- Text
- Display,
- Eotf,
- Matrix,
- Oetf,
- Ycbcr,
- Peak,
- Transcode,
- Brightness,
- Ootf,
- Conversion,
- Perceptual,
- Quantiser,
- Hybrid,
- Transcoding

BBC_HDRTV_PQ_HLG_Transcode

Display Light Scene Light Transcode **PQ** **to** **HLG** for a Common Display Brightness System Overview The transcode process outlined in ITU-R BT.2390 is as follows: **PQ** Signal Display Light **PQ** EOTF **HLG** EOTF -1 **HLG** Signal Figure 1: **PQ** TO **HLG** High Level Overview where the **HLG** EOTF -1 consists of an inverse Op**to**-Optical Transfer Function (OOTF -1 ) followed by the **HLG** OETF: **PQ** Signal **PQ** EOTF Display Light OOTF -1 Scene Light **HLG** OETF **HLG** Signal Peak Mastering Level, Colour Space Figure 2: **PQ** To **HLG** Overview The OOTF -1 process can be broken down as follows: Peak Mastering Level Colour Space RGB **to** Y Y Y 1/γ **Gamma** -1 Y (1-γ)/γ Ratio Figure 3: OOTF -1 procedure X X X {R,G,B}· Y (1-γ)/γ The **PQ** EOTF and **HLG** OETF are defined by BT.2100-0.

Step by Step Guide Below is a fully explained procedure for the transcode process. This process is appropriate for implementation in a 3D look up table (LUT). Note, the range of the values at each stage is between 0.0 and 1.0. 1. Apply the **PQ** EOTF **to** the signal, as per Table 4 in BT. 2100-0. Note the multiplication by 10000 is not required. This is now display light in the range of 0.0 **to** 1.0, where 1.0 represents 10000 cd/m 2 . Y max c 1 m 1 m 1 2 E c ,0 2 c E 3 1 1 m2 2. Normalise the display signal using the peak mastering level. The mastering level can be obtained from analysing the signal, or alternatively, may be available as metadata, e.g. by knowing which mastering moni**to**r was used. For a **PQ** signal graded on a 1000 cd/m 2 display, there should be no data above 1000 cd/m 2 as this would have been clipped by the display. Therefore, the signal should be normalised so that 1.0 now corresponds **to** 1000 cd/m 2 . Similarly, for **PQ** content graded at 4000 cd/m 2 , there should be no data above 4000 cd/m 2 as this would have been clipped by the display. Therefore, the signal should be normalised so that 1.0 now corresponds **to** 4000 cd/m 2 . F d Y *10000 min , 1. 0 Lw where Y is the {R,G,B} signal, and L w is the peak brightness of mastering display in cd/m 2 . This signal is display referred linear. 3. The OOTF -1 is now applied **to** convert the display linear signal **to** a scene linear signal. First the display luminance of the display is calculated. Note that the coefficients in the conversion must correspond **to** the correct colour primaries of the signal. BT.2020 primaries have been used for the conversion below. Y 0.2627 R 0.6780G 0. 0593B d d d d

- Page 1: Perceptual Quantiser (PQ) to Hybrid
- Page 5 and 6: Transcode HLG to PQ for a Common Di
- Page 7 and 8: HLG content shown on a 1000 cd/m 2
- Page 9: YCbCr2020 signal YCbCr to RGB using