Methods and devices for entropy coding in scalable video compression

A decoder for decoding a block of enhancement-layer transform domain data for an encoded video and corresponding to a reconstructed block of reference-layer transform domain data, the decoder comprising:

• a processor;
• a memory;
• and
• a decoding application stored in memory and containing instructions for configuring the processor to, for an enhancement-layer element of the block of enhancement-layer transform domain data, wherein the block of enhancement-layer transform domain data is of size W×H, wherein the reconstructed block of reference-layer transform domain data is of size W/R×H/R, and wherein R comprises a non-unity scale factor:
• determine whether the enhancement-layer element is located in an upper-left W/R×H/R portion of the block of enhancement-layer transform domain data and,
• if the enhancement-layer element is within the upper left W/R×H/R portion, determine a context for that enhancement-layer element based, at least in part, upon a plurality of elements in the reconstructed block of reference-layer transform domain data without upscaling, wherein the plurality of elements are identified by a template that selects the plurality of elements in the reference-layer and wherein the position of the template in the reconstructed block reference-layer of transform domain data is based upon the position of that enhancement-layer element in the block of enhancement-layer transform domain data, and
• if the enhancement-layer element is not within the upper left W/R×H/R portion, determine the context for that enhancement-layer element using single-layer contexts;
• entropy decode that enhancement-layer element using its determined context;
• and
• reconstruct and output for display a block of image data based on the block of enhancement-layer transform domain data.

A non-transitory processor-readable medium storing processor-executable instructions which, when executed, cause one or more processors to decode a block of enhancement-layer transform domain data for an encoded video and corresponding to a reconstructed block of reference-layer transform domain data, wherein the instructions, when executed, cause the one or more processors to:

• for an enhancement-layer element of the block of enhancement-layer transform domain data, wherein the block of enhancement-layer transform domain data is of size W×H, wherein the reconstructed block of reference-layer transform domain data is of size W/R×H/R, and wherein R comprises a non-unity scale factor,
• determine whether the enhancement-layer element is located in an upper-left W/R×H/R portion of the block of enhancement-layer transform domain data and,
• if the enhancement-layer element is within the upper left W/R×H/R portion, determine a context for that enhancement-layer element based, at least in part, upon a plurality of elements in the reconstructed block of reference-layer transform domain data without upscaling, wherein the plurality of elements are identified by a template that selects the plurality of elements in the reference-layer and wherein the position of the template in the reconstructed block of reference-layer transform domain data is based upon the position of that enhancement-layer element in the block of enhancement-layer transform domain data, and
• if the enhancement-layer element is not within the upper left W/R×H/R portion, determine the context for that enhancement-layer element using single-layer contexts;
• entropy decode that enhancement-layer element using its determined context;
• and
• reconstruct and output for display a block of image data based on the block of enhancement-layer transform domain data.