Method and apparatus for digital image decoding

A digital image decoding apparatus for decoding encoded data of an image with a given size, said digital image decoding apparatus comprising:

• a frame memory having a capacity for storing data on a frame basis;
• a decoding section for inputting the encoded data which is encoded in accordance with an inter/intra-frame coding in a digital image coding apparatus and decoding the encoded data in accordance with an inter/intra-frame decoding on the frame basis and outputting decoded data;
• a compressing section, locating between the frame memory and the decoding section, for inputting the decoded data outputted from the decoding section, compressing the decoded data in accordance with a non-inter/intra-frame coding and outputting compressed data to the frame memory so as to store the compressed data to the frame memory;
• and
• an expanding section, locating between the frame memory and the decoding section, for reading out and expanding the compressed data stored in the frame memory and in accordance with a non-inter/intra-frame decoding and outputting expanded data to the decoding section,
• wherein said decoding section decodes the encoded data sequentially on a block basis and outputs block-based decoded data;
• and
• wherein said compressing section compresses the block-based decoded data in a period shorter than a period for decoding the block-based encoded data in said decoding section.

A digital image decoding apparatus for decoding encoded data of an image with a given size, said digital image decoding apparatus comprising:

• a frame memory having a capacity for storing data on a frame basis;
• a decoding section for inputting the encoded data which is encoded in accordance with an inter/intra-frame coding in a digital image coding apparatus and decoding the encoded data in accordance with an inter/intra-frame decoding on the frame basis and outputting decoded data;
• a compressing section, locating between the frame memory and the decoding section, for inputting the decoded data outputted from the decoding section, compressing the decoded data in accordance with a non-inter/intra-frame coding and outputting compressed data to the frame memory so as to store the compressed data to the frame memory;
• an expanding section, locating between the frame memory and the decoding section, for reading out and expanding the compressed data stored in the frame memory and in accordance with a non-inter/intra-frame decoding and outputting expanded data to the decoding section,
• wherein said decoding section decodes the encoded data including profile information of a coding method for the encoded data;
• and
• a profile judging section for receiving the encoded data and judging the profile of the coding method;
• wherein said compressing section, including a plurality of modes of compression, receives the profile information and selects one of the plurality of modes optimal to the coding method.

A digital image decoding apparatus for decoding encoded data of an image with a given size, said digital image decoding apparatus comprising:

• a frame memory having a capacity for storing the encoded data on a frame basis;
• a decoding section for decoding the encoded data on the frame basis and outputting decoded data;
• a compressing section for compressing the decoded data and outputting compressed data;
• and
• an expanding section for reading out and expanding the compressed data stored in the frame memory and outputting expanded data;
• wherein said decoding section decodes the encoded data on a block basis and outputs a block of M pixels×N pixels×r bits of the decoded data;
• wherein said compressing section compresses the block-based decoded data to the block-based compressed data through a conversion method, which calculates a coefficient of image quality of the block-based decoded data, and allocates a longer bit-length to the block-based decoded data for a coefficient highly influential on image quality, and a shorter bit-length to the decoded data for a less influential coefficient;
• and
• wherein said compressing section converts the block-based decoded data into a fixed bit-length of the block-based compressed data.

A digital image decoding apparatus for decoding encoded data of an image with a given size, said digital image decoding apparatus comprising:

• a frame memory having a capacity for storing the encoded data on a frame basis;
• a decoding section for decoding the encoded data on the frame basis and outputting decoded data;
• a compressing section for compressing the decoded data and outputting compressed data;
• and
• an expanding section for reading out and expanding the compressed data stored in the frame memory and outputting expanded data;
• wherein said frame memory includes a predictive frame memory for storing the encoded data of a predictive frame to be used for predictive decoding the encoded data in said decoding section, and a display frame memory for storing the encoded data of a display frame to be used for display;
• wherein said compressing section compresses the decoded data of the predictive frame to be stored in said predictive frame memory as compressed predictive data, and the decoded data of the display frame to be stored in said display frame memory as compressed display data;
• wherein said expanding section includes,
• a predictive data expanding section for expanding the compressed data of the predictive frame stored in said predictive frame memory and outputting expanded predictive data, and
• a display data expanding section for expanding the compressed data of the display frame stored in said display frame memory and outputting the expanded display data for display;
• wherein said compressing section compresses the frame-based decoded predictive data on a block basis and outputs the compressed data on the block basis;
• wherein said predictive data expanding section reads out a block of the compressed predictive data on the block basis including at least a part of a block data of K pixels×L lines required by said decoding section, the required block data being a part of a predictive frame stored in said predictive frame memory, expands the read out block of the block-based compressed predictive data, and outputs the block-based expanded predictive data of the read out block including the required block data of K pixels×L lines to said decoding section;
• wherein said predictive data expanding section includes a block memory for storing the block-based expanded predictive data of the read out block from said predictive frame memory, and
• wherein said block memory is updated on a block basis each time block data required by said decoding section is renewed.

