Efficient Use of Quantization Parameters in Machine-Learning Models for Video Coding

An apparatus for encoding an image block using a first quantization parameter, comprising:

• a processor that:
• presents, to a machine-learning model, the image block and a first value corresponding to the first quantization parameter,
• wherein the first value results from a non-linear function using the first quantization parameter as input,
• wherein the non-linear function relates to a second function used to calculate, using the first quantization parameter, a Lagrange multiplier that is used in a rate-distortion calculation, and
• wherein the machine-learning model is trained to output mode decision parameters for encoding the image block by:
• using training data as inputs to the training of the machine-learning model, each training datum including:
• a training block that is encoded by an encoder;
• second mode decision parameters used by the encoder for encoding the training block;
• and
• a second value corresponding to a second quantization parameter,
• wherein the encoder used the second quantization parameter for encoding the training block, and
• wherein the second value results from the non-linear function using the second quantization parameter as input;
• obtains first mode decision parameters from the machine-learning model;
• and
• encodes, in a compressed bitstream, the image block using the first mode decision parameters.

An apparatus for decoding an image block, comprising:

• a processor that:
• receives, in a compressed bitstream, an indication of a quad-tree partitioning of the image block into sub-blocks, wherein an encoder determined the quad-tree partitioning of the image block using a machine-learning model that is trained by:
• using training data as inputs to train the machine-learning model, each training datum including
• a training block that is encoded by the encoder,
• mode decision parameters used by the encoder for encoding the training block, and
• a value corresponding to a quantization parameter,
• wherein the encoder used the quantization parameter for encoding the training block,
• wherein the value results from a non-linear function using the quantization parameter as input, and
• wherein the non-linear function relates to a second function used to calculate, using the quantization parameter, a multiplier that is used in a rate-distortion calculation;
• and
• decodes the image block using the indication of the quad-tree partitioning of the image block.