JP2007235756A5

JP2007235756A5 -

Info

Publication number: JP2007235756A5
Application number: JP2006056897A
Authority: JP
Filing date: 2006-03-02
Publication date: 2009-04-02
Anticipated expiration: 2026-03-02

Claims

Image data, input in a pixel block units I Table a plurality of pixels, an image coding apparatus for coding to the pixel block,
First encoding means for generating lossy encoded data for each pixel block using a quantization matrix Qi specified by a first parameter i;
Second encoding means for generating lossless encoded data for each pixel block;
Code length detection means for detecting the code length Ly of the lossy encoded data obtained by the first encoding means and the code length Lx of the lossless encoded data obtained by the second encoding means;
Using the boundary function fi, j () having a nonlinear boundary line specified by the first parameter i and the second parameter j, the code amounts Lx and Ly detected by the code length detection means are determined. And selecting means for selecting one of the lossy encoded data and the lossless encoded data as encoded data of the pixel block of interest to be stored in the output memory,
History information storage means for storing history information of selection processing by the selection means;
Monitoring the encoded data amount stored in the output memory, when the encoded data amount exceeds the goal amount, the boundary function fi, the first parameter i that define j (), the second Control means for updating at least one of the parameters j based on history information stored in the history information storage means,
The selection means includes
Condition: Ly <fi, j (Lx)
If the condition is satisfied, the lossy encoded data is selected.If the condition is not satisfied, the lossless encoded data is selected.
When the horizontal axis is a lossless encoded data length and the vertical axis is an irreversible encoded data length, the nonlinear boundary function fi, j () is shifted in the vertical axis direction according to the first parameter i. An image encoding apparatus, wherein the nonlinear boundary line is a function that shifts in a horizontal direction according to the second parameter j.

The control means further comprises means for re-inputting image data in accordance with the first parameter i and the second parameter j after the update process when it is determined that the encoded data amount exceeds the target amount. The image coding apparatus according to claim 1, further comprising:

And a work memory for storing the lossless encoded data generated by the second encoding means;
The lossless encoded data stored in the work memory is decoded, lossy encoded data is generated according to the quantization matrix Qi indicated by the first parameter i, and the lossy encoded data and the data before re-encoding are generated. Re-encoding means for selecting any one of the lossless encoded data according to the boundary function fi, j () and outputting the re-encoded data;
When the control means determines that the encoded data amount exceeds the target amount,
(A) discard the encoded data stored in the output memory;
(B) The quantization matrix Qi specified by the first parameter i after update processing is set in the first encoding unit and the re-encoding unit, and the codes by the first and second encoding units are set. And re-encoding by the re-encoding means is started,
(C) The re-encoded data obtained by the re-encoding unit is stored in the output memory.

The selection means has a look-up table corresponding to the boundary function fi, j (),
The lookup table inputs the lossless encoded data length Lx, the lossy encoded data length Ly, and the first and second parameters i and j as addresses, and indicates whether or not the condition is satisfied The image encoding device according to any one of claims 1 to 3, wherein data is stored.

The history information storage means stores a total code amount M1 of lossless encoded data selected to be stored in the output memory and a total code amount M2 of selected lossy encoded data;
The control means is configured such that M1 and M2 when it is determined that the amount of encoded data stored in the output memory exceeds the target amount,
Condition: M1 <M2
The first parameter i is updated when the condition is satisfied, and the second parameter is updated when the condition is not satisfied. 5. Image encoding device.

The history information storage means includes
The data length of lossless encoded data for each pixel block selected for storage in the output memory;
A data length of lossy encoded data for each pixel block selected for storage in the output memory;
For each of a plurality of candidates that can be employed during the next re-encoding, store the predicted lossy encoded data length for each pixel block and the prediction selection information by the selection unit,
The control means includes
The predicted encoded data amount to be stored in the output memory when it is assumed that each candidate is encoded is the lossless encoded data length, the predicted lossy encoded data length, and the prediction selection information. Based on
The calculated predicted encoded data amount of each candidate is compared with the target amount, and the first parameter i and the second parameter j are updated according to the candidate parameter whose difference from the target amount is minimized. The image encoding device according to claim 1, wherein the image encoding device is an image encoding device.

The image according to any one of claims 1 to 6, wherein the first encoding unit is a JPEG encoding unit, and the second encoding unit is a JPEG-LS encoding unit. Encoding device.

Image data, input in a pixel block units I Table a plurality of pixels, an image coding method for coding to the pixel block,
A first encoding step of generating lossy encoded data for each pixel block using a quantization matrix Qi identified by a first parameter i;
A second encoding step for generating lossless encoded data for each pixel block;
A code length detection step of detecting a code length Ly of the lossy encoded data obtained in the first encoding step, a code length Lx of the lossless encoded data obtained in the second encoding step;
The code amounts Lx and Ly detected in the code length detection step are determined using a boundary function fi, j () having a non-linear boundary line specified by the first parameter i and the second parameter j. A selection step of selecting either the lossy encoded data or the lossless encoded data as the encoded data of the target pixel block to be stored in the output memory;
A history information storage step for storing history information of selection processing by the selection step;
Monitoring the encoded data amount stored in the output memory, when the encoded data amount exceeds the goal amount, the boundary function fi, the first parameter i that define j (), the second A control step of updating at least one of the parameters j in accordance with the history information stored in the history information storage step,
The selection step includes
Condition: Ly <fi, j (Lx)
When the condition is satisfied, the lossy encoded data is selected, and when the condition is not satisfied, the lossless encoded data is selected,
When the horizontal axis is a lossless encoded data length and the vertical axis is an irreversible encoded data length, the nonlinear boundary function fi, j () is shifted in the vertical axis direction according to the first parameter i. An image coding method, wherein the nonlinear boundary line is a function that shifts in a horizontal direction according to the second parameter j.

The computer program for making a computer perform each process of Claim 8.

A computer-readable storage medium storing the computer program according to claim 9.