Color space
A color space says which colors a video can use and how they are written down, for example BT.709, BT.2020, RGB or YCbCr.
A color space is the box of colors a video is allowed to use, plus the way those colors are written down.
It is like a box of crayons: HD video gets a normal box, and 4K HDR video can get a bigger box with deeper reds and greens. The source and the screen must agree on which box is used, or colors look wrong.
Can the HDfury Vertex convert the colour space (RGB, YCbCr, BT.709, BT.2020)?
YESYes. In Custom Scaling each output can use Follow Input or a fixed colour space: RGB FULL, RGB BT2020, or 4:4:4, 4:2:2 or 4:2:0 in BT.709 or BT2020. With No Scaling the colour space passes untouched.
How to use it with the Vertex:
- Set the SCALE slide switch to the middle, Custom Scaling/GUI (p.12).
- USB GUI > SCALER > Custom Scaling: pick the colour space; Follow Input is the default (p.30).
- RS232: #set scale custom (p.49).
- Check the result on the OLED or in the GUI TX0/TX1 lines (p.19, p.27).
What it is
In home video, "color space" is used for two things. The first is the range of colors (the gamut): BT.709 is the standard for HD video, BT.2020 is the much wider standard for UHD and HDR, and DCI-P3 sits in between and is often used to master films. BT.2020 covers about 75.8% of the colors people can see, BT.709 about 35.9%.
The second is how each pixel is coded. RGB stores red, green and blue. YCbCr stores brightness (Y) and two color-difference values (Cb, Cr). Video on discs and streams is stored as YCbCr, often with reduced color detail (chroma subsampling such as 4:2:0). RGB can also be full range or limited range; when source and display disagree, blacks look grey or dark detail disappears.
The source tells the display which color space it is sending in a small data packet called the AVI InfoFrame. BT.2020 is about color, not brightness: it usually comes together with HDR, but it is not the same thing.
On the Vertex
With No Scaling (passthrough) the Vertex leaves the color space untouched (p.12). With Custom Scaling you can pick a color space per output: Follow Input (default), RGB FULL, RGB BT2020, 4:4:4 BT.709, 4:4:4 BT2020, 4:2:2 BT.709, 4:2:2 BT2020, 4:2:0 BT.709 or 4:2:0 BT2020 (p.30). Follow Input is the safe choice unless a display needs a conversion.
The OLED and GUI show the color space of every input and output, for example "422 BT2020" (p.19, p.27). In Automix EDID mode you can force BT2020/xvYCC support, or remove YCbCr support, in the EDID (p.28). Advanced users can also change the colorimetry the display is told about by editing the AVI InfoFrame; wrong values can blank the screen (p.34).
Common questions
Should I send RGB or YCbCr?
Both can show the same picture if source and display agree. Video is stored as YCbCr, so YCbCr avoids an extra conversion; with RGB, a full/limited range mismatch is the usual cause of grey blacks or crushed shadows.
Does BT.2020 mean the signal is HDR?
No. BT.2020 describes the colors; HDR describes the brightness curve (PQ or HLG). An HDR signal almost always uses BT.2020 colors, but BT.2020 can also be sent without HDR.
Will changing the color space on the Vertex improve my picture?
Normally not. Converting only helps when a display cannot accept the incoming format; otherwise leave the scaler on Follow Input or No Scaling (p.12, p.30).