Ffmpeg Probe

Ffmpeg Probe

Context: $ARGUMENTS

Quick start

• Everything, JSON: ffprobe -v error -show_format -show_streams -of json in.mp4 → Step 1
• Single field (duration / fps / resolution / codec): → Step 3, one-liners
• Keyframes / chapters / metadata: → Step 1 (pick section)
• HDR detection: → Step 3, HDR recipe
• Python helper w/ subcommands: uv run ${CLAUDE_SKILL_DIR}/scripts/probe.py summary --input in.mp4

When to use

• User says "inspect", "what codec is this", "how long", "what resolution", "is it HDR", "get the bitrate", "dump metadata", "list tracks".
• You need machine-readable media info for a downstream step (e.g. before transcoding, cutting, or streaming).
• For playback/preview use ffmpeg-playback; for transcoding use ffmpeg-transcode; for raw extradata/bitstream inspection use ffmpeg-bitstream.

Step 1 — Pick what to dump

ffprobe organises output into sections. Combine as many -show_* flags as needed:

For -show_frames / -show_packets, always combine with either -select_streams and/or -read_intervals to bound the output:

ffprobe -v error -select_streams v:0 -read_intervals "%+#20" -show_frames -of json in.mp4
# reads the first 20 packets of v:0 (the `%+#N` form = first N packets)

Step 2 — Pick output format

Rule of thumb: json for automation, default=…nokey=1 for shell one-liners, csv when you want to paste into a sheet.

Step 3 — Run it (recipes)

Full dump, JSON (the default starting point):

ffprobe -v error -show_format -show_streams -of json in.mp4

Duration in seconds (float):

ffprobe -v error -show_entries format=duration \
  -of default=noprint_wrappers=1:nokey=1 in.mp4

Resolution as 1920x1080:

ffprobe -v error -select_streams v:0 \
  -show_entries stream=width,height -of csv=s=x:p=0 in.mp4

FPS as a fraction (30000/1001, 25/1, …):

ffprobe -v error -select_streams v:0 \
  -show_entries stream=r_frame_rate \
  -of default=nokey=1:noprint_wrappers=1 in.mp4

Parse the fraction yourself — it is not a float. See Gotchas.

Codec name (video / audio):

ffprobe -v error -select_streams v:0 -show_entries stream=codec_name \
  -of default=nokey=1:noprint_wrappers=1 in.mp4
ffprobe -v error -select_streams a:0 -show_entries stream=codec_name \
  -of default=nokey=1:noprint_wrappers=1 in.mp4

Bitrate (stream level first, then container fallback):

ffprobe -v error -select_streams v:0 -show_entries stream=bit_rate \
  -of default=nokey=1:noprint_wrappers=1 in.mp4
# fallback if "N/A":
ffprobe -v error -show_entries format=bit_rate \
  -of default=nokey=1:noprint_wrappers=1 in.mp4

Audio channel layout / channel count / sample rate:

ffprobe -v error -select_streams a:0 \
  -show_entries stream=channel_layout,channels,sample_rate \
  -of default=noprint_wrappers=1 in.mp4

Color info (for HDR / BT.2020 / BT.709 classification):

ffprobe -v error -select_streams v:0 \
  -show_entries stream=color_space,color_primaries,color_transfer,color_range,pix_fmt \
  -of json in.mp4

HDR detection (full recipe):

ffprobe -v error -select_streams v:0 \
  -show_entries stream=color_transfer,color_primaries,color_space:stream_side_data_list \
  -of json in.mp4

Classify:

• color_transfer=smpte2084 + color_primaries=bt2020 → HDR10 (also check mastering_display_metadata / content_light_level in side_data_list for HDR10).
• color_transfer=arib-std-b67 → HLG.
• side_data_type="DOVI configuration record" → Dolby Vision.
• Otherwise → SDR (usually bt709).

Frame count (exact — SLOW, decodes whole stream):

ffprobe -v error -count_frames -select_streams v:0 \
  -show_entries stream=nb_read_frames -of csv=p=0 in.mp4

Prefer the fast path first:

ffprobe -v error -select_streams v:0 -show_entries stream=nb_frames \
  -of default=nokey=1:noprint_wrappers=1 in.mp4
# "N/A" → fall back to -count_frames, or compute duration * fps.

Keyframe timestamps:

ffprobe -v error -select_streams v:0 -show_frames \
  -show_entries frame=pkt_pts_time,pict_type \
  -of csv=p=0 in.mp4 | awk -F, '$2=="I" {print $1}'

All packets (use intervals — raw -show_packets is huge):

ffprobe -v error -select_streams v:0 -read_intervals "10%+30" \
  -show_packets -of json in.mp4
# reads 30 seconds starting 10% into the file

Chapters:

ffprobe -v error -show_chapters -of json in.mkv

Metadata tags (format + per-stream):

ffprobe -v error -show_entries format_tags:stream_tags -of json in.mp4

Available scripts

• scripts/probe.py — stdlib-only wrapper. Subcommands:
  • summary --input I — human-readable container / V / A summary.
  • json --input I — full -show_format -show_streams JSON to stdout.
  • field --input I --query KEY — dotted path: format.duration, stream.v.width, stream.v.fps, stream.a.channels, …
  • keyframes --input I — keyframe PTS times, one per line.
  • hdr --input I — prints one of SDR, HDR10, HLG, DolbyVision.
  • compare --inputs A.mp4 B.mp4 — side-by-side field diff.
  • Every subcommand supports --verbose and --dry-run (prints the underlying ffprobe command instead of executing).

Workflow

# Quick human summary:
uv run ${CLAUDE_SKILL_DIR}/scripts/probe.py summary --input in.mp4

# One field for a shell variable:
FPS=$(uv run ${CLAUDE_SKILL_DIR}/scripts/probe.py field --input in.mp4 --query stream.v.fps)

# HDR class:
uv run ${CLAUDE_SKILL_DIR}/scripts/probe.py hdr --input in.mp4

Reference docs

• Read references/queries.md for the full -show_entries field table, stream-specifier syntax, output-format cheat sheet, an HDR detection flowchart, timebase math, and a 30+ one-liner library.

Gotchas

• r_frame_rate is a FRACTION (30000/1001, 24000/1001, 25/1), not a float. Always parse num/den. probe.py does this; raw shell consumers must too.
• avg_frame_rate ≠ r_frame_rate on VFR content. r_frame_rate is the lowest framerate that exactly describes every timestamp (effectively "base" rate); avg_frame_rate = total frames / duration. For CFR they match; for VFR use avg_frame_rate for "how many FPS on average", r_frame_rate for "what does each timestamp snap to".
• -count_frames decodes the whole stream. Slow on long videos. Prefer stream=nb_frames first; most MP4/MOV muxers write it. MKV usually does not.
• bit_rate at stream level is often N/A for streams inside MKV/WebM and some fragmented MP4s. Fall back to format.bit_rate, or compute file_size * 8 / duration.
• Use -v error to silence stderr noise when piping (otherwise ffprobe prints banner + build info to stderr and callers assume it failed).
• Stream specifier v:0 picks the first video stream — after -select_streams, the remaining stream's original index is still in its JSON, but counting positions in the filtered output is different. Always identify streams by index, not by position.
• Packet/frame timestamps are in timebase units. Seconds = pts * time_base.num / time_base.den. ffprobe exposes *_time convenience fields (pkt_pts_time, best_effort_timestamp_time) already in seconds — prefer those.
• -read_intervals "10%+30" = start at 10% of duration, read 30 seconds. "%+#20" = from start, 20 packets. Great for sampling huge files without dumping gigabytes of JSON.
• side_data_list (a.k.a. -show_entries stream_side_data_list) is where HDR10 mastering display, content light level, Dolby Vision config, and stereoscopic 3D layout live. Not in the main stream dict.
• Raw files (headerless YUV/PCM) need explicit demuxer hints: ffprobe -f rawvideo -video_size 1920x1080 -pix_fmt yuv420p -framerate 24 in.yuv.
• -show_entries section syntax uses : between sections, , between fields: -show_entries format=duration:stream=codec_name,bit_rate.
• -of json is nested: {"streams":[{...}], "format":{...}}. Flatten with jq or -of flat if you need grep-friendly output.
• "N/A" is a literal string, not null — parsers must coerce.
• -hide_banner is implied when -v error is set, but set both to be safe across ffmpeg versions.

Examples

Example 1: "What's the resolution and fps of this mp4?"

ffprobe -v error -select_streams v:0 \
  -show_entries stream=width,height,r_frame_rate \
  -of csv=p=0 in.mp4
# -> 1920,1080,30000/1001

Example 2: "Is this file HDR?"

uv run ${CLAUDE_SKILL_DIR}/scripts/probe.py hdr --input in.mp4
# -> HDR10

Example 3: "Get duration in seconds into a shell variable"

DUR=$(ffprobe -v error -show_entries format=duration \
  -of default=noprint_wrappers=1:nokey=1 in.mp4)
echo "$DUR"    # 128.458667

Example 4: "Dump all keyframe timestamps to a file"

ffprobe -v error -select_streams v:0 -show_frames \
  -show_entries frame=pkt_pts_time,pict_type \
  -of csv=p=0 in.mp4 | awk -F, '$2=="I"{print $1}' > keyframes.txt

Example 5: "Compare two encodes"

uv run ${CLAUDE_SKILL_DIR}/scripts/probe.py compare --inputs orig.mp4 encoded.mp4

Troubleshooting

Error: Invalid data found when processing input

Cause: file is truncated, or container is wrong (e.g. .mp4 is actually a .ts). Solution: try ffprobe -v error -show_format file (no -show_streams) to see the detected format_name. If it's mpegts, treat as .ts. If ffprobe still fails, the file is likely corrupt — try ffmpeg -err_detect ignore_err -i ….

bit_rate=N/A on every stream

Cause: muxer didn't write per-stream bitrate (common in MKV, WebM, fragmented MP4). Solution: use format.bit_rate, or compute size_bytes * 8 / duration_seconds from -show_entries format=size,duration.

r_frame_rate=0/0

Cause: codec/container has no concept of a frame rate (image, some audio-only containers probed for a non-existent video stream). Solution: guard against num==0 || den==0 in parsers; skip fps reporting.

nb_frames=N/A but I need an exact count

Cause: muxer doesn't store it. Solution: either compute duration * avg_frame_rate (approximate, fine for CFR) or use -count_frames (slow, exact).

Output is truncated / stops mid-JSON

Cause: you hit a pipe or buffer limit dumping -show_frames / -show_packets on a long file. Solution: always scope with -select_streams + -read_intervals; stream JSON to a file with > rather than piping through an aggressive consumer.

Option not found for -show_entries

Cause: very old ffprobe (< 1.0). Solution: upgrade; on macOS brew install ffmpeg.