The present application is a 371 US Nationalization of International Patent Application No. PCT/GB2018/053553, filed Dec. 6, 2018, which claims priority to United Kingdom Patent Application No. 1720365.4, filed Dec. 6, 2017, the entire disclosures of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to processing signal data using an upsampling adjuster.

BACKGROUND

Compression and decompression of signals is an important consideration in many known systems.

Many types of signal, for example video, images, audio or volumetric signals, may be compressed and encoded for transmission, for example over a data communications network. Other signals may be stored in a compressed form, for example on a storage medium such as a Digital Versatile Disc (DVD). When such a signal is decoded, it may be desired to increase a level of quality of the signal and/or recover as much of the information contained in the original signal as possible.

Some known systems exploit scalable encoding techniques. Scalable encoding involves encoding a signal along with information to allow the reconstruction of the signal at different levels of quality, depending on the capabilities of the decoder and the available bandwidth. However, relatively large amounts of information may need to be stored and/or transmitted, particularly as the usage of higher quality, higher definition video becomes more widespread.

Some known scalable encoding systems use an upsampler to upsample signal data. There may be differences, however, between the upsampled data and the original signal. Inefficiencies may result in relation to encoding data used by a decoder to reconstruct the original signal.

SUMMARY

According to a first aspect of the present invention, there is provided a method of processing signal data at an encoder device, the method comprising:

obtaining a representation of a signal at a first level of quality;

upsampling the representation at the first level of quality using an upsampler in the encoder device to derive a preliminary representation of the signal at a second, higher level of quality;

deriving adjustment data using the representation at the first level of quality as an input to an upsampling adjuster arranged in parallel with the upsampler in the encoder device, the adjustment data being useable by the encoder device to adjust the preliminary representation;

using the preliminary representation and the adjustment data to derive an adjusted representation of the signal at the second level of quality; and

deriving, using the adjusted representation, residual data useable by a decoder device to reconstruct a reference representation of the signal at the second level of quality using the adjusted representation.

According to a second aspect of the present invention, there is provided a method of processing signal data at a decoder device, the method comprising:

obtaining a representation of a signal at a first level of quality;

upsampling the representation at the first level of quality using an upsampler in the decoder device to derive a preliminary representation of the signal at a second, higher level of quality;

deriving adjustment data using the representation at the first level of quality as an input to an upsampling adjuster arranged in parallel with the upsampler in the decoder device, the adjustment data being useable by the decoder device to adjust the preliminary representation;

using the preliminary representation and the adjustment data to derive an adjusted representation of the signal at the second level of quality;

receiving data useable by the decoder device to derive residual data useable by the decoder device to reconstruct a reference representation of the signal at the second level of quality using the adjusted representation;

deriving the residual data using the received data; and

reconstructing the reference representation using the adjusted representation and the residual data.

According to a third aspect of the present invention, there is provided a method of processing signal data at an encoder device, the method comprising:

obtaining a representation of a signal at a first level of quality;

upsampling the representation at the first level of quality using a first upsampler in the encoder device to derive a first preliminary representation of the signal at a second, higher level of quality;

deriving first adjustment data using the representation at the first level of quality as an input to a first upsampling adjuster arranged in parallel with the first upsampler in the encoder device, the first adjustment data being useable by the encoder device to adjust the first preliminary representation;

using the first preliminary representation and the first adjustment data to derive a first adjusted representation of the signal at the second level of quality;

deriving, using the first adjusted representation, first residual data useable by a decoder device to reconstruct a reference representation of the signal at the second level of quality using the first adjusted representation;

using the first adjusted representation and the first residual data, reconstructing the reference representation at the second level of quality;

upsampling the reference representation at the second level of quality using a second upsampler in the encoder device to derive a second preliminary representation of the signal at a third level of quality, higher than the second level of quality;

deriving second adjustment data using the reference representation at the second level of quality and data output from the first upsampling adjuster as inputs to a second upsampling adjuster arranged in parallel with the second upsampler in the encoder device, the second adjustment data being useable by the encoder device to adjust the second preliminary representation;

using the second preliminary representation and the second adjustment data to derive a second adjusted representation of the signal at the third level of quality; and

deriving, using the second adjusted representation, second residual data useable by a decoder device to reconstruct a reference representation of the signal at the third level of quality using the second adjusted representation.

According to a fourth aspect of the present invention, there is provided a method of processing signal data at a decoder device, the method comprising:

obtaining a representation of a signal at a first level of quality;

upsampling the representation at the first level of quality using a first upsampler in the decoder device to derive a first preliminary representation of the signal at a second, higher level of quality;

deriving first adjustment data using the representation at the first level of quality as an input to a first upsampling adjuster arranged in parallel with the first upsampler in the decoder device, the first adjustment data being useable by the decoder device to adjust the first preliminary representation;

using the first preliminary representation and the first adjustment data to derive a first adjusted representation of the signal at the second level of quality;

receiving first data useable by the decoder device to derive first residual data useable by the decoder device to reconstruct a reference representation of the signal at a second, higher level of quality using the first adjusted representation;

deriving the first residual data using the received first data;

reconstructing the reference representation at the second level of quality using the first adjusted representation and the first residual data;

upsampling the reference representation at the second level of quality using a second upsampler in the decoder device to derive a second preliminary representation of the signal at a third level of quality, higher than the second level of quality;

deriving second adjustment data using the reference representation at the second level of quality and data output from the first upsampling adjuster as inputs to a second upsampling adjuster arranged in parallel with the second upsampler in the decoder device, the second adjustment data being useable by the decoder device to adjust the second preliminary representation;

using the second preliminary representation and the second adjustment data to derive a second adjusted representation of the signal at the third level of quality;

receiving second data useable by the decoder device to derive second residual data useable by the decoder device to reconstruct a reference representation of the signal at the third level of quality using the second adjusted representation;

deriving the second residual data using the received second data; and

reconstructing the reference representation at the third level of quality using the second adjusted representation and the second residual data.

According to a fifth aspect of the present invention, there is provided an apparatus arranged to perform a method according to any of the first, second, third or fourth aspects of the present invention.

According to a sixth aspect of the present invention, there is provided a computer program comprising instructions which, when executed, cause an apparatus to perform a method according to any of the first, second, third or fourth aspects of the present invention.

