Targeted display color volume specification via color remapping information (CRI) messaging
Given existing color remapping information (CRI) messaging variables, methods are described to communicate color volume information for a targeted display to a downstream receiver. Bits 7:0 of the 32-bit colour_remap_id are used to extract a first value. If the first value is not a reserved value, then the first value is used as an index to a look-up table to generate a first luminance value for a targeted display, otherwise a second value is generated based on bits 31:9 in the colour_remap_id messaging variable and the first luminance value for a targeted display is generated based on the second value. The methods may be applied to communicate via CRI messaging a minimum luminance value, a maximum luminance value, and color primaries information of the targeted display.
1. A method on a decoder to extract color volume information for a targeted display, the method executed on a processor, the method comprising:
by apparatus comprising one or more data processors configured by software, one or more programmable logic devices, one or more logic circuits or a combination thereof:
receiving a colour_remap_id messaging variable identifying color remapping information, wherein the colour_remap_id messaging variable comprises 32 bits;
generating a first value based on bits 7 : 0 of the colour_remap_id messaging variable;
checking whether the first value is a reserved value;
if the first value is not the reserved value, then using the first value as an index to a look-up table to generate a first luminance value for a targeted display, otherwise
generating a second value based on bits 31 : 9 in the colour_remap_id messaging variable; and
generating the first luminance value for the targeted display based on the second value.
2. The method of claim 1 , wherein the first luminance value comprises the minimum or the maximum luminance value of the targeted display.
3. The method of claim 1 , wherein the first value is generated based on bits 3 : 0 of the colour_remap_id value and the second value is generated based on bits 18 : 9 of the colour_remap_id value.
4. The method of claim 1 , wherein the second value is encoded according to the inverse EOTF specified in SMPTE ST 2084.
5. The method of claim 4 , wherein generating the first luminance value for the targeted display comprises computing:
PQ (target_min_lum/10,000),
wherein target_min_lum denotes the second value and PQ(x) denotes a function mapping input x values to output luminance values according to the EOTF defined in SMPTE ST 2084.
6. The method of claim 3 , wherein the reserved value comprises the value 15.
7. The method of claim 3 , wherein the LUT for the first value comprises 15 values in logarithmic space, between 0.0001 and 10,000.
8. The method of claim 3 , wherein the LUT for the first value comprises the values 0.5 and 0.05.
9. The method of claim 1 , further comprising:
generating a third value based on bits 7 : 0 of the colour_remap_id messaging variable;
checking whether the third value is the reserved value;
if the third value is not the reserved value, then using the third value as an index to the look-up table to generate a second luminance value for the targeted display, otherwise
generating a fourth value based on bits 31 : 9 in the colour_remap_id messaging variable; and
generating the second luminance value for the targeted display based on the fourth value.
10. The method of claim 9 , wherein the third value is generated based on bits 7 : 4 of the colour_remap_id value and the fourth value is generated based on bits 28 : 19 of the colour_remap_id value.
11. The method of claim 9 , wherein the fourth value is encoded according to the inverse EOTF specified in SMPTE ST 2084.
12. The method of claim 1 , further comprising:
generating a color primaries index value based on bits 30 : 29 of the colour_remap_id messaging variable; and
generating one or more chromaticity values for the color primaries of the targeted display based on the color primaries index value.
13. An apparatus comprising a processor and configured to perform the method recited in claim 1 .
14. A non-transitory computer-readable storage medium having stored thereon computer-executable instruction for executing a method with one or more processors in accordance with claim 1 .