Your stream eats red text and thin lines. That is 4:2:0.
Small red text turns to mush on stream and looks perfect on your monitor. No encoder setting fixes it, because the damage happens before encoding.
Your overlay looks sharp in OBS. On the platform the red text has fuzzy edges and the thin lines wobble.
You raise the bitrate. Almost nothing changes.
What 4:2:0 throws away
Video splits a pixel into brightness and colour. Your eye is far better at brightness detail than colour detail, so video formats keep all the brightness and throw away most of the colour.
In 4:2:0 the colour is stored at half width and half height. One colour sample covers a block of four pixels. Brightness stays at full resolution.
So a 1920 by 1080 stream carries 1920 by 1080 brightness and 960 by 540 colour. Three quarters of the colour is gone before the encoder starts work.
Subsampling happens when the frame is converted for encoding. There is no colour detail left for the extra bits to describe.
What survives and what does not
| Design choice | How it holds up |
|---|---|
| White or light grey text on dark | Fine. The contrast is brightness, which keeps full resolution. |
| Saturated red on black | Worst case. Red and black are close in brightness, so the edge lives entirely in the colour channel. |
| Saturated blue on black | Almost as bad, and blue is dim to begin with. |
| Thin coloured borders and 1px rules | They shimmer. A one-pixel line is smaller than one colour sample. |
| Coloured text with a dark outline | Holds up. The outline puts the edge back into brightness. |
How to design around it
- Make the contrast a brightness difference, not a colour difference. Light on dark or dark on light.
- Add a 2px dark outline or drop shadow to any coloured text.
- Set overlay text at least 24px at 1080p. Below that the colour blocks are visible.
- Push saturated red toward orange or pink. Both carry more brightness.
- Test on the platform, not in the preview. OBS shows you 4:4:4 that nobody else will see.
The exception worth knowing
Local recording can hold more colour than a stream. If your encoder offers 4:4:4 or 4:2:2 for recording, the file keeps detail the stream never had.
That matters when you cut clips later. Text that smeared live can be sharp in the upload, and the fix costs nothing but disk.
Sources
The Rig Wire reports on streaming technology from public documentation, source repositories and vendor releases. We did not bench-test what is described here. When we have tested something, we say so.