Method and apparatus for transmission of image data

• US 5,617,333 A
• Filed: 11/23/1994
• Issued: 04/01/1997
• Est. Priority Date: 11/29/1993
• Status: Expired due to Fees

• Current Assignee: Kokusai Electric Co., Ltd.
• Original Assignee: Kokusai Electric Co., Ltd.
• Inventors: Yokokawa, Eiji, Sato, Hiroyo, Oyamada, Ouichi, Arayashiki, Akifumi
• Primary Examiner(s): Voeltz, Emanuel T.
• Assistant Examiner(s): PEESO, THOMAS R
• Application Number:
  US08/346,922
• Time in Patent Office: 860 Days
• Field of Search: 364/514 A, 364/514 R, 371/2.1, 371/30, 371/35, 371/37.1, 341/58, 341/107, 382/56, 382/57, 348/608
• US Class Current: 709/247
• CPC Class Codes: H04N 1/409 Edge or detail enhancement; Noise or error suppression
• CPC Class Codes: H04N 19/60 using transform coding
• CPC Class Codes: H04N 19/895 in combination with error concealment

Abstract

In an improved image data transmission system, an image data partitioning unit is provided at the transmitter section to partition an input image data into a predetermined number of picture elements (blocks) so that same picture elements of the image data can be subject to source image encoding and forward error correction encoding. At the receiver section, picture elements in each of the data blocks are subject to error correction decoding and source image decoding. The receiver section is provided with an image data interpolator which works, when an transmission error is detected, to interpolate with a substitution data the data in a block in which the error has been detected or data in other block to which the error has been propagated as it is. After the interpolation, a reconstructed image data is delivered.

Claims

1. A method for transmission of image data, wherein an input digital image data is transmitted by encoding the source image data, encoding the coded image data for error correction and modulating it transmission over a transmission line, and is reconstructed by demodulating the image data received over the transmission line, decoding it for error correction and decoding it to the source image, comprising the steps of:

partitioning the input data of a source image into a predetermined number of data blocks each of which including a plurality of picture elements from which the source image can be decoded;

encoding each partitioned block for the source image and also encoding for correction of an error, if any, in the block;

decoding each of the received blocks for error correction to detect any error caused in the block during transmission;

discarding a block of the image data which has been decoded to the source image and contains a transmission-caused error or a block to which the error has been propagated as it is;

interpolating the block of the image data containing the transmission-caused error or the block to which the error has been propagated as it is, with a previously stored substitution block which can be decoded and as set in the place of the block containing the error, and then reconstructing the image data.

2. A method as set forth in claim 1, wherein when a correct data other than any interpolated data, is required at the receiver section, a send request for an image data is arbitrarily made for data transmission from the transmitter section.

3. A method for transmission of image data according to claim 1, further comprising a step, after the step of reconstructing the image data, of replacing in order the substitution block with a picture element value estimated from the correlation with blocks adjacent to the block in which the error has been detected.

4. An apparatus for transmission of image data, comprising:

a transmitter section having;

an image data partitioning unit which partitions an input image data into a predetermined number of blocks which can be decoded to the source image,

a source image encoder which encodes each of the partitioned data blocks and an error correction encoder, and

a modulator which converts the coded data to a signal suitable for transmission on a transmission line used; and

a receiver section having a demodulator which receives and converts the modulated signal to provide a digital signal,

an error correction decoder which detects an error, if any, in the digital signal demodulated by the demodulator, and

a source image decoder which decodes an error-free image data as it is,

the receiver section further having an image data interpolator which interpolates, if an error has been detected by the error correction decoder, a data block in which the error is included or other data block to which the error has been propagated, with a substitution data.

5. An apparatus as set forth in claim 4, wherein an interpolation data is stored beforehand in the image data interpolator and used as the substitution data when an error is detected by the error correction decoder.

6. An apparatus as set forth in claim 4, further comprising an image data interpolator which uses as the substitution data a data estimated based on the correlation with the block in which an error has been detected.

