The QP table modes are enabled by using QpCtrlMode = LOAD_QP or QpCtrlMode = LOAD_QP | RELATIVE_QP.
In this case, the reference model uses the file QPs.hex in working directory to specify the QP values at LCU level. Each line of QPs.hex contains one 8-bit hexadecimal value. For H.264 (AVC), there is one byte per 16×16 MB (in raster scan format): absolute QP in [0;51] or relative QP in [‑32;31]. For H.265 (HEVC), there is one byte per 32×32 LCU (in raster scan format): absolute QP in [0;51] or relative QP in [‑32;31].
For example, to specify the following relative QP table:
| ‑1 | ‑2 | 0 | 1 | 1 | 4 |
| ‑4 | ‑1 | 1 | 2 | 2 | 1 |
| ‑1 | 0 | ‑1 | 1 | 1 | 4 |
| 0 | 0 | ‑2 | 2 | 2 | 6 |
| 1 | ‑2 | 0 | 1 | 4 | 2 |
The QPs.hex file for H.265 (HEVC) is:
3F
3E
00
01
01
04
3C
3F
...If a file with name equal to QP_<frame number>.hex is present in the working folder, the encoder uses it for frame number <frame number> instead of QPs.hex.
For example if you have the following files in the working folder:
- QP_0.hex
- QP_4.hex
- QPs.hex
The encoder uses QP_0.hex for frame #0, QP_4.hex for frame #4 and QPs.hex for all other frames (i.e. frame #1, #2, #3, #5, #6 ...).