); em=int((e-eh*3600)/60); es=e-eh*3600-em*60
    printf "%02d:%02d:%06.3f %02d:%02d:%06.3f\n", sh, sm, ss2, eh, em, es
  }
  printf "%d segments\n", kept > "/dev/stderr"
}' "$TMP/scores.csv" "$TMP/scores.csv" > "$TMP/segments.txt"

NSEG=$(wc -l < "$TMP/segments.txt")
if [ "$NSEG" -eq 0 ]; then
  echo "no motion segments in $IN"
  rm "$IN"
  echo "deleted $IN (no motion)"
  exit 0
fi

# pass 3: VAAPI encode each segment
i=0
while read -u 3 s e; do
  seg="$TMP/seg_$(printf '%04d' $i).mkv"
  ffmpeg -y -loglevel error -vaapi_device /dev/dri/renderD128 \
    -ss "$s" -to "$e" -i "$IN" \
    -vf "format=nv12,hwupload" -c:v h264_vaapi -qp 18 -an "$seg"
  echo "file '$seg'" >> "$TMP/concat.txt"
  i=$((i+1))
done 3< "$TMP/segments.txt"

# pass 4: concatenate
ffmpeg -y -loglevel error -f concat -safe 0 -i "$TMP/concat.txt" -c copy "$OUT"
echo "wrote $OUT ($(du -h "$OUT" | cut -f1))"
rm "$IN"
echo "deleted $IN"