7. An apparatus as set forth in claim 4, further comprising an image data interpolator which uses as the substitution data a data estimated based on the correlation with the blocks adjacent to a block in which an error has been detected.

8. A method for transmission of image data, comprising the steps of transmitting an input digital image data by encoding the source image data, encoding the coded image data for error correction and modulating it for transmission over a transmission line, and demodulating the image data received over the transmission line, decoding it for error correction, decoding it to the source image and providing a reconstructed image data, wherein

at the transmission side, a plurality of MCUs, minimum units of image data to be subject to source image encoding, is taken as a transmission block, a HDLC frame is generated for each transmission block and used as a modulated signal;

and

at the reception side, the received and demodulated signal is checked for any transmission error for each HDLC frame, the transmission block in an HDLC frame in which a transmission error has been detected is replaced with a substitution block stored beforehand and is subjected to source image decoding.

9. An image data receiver, comprising:

a demodulator which receives and demodulates a modulated signal transmitted over a transmission line and which carries an HDLC frame having a plurality of MCUs, minimum units of image data to be subject to source image encoding of digital image data;

an HDLC frame disassembler which checks the signal output of the demodulator for any transmission error in each HDLC frame, disassembles transmission blocks in an HDLC frame having no transmission error into individual MCUs, while delivering a signal indicative of a transmission error detected in an HDLC frame, replacing the transmission block in that HDLC frame with an external substitution block and then disassembling the substitution block into individual MCUs;

a memory in which different kinds of substitution blocks are stored beforehand; and

a transmission block substitution unit which, when supplied with a signal indicative of the error from the HDLC frame disassembler, reads a suitable substitution block from the memory and supplies it to the HDLC frame disassembler,

the output of the HDLC frame disassembler being subjected to source image decoding to reconstruct the digital image data.

10. An image data receiver as set forth in claim 9, the transmission block substitution unit comprising:

a parameter calculator which, when supplied with a signal indicative of an error, calculates a parameter from a compressed/expanded data extracted from a transmission block in a preceding frame having no error;

a substitution block selector/generator which uses the calculated parameter to select a suitable substitution block from the memory and delivers a signal which designates the number for the selected substitution block;

an address calculator which calculates an address in the memory from the block number designation signal and delivers an address corresponding to the designated number; and

a memory data transfer unit which receives the address signal from the address calculator and transfers a substitution block at the address in the memory to the HDLC frame disassembler.

11. An image data receiver as set forth in claim 10, wherein the transmission block substitution unit has a function of giving an arbitrary image data to the transmission block to write a substitution block into the memory.

12. A method for transmission of image data, in which an image data is partitioned into a plurality of blocks, image data in each block is subject to orthogonal transform and then a coded data generated by compression after encoding the image data in each block and an attribute data necessary for restoration of the image data by decoding and inverse orthogonal transform at the reception side are transmitted;

wherein

at the transmission side, the coded data in each block is additionally assigned the attribute data and a frame check code to form a data frame for transmission; and

at the reception side, each time one of the data frames is received, the frame check code added to the frame is used to check for any transmission error in the frame and the attribute data is extracted from a frame having no error to restore a still image.

13. A method as set forth in claim 12, wherein, when a transmission error is detected in a frame as a result of the error checking with the frame check code, the coded data in that frame is reformatted into a predetermined special bit pattern once and the special bit pattern is replaced with a value estimated based on the correlation with the adjacent image data on the display screen at the time of image restoration.

14. A method as set forth in claim 12, wherein the orthogonal transform is a discrete cosine transform.

15. A method as set forth in claim 12, wherein the attribute data is a data of 1 byte consisting of 4 bits for compression ratio, 3 bits for image size and 1 bit for compression method.

16. An apparatus for transmission of image data, comprising:

a first means of partitioning an image data into a plurality of blocks, orthogonal-transforming image data in each block and compressing it by encoding to provide a coded data;

a second means of adding to the coded data in each block a frame check code and an attribute data necessary for restoration of a still image by decoding and inverse orthogonal transform, to thereby form a frame for transmission; and

a third means of checking for any transmission error in each received frame with reference to the frame check code added to that frame and extracting the attribute data from a frame having no such error for restoration of the image.

