Patent ID: 11936879
Assignee: KAKADU R & D PTY LTD
Field: Audio-visual technology (Electrical engineering)
Classification: CPC H | IPC H

Claim 0:
1. A method for complexity constrained encoding of code-streams, including JPEG 2000 and High Throughput JPEG 2000 code-streams, subject to an overall target length constraint, involving the steps of:
a. collecting information about the sub-band samples produced by spatial transformation;
b. generation of coded length estimates from said collected information, for a plurality of potential bit-plane truncation points, where coded length estimates are formed incrementally, as sub-band samples become available from the spatial transformation;
c. determination of a quantization parameter (QP value) from these length estimates, such that after mapping the QP value to a base bit-plane index for each relevant code-block of each sub-band, the estimated overall coded length when truncating at these hit-plane indices is not expected to exceed said overall target length constraint;
d. mapping said QP value to a base bit-plane index for each code-block;
e. encoding each relevant code-block to a precision associated with the corresponding base bit-plane index, and encoding one or more additional coding passes from each such code-block; and
f. subjecting all such generated coding passes to a post-compression rate-distortion optimization process to determine a final set of coding passes emitted from each code-block as the compressed result,
where the QP value is updated incrementally according to a coded length budget that starts out equal to the overall target length constraint, and code-blocks become available incrementally for coding, said code-blocks being identified as “dispatched code-blocks,” involving the following steps:
i. collection of length estimates that are based on the samples that have become available for a sub-band into estimated length records;
ii. generation of forecast length records which anticipate the coded lengths that would be estimated for the samples that have not yet become available for the sub-band;
iii. incremental determination of a QP value, based on the estimated length records and forecast length records, such that after mapping the QP value to a base bit-plane index for each non-dispatched code-block of each sub-band, the estimated overall coded length for non-dispatched code-blocks, when truncating at these bit-plane indices, is not expected to exceed the remaining length budget;
iv. mapping said QP value to a base bit-plane index for non-dispatched code-blocks for which sub-band samples are available, such code-blocks being identified as “active code-blocks”;
v. entering the active code-blocks into the set of dispatched code-blocks, while subtracting the estimated coded lengths, corresponding to truncation at their respective base bit-plane indices, from the coded length budget;
vi. encoding dispatched code-blocks to the precision associated with their respective base bit-plane indices, and encoding one or more additional coding passes from each such code-block; and
vii. making all such generated coding passes available to the post-compression rate-distortion optimization process.