HDMI signals

Deep Colour

8-bit, 10-bit and 12-bit HDMI colour depth

Deep Colour is where banding, bandwidth and HDR meet. On the Diva it is one of the custom scaling parameters for TX0, and it is also one of the things the unit reports about every signal it receives.

A standard HDMI signal uses eight bits for each of the three colour components, which is 24 bits per pixel. Deep Colour, added in HDMI 1.3, is anything above that: 10 bits per component makes 30 bits per pixel, 12 bits makes 36 and 16 bits makes 48. The Diva labels the options in exactly that pairing, as 8-bit/24-bit, 10-bit/30-bit, 12-bit/36-bit and 16-bit/48-bit.

Extra bits buy gradation, not brightness. Eight bits give 256 steps per component, ten give 1024, and the difference shows up as banding in a slow sky or a fade to black rather than in a test pattern. HDR10 content is mastered at 10 bits for that reason, since a wider luminance range stretched over 256 steps bands visibly.

The cost is bandwidth, and it scales directly with the bit depth. 4K60 4:4:4 fits an 18Gbps link at 8-bit and does not fit at 10-bit or 12-bit. That is why deep colour and chroma subsampling are decided together: 4:2:2 at 12-bit fits where 4:4:4 at 12-bit does not.

Setting deep colour on the HDfury Diva

The control lives in the SCALER section of the web server, under Custom Scaling, and it applies to the TX0 upscale output port. Choose Custom Scaling, pick a deep colour value, then click SEND: nothing you change there takes effect until you do. Scale mode itself can also be set from the OLED menu or over control, where the command is set scale custom, with none and auto as the other two values, although the custom parameters themselves are defined only in the web server.

Follow Input

The default. The outgoing signal keeps whatever bit depth arrived, so a resolution change does not quietly alter anything else.

8-bit/24-bit

Forces the standard depth. Useful for a sink that mishandles deep colour, or to keep a 4:4:4 signal inside 18Gbps.

10-bit/30-bit

The depth HDR10 is mastered at, within reach at 4K when the chroma format leaves room for it.

12-bit/36-bit

The depth a 4:2:2 signal already occupies internally.

16-bit/48-bit

The highest the dropdown offers, and far beyond what most displays accept.

What the Diva reports

The bit depth of the incoming signal appears on the OLED and in the INFO section, written as 8b or 12b. Two of those readings surprise people. Any 4:2:2 signal is always processed at 12-bit and never clipped, so the Diva describes such signals as up to 12b. Dolby Vision modes 0 and 1 travel through an 8-bit RGB container, so RGB 8b during Dolby Vision playback is normal and nothing has been lost.

All glossary terms