claude-video-analyze

claude-video-analyze — Video Analysis and Quality Assessment

All analysis operations are read-only and safe to auto-execute without confirmation.

Quick Info (Most Common)

Full metadata dump (resolution, codec, duration, bitrate, audio, chapters):

ffprobe -v error -print_format json -show_format -show_streams -show_chapters "$INPUT"

One-liner summary (human-readable):

ffprobe -v error -select_streams v:0 -show_entries stream=codec_name,width,height,r_frame_rate,bit_rate,pix_fmt \
  -show_entries format=duration,size,bit_rate,format_name -of default "$INPUT"

Specific Properties

Resolution:

ffprobe -v error -select_streams v:0 -show_entries stream=width,height -of csv=s=x:p=0 "$INPUT"

Duration (seconds):

ffprobe -v error -show_entries format=duration -of default=nw=1:nk=1 "$INPUT"

Codec:

ffprobe -v error -select_streams v:0 -show_entries stream=codec_name -of default=nw=1:nk=1 "$INPUT"

Framerate:

ffprobe -v error -select_streams v:0 -show_entries stream=r_frame_rate -of default=nw=1:nk=1 "$INPUT"

Bitrate (video stream):

ffprobe -v error -select_streams v:0 -show_entries stream=bit_rate -of default=nw=1:nk=1 "$INPUT"

Pixel format:

ffprobe -v error -select_streams v:0 -show_entries stream=pix_fmt -of default=nw=1:nk=1 "$INPUT"

Audio info:

ffprobe -v error -select_streams a -show_entries stream=codec_name,channels,sample_rate,bit_rate -of json "$INPUT"

HDR Detection

ffprobe -v quiet -select_streams v:0 -show_entries stream=color_transfer,color_primaries,color_space \
  -of default=nw=1 "$INPUT"

| color_transfer | Meaning | |---------------|---------| | smpte2084 | HDR10 / Dolby Vision | | arib-std-b67 | HLG | | bt709 | SDR | | Unknown/empty | Likely SDR |

Keyframe Analysis

List all keyframe timestamps:

ffprobe -v error -select_streams v:0 -skip_frame nokey \
  -show_entries frame=pkt_pts_time -of csv=p=0 "$INPUT"

Count keyframes:

ffprobe -v error -select_streams v:0 -skip_frame nokey \
  -show_entries frame=pkt_pts_time -of csv=p=0 "$INPUT" | wc -l

GOP structure (I/P/B frame distribution):

ffprobe -v error -select_streams v:0 -show_entries frame=pict_type -of csv=p=0 "$INPUT" | \
  sort | uniq -c | sort -rn

Scene Detection

FFmpeg native (fast, basic):

ffmpeg -i "$INPUT" -vf "scdet=s=1:t=14" -f null - 2>&1 | grep "lavfi.scd.time"

PySceneDetect (professional-grade, 5 algorithms):

# Adaptive detection (recommended for most content)
scenedetect -i "$INPUT" detect-adaptive -t 3.0 list-scenes

# Content-aware detection
scenedetect -i "$INPUT" detect-content -t 27.0 list-scenes

# Save scene images and split video
scenedetect -i "$INPUT" detect-adaptive -t 3.0 save-images split-video list-scenes

Audio Loudness Measurement

ffmpeg -i "$INPUT" -af loudnorm=I=-14:TP=-1.5:LRA=11:print_format=json -f null - 2>&1 | tail -12

Returns: input_i (integrated loudness), input_tp (true peak), input_lra (loudness range).

Quality Assessment

VMAF (Netflix perceptual quality, 0-100)

Compares distorted (encoded) vs reference (original):

ffmpeg -i distorted.mp4 -i reference.mp4 \
  -lavfi "libvmaf=model=version=vmaf_v0.6.1:log_fmt=json:log_path=vmaf_results.json" -f null -

| VMAF Score | Quality | |-----------|---------| | 93-100 | Excellent (indistinguishable from source) | | 80-93 | Good (minor artifacts visible on close inspection) | | 60-80 | Fair (noticeable quality loss) | | <60 | Poor |

SSIM and PSNR

# All three metrics at once
ffmpeg -i distorted.mp4 -i reference.mp4 \
  -lavfi "libvmaf=feature=name=psnr:feature=name=float_ssim:log_fmt=json:log_path=quality.json" -f null -

| Metric | Good | Excellent | |--------|------|-----------| | PSNR | >30 dB | >40 dB | | SSIM | >0.95 | >0.98 |

Optimal CRF Finder

Encode at multiple CRF values, measure VMAF for each, find the quality-size sweet spot:

for CRF in 18 20 22 24 26 28 30; do
  ffmpeg -y -i "$INPUT" -c:v libx264 -crf $CRF -preset medium "/tmp/crf_test_${CRF}.mp4"
  SIZE=$(stat -c%s "/tmp/crf_test_${CRF}.mp4")
  VMAF=$(ffmpeg -i "/tmp/crf_test_${CRF}.mp4" -i "$INPUT" \
    -lavfi "libvmaf=log_fmt=json:log_path=/tmp/vmaf_${CRF}.json" -f null - 2>&1 | \
    grep -oP 'VMAF score: \K[\d.]+')
  echo "CRF $CRF: ${SIZE} bytes, VMAF: $VMAF"
  rm -f "/tmp/crf_test_${CRF}.mp4" "/tmp/vmaf_${CRF}.json"
done

Bitrate Analysis

Average bitrate:

ffprobe -v error -show_entries format=bit_rate -of default=nw=1:nk=1 "$INPUT" | awk '{printf "%.1f Mbps\n", $1/1000000}'

Per-frame bitrate (for variable bitrate analysis):

ffprobe -v error -select_streams v:0 -show_entries packet=size,pts_time -of csv=p=0 "$INPUT" | head -100

Chapter Detection

ffprobe -v error -print_format json -show_chapters "$INPUT"

Generate Comprehensive Report

For a full video report, run all of the above and format the output. Key sections:

1. File info (name, size, container format)
2. Video stream (codec, resolution, framerate, bitrate, pixel format, HDR status)
3. Audio stream(s) (codec, channels, sample rate, bitrate, loudness)
4. Chapters (if present)
5. Keyframe structure (GOP length, keyframe interval)
6. Recommendations (codec efficiency, loudness compliance, compatibility issues)

Reference

Load references/analyze.md for VMAF/SSIM/PSNR quality metric details, scene detection parameters, and advanced FFprobe recipes.