Video

Playback and container/codec info#

What it does. Plays the video with a synced transport and reports container/codec, resolution, frame rate, and bitrate.

How to reach it. Drop any recognised video file. Built in web/assets/js/renderers/video.js.

Notes / limits. Frame rate is parsed from MP4 container metadata with an FFmpeg fallback for containers the browser can't introspect natively (per the repo root README.md).

Frame capture and analysis#

What it does. Steps through video frames and analyses any single frame as a full photo (EXIF-less, since it's a grabbed frame, but the same histogram/OCR/etc. pipeline).

How to reach it. Prev frame/Next frame step through frames; Analyse frame (also Analyse in Photo section in alternate flows) sends the current frame to the full photo analyser (renderPhoto via photo.js). Built in video.js.

Sonify a frame#

What it does. Turns the current video frame into sound, same as the photo sonify feature.

How to reach it. Click Sonify on the current frame. Lazy-imports sonify.js - see images.md for full control detail.

Contact sheet#

What it does. Builds a thumbnail grid of frames sampled across the video.

How to reach it. Click Generate contact sheet (shown once there are enough frames, 8+). Built in video.js.

Audio track extraction#

What it does. Extracts the video's audio track and runs it through the full audio analyser (waveform, spectrogram, LUFS, etc.).

How to reach it. Download audio (WAV) downloads the extracted track; Analyse audio runs it through audio.js's full pipeline; Analyse photo (on the paired still) runs the current frame through photo.js. Built in video.js, reusing audio.js's makeSpectrogramPanel/buildHistogramCard/buildWaveformCard.

Notes / limits. For codecs the browser can decode video but not audio for (or vice versa), video-sync.js's "audio companion" mechanism plays a separately-extracted <audio> element in lockstep with the muted <video>, so playback stays in sync with no echo - see "Multi-player sync" below.

Reversed video#

What it does. Re-encodes the video playing backwards - picture and sound - via FFmpeg, unlike audio reverse (which is instant sample-flipping, since video needs the picture itself re-encoded).

How to reach it. Click ↺ Reverse video. Built in video.js.

How to use it. Once rendered: Analyse reversed re-runs the full pipeline on the reversed clip; Download reversed (MP4) saves it.

Notes / limits. Explicitly warned as slow in the UI copy ("this isn't as straightforward as it seems... going to take a while") - a full FFmpeg re-encode, not a cheap operation.

Scene change detection#

What it does. Samples the video at a fixed interval and compares consecutive frames by mean per-channel pixel difference; a jump past a threshold is marked as a scene change with a thumbnail and confidence score.

How to reach it. Runs automatically for smaller videos; click Detect scene changes to run it manually (always required for large videos, which skip the automatic run - shown as "Skipped automatically for large videos (N MB)"). Run again (current part) re-scans just the currently loaded segment on segmented/salvaged playback. Built in video.js.

How to use it. Click any result thumbnail or timeline marker to jump the player there.

Segmented playback#

What it does. For very large or specially-loaded videos, plays through the content in segments rather than loading it all at once.

How to reach it. Prev/Next step between segments. Built in video.js.

Integrity: SHA-256#

What it does. Computes the file's full SHA-256 hash.

How to reach it. Click Compute SHA-256 (the hash isn't computed automatically for video since it reads the whole file). Built in video.js.

Truncated/unfinalised recording salvage#

What it does. Recovers playable video from a truncated/unfinalised ISOBMFF (MP4/MOV) recording whose moov index is missing - the classic "camera/card was interrupted before finalising" or "file copy stopped early" corruption, seen on Sony XAVC, GoPro, DJI, and phone recordings. With no moov there are no sample tables to index frames, but the raw encoded video is still present in the mdat box.

How to reach it. Automatic detection when a dropped MP4/MOV has no moov (video-recover.js's detectMoovlessMp4()); the video section shows a Salvage video call-to-action. Built in video-recover.js, orchestrated by video.js.

How to use it. The video's H.264/H.265 stream is carved out of mdat (MP4 stores NAL units length-prefixed, interleaved with audio/metadata the recovery can't index; it walks the chain validating each NAL against the next and resyncing byte-by-byte across gaps, re-emitting each as Annex B). If the file's SPS/PPS codec setup was stored only in the (missing) moov's avcC box rather than in-band, the "Reference clip needed" panel appears: click Choose reference clip..., pick a healthy clip shot on the same camera in the same mode (same resolution and codec), and Analyser borrows its parameter sets to make the carved stream decodable. Click Salvage video to run the recovery; the result plays through the site's raw-stream segmented player.

Notes / limits. Verified against real Sony FX30 XAVC footage. The recovery module is pure logic (no DOM) with an abstracted byte-source reader, so it runs identically under the browser File API and a Node test harness.

Undecodable codec conversion#

What it does. Re-encodes a video whose codec the browser can't decode into H.264/MP4 via FFmpeg so it can be played and analysed in full.

How to reach it. Click Convert to H.264 and play, shown when playback fails on an unsupported codec. Built in video.js.

Notes / limits. Lossy re-encode; can take a while for long or high-resolution clips.

First-frame extraction (no native preview)#

What it does. Grabs a single frame via FFmpeg for a format with no native browser preview.

How to reach it. Click Extract first frame, shown when there's no default preview available. Built in video.js.

AVI container parsing#

What it does. Browsers can't play most AVI files (typically Motion-JPEG video + PCM audio), so Analyser parses the RIFF container itself: reads the header for dimensions/codec/audio format, pulls the raw MJPEG frames and PCM audio out of the movi list, and re-wraps the PCM as a WAV the browser can play.

How to reach it. Automatic fallback when the native <video> path fails on an .avi. Built in video-avi.js, used by video.js.

Notes / limits. Pure parsing, no DOM or cross-module dependencies.

Multi-player sync#

What it does. When an analysis shows more than one <video> of the same clip at once (the main player, a section-03 mini player, a gyro mini player), all registered players stay on the same transport: play/pause/seek one and the others follow.

How to reach it. Automatic wherever multiple synced players exist for one clip. Built in web/assets/js/core/video-sync.js.

Notes / limits. Exclusive audio: since every synced player decodes the clip independently, only one may be audible at a time (echo otherwise) - whichever player the user presses becomes the "audio owner" and is unmuted, muting every other synced player. Programmatic play/pause/seek propagated to followers is tagged so it doesn't echo back and cause a feedback loop. An "audio companion" <audio> element (used when the video codec is playable but its audio isn't, or vice versa) shadows the audio owner's transport rather than joining the synced-video set directly.