System and method for video coding

An encoder, comprising:

• a block splitter, which, in operation, splits a first image into a plurality of blocks;
• an intra predictor, which, in operation, predicts blocks included in the first image, using reference blocks included in the first image;
• an inter predictor, which, in operation, predicts blocks included in the first image, using reference blocks included in a second image different from the first image;
• a loop filter, which, in operation, filters blocks included in the first image;
• a transformer, which, in operation, transforms a prediction error between an original signal and a prediction signal generated by the intra predictor or the inter predictor, to generate transform coefficients;
• a quantizer, which, in operation, quantizes the transform coefficients to generate quantized coefficients;
• and
• an entropy encoder, which, in operation, variable encodes the quantized coefficients to generate an encoded bitstream including the encoded quantized coefficients and control information,
• wherein predicting a block includes:
• determining whether to split a current luma virtual pipeline decoding unit (VPDU) into smaller blocks;
• in response to a determination not to split the current luma VPDU into smaller blocks, not scaling prediction residuals of chroma samples based on prediction residuals of luma samples;
• and
• in response to a determination to split the luma VPDU into smaller blocks, scaling the prediction residuals of chroma samples based on prediction residuals of luma samples.

A decoder, comprising:

• circuitry;
• memory coupled to the circuitry;
• wherein the circuitry, in operation, performs the following:
• determining whether to split a current luma virtual pipeline decoding unit (VPDU) into smaller blocks;
• in response to a determination not to split the current luma VPDU into smaller blocks, not scaling prediction residuals of chroma samples based on prediction residuals of luma samples;
• in response to a determination to split the luma VPDU into smaller blocks, scaling the prediction residuals of chroma samples based on prediction residuals of luma samples;
• and
• decoding the block based on the prediction residuals of chroma samples.

A decoding device, comprising:

• a decoder, which, in operation, decodes an encoded bitstream to output quantized coefficients;
• an inverse quantizer, which, in operation, inverse quantizes the quantized coefficients to output transform coefficients;
• an inverse transformer, which, in operation, inverse transforms the transform coefficients to output a prediction error;
• an intra predictor, which, in operation, predicts blocks included in a first image, using a reference blocks included in the first image;
• an inter predictor, which, in operation, predicts blocks included in the first image, using reference blocks included in a second image different from the first image;
• a loop filter which, in operation, filters blocks included in the first image;
• and
• an output, which, in operation, outputs a picture including the first image,
• wherein predicting a block includes:
• determining whether to split a current luma virtual pipeline decoding unit (VPDU) into smaller blocks;
• in response to a determination not to split the current luma VPDU into smaller blocks, not scaling prediction residuals of chroma samples based on prediction residuals of luma samples;
• and
• in response to a determination to split the luma VPDU into smaller blocks, scaling the prediction residuals of chroma samples based on prediction residuals of luma samples.

An encoding method, comprising:

• determining whether to split a current luma virtual pipeline decoding unit (VPDU) into smaller blocks;
• in response to a determination not to split the current luma VPDU into smaller blocks, not scaling prediction residuals of chroma samples based on prediction residuals of luma samples;
• in response to a determination to split the luma VPDU into smaller blocks, scaling the prediction residuals of chroma samples based on prediction residuals of luma samples;
• and
• encoding the block based on the prediction residuals of chroma samples.

A decoding method, comprising:

• determining whether to split a current luma virtual pipeline decoding unit (VPDU) into smaller blocks;
• in response to a determination not to split the current luma VPDU into smaller blocks, not scaling prediction residuals of chroma samples based on prediction residuals of luma samples;
• in response to a determination to split the luma VPDU into smaller blocks, scaling the prediction residuals of chroma samples based on prediction residuals of luma samples;
• and
• decoding the block based on the prediction residuals of chroma samples.