A digital image decoding apparatus for decoding encoded data of an image with a given size, said digital image decoding apparatus comprising:

• a frame memory having a capacity for storing the encoded data on a frame basis;
• a decoding section for decoding the encoded data on the frame basis and outputting decoded data;
• a compressing section for compressing the decoded data and outputting compressed data;
• and
• an expanding section for reading out and expanding the compressed data stored in the frame memory and outputting expanded data;
• wherein said frame memory includes a predictive frame memory for storing the encoded data of a predictive frame to be used for predictive decoding the encoded data in said decoding section, and a display frame memory for storing the encoded data of a display frame to be used for display;
• wherein said compressing section compresses the decoded data of the predictive frame to be stored in said predictive frame memory as compressed predictive data, and the decoded data of the display frame to be stored in said display frame memory as compressed display data;
• wherein said expanding section includes,
• a predictive data expanding section for expanding the compressed data of the predictive frame stored in said predictive frame memory and outputting expanded predictive data, and
• a display data expanding section for expanding the compressed data of the display frame stored in said display frame memory and outputting the expanded display data for display;
• wherein said compressing section compresses the frame-based decoded display data on a block basis and outputs the compressed display data on the block basis;
• wherein said display data expanding section reads out the compressed display data stored in said display frame memory on the block basis, expands the read out block-based compressed display data, and outputs the block-based expanded display data sequentially in a horizontal scanning direction;
• wherein said display data expanding section includes,
• a block memory for storing the read out block of the block-based expanded display data sequentially with a width and direction in accordance with the horizontal scanning direction;
• and
• wherein said display data expanding section outputs the block-based expanded display data read out from said display memory in response to an image display scan line.

A digital image decoding apparatus for decoding encoded data of an image with a given size, said digital image decoding apparatus comprising:

• a frame memory having a capacity for storing data on a frame basis;
• a decoding section for inputting the encoded data which is encoded in accordance with an inter/intra-frame coding in a digital image coding apparatus and decoding the encoded data in accordance with an inter/intra-frame decoding on the frame basis and outputting decoded data;
• a compressing section, locating between the frame memory and the decoding section, for inputting the decoded data outputted from the decoding section, compressing the decoded data in accordance with a non-inter/intra-frame coding and outputting compressed data to the frame memory so as to store the compressed data to the frame memory;
• an expanding section, locating between the frame memory and the decoding section, for reading out and expanding the compressed data stored in the frame memory and in accordance with a non-inter/intra-frame decoding and outputting expanded data to the decoding section,
• wherein said compressing section includes
• a plurality of quantizers, each of which has a table for a unique quantization and outputs a unique quantized result of the decoded data, an optimal table selector for comparing the unique quantized results for selecting a table optimal to the decoded data from among the plurality of tables, and
• a selector for selecting an output from one of the plurality of quantizers having the optimal table selected by said optimal table selector.

A digital image decoding apparatus for decoding encoded data of an image with a given size, said digital image decoding apparatus comprising:

• a frame memory having a capacity for storing the encoded data on a frame basis;
• a decoding section for decoding the encoded data on the frame basis and outputting decoded data;
• a compressing section for compressing the decoded data and outputting compressed data;
• and
• an expanding section for reading out and expanding the compressed data stored in the frame memory and outputting expanded data;
• a compression rate judging section for receiving image size information for indicating the given size of the image and judging a rate of compression for the compressed data to be stored in said frame memory based upon the given size of the image and a capacity of said frame memory;
• wherein said compressing section compresses the decoded data based upon the rate of compression and outputs the compressed data to said frame memory;
• and
• wherein said expanding section reads out the compressed data from said frame memory and expands the compressed data based upon the rate of compression.

A digital image decoding apparatus for decoding encoded data of an image with a given size, said digital image decoding apparatus comprising:

• a frame memory having a capacity for storing the encoded data on a frame basis;
• a decoding section for decoding the encoded data on the frame basis and outputting decoded data;
• a compressing section for compressing the decoded data and outputting compressed data;
• and
• an expanding section for reading out and expanding the compressed data stored in the frame memory and outputting expanded data;
• wherein said decoding section decodes the encoded data including profile information of a coding method for the encoded data;
• said digital image decoding apparatus further comprising:
• a profile judging section for receiving the encoded data and judging the profile of the coding method;
• and
• wherein said compressing section, including a plurality of modes of compression, receives the profile information and selects one of the plurality of modes optimal to the coding method;
• wherein said profile judging section judges the coding method at least one of a bidirectional prediction inter-frame coding method for predicting a frame based upon past and future frames and of a forward prediction inter-frame coding method based upon a past frame;
• and
• wherein said compressing section compresses the decoded data including bidirectional prediction inter-frame encoding method and does not compress the decoded data including the forward prediction inter-frame encoding method.

