Compression Input — gradient-sky at CRF 51
The gradient-sky plate at CRF 51 — extreme — the codec's limit artefacts. Encoded from the original frames rather than transcoded from the reference, so it carries exactly one generation of loss and the comparison is clean. On this plate the damage shows as banding across the smooth gradient, which is the artefact viewers notice first and metrics score most poorly.
Specifications
- Resolution
- 640x360
- Fps
- 24
- Codec
- H.264 (libx264)
- Crf
- 19
- Preset
- slow
- Artefact Severity
- extreme — the codec's limit
- Role
- artefact-removal input
- Reference
- vid-compress-gradient-sky-gt
- Base Plate
- gradient-sky
What is a .mp4 file?
MP4 (MPEG-4 Part 14) is a widely supported multimedia container based on ISOBMFF that holds video, audio, subtitles, and metadata, most commonly H.264 or H.265 video with AAC audio. It supports streaming, chapters, and multiple tracks. It is the dominant format for distributing and playing digital video.
How to use this file
Use an example MP4 to test container demuxing, track and codec detection, seeking and streaming, and transcoding or thumbnail-extraction pipelines.
How to use this file for testing
“Compression Input — gradient-sky at CRF 51” is a deterministic Novus Examples fixture for Compression artefacts, Video codecs, Video QA. The same footage at a ladder of quantiser settings from near-lossless down to visibly broken, each paired with its high-quality source — for testing artefact-removal models and for calibrating quality metrics against known encoder settings.
Documented properties for this file: artefact-removal input · 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="gradient-sky-crf51.mp4"></video>Related files
- mp4Compression Input — detail-chart at CRF 28The detail-chart plate at CRF 28 — mild artefacts. Encoded from the original frames rather than transcoded from the reference, so it carries exactly one generation of loss and the comparison is clean. On this plate the fine wedges collapse first, showing exactly which spatial frequencies the quantiser discarded.
- mp4Compression Input — detail-chart at CRF 36The detail-chart plate at CRF 36 — clearly visible artefacts. Encoded from the original frames rather than transcoded from the reference, so it carries exactly one generation of loss and the comparison is clean. On this plate the fine wedges collapse first, showing exactly which spatial frequencies the quantiser discarded.
- mp4Compression Input — detail-chart at CRF 44The detail-chart plate at CRF 44 — severe artefacts. Encoded from the original frames rather than transcoded from the reference, so it carries exactly one generation of loss and the comparison is clean. On this plate the fine wedges collapse first, showing exactly which spatial frequencies the quantiser discarded.
- mp4Compression Input — detail-chart at CRF 51The detail-chart plate at CRF 51 — extreme — the codec's limit artefacts. Encoded from the original frames rather than transcoded from the reference, so it carries exactly one generation of loss and the comparison is clean. On this plate the fine wedges collapse first, showing exactly which spatial frequencies the quantiser discarded.
- mp4Compression Input — text-motion at CRF 28The text-motion plate at CRF 28 — mild artefacts. Encoded from the original frames rather than transcoded from the reference, so it carries exactly one generation of loss and the comparison is clean. On this plate the damage shows as ringing around glyph edges, where legibility gives a pass/fail signal that needs no metric.
- mp4Compression Input — text-motion at CRF 36The text-motion plate at CRF 36 — clearly visible artefacts. Encoded from the original frames rather than transcoded from the reference, so it carries exactly one generation of loss and the comparison is clean. On this plate the damage shows as ringing around glyph edges, where legibility gives a pass/fail signal that needs no metric.
Generated by generation/video_ai_suites.py. Free for any use, no attribution required — license.