Embedding data within transformed coefficients using bit partitioning operations

A method of decoding signal data, the method comprising:

• obtaining an encoded bitstream;
• decoding the encoded bitstream to obtain an initial set of coefficient bits representing values for a set of transformed coefficients, the values being generated during encoding by applying at least a transform operation to blocks of signal data derived from an input signal;
• extracting userdata from a set of end bits of the initial set of coefficient bits, wherein the userdata is arranged as groups of bits, where each group of bits has a length that is equal to a size of a bit shift performed as a part of a bit shift operation;
• applying the bit shift operation to the initial set of coefficient bits, the bit shift operation being in a direction that is opposite to a direction of a bit shift operation applied during encoding, the bit shift operation generating a reconstructed set of coefficient bits, the bit shift operation shifting the coefficient bits by a predefined number of bits, which is based on the lengths of the groups of bits for the userdata;
• and
• instructing further decoding of the reconstructed set of coefficient bits, the further decoding comprising applying at least an inverse transform operation to values represented by the reconstructed set of coefficient bits, wherein the further decoding is used to generate a reconstruction of the input signal, wherein decoding the encoded bitstream comprises at least run-length decoding, and wherein further decoding of the reconstructed set of coefficient bits comprises applying an inverse quantisation operation prior to the inverse transform operation.

An encoder comprising:

• a coefficient interface to obtain coefficient bits representing values for a set of transformed coefficients, the values being generated by applying at least a transform operation to blocks of signal data derived from an input signal being encoded;
• a userdata interface to obtain userdata bits representing custom data to add to an encoded signal bitstream, wherein the userdata bits are arranged as groups of bits, where each group of bits has a length that is equal to a size of a bit shift performed as a part of a bit shift operation;
• a userdata insertion component to apply a-the bit shift operation to the coefficient bits and to set values of a set of additional bits added to the coefficient bits based on the userdata, the bit shift operation shifting the coefficient bits by a predefined number of bits, where that predefined number of bits is based on the lengths of the groups of bits for the userdata bits;
• and
• a bitstream encoding interface to output a modified set of coefficient bits as generated by the userdata insertion component for generation of an encoded bitstream,
• wherein a bitstream encoder is communicatively coupled to the bitstream encoding interface comprising at least a run-length encoder to generate an encoded bitstream.

A decoder comprising:

• a decoded bitstream interface to obtain an initial set of coefficient bits representing values for a set of transformed coefficients, the initial set of coefficient bits being decoded from an obtained encoded bitstream, the values being generated during encoding by applying at least a transform operation to blocks of signal data derived from an input signal;
• a userdata extraction component to extract userdata from a set of end bits of the initial set of coefficient bits and then to apply a bit shift operation to the initial set of coefficient bits, the bit shift operation generating a reconstructed set of coefficient bits, wherein the userdata is arranged as groups of bits, where each group of bits has a length that is equal to a size of a bit shift performed as a part of the bit shift operation;
• a coefficient decoding interface to output the reconstructed set of coefficient bits for further decoding, the further decoding comprising applying at least an inverse transform operation to values represented by the reconstructed set of coefficient bits, wherein the further decoding is used to generate a reconstruction of the input signal;
• and
• a bitstream decoder communicatively coupled to the decoded bitstream interface comprising at least a run-length encoder to decode the obtained encoded bitstream.