video-analysis

Original：🇺🇸 English

Translated

Analyze video files using ffprobe, mp4dump, and jq. Use when investigating video samples, keyframes, MP4 box structure, codec info, packet timing, or debugging video playback issues.

4installs

Sourceeditframe/skills

Added on2026-05-01

NPX Install

npx skill4agent add editframe/skills video-analysis

SKILL.md Content

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Video Analysis

Analyze MP4/video files using CLI tools. All commands output JSON for jq filtering.

FFprobe Basics

Format + Streams (most common)

bash

ffprobe -v quiet -print_format json -show_format -show_streams FILE.mp4

Key fields:

.format.duration

,

.streams[].codec_name

,

.streams[].codec_type

Stream selection

bash

-select_streams v:0   # first video stream
-select_streams a:0   # first audio stream
-select_streams v     # all video streams

Packets (sample-level data)

bash

ffprobe -v quiet -print_format json -show_packets FILE.mp4

Key fields:

.packets[].pts_time

,

.packets[].flags

,

.packets[].size

Flag meanings:

= keyframe,

= discard,

= none

Keyframe packets only

bash

ffprobe -v quiet -print_format json -show_packets -select_streams v:0 FILE.mp4 | \
  jq '[.packets[] | select(.flags | test("K"))]'

Count keyframes

bash

ffprobe -v quiet -print_format json -show_packets -select_streams v:0 FILE.mp4 | \
  jq '[.packets[] | select(.flags | test("K"))] | length'

Frames (decoded frame info)

bash

ffprobe -v quiet -print_format json -show_frames FILE.mp4

Key fields:

.frames[].pict_type

(I/P/B),

.frames[].key_frame

,

.frames[].pts_time

Limit frame count (faster)

bash

ffprobe -v quiet -print_format json -show_frames -read_intervals "%+#100" FILE.mp4

Reads first 100 frames only.

Common Queries

Duration

bash

ffprobe -v quiet -show_entries format=duration -of csv=p=0 FILE.mp4

Frame count

bash

ffprobe -v quiet -select_streams v:0 -show_entries stream=nb_frames -of csv=p=0 FILE.mp4

Codec info

bash

ffprobe -v quiet -print_format json -show_streams FILE.mp4 | \
  jq '.streams[] | {codec: .codec_name, type: .codec_type, profile: .profile}'

Video dimensions

bash

ffprobe -v quiet -select_streams v:0 -show_entries stream=width,height -of csv=p=0 FILE.mp4

Sample rate / channels (audio)

bash

ffprobe -v quiet -select_streams a:0 -show_entries stream=sample_rate,channels -of csv=p=0 FILE.mp4

MP4 Box Structure (mp4dump)

bash

mp4dump --format json FILE.mp4

Key boxes

```
ftyp
```
: file type/brand
```
moov
```
: movie metadata (contains all track info)
```
mvhd
```
: movie header (duration, timescale)
```
trak
```
: track container
```
mdhd
```
: media header (per-track timescale/duration)
```
stbl
```
: sample table (stts, stss, stsz, stco)
```
stss
```
: sync sample table (keyframe positions)
```
moof
```
: movie fragment (fragmented MP4)
```
mdat
```
: media data

Find specific box

bash

mp4dump --format json FILE.mp4 | jq '.. | objects | select(.name == "mvhd")'

Fragmented MP4 check

bash

mp4dump --format json FILE.mp4 | jq '[.. | objects | select(.name == "moof")] | length'

Non-zero = fragmented.

JQ Patterns

Filter by field value

bash

jq '.streams[] | select(.codec_type == "video")'

Extract specific fields

bash

jq '.streams[] | {codec: .codec_name, duration: .duration}'

Count items

bash

jq '.packets | length'

First N items

bash

jq '.packets[:10]'

Sum values

bash

jq '[.packets[].size | tonumber] | add'

CSV Output (for scripting)

bash

ffprobe -v quiet -select_streams v:0 -show_entries packet=pts_time,flags,size -of csv=p=0 FILE.mp4

Output:

0.000000,1263,K__

(one line per packet)

Test Assets

Sample files in

elements/test-assets/

:

```
10s-bars.mp4
```
- 10s color bars with audio
```
frame-count.mp4
```
- frame counting test
```
bars-n-tone.mp4
```
- multi-track test

video-analysis

NPX Install

Tags

SKILL.md Content

Video Analysis

FFprobe Basics

Format + Streams (most common)

Stream selection

Packets (sample-level data)

Keyframe packets only

Count keyframes

Frames (decoded frame info)

Limit frame count (faster)

Common Queries

Duration

Frame count

Codec info

Video dimensions

Sample rate / channels (audio)

MP4 Box Structure (mp4dump)

Key boxes

Find specific box

Fragmented MP4 check

JQ Patterns

Filter by field value

Extract specific fields

Count items

First N items

Sum values

CSV Output (for scripting)

Test Assets