Coast drift: 24-second continuous film
A 24 second 512x288 H.264 film at 24 fps, 576 frames, written with the moov atom first so it can be seeked before it has finished downloading. Twelve generated segments crossfaded into one continuous take. Across 575 transitions the mean inter-frame change is 0.0139 and the strongest single transition is 0.1614, with 0 above 0.3. A deliberate hard cut between two unrelated films measures 0.311 by the same method, so the worst join here sits 0.1496 below a real cut. At eleven times the length of any other clip in this library, it is the only footage here long enough to seek through, chapter, or scrub. Stylised rather than photographic: this is the 1.3B model at 512x288, the subject drifts over 24 seconds, and a dark rendering artefact recurs in a few frames. It is a fixture for duration, seeking and stitch measurement, not showcase footage.
Browser-playable test video · 24 seconds
Specifications
- Film
- film-coast-drift
- Duration Seconds
- 24
- Segments
- 12
- Synthetic
- true
- Disclosure
- AI-generated / synthetic video. Not a recording of a real person, place or event.
- Schema Version
- 1
- Width
- 512
- Height
- 288
- Frames
- 576
- Fps
- 24
- Codec
- h264
- Faststart
- true
- Mean Scene Change
- 0.0139
- Max Scene Change
- 0.1614
- Transitions Above0 3
- 0
- Hard Cut Reference
- 0.311
- Model
- wan2.1_t2v_1.3B
- Alt Text
- A slow continuous drift along a rocky coastline, waves breaking, overcast sky, steady aerial movement, one unbroken shot
- Alt Text Source
- prompt
Testing contract
Expected to pass- Scenario
- Open the file and seek to 12 seconds without downloading it in full.
- Expected result
- The moov atom precedes mdat, so a ranged request can seek immediately. Duration reports 24.000 seconds across 576 frames at 24 fps.
What is a .mp4 file?
MP4 (MPEG-4 Part 14) is the dominant container for digital video, holding video, audio, subtitle, and metadata tracks in a tree of typed boxes. `ftyp` declares the brand, `moov` carries the sample tables that make seeking possible, and `mdat` holds the media; when an encoder writes `moov` last, playback cannot begin until the file has fully downloaded, which a faststart remux fixes. It derives from Apple's QuickTime format, generalized by ISO into the ISOBMFF base that MOV, 3GP, and HEIF share.
How to use this file
Use an example MP4 to test box parsing and track detection, seeking, range-request streaming, and transcode or thumbnail pipelines: verifying that a file with a trailing `moov` box is still handled, and that codec support is checked per track rather than inferred from the extension.
How to use this file for testing
“Coast drift: 24-second continuous film” is a deterministic Novus Examples fixture for Video QA, Media handling. Short 270p clips with known scene cuts, freezes, black frames, flash frames, and burned-in captions, for detection and QC tooling.
Documented properties for this file: 512×288 · 24 fps. Compare results against paired or grouped companions on this page when present (clean↔damaged, searchable↔scanned, or format twins) so scores stay reproducible across runs.
Download the file once, keep the path stable in CI or local scripts, and treat the spec table as the contract: dimensions, seeds, field lists, and roles are intentional. Corrupt or invalid samples are labelled as such, expect parsers to fail loudly rather than silently accept them.
Media fixtures are short and synthetic by design. Prefer waveform or transcript ground truth in the same group when measuring ASR, trim, upscale, or sync tools; do not assume broadcast-quality masters.
Code examples
<video controls preload="metadata" width="640" src="film-coast-drift.mp4"></video>Related files
- mp4Market walk: 24-second continuous filmA 24 second 512x288 H.264 film at 24 fps, 576 frames, written with the moov atom first so it can be seeked before it has finished downloading. Twelve generated segments crossfaded into one continuous take. Across 575 transitions the mean inter-frame change is 0.0217 and the strongest single transition is 0.2597, with 0 above 0.3. A deliberate hard cut between two unrelated films measures 0.311 by the same method, so the worst join here sits 0.0513 below a real cut. At eleven times the length of any other clip in this library, it is the only footage here long enough to seek through, chapter, or scrub. Stylised rather than photographic: this is the 1.3B model at 512x288, the subject drifts over 24 seconds, and a dark rendering artefact recurs in a few frames. It is a fixture for duration, seeking and stitch measurement, not showcase footage.
- mp4Street at dusk: 24-second continuous filmA 24 second 512x288 H.264 film at 24 fps, 576 frames, written with the moov atom first so it can be seeked before it has finished downloading. Twelve generated segments crossfaded into one continuous take. Across 575 transitions the mean inter-frame change is 0.0206 and the strongest single transition is 0.2395, with 0 above 0.3. A deliberate hard cut between two unrelated films measures 0.311 by the same method, so the worst join here sits 0.0715 below a real cut. At eleven times the length of any other clip in this library, it is the only footage here long enough to seek through, chapter, or scrub. Stylised rather than photographic: this is the 1.3B model at 512x288, the subject drifts over 24 seconds, and a dark rendering artefact recurs in a few frames. It is a fixture for duration, seeking and stitch measurement, not showcase footage.
- vttMarket walk: scrub-preview indexThe WebVTT index for the sprite sheet in this group: 24 cues, one per second, each naming a rectangle of the sheet with an xywh media fragment. The sheet and this index are each useless alone, which is why they are paired.
- vttStreet at dusk: scrub-preview indexThe WebVTT index for the sprite sheet in this group: 24 cues, one per second, each naming a rectangle of the sheet with an xywh media fragment. The sheet and this index are each useless alone, which is why they are paired.
- webmAlpha Channel: Opaque VP9 TwinThe same codec and container with NO alpha plane, as the control for the alpha clip in this group. Useful for checking that alpha detection reads the pixel format rather than assuming every WebM is transparent, and for confirming a compositing bug is in the alpha handling rather than in the player.
- webmAlpha Channel: VP9 in WebMVideo with a real per-pixel alpha channel: VP9 yuva420p in WebM, the one alpha path browsers decode natively. Composite it over a page background and the transparency is genuine, not a chroma key. Roughly 90% of each frame is fully transparent. Two traps this file exists to expose. First, auto-alt-ref must be disabled at encode time or libvpx silently drops the alpha plane, producing a valid file with no transparency and no error. Second, WebM stores VP9 alpha in BlockAdditional and signals it with AlphaMode=1, so FFmpeg's NATIVE vp9 decoder reports pix_fmt yuv420p and decodes fully opaque: you must force `-c:v libvpx-vp9` to see the alpha at all. Probing this file with default settings and concluding it has no alpha is the expected mistake.
Generated by generation/comfy_film_wave.py. Free for any use, no attribution required, license.