A digital image decoding apparatus for decoding encoded data of an image with a given size, said digital image decoding apparatus comprising:

• a frame memory having a capacity for storing data on a frame basis;
• a decoding section for inputting the encoded data which is encoded in accordance with an inter/intra-frame coding in a digital image coding apparatus and decoding the encoded data in accordance with an inter/intra-frame decoding on the frame basis and outputting decoded data;
• a compressing section, locating between the frame memory and the decoding section, for inputting the decoded data outputted from the decoding section, compressing the decoded data in accordance with a non-inter/intra-frame coding and outputting compressed data to the frame memory so as to store the compressed data to the frame memory;
• an expanding section, locating between the frame memory and the decoding section, for reading out and expanding the compressed data stored in the frame memory and in accordance with a non-inter/intra-frame decoding and outputting expanded data to the decoding section,
• wherein said compressing section includes a quantizing section for quantizing the decoded data on a block basis of M×N pixels to output the block-based compressed data;
• and
• wherein said expanding section includes an expander for dequantizing the block-based compressed data and outputting the expanded data on the block basis of M×N pixels.

A digital image decoding apparatus for decoding encoded data of an image with a given size, said digital image decoding apparatus comprising:

• a frame memory having a capacity for storing the encoded data on a frame basis;
• a decoding section for decoding the encoded data on the frame basis and outputting decoded data;
• a compressing section for compressing the decoded data and outputting compressed data;
• and
• an expanding section for reading out and expanding the compressed data stored in the frame memory and outputting expanded data;
• wherein said compressing section includes a quantizing section for quantizing the decoded data on a block basis of M×N pixels to output the block-based compressed data;
• wherein said expanding section includes an expander for dequantizing the block-based compressed data and outputting the expanded data on the block basis of M×N pixels;
• wherein said quantizing section includes a plurality of quantizers, each of which has a unique characteristic of quantization,
• wherein said compressing section includes,
• a characteristic searching section for searching a characteristic of the block-based decoded data of M×N pixels, and
• a quantizer selector for selecting one of the plurality of quantizers in said quantizing section based upon the characteristic searched by said characteristic searching section, and activating a selected quantizer exclusively for quantizing the block-based decoded data of M×N pixels,
• wherein said quantizer selector includes,
• a maximum value detector for receiving the block-based decoded data of M×N pixels, and calculating a maximum value of a difference between adjacent pixels and outputting a maximum value as a first characteristic,
• a minimum value detector for receiving the block-based decoded data of M×N pixels, and calculating a minimum value of the difference between adjacent pixels and outputting a minimum value as a second characteristic,
• a characteristic quantization table for quantizing the first characteristic of the maximum value and the second characteristic of the minimum value, respectively,
• a characteristic quantizer for receiving and quantizing the maximum and minimum values with reference to the characteristic quantization table, and outputting maximum and minimum quantized values, respectively,
• a select table for selecting one of the plurality of quantizers in said quantizing section based upon the maximum and minimum quantized values, and
• a selector for selecting one of the plurality of quantizers optimal to the decoded data based upon said select table.

A method for digital image decoding, the method comprising the steps of:

• inputting encoded data through an inter-/intra-frame coding on a block basis of M×N pixels;
• after the inputting step, decoding the encoded data through an inter/intra-frame decoding on a block basis of M×N pixels;
• after the decoding step, compressing the block-based decoded data of M×N pixels through quantization, not through an inter/intra-frame coding, and outputting block-based compressed data;
• after the compressing step, storing a predictive frame of the block-based compressed data on a frame basis in a predictive frame memory of a frame memory, the predictive frame being used to decode the encoded data through inter-/intra- frame coding;
• after the compressing step, storing a display frame of the block-based compressed data in a display frame memory of the frame memory, the display frame being used to display an image;
• after the predictive frame storing step, expanding the compressed predictive frame data read out from the predictive frame memory through a dequantization, not through an inter/intra-frame decoding, of the compressed predictive frame data, and supplying an expanded predictive frame data to said decoding step;
• after the display frame storing step, expanding the compressed display data read out from the display frame memory, through a dequantization, not through an inter/intra-frame decoding, of the compressed display frame data, and outputting an expanded display frame data as image display data;
• and
• judging a rate of compression of the block-based decoded data based upon a size of image judged by the encoded data in connection with a storage capacity of the frame memory and providing said compressing step with the rate of compression as compression rate information.