Enhancement decoder for video signals with multi-level enhancement and coding format adjustment

A method of encoding a video signal, the method comprising:

• receiving an input signal, the input signal being at a first bit depth;
• converting the input signal to a second bit depth to produce a converted input signal, the second bit depth being lower than the first bit depth;
• instructing the encoding of a signal derived from the converted input signal to produce a first encoded data stream at the second bit depth;
• instructing the decoding of the first encoded data stream to produce a first decoded data stream, the first decoded data stream being at the second bit depth;
• converting a signal derived from the first decoded data stream to the first bit depth to produce a first reconstruction of the input signal;
• and
• encoding a residual data stream as a difference between a signal derived from the first reconstruction of the input signal and the input signal to produce a second encoded data stream at the first bit depth,
• wherein the second encoded stream comprises:
• a first encoded sub-stream comprising, at the first bit depth, an encoding of a residual signal generated based on a comparison of the input signal and a signal derived from the first reconstruction of the input signal;
• and
• a second encoded sub-stream comprising, at the first bit depth, an encoding of a residual signal generated based on a comparison of the input signal and a signal derived from a decoding of the first encoded sub-stream.

A method of decoding a video signal, the method comprising:

• obtaining a decoding of a first encoded data stream as a first decoded data stream at a first bit depth;
• converting a signal derived from the first decoded data stream to a second bit depth to produce a first reconstruction of an original input signal, the second bit depth being higher than the first bit depth;
• decoding a second encoded data stream to produce residual data at the second bit depth;
• combining the residual data with a signal derived from the first reconstruction of the original input signal to produce an enhanced reconstruction of the original input signal at the second bit depth,
• wherein the residual data comprises:
• a first residual sub-stream comprising, at the second bit depth, first residual data for combing with the signal derived from the first reconstruction of the original input signal;
• and
• a second residual sub-stream comprising, at the second bit depth, second residual data for combining with a signal enhanced with the first residual data to produce the enhanced reconstruction of the original input signal at the second bit depth.

A video decoder comprising at least one processor and memory, the video decoder being configured to:

• obtain a decoding of a first encoded data stream as a first decoded data stream at a first bit depth;
• convert a signal derived from the first decoded data stream to a second bit depth to produce a first reconstruction of an original input signal, the second bit depth being higher than the first bit depth;
• decode a second encoded data stream to produce residual data at the second bit depth;
• combine the residual data with a signal derived from the first reconstruction of the original input signal to produce an enhanced reconstruction of the original input signal at the second bit depth,
• wherein the residual data comprises:
• a first residual sub-stream comprising, at the second bit depth, first residual data for combing with the signal derived from the first reconstruction of the original input signal;
• and
• a second residual sub-stream comprising, at the second bit depth, second residual data for combining with a signal enhanced with the first residual data to produce the enhanced reconstruction of the original input signal at the second bit depth.

An encoded bit stream comprising:

• at least a second encoded signal having a second bit depth, the second encoded signal comprising an encoding of a residual data stream for combination with a decoding of a first encoded signal having a first bit depth, the first encoded signal comprising an encoding of an original input video signal at the first bit depth, the second encoded signal comprising:
• a first encoded sub-stream comprising, at the second bit depth, an encoding of a residual signal generated based on a comparison of the original input video signal and a signal derived from a first reconstruction of the input signal;
• a second encoded sub-stream comprising, at the second bit depth, an encoding of a residual signal generated based on a comparison of the original input video signal and a signal derived from a decoding of the first encoded sub-stream;
• and
• metadata for reconstructing the original input video signal at the second bit depth, the metadata comprising frame-based metadata for outputting one or more of a high dynamic range (HDR) signal and a wide colour gamut (WCG) signal.