17. A method as set forth in claim 16, wherein the third means is so designed to reformat, when a transmission error is detected in a frame as a result of the error checking with the frame check code, the coded data in that frame into a predetermined special bit pattern once and replacing the special bit pattern with a value estimated from the correlation with the adjacent image data on the display screen at the time of image restoration.

18. A method of image data interpolation in an image data transmission in which an input digital image data is subjected to source image encoding, forward error correction encoding and then to modulation, and transmitted over a transmission line;

and the data received over the transmission is subjected to demodulation, error correction decoding and source image decoding to provide a reconstructed image data, comprising the steps of;

determining an equation in which variables at coordinates of a picture element in the image data, having incurred an error or loss during the transmission, are expressed with those at coordinates of picture elements adjacent to that picture element;

calculating the equation to regenerate each picture element incurring the error or loss; and

using the regenerated picture element to interpolate the image data incurring the error or loss, thereby providing a reconstructed image data.

19. A method for transmission of image data, comprising the steps of transmitting an input digital image data by encoding the source image data, encoding the coded image data for error correction and modulating it for transmission over a transmission line, and demodulating the image data received over the transmission line, decoding it for error correction, decoding it to the source image and providing a reconstructed image data, wherein, when the image data has incurred an error or loss during the transmission, a weighted mean is determined by weighting the picture element values in the normally received portion of the image data in dependence of a distance between the picture elements in the normally received portion and those in the lost portion and the orientations of the normally received picture elements to interpolate the image data in the error or lost portion and a reconstructed image data is provided after the interpolation.

20. A method as set forth in claim 19, wherein the interpolation of the image data in the error or lost portion is done after all the image data of an original image have been received.

21. A method for transmission of image data, comprising the steps of transmitting an input digital image data by encoding the source image data, encoding the coded image data for error correction and modulating it for transmission over a transmission line, and demodulating the image data received over the transmission line, decoding it for error correction, decoding it to the source image and providing a reconstructed image data, wherein

the input data of a source image is partitioned into a predetermined number of data blocks from which the source image can be decoded;

each partitioned block is coded for the source image and also coded for correction of an error, if any, in the block;

each of the received blocks is decoded to detect any error caused in the block during transmission;

a block of the image data of which each block has been decoded to the source image that contains a transmission-caused error, or a block to which the error has been propagated as it is, is corrected with a picture element value estimated from the correlation of the block in consideration with its associated block; and

then

the image data is reconstructed, wherein when a correct data other than any interpolated data, is required at the receiver section, a send request for an image data is arbitrarily made for data transmission from the transmitter section.

22. A method as set forth in claim 21 wherein the associated blocks are those adjacent to the block in which the error has been detected, wherein when a correct data other than any interpolated data, is required at the receiver section, a send request for an image data is arbitrarily made for data transmission from the transmitter section.

23. An apparatus for transmission of image data, comprising:

a transmitter section having;

an image data partitioning unit which partitions an input image data into a predetermined number of blocks which can be decoded to the source image,

a source image encoder which encodes each of the partitioned data blocks and an error correction encoder, and

a modulator which converts the coded data to a signal suitable for transmission on a transmission line used, and

a receiver section having;

a demodulator which receives and converts the modulated signal to provide a digital signal,

an error correction decoder which detects an error, if any, in the digital signal demodulated by the demodulation, and

a source image decoder which decodes an error-free image data as it is;

said receiver section further including an image data interpolator which interpolates, if an error has been detected by the error correction decoder, a data block in which the error is included or other data block to which the error has been propagated, with a substitution data,

said interpolator having memory means in which an interpolation data which can be decoded is stored beforehand, and said interpolation data having used as the substitution data when then the error is detected by the error correction decoder, and

said interpolator adapted to further interpolate certain block of said interpolation data with a data estimated based on the correction with the blocks adjacent to the interpolated block.

24. A method for transmission of digital image data including the steps of transmitting an input digital image data by encoding the image data and modulating it for transmission over a transmission line, and demodulating the image data received over the transmission line, decoding it to the image data and providing a reconstructed image data, comprising;

at the transmission side, a plurality of MCUs (minimum units of image data) is taken as a transmission block, a HDLC frame is generated for each transmission block and used as a modulated signal; and

at the reception side, the received and demodulated signal is checked for any transmission error for each HDLC frame,

the transmission block in the HDLC frame in which a transmission error has been detected is discarded.

a parameter is calculated from a compressed/expanded data extracted from the transmission block in a preceding frame having no error,

the calculated parameter is used to select a suitable substitution block among a plurality of substitution blocks stored beforehand in memory means,

a signal indicative of number for the selected substitution block is delivered,

an address of the substitution block in the memory means is calculated from the block number designation signal,

the selected substitution block is read out from the memory means,

the transmission block in the HDLC frame having transmission error is replaced with the selected substitution block, and then disassembled into individual MCUs to be subjected to source image decoding for the reconstruction of the digital image data.

25. A digital image data receiver, comprising:

a demodulator which receives and demodulates a modulated signal transmitted over a transmission line and which carries an HDLC frame having a plurality of MCUs, minimum units of image data to be subject to source image encoding of digital image data;

an HDLC frame disassembler which checks the signal output of the demodulator for any transmission error in each HDLC frame, disassembles transmission blocks in an t HDLC frame having no transmission error into individual MCUs, while delivering a signal indicative of a transmission error detected in an HDLC frame, replacing the transmission block in that HDLC frame with an external substitution block and then disassembling the substitution block into individual MCUs;

a memory in which different kinds of substitution blocks are stored beforehand; and

a transmission block substitution unit including,

a parameter calculator which, when supplied with a signal indicative of the error from the HDLC frame disassembler, calculates a parameter from a compressed/expanded data extracted from a transmission block in a preceding frame having no error,

a substitution block selector/generator which uses the calculated parameter to select a suitable substitution block from the memory and delivers a signal indicative of the number for the selected substitution block,

an address calculator which calculates an address in the memory from the block number designation signal and delivers an address corresponding to the designated number, and

a memory data transfer unit which receives the address signal from the address calculator and transfers a substitution block at the address in the memory to the HDLC frame disassembler,

the output of the HDLC frame disassembler being subjected to source image decoding to reconstruct the digital image data.

26. A method for transmission of image data in which an image data is partitioned into a plurality of blocks, image data in each block is subject to orthogonal transform and then a coded data generated by compression after encoding the image data in each block and an attribute data necessary for restoration of the image data by decoding and inverse orthogonal transform at the reception side are transmitted, wherein

at the transmission side, the coded data in each block is additionally assigned the attribute data and a frame check code to form a data frame for transmission, and

at the reception side, each time one of the data frames is received, the frame check code added to the frame is used to check for any transmission error in the frame, the attribute data is extracted from a frame having no error to restore a still image, and when the transmission error is detected in a frame as a result of the error checking with the frame check code, the coded data in that frame is reformatted into a predetermined special bit pattern once and the special bit pattern is replaced with a value estimated based on the correlation with the adjacent image data on the display screen at the time of image restoration.

27. An apparatus for transmission of image data, comprising:

first means for partitioning an image data into a plurality of blocks, orthogonal-transforming image data in each block and compressing it by encoding to provided a coded data;

second means for adding to the coded data in each block a frame check code and an attribute data necessary for restoration of a still image by decoding and inverse orthogonal transform, to form a frame for transmission; and

third means for checking any transmission error in each received frame with reference to the frame check code added to that frame, and extracting the attribute data from a frame having no such error for restoration of the image,

said third means being so designed to reformat, when the transmission error is detected in a frame as a result of the error checking with the frame check code, the coded data in that frame into a predetermined special bit pattern once and the special bit pattern is replaced with a value estimated based on the correlation with the adjacent image data on the display screen at the time of image restoration.