Foreground clips with per-frame alpha ground truth

Moving subjects over known backgrounds, shipped with the exact alpha matte used to composite them, for scoring background removal and green-screen keying frame by frame.

12 of 12 files

Base Plate — Orbit — Hard-Edged Solids

A green disc and a red square orbiting the centre in antiphase over a grid. Hard edges and flat fills make the boundary unambiguous, so segmentation and tracking output can be scored against exact geometry rather than a judgement call. One of eight shared base plates: every AI-video suite in this library degrades one of these rather than inventing its own footage, so results across suites are comparable. Encoded at CRF 14 — well above the house CRF 30 — because a reference compressed as hard as the material under test puts the measurement floor above the effect being measured.

File: MP4 · Base Plates · 640x360
Use case: Video segmentationVideo matting+1· Conversion set

Base Plate — Subject on Chroma Field

An anti-aliased figure moving over a chroma-green field with a deliberate lighting falloff, so the key is not perfectly flat. Ships with a per-frame alpha ground truth, which is what makes matting output measurable instead of merely inspectable. One of eight shared base plates: every AI-video suite in this library degrades one of these rather than inventing its own footage, so results across suites are comparable. Encoded at CRF 14 — well above the house CRF 30 — because a reference compressed as hard as the material under test puts the measurement floor above the effect being measured.

File: MP4 · Base Plates · 640x360
Use case: Video mattingVideo segmentation+1· Conversion set

Matting Ground Truth — Per-Frame Alpha Matte

The exact per-frame alpha used to composite every clip in this group, as an 8-bit greyscale clip: white is opaque subject, black is background, and edges carry genuine intermediate values because the matte is anti-aliased rather than binary. This is what makes matting output measurable — compare a predicted alpha against this frame by frame instead of inspecting a composite and forming an opinion.

File: MP4 · Matting · 640x360
Use case: Video mattingVideo segmentation+1· Conversion set

Matting Input — Subject on Chroma Green

The canonical keying setup: the subject over a chroma-green field carrying a deliberate vertical lighting falloff, because a perfectly flat key is unrealistically easy. Pull a key, then score the resulting alpha against the ground-truth matte in this group.

File: MP4 · Matting · 640x360
Use case: Video mattingVideo QA· Conversion set

Matting Input — Subject on Office interior

The same subject and the same alpha, composited over office interior — no chroma screen, which is the case a general background-removal model actually has to handle. Score the predicted alpha against the ground-truth matte in this group.

File: MP4 · Matting · 640x360
Use case: Video mattingVideo segmentation+1· Conversion set

Matting Input — Subject on Outdoor daylight

The same subject and the same alpha, composited over outdoor daylight — no chroma screen, which is the case a general background-removal model actually has to handle. Score the predicted alpha against the ground-truth matte in this group.

File: MP4 · Matting · 640x360
Use case: Video mattingVideo segmentation+1· Conversion set

Matting Input — Subject on Dark studio

The same subject and the same alpha, composited over dark studio — no chroma screen, which is the case a general background-removal model actually has to handle. Score the predicted alpha against the ground-truth matte in this group.

File: MP4 · Matting · 640x360
Use case: Video mattingVideo segmentation+1· Conversion set

Matting Input — Subject on Busy patterned

The same subject and the same alpha, composited over busy patterned — no chroma screen, which is the case a general background-removal model actually has to handle. Score the predicted alpha against the ground-truth matte in this group.

File: MP4 · Matting · 640x360
Use case: Video mattingVideo segmentation+1· Conversion set

Matting Input — Subject on Colour close to subject

The same subject and the same alpha, composited over colour close to subject — no chroma screen, which is the case a general background-removal model actually has to handle. The background colour deliberately sits close to the subject's own, so colour alone cannot separate them and the model must use shape and motion. Score the predicted alpha against the ground-truth matte in this group.

File: MP4 · Matting · 640x360
Use case: Video mattingVideo segmentation+1· Conversion set

Segmentation Ground Truth — Instance Masks

Per-frame instance masks for the orbit plate, colour-coded so the three objects are separable: red is the disc, green the square, blue the centre marker, black the background. Instance identity is stable across frames, which is what makes this usable for video object segmentation and tracking rather than only per-frame segmentation. Note the mask is encoded lossily like every other clip here, so threshold rather than testing for exact equality.

File: MP4 · Segmentation · 640x360
Use case: Video segmentationVideo matting+1· Conversion set

Segmentation Input — Trimap (Foreground / Unknown / Background)

A three-level trimap derived from the instance masks: definite foreground, definite background, and a nine-pixel unknown band around every boundary. This is the input interactive matting and rotoscoping tools actually take, and the band is where all the difficulty lives — a matte is only as good as its handling of that region.

File: MP4 · Segmentation · 640x360
Use case: Video segmentationVideo matting+1· Conversion set

Alpha Channel — VP9 in WebM

Video 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.

File: WEBM · Alpha · 480x270
Use case: Video codecsVideo matting+2· Conversion set