Method and apparatus for encoding transmitting and receiving image by pulse code modulation

• US 4,809,067 A
• Filed: 05/26/1987
• Issued: 02/28/1989
• Est. Priority Date: 05/26/1986
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Goda, Naofumi, Kikuchi, Hiroaki, Asano, Kenichi, Tanno, Okikazu
• Primary Examiner(s): Britton, Howard W.
• Assistant Examiner(s): Kostak, Victor R.
• Application Number:
  US07/053,627
• Time in Patent Office: 644 Days
• Field of Search: 358/105, 358/136, 358/135, 358/133, 358/12, 358/260, 358/261, 375/122, 375/27, 340/347 AD
• US Class Current: 375/240.12
• CPC Class Codes: G06T 9/008 Vector quantisation
• CPC Class Codes: H04N 19/124 Quantisation
• CPC Class Codes: H04N 19/13 Adaptive entropy coding, e.g. adaptive variable length coding [AVLC] or context adaptive binary arithmetic coding [CABAC]
• CPC Class Codes: H04N 19/137 Motion inside a coding unit, e.g. average field, frame or block difference
• CPC Class Codes: H04N 19/146 Data rate or code amount at the encoder output
• CPC Class Codes: H04N 19/147 according to rate distortion criteria rate-distortion as a criterion for motion estimation H04N19/567
• CPC Class Codes: H04N 19/149 by estimating the code amount by means of a model, e.g. mathematical model or statistical model
• CPC Class Codes: H04N 19/15 by monitoring actual compressed data size at the memory before deciding storage at the transmission buffer
• CPC Class Codes: H04N 19/152 by measuring the fullness of the transmission buffer
• CPC Class Codes: H04N 19/172 the region being a picture, frame or field
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock
• CPC Class Codes: H04N 19/196 being specially adapted for the computation of encoding parameters, e.g. by averaging previously computed encoding parameters processing of motion vectors H04N19/513
• CPC Class Codes: H04N 19/42 characterised by implementation details or hardware specially adapted for video compression or decompression, e.g. dedicated software implementation H04N19/635 takes precedence
• CPC Class Codes: H04N 19/50 using predictive coding H04N19/61 takes precedence
• CPC Class Codes: H04N 19/503 involving temporal prediction adaptive coding with adaptive selection between spatial and temporal predictive coding H04N19/107; adaptive coding with adaptive selection among a plurality of temporal predictive coding modes H04N19/109
• CPC Class Codes: H04N 19/51 Motion estimation or motion compensation
• CPC Class Codes: H04N 19/61 in combination with predictive coding
• CPC Class Codes: H04N 19/91 Entropy coding, e.g. variable length coding [VLC] or arithmetic coding
• CPC Class Codes: H04N 19/94 Vector quantisation

Abstract

An image encoding/transmitting apparatus and method implemented by applying the vector quantization technology utilizing the differential pulse code modulation system in which an estimated error signal is compared with a threshold value to generate a change or movement detection signal and a differential signal, which are then quantized so as to be transmitted and received wherein the polarity of the differential signal is judged by a polarity judgment circuit, a polarity is assigned to the threshold value based on the judgment value by a polarity adding circuit, the differential signal is corrected depending on the threshold value with the polarity, and the corrected differential signal is quantized so as to be transmitted and received.

Claims

1. An image encoding/transmitting apparatus using a differential pulse code modulation system in which an estimated error signal and a threshold value are compared with each other to generate a movement detection signal and a differential signal and the movement detection signal and the differential signal are quantized and thereafter subjected to a transmission and a reception;

wherein the polarity of the differential signal is judged in said encoding/transmitting apparatus, a polarity is assigned to the threshold value based on the judgment, the differential signal is corrected depending on the threshold value with the polarity, and the resultant corrected differential signal is quantized and thereby is communicated.

2. An image encoding/transmitting apparatus according to claim 1 wherein said corrected differential signal is generated by subtracting the threshold with the polarity from the differential signal.

3. An image encoding/transmitting apparatus using a differential pulse code modulation system including a transmission circuit for effecting a datum compression and transmission by achieving a differential pulse modulation on a digital input signal and a reception circuit corresponding to the transmission circuit wherein:

said transmission circuit includes;

an estimating circuit for calculating an estimation signal to estimate the digital input signal;

a movement detection circuit for outputting a differential signal depending on an estimated error signal being a difference between the input signal and the estimation signal and a threshold value for smoothing an amount of a transmission data;

a quantizing circuit for quantizing the differential signal;

a transmission data buffer circuit for temporarily storing the quantized transmission signal;

a threshold generating circuit for generating and controlling the threshold value; and

a local decoding circuit for locally decoding the quantized signal to calculate the estimation signal,

wherein said reception circuit includes;

a receiving data buffer circuit for temporarily storing a received signal;

a local decoding circuit for decoding the received signal; and

an adder for calculating a regenerated signal from the decoded signal and the estimation signal,

wherein said quantizing circuit includes;

an adaptive quantizing circuit having a plurality of quantization characteristics and a characteristic selecting circuit for selecting said quantizing characteristic depending on the threshold value, and

wherein said local decoding circuits of said transmission circuit and said reception circuit each includes;

an adaptive local decoding circuit having a plurality of decoding characteristics corresponding to the quantizing circuit and

a characteristic selecting circuit for selecting said decoding characteristic depending on the threshold value.

4. An image encoding/transmitting apparatus according to claim 3 wherein said quantizing characteristic selected by said quantizing circuit is such that a quantization output of the differential signal within an invalid data range (within a specification of the corresponding threshold value) is "0".

5. An image encoding/transmitting apparatus including a vector quantizer wherein said vector quantizer comprises:

a quantization preprocessing circuit for subsampling an image signal, for thinning out pixels from the image signal according to a pixel ratio, and for generating from the pixel signal an n-dimensional vector;

a group of input buffers for respectively storing each said input vector in a sequence of a quantization processing and for repetitiously reading the input vector at an interval of the processing period;

a vector output circuit for beforehand preparing an output vector corresponding to a probability distribution of the input vector and for selecting and outputting the output vector based on an index input;

a distortion computation circuit for computing a distance between the input vector and the output vector selected and output;

a plurality of encoding sections disposed corresponding to the buffers;

index output generating means for generating an index for a period of a subsequent processing based on the calculated distance value outputted from said each encoding section and the input vector and for sending the index to each said vector output circuit; and

a quantized index output circuit for generating an index of a quantizer from said generated index and for outputting the index.

6. An image encoding/transmitting method comprising:

a preprocessing step for generating blocks of pixels, each block containing a plurality pixels in the neighborhood of each other in an image of an image input signal, for generating a vector signal for each said block, and for outputting said vector signal;

a movement compensation processing step for generating a plurality of reference blocks by use of a frame memory storing an image of vector signals ahead in time by one frame with respect to a current vector signal, each said reference block including a block existing at a same position as a current input block, for respectively calculating a reference vector signal, for achieving a distortion computation between the vector signal and each said reference vector signal, for selecting a block having a minimum distortion, and for outputting a position information of the selected block;

an encoding processing step for calculating a differential vector signal by executing a subtraction between the input block and the selected block, for encoding only the position information of the selected block in a case where an average value and a variance of the differential vector signal each are within a range of a threshold value and for calculating an encoded signal, and for sending the encoded signal to a transmission data buffer; and

for encoding the position information of the selected block and the differential vector signal in a case where the average and the variance of the differential vector signal is beyond the range of the threshold and for sending the encoded signal to the transmission data buffer;

a threshold value control step for controlling the threshold value depending on an amount of the encoded signal temporarily stored in the transmission data buffer, for decreasing the threshold value when the encoded signal amount is small, and for increasing the threshold value when the encoded signal amount is great; and

an auxiliary threshold control step for reducing the threshold value when a distance between the current input block and the selected block calculated by the movement compensation step is great.

7. An image encoding/transmitting method according to claim 6 wherein a sum of absolute values of said differential vector signals is calculated and the sum of absolute values and the threshold value are utilized.

8. An image encoding/transmitting method comprising:

a preprocessing step for effecting an analog-to-digital conversion on an image input signal to generate a digital signal and for storing the digital signal in a frame memory for each frame;

an encoding processing step for effecting a smoothing operation on the digital signal based on an encoding control parameter such as a threshold value and for encoding the smoothed digital signal;

a transmission control processing step for temporarily storing the encoded signal for each frame in a transmission data buffer and for sending the encoded signal to a transmission control unit;

an encoding control parameter control step for controlling the encoding control parameter based on an amount of the encoded signals temporarily stored in the transmission data buffer associated with a previous frame; and

an auxiliary encoding control parameter control step for extracting a portion of a current digital signal stored in the frame memory, for effecting a pseudo encoding on the portion based on the encoding control parameter calculated depending on the amount of the encoded signals of the preceding frame, and for correcting the encoding control parameter based on an amount of the pseudo encoded signals having undergone the pseudo encoding, thereby causing the encoding control parameter to have an optimum value.