Quantization Parameters File Format - Quantization Parameters File Format - 3.0 English - PG447

When QPCtrlMode is set to LOAD_QP, the parameter specifies the location of the files containing the QP tables to use for each frame.

[SETTINGS]
QPCtrlMode = LOAD_QP
# or QPCtrlMode = LOAD_QP | RELATIVE_QP

[INPUT]
QpTablesFolder = <path>

QP table files must be in the current working directory, or in the directory given by the QPTablesFolder parameter if specified. QP table files must be named QPs.hex, in case the same QP table must be applied to all frames. For different QP tables for each frame, QP table files must be named QP_<frame_number>.hex.

QP table file must contains six lines per LCU, each line containing one 32-bit hexadecimal value.

For AVC, and for HEVC 32x32, QP/delta QPs are stored as 8 bits signed, and must be in range [-51; 51]. For HEVC, 16x16 delta QPs are stored on 6 bits signed, in range [-32; 31].

Lambda Factor

With LOAD_LDA a customized lambda can be provided to replace the ones used in RDO choices. This is a table with 2 lambdas per QP values. The Lambda Factor in the QP table is used to modify locally the lambda of the corresponding CTB. The Lambda Factor is an 8-bit value with 3 bits for integer part and 5 bits for fractional part (that is,value is using a 1/32th precision. The default value is 0x20 which corresponds to 1.0, for example, Lambda Factor = 0x1C correspond 0.875) The default Lambda table (or the provided lambda table using LOAD_LDA) is multiplied by this Lambda Factor before being used in the RDO.

Force DC Only

This flag, only the DC coefficient is kept after the Transform/Quantization. All ACs coefficients are removed. The flag does NOT force intra_DC prediction mode.

Force MVO

This flag forces Motion Vector = (0,0) and removes all coefficients after Transform/Quantization (all DC and ACs coefficients are removed). The block will be encoded as skip if the predicted Motion Vector is already (0,0), and if the number of bits needed to encode in skip is lower than the number of bits needed to encode it as MVP.

Force Intra

This flag forces intra-prediction. Force-MV0 flag forces inter-prediction with 0,0) motion vector and no residual. Both flags are propagated to sub-blocks, and mutually exclusive.

AVC example for one LCU:

10420020 
00000000
00000000
00000000
00000000
00000000

In this and following example:

• QPxdQP = 32
• Force Intra = 0
• ForceMv0 = 0
• DC only = 0
• MinBlkSize = 2
• MaxBlkSize = 4
• LambdaFactor = 16 (must contain 6 lines per LCU, therefore the 0s padding)

HEVC Example:

10420020
7E02813F
00000000
00000000
00000000
00000000

The 2^nd line: (note block 0 is stored in least significant bits)

dQP[0] = -1, Force Intra = 0, Force MV0 = 0,

dQP[1] = 1, Force Intra = 0, Force MV0 = 1,

dQP[2] = 2, Force Intra = 0, Force MV0 = 0,

dQP[3] = -2, Force Intra = 1, Force MV0 = 0