123 lines
4.8 KiB
Bash
Executable File
123 lines
4.8 KiB
Bash
Executable File
#!/usr/bin/env bash
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# compare_snapshot.sh (robust v2)
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# Compare two MP4s by grabbing a snapshot at a given time and measuring SSIM/PSNR.
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#
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# Usage:
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# ./compare_snapshot.sh <file1.mp4> <file2.mp4> [time_seconds] [scale] [--verbose]
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# Examples:
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# ./compare_snapshot.sh A.mp4 B.mp4
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# ./compare_snapshot.sh A.mp4 B.mp4 12 320:-1 --verbose
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#
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# Exit codes: 0 = ran ok (doesn't imply "very close"), 2 = usage error, 3 = ffmpeg failure
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set -u # keep -e/-o pipefail off to avoid silent exits from grep/awk mismatches
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f1="${1:-}"; f2="${2:-}"
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t="${3:-12}"
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scale="${4:-320:-1}"
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verbose=0
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[[ "${5:-}" == "--verbose" ]] && verbose=1
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if [[ -z "${f1}" || -z "${f2}" ]]; then
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echo "Usage: $0 <file1.mp4> <file2.mp4> [time_seconds] [scale] [--verbose]" >&2
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exit 2
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fi
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for f in "$f1" "$f2"; do
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[[ -f "$f" ]] || { echo "Not found: $f" >&2; exit 2; }
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done
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tmpdir="$(mktemp -d)"
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trap 'rm -rf "$tmpdir"' EXIT
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shot1="$tmpdir/shot1.png"
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shot2="$tmpdir/shot2.png"
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log="$tmpdir/metrics.log"
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# Helper for verbose prints
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vprint() { [[ $verbose -eq 1 ]] && echo "[DBG]" "$@" >&2; }
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# 1) Extract frames (accurate seek: -ss after -i)
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# Use -y to avoid “file exists” issues, and format to a stable pixel format.
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cmd1=(ffmpeg -hide_banner -v error -y -i "$f1" -ss "$t" -frames:v 1 -vf "scale=$scale,format=yuv420p" "$shot1")
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cmd2=(ffmpeg -hide_banner -v error -y -i "$f2" -ss "$t" -frames:v 1 -vf "scale=$scale,format=yuv420p" "$shot2")
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vprint "${cmd1[@]}"
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"${cmd1[@]}" || { echo "Failed to extract snapshot from $f1 at ${t}s." >&2; exit 3; }
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vprint "${cmd2[@]}"
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"${cmd2[@]}" || { echo "Failed to extract snapshot from $f2 at ${t}s." >&2; exit 3; }
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# Sanity check: files exist and non-empty
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if [[ ! -s "$shot1" || ! -s "$shot2" ]]; then
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echo "Snapshot extraction produced empty files. Try a different time or scale." >&2
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[[ $verbose -eq 1 ]] && ls -l "$tmpdir" >&2
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exit 3
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fi
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# 2) Compare with SSIM (+ PSNR). Different ffmpeg builds print slightly different lines.
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# We send stderr to $log and parse multiple possible formats.
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cmp_cmd=(ffmpeg -hide_banner -v info -i "$shot1" -i "$shot2" -lavfi "ssim;[0:v][1:v]psnr" -f null -)
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vprint "${cmp_cmd[@]}"
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"${cmp_cmd[@]}" > /dev/null 2> "$log" || true
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# Try to parse SSIM "All:" first, fallback to Y channel, then average/mean lines.
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ssim_all="$(grep -Eo 'All:[0-9]+(\.[0-9]+)?' "$log" | head -n1 | cut -d: -f2 || true)"
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[[ -z "$ssim_all" ]] && ssim_all="$(grep -Eo 'SSIM [^ ]* All:[0-9]+(\.[0-9]+)?' "$log" | awk -F'All:' '{print $2}' | head -n1 || true)"
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[[ -z "$ssim_all" ]] && ssim_all="$(grep -Eo 'SSIM Y:[0-9]+(\.[0-9]+)?' "$log" | head -n1 | cut -d: -f2 || true)"
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# Parse PSNR average if present (may appear as "average:xx.xx" or "avg:xx.xx").
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psnr_all="$(grep -Eo 'average:[0-9]+(\.[0-9]+)?' "$log" | head -n1 | cut -d: -f2 || true)"
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[[ -z "$psnr_all" ]] && psnr_all="$(grep -Eo 'avg:[0-9]+(\.[0-9]+)?' "$log" | head -n1 | cut -d: -f2 || true)"
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# 3) Print summaries of the source files (optional but handy)
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summarize() {
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local f="$1"
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local dur vinfo fps w h vcodec rfr
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dur=$(ffprobe -v error -show_entries format=duration -of default=nw=1:nk=1 "$f" 2>/dev/null || echo "")
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vinfo=$(ffprobe -v error -select_streams v:0 -show_entries stream=codec_name,width,height,r_frame_rate -of csv=p=0 "$f" 2>/dev/null | head -n1)
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IFS=',' read -r vcodec w h rfr <<<"$vinfo"
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if [[ "$rfr" == */* ]]; then
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fps=$(awk -v r="$rfr" 'BEGIN{split(r,a,"/"); if(a[2]==0) print 0; else printf "%.3f", a[1]/a[2]}')
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else
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fps=$(awk -v r="$rfr" 'BEGIN{printf "%.3f", r+0}')
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fi
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printf " Duration: %.3fs | Video: %s, %sx%s @ %s fps\n" "${dur:-0}" "${vcodec:-?}" "${w:-?}" "${h:-?}" "${fps:-?}"
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}
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echo "Snapshot comparison at t=${t}s (scaled to ${scale}):"
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echo "File 1: $f1"; summarize "$f1"
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echo "File 2: $f2"; summarize "$f2"
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echo
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# 4) Handle cases where parsing failed
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if [[ -z "$ssim_all" && -z "$psnr_all" ]]; then
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echo "Could not parse SSIM/PSNR from ffmpeg output."
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[[ $verbose -eq 1 ]] && { echo "--- ffmpeg log ---"; cat "$log"; echo "-------------------"; }
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echo "Tips: try a different time (e.g. 5 or 30), or a different scale (e.g. 640:-1)."
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exit 0
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fi
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# 5) Report metrics and give a verdict
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printf "Metrics:\n"
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[[ -n "$ssim_all" ]] && printf " SSIM (All): %s (1.00 = identical)\n" "$ssim_all"
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[[ -n "$psnr_all" ]] && printf " PSNR avg: %s dB\n" "$psnr_all"
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echo
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# Verdict from SSIM (fallback to PSNR if SSIM missing)
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verdict="Different"
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if [[ -n "$ssim_all" ]]; then
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verdict=$(awk -v s="$ssim_all" 'BEGIN{
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if (s+0 >= 0.97) print "Very close (near-identical)";
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else if (s+0 >= 0.90) print "Close";
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else print "Different";
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}')
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elif [[ -n "$psnr_all" ]]; then
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verdict=$(awk -v p="$psnr_all" 'BEGIN{
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if (p+0 >= 40) print "Very close (near-identical)";
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else if (p+0 >= 30) print "Close";
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else print "Different";
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}')
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fi
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echo "Verdict: $verdict"
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# Optional: show where log is if verbose
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[[ $verbose -eq 1 ]] && { echo "(Log at: $log)"; }
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