#!/bin/bash
# C3 + C4: per-codec frame-0 byte-compare + frame-30s SSIM Y, both against SW reference.
set -u
OUT=$HOME/measurements/p3
mkdir -p $OUT
codecs=("h264:h264.mp4" "vp8:vp8.webm" "mpeg2:mpeg2.ts")
W=1280; H=720

for spec in "${codecs[@]}"; do
  codec=${spec%%:*}; ext=${spec#*:}
  cf=$HOME/measurements/encoded/bbb_60s_720p.${ext}
  log=$OUT/bitexact_${codec}
  > $log

  echo "=== $codec ===" | tee $log

  # Frame 0 SW
  ffmpeg -hide_banner -loglevel error -y -i "$cf" \
      -frames:v 1 -f rawvideo -pix_fmt yuv420p $OUT/sw_${codec}_f0.yuv </dev/null
  # Frame 0 HW
  LIBVA_DRIVER_NAME=v4l2_request ffmpeg -hide_banner -loglevel error -y \
      -hwaccel vaapi -hwaccel_output_format vaapi \
      -i "$cf" -vf "hwdownload,format=nv12,format=yuv420p" \
      -frames:v 1 -f rawvideo -pix_fmt yuv420p $OUT/hw_${codec}_f0.yuv </dev/null 2>/dev/null

  sz_sw=$(stat -c%s $OUT/sw_${codec}_f0.yuv 2>/dev/null || echo 0)
  sz_hw=$(stat -c%s $OUT/hw_${codec}_f0.yuv 2>/dev/null || echo 0)
  sha_sw=$(sha256sum $OUT/sw_${codec}_f0.yuv 2>/dev/null | cut -c1-16)
  sha_hw=$(sha256sum $OUT/hw_${codec}_f0.yuv 2>/dev/null | cut -c1-16)
  diff_bytes=$(cmp -l $OUT/sw_${codec}_f0.yuv $OUT/hw_${codec}_f0.yuv 2>/dev/null | wc -l)
  expected=$((W * H * 3 / 2))
  c3_status=$([ "$sw_sw" = "$sha_hw" ] || [ "$diff_bytes" = "0" ] && echo "byte-identical" || echo "diff=$diff_bytes")

  echo "  C3 frame-0:" | tee -a $log
  echo "    sw size=$sz_sw sha=$sha_sw" | tee -a $log
  echo "    hw size=$sz_hw sha=$sha_hw" | tee -a $log
  echo "    diff_bytes=$diff_bytes  expected_size=$expected" | tee -a $log
  if [ "$diff_bytes" = "0" ] && [ "$sz_sw" = "$expected" ]; then
    echo "    -> C3 PASS (byte-identical)" | tee -a $log
  else
    # Compute SSIM on frame 0 as fallback
    ssim_f0=$(ffmpeg -hide_banner -loglevel info -nostats \
        -s ${W}x${H} -pix_fmt yuv420p -i $OUT/hw_${codec}_f0.yuv \
        -s ${W}x${H} -pix_fmt yuv420p -i $OUT/sw_${codec}_f0.yuv \
        -lavfi "[0:v][1:v]ssim" -f null - 2>&1 | grep -oE "Y:[0-9.]+" | head -1)
    echo "    -> C3 byte diff present, frame-0 SSIM ${ssim_f0}" | tee -a $log
  fi

  # Frame 30s SW
  ffmpeg -hide_banner -loglevel error -y -i "$cf" \
      -vf "select=eq(n\,720)" -vsync 0 -frames:v 1 -f rawvideo -pix_fmt yuv420p $OUT/sw_${codec}_f720.yuv </dev/null
  # Frame 30s HW
  LIBVA_DRIVER_NAME=v4l2_request ffmpeg -hide_banner -loglevel error -y \
      -hwaccel vaapi -hwaccel_output_format vaapi \
      -i "$cf" -vf "hwdownload,format=nv12,format=yuv420p,select=eq(n\,720)" \
      -vsync 0 -frames:v 1 -f rawvideo -pix_fmt yuv420p $OUT/hw_${codec}_f720.yuv </dev/null 2>/dev/null

  diff720=$(cmp -l $OUT/sw_${codec}_f720.yuv $OUT/hw_${codec}_f720.yuv 2>/dev/null | wc -l)
  ssim=$(ffmpeg -hide_banner -loglevel info -nostats \
      -s ${W}x${H} -pix_fmt yuv420p -i $OUT/hw_${codec}_f720.yuv \
      -s ${W}x${H} -pix_fmt yuv420p -i $OUT/sw_${codec}_f720.yuv \
      -lavfi "[0:v][1:v]ssim" -f null - 2>&1 | grep -oE "[YUV All]:[0-9.()+ ]+" | tr "\n" " ")

  echo "  C4 frame-720 (t=30s):" | tee -a $log
  echo "    diff_bytes=$diff720  ssim: $ssim" | tee -a $log
done

echo "=== done $(date -Iseconds) ==="