#!/bin/bash
# C5: per-codec FPS at N=3 runs. Wall-time measurement, no output file written.
set -u
OUT=$HOME/measurements/p3
mkdir -p $OUT
codecs=("h264:h264.mp4" "vp8:vp8.webm" "mpeg2:mpeg2.ts")

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

  echo "=== $codec ===" | tee $log
  for run in 1 2 3; do
    t0=$(date +%s.%N)
    out=$(LIBVA_DRIVER_NAME=v4l2_request timeout 30 ffmpeg -hide_banner -benchmark -loglevel error \
        -hwaccel vaapi -hwaccel_output_format vaapi \
        -i "$cf" -vf "hwdownload,format=nv12" -f null - 2>&1 </dev/null)
    t1=$(date +%s.%N)
    el=$(awk "BEGIN { printf \"%.3f\", $t1-$t0 }")
    fps_calc=$(awk "BEGIN { printf \"%.2f\", 1440.0 / ($t1-$t0) }")
    fps_self=$(echo "$out" | grep -oE "fps=[ ]*[0-9.]+" | tail -1 | awk -F= "{print \$2}" | tr -d " ")
    frames=$(echo "$out" | grep -oE "frame=[ ]*[0-9]+" | tail -1 | awk -F= "{print \$2}" | tr -d " ")
    bench=$(echo "$out" | grep "^bench:" | tail -1)
    echo "  run $run: elapsed=${el}s fps_calc=$fps_calc fps_self=$fps_self frames=$frames" | tee -a $log
    [ -n "$bench" ] && echo "    $bench" | tee -a $log
  done

  # Compute mean and stddev
  awk '/^  run/ { gsub("elapsed=","",$3); gsub("s","",$3); el[NR]=$3; sum+=$3; n++ }
       END {
         if (n>0) {
           mean=sum/n
           for (i in el) ss += (el[i]-mean)^2
           sd=sqrt(ss/n)
           printf "  N=%d mean=%.3fs sigma=%.3fs  fps=%.2f±%.2f\n", n, mean, sd, 1440/mean, 1440*sd/(mean*mean)
         }
       }' $log | tee -a $log
done

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