Image decoding apparatus

Abstract

Provided in an image decoding apparatus including an input unit for inputting a code stream; a low frequency sub-band component decoding unit for decoding a low frequency component; a high frequency sub-band component decoding unit for decoding a high frequency component; a substitute image producing unit for processing the low frequency component decoded image to produce a substitute image; an error detecting unit for detecting an error when a decoding operation is carried out; a timing producing unit for producing a timing signal; a remaining decoding time calculating unit for calculating a remaining decoding time based on both the error detection signal and the timing signal; an output image control unit for controlling to adaptively select an output image based on the error detection signal and the decoding process time signal; and an output image selecting unit for selecting any one of the high frequency component decoded image and the substitute image based on the control operation by the output image control means, and for outputting the selected image as a display image.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a block diagram for showing an arrangement of an image decoding apparatus according to Embodiment 1 of the present invention;

FIG. 2 is a flow chart for explaining operations of an output image control means 9 according to Embodiment 1 of the present invention;

FIG. 3 is a block diagram for showing an arrangement of an image decoding apparatus according to Embodiment 2 of the present invention;

FIG. 4 is a flow chart for explaining operations of an output image control means 9 according to Embodiment 2 of the present invention;

FIG. 5 is a block diagram for showing an arrangement of an image decoding apparatus according to Embodiment 3 of the present invention;

FIG. 6 is a flow chart for explaining operations of an output image control means 9 according to Embodiment 3 of the present invention; and

FIG. 7 is a flow chart for explaining operations which are continued to those of FIG. 6.

Claims

1. An image decoding apparatus, comprising: an input means for inputting a code stream which has been coded in a plurality of sub-band components and for resolving the input code stream to obtain a low frequency component code stream and a high frequency component code stream, which are outputted;a low frequency sub-band component decoding means for decoding the low frequency component code stream so as to output a low frequency component decoded image;a high frequency sub-band component decoding means for decoding the high frequency component code stream so as to output a high frequency component decoded image;a substitute image producing means for processing the low frequency component decoded image from the low frequency sub-band component decoding means so as to produce a substitute image;an error detecting means for detecting an error occurred when the high frequency component code stream and the low frequency component code stream are decoded;a timing producing means for producing a timing signal used in a decoding process;a remaining decoding time calculating means for calculating a remaining time to perform the decoding process based on an error detection signal from the error detecting means and the timing signal from the timing producing means, and for outputting a decoding process time signal;an output image control means for controlling to adaptively select an output image based on the error detection signal from the error detecting means and the timing signal from the timing producing means; andan output image selecting means for selecting any one of the high frequency component decoded image from the high frequency sub-band component decoding means and the substitute image from the substitute image producing means based on the control operation by the output image control means, and for outputting the selected image as a display image.

2. The image decoding apparatus as claimed in claim 1, wherein: in the case that an error is not detected in the high frequency component based on the error detection signal from the error detecting means, the output image control means outputs an image selection control signal to the output image selecting means in order to select the high frequency component decoded image from the output image selecting means as the display image;in the case that an error is detected in the high frequency component based on the error detection signal from the error detecting means, and further, a re-decoding process time is left based on the decoding process time from the remaining decoding time calculating means, the output image control means outputs a substitute decoding parameter to the high frequency sub-band decoding means and outputs an image selection control signal to the output image selecting means in order to cause the high frequency sub-band component decoding means to execute a re-decoding operation, so as to select the high frequency component decoded image from the high frequency sub-band component decoding means as the display image; andin the case that an error is detected in the high frequency component based on the error detection signal from the error detecting means, and further, a re-decoding process time becomes short based on the decoding process time from the remaining decoding time calculating means, the output image control means outputs a substitute image production signal to the substitute image producing means and outputs an output image control signal to the output image selecting means in order to select the substitute image from the substitute image producing means as the display image.

3. The image decoding apparatus as claimed in claim 1 further comprising a preceding frame image storage means for storing thereinto an image of a preceding frame and interframe difference acquiring means for acquiring an interframe difference between the preceding frame and the present frame, wherein: the substitute image producing means further produces a substitute image by employing a preceding frame decoded image;in the case that an error is not detected in both in a low frequency component and a high frequency component based on the error detection signal from the error detecting means, the output image control means outputs an image selection control signal to the output image selecting means in order to output the high frequency component decoded image signal from the high frequency sub-band component decoding means as the display image;in such a case that an error is not detected in a low frequency component but an error is detected in a high frequency component based on the error detection signal from the error detecting means, and further, a re-decoding process is left based on the decoding process time signal from the remaining decoding time calculating means, the output image control means outputs a substitute decoding parameter to the high frequency sub-band component decoding means and also outputs an image selection control signal to the output image selecting means in order to output the high frequency component decoded image from the high frequency sub-band component decoding means as the display image;in such a case that an error is not detected in a low frequency component but an error is detected in a high frequency component based on the error detection signal from the error detecting means, a re-decoding process is left based on the decoding process time signal from the remaining decoding time calculating means, and further, the interframe difference from the interframe difference acquiring means is larger than a defined value, the output image control means outputs a substitute image production signal to the substitute image producing means and also outputs an image selection control signal to the output image selecting means in order to select the substitute image from the substitute image producing means as the display image; andin such a case that an error is not detected in a low frequency component but an error is detected in a high frequency component based on the error detection signal from the error detecting means, a re-decoding process is left based on the decoding process time signal from the remaining decoding time calculating means, and further, the interframe difference from the interframe difference acquiring means is smaller than or equal to the defined value, or in such a case that an error is detected in the low frequency component based on the error detection signal from the error detecting means, the output image control means outputs a substitute image production signal to the substitute image producing means and also outputs an image selection control signal to the output image selecting means in order to select the substitute image as the display image by adopting the preceding frame decoded image from the substitute image producing means.

4. The image decoding apparatus as claimed in claim 1, wherein the output image control means adaptively selects the output image based on an error detection result of color information of the high frequency component contained in the code stream.