Glossary
The desk uses a small, fixed vocabulary. This sheet defines each term as it is used across the portal, so a figure on one page reads the same way on another.
Measurement terms
Rate factor. The scale that drives constant-quality rate control; a higher value lowers the size and raises the distortion. Bitrate is the number of compressed bits per unit of time. Rung is one resolution and quality step inside a delivery ladder. Distortion curve is the plot of a quality score against a rate factor for one clip.
Run note. The record of a single encode, listing every option that touched the output. Bench class is the documented summary of the host a timing figure came from. Repeat spread is the difference between repeated runs of the same note.
Codec terms
Macroblock. The fixed grid unit of H.264. Coding tree unit. The larger, variable partition used by HEVC. Superblock. The AV1 partition unit, which can be split many ways before prediction begins. Transform. The step that turns residual values into coefficients that compress well. Quantisation. The step that discards coefficient precision.
Picture group. The closed run of frames between two reference frames. Reference frame. A frame other frames may predict from. Entropy coding. The final lossless stage that packs symbols into bits. Reconstruction depth. The bits per sample kept after decode, such as eight-bit or ten-bit.
| Term | Stage |
|---|---|
| rate factor | Standards |
| rung | Encode |
| distortion curve | Verify |
| run note | Prep |
Container terms
Container. The package that holds compressed streams and their index. Elementary stream. A single compressed track without a container. Sample index. The table of offsets, sizes and times that lets a player seek. Timescale. The unit that turns frame counts into a clock.
How to use the sheet
When a page names a term, this sheet holds its definition. When two pages seem to disagree, the vocabulary here is the tie-breaker. Corrections go to the desk through the contact sheet.