US 6,212,236 B1Granted

Image decoding apparatus

AssigneeMatsushita Electric Industrial Co., Ltd.

InventorsHideshi Nishida, Kozo Kimura, Makoto Hirai, Tokuzo Kiyohara

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Abstract

Bitstream analyzing unit 111 fetches a coded block pattern and a coded quantized DCT coefficient from each block in a bitstream. Entropy decoding unit 112 decodes the coded block pattern into a block pattern and decodes the coded quantized DCT coefficient into pairs of a run length and an effectiveness factor. Dequantization unit 115 generates orthogonal transformation coefficients from the pairs of a run length and an effectiveness factor. Inverse Discrete Cosine Transform (IDCT) unit 110 generates a difference image from the orthogonal transformation coefficients. Decode controlling unit 110 instructs first selecting unit 118 to select constants “0”output from first constant generating unit 117 when the image is a “skipped” block. Image storage unit 120 stores a plurality of reference frame pictures having been decoded. Image restoring unit 119 restores an original block by adding a decoded difference image to a reference block read from the reference frame pictures stored in the image storage unit 120.

Claims41

Dependent claims

An image decoding apparatus for decoding coded data to generate moving pictures, the image decoding apparatus comprising:

extracting means for extracting a coded unit image from the coded data, wherein the coded unit image includes difference information which indicates whether an original unit image of the coded unit image is equal to a reference unit image which is a part of a frame picture having been decoded, and, during a predictive coding process, the original unit image is transformed into the coded unit image which includes difference values between pixel values of the original unit image and pixel values of the reference unit image when the difference information indicates that the original unit image is different from the reference unit image, wherein the coded unit image including the difference values is also called a coded difference unit image, the original unit image and the reference unit image each having a same, predetermined number of pixels;
difference decoding means for decoding the coded difference unit image including the difference values to generate a difference unit image;
preventing means for preventing the difference decoding means from generating the difference unit image when the extracted difference information indicates that the original unit image of the coded unit image is equal to the reference unit image;
first constant generating means for generating a first constant image which is composed of constants “0”;
first image selecting means for selecting the first constant image when the difference information indicates that the original unit image is equal to the reference unit image and selecting the difference unit image when the difference information indicates that the original unit image is different from the reference unit image;
and
image restoring means for restoring the original unit image by adding a result selected by the first image selecting means to the reference unit image.

4 more elements

An image decoding apparatus for decoding coded data to generate moving pictures, the image decoding apparatus comprising:

effectiveness factor generating means for extracting a coded unit image from the coded data, decoding the extracted coded unit image to generate one or more pairs of an effectiveness factor and a run length, wherein original unit images making up frame pictures of moving pictures are coded in sequence for each frame picture to turn into coded unit images, each original unit image having a predetermined number of pixels;
first error detecting means for detecting an out-of-range error which indicates that the coded unit image includes a value exceeding a predetermined range,
second constant generating means for generating constants “0” when the first error detecting means does not detect the out-of-range error, wherein the constants “0” generated by the second constant generating means are called second constants;
second image selecting means, when the first error detecting means does not detect the out-of-range error, for selecting as many second constants as specified by the run lengths generated by the effectiveness factor generating means and generating a coefficient sequence by combining the selected second constants with the effectiveness factors generated by the effectiveness factor generating means;
dequantization means for executing a dequantization on the coefficient sequence to generate an orthogonal transformation coefficient sequence;
conversion means for executing an inverse orthogonal transformation on the orthogonal transformation coefficient sequence to restore the original unit image,
image storage means for storing one or more reference frame pictures having been decoded and a first frame picture which is a currently decoded frame picture;
partial restoring means for reading a reference unit image from the reference frame pictures stored in the image storage means, restoring the original unit image by adding the unit image selected by the first image selecting means to the read reference unit image, and writing the restored original unit image into the first frame picture stored in the image storage means;
first error controlling means for instructing the effectiveness factor generating means to stop decoding the coded unit image and to extract a next coded unit image from the coded data when the first error detecting means detects the out-of-range error;
and
error image restoring means for generating a replacement unit image using a reference unit image of the reference frame pictures stored in the image storage means and writing the replacement unit image into the first frame picture stored in the image storage means in place or the coded unit image when the first error detecting means detects the out-of-range error.

8 more elements

An image decoding apparatus for decoding coded data to generate moving pictures, the image decoding apparatus comprising:

effectiveness factor generating means for extracting a coded unit image from the coded data, decoding the extracted coded unit image to generate one or more pairs of an effectiveness factor and a run length, wherein original unit images making up a frame pictures of moving pictures are coded in sequence for each frame picture to turn into coded unit images, each original unit image having a predetermined number of pixels;
second constant generating means for generating constants “0,” wherein the constants “0” generated by the second constant generating means are called second constants;
second image selecting means for selecting as many second constants as specified by the run lengths generated by the effectiveness factor generating means and generating a coefficient sequence by combining the selected second constants with the effectiveness factors generated by the effectiveness factor generating means;
dequantization means for executing a dequantization on the coefficient sequence to generate an orthogonal transformation coefficient sequence;
conversion means for executing an inverse orthogonal transformation on the orthogonal transformation coefficient sequence to generate a unit image;
image storage means for storing one or more reference frame pictures having been decoded and a first frame picture which is a currently decoded frame picture;
partial restoring means for reading a reference unit image from the reference frame pictures stored in the image storage means, restoring the original unit image by adding the unit image selected by the first image selecting means to the read reference unit image, and writing the restored original unit image into the first frame picture stored in the image storage means;
second error detecting means for detecting a motion compensation error;
error image restoring means for generating a replacement unit image using a reference unit image or the reference frame pictures stored in the image storage means and writing the replacement unit image into the first frame picture stored in the image storage means in place of the coded unit image when the second error detecting means detects the motion compensation error;
and
second error controlling means for instructing the effectiveness factor generating means to stop decoding the coded unit image and to extract a next coded unit image from the coded data when the second error detecting means detects the motion compensation error.

8 more elements

Dependencies are inferred from the claim text.