Image signal band compressing system for digital video tape recorder

• US 5,299,019 A
• Filed: 12/18/1992
• Issued: 03/29/1994
• Est. Priority Date: 02/28/1992
• Status: Expired due to Term

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Chung, Tae Y., Pack, Seung K.
• Primary Examiner(s): Coles, Sr., Edward L.
• Assistant Examiner(s): Williams, Kimberly A.
• Application Number:
  US07/992,692
• Time in Patent Office: 466 Days
• Field of Search: 358/261.1, 358/261.2, 358/261.3, 358/261.4, 358/262.1, 358/426, 358/432, 358/433, 358/530, 358/539, 382/50, 382/56
• US Class Current: 382/236
• CPC Class Codes: H04N 19/105 Selection of the reference unit for prediction within a chosen coding or prediction mode, e.g. adaptive choice of position and number of pixels used for prediction
• CