To achieve "extra quality" in a compressed format, encoders use a process called "Variable Bitrate" (VBR). Unlike Constant Bitrate, which uses the same amount of data for every second of film, VBR identifies complex scenes—like fast action or intricate textures—and allocates more data to them. Conversely, it saves space on simple scenes, such as static backgrounds or dark frames. This intelligent distribution ensures that the viewer sees no "blocking" or "pixelation" in the moments that matter most.
This reduces redundancy within a single frame. For example, if a scene features a clear blue sky, the codec saves data by grouping the blue pixels together rather than processing each individual pixel.
| Artifact Type | Description | Consumer Perception | | :--- | :--- | :--- | | | 8x8 pixel grid visible in skies/fog | "Pixelated" – Low quality impression | | Bandwidth | Smooth gradients become color steps | Unnatural skin tones, banding | | Mosquito Noise | Haloing around sharp edges (subtitles, text) | Distracting, amateurish | | Temporal Flicker | Inconsistent compression between frames | Headaches, eye strain | | Audio Compression | Loss of dynamic range (quiet/loud extremes) | Flat, lifeless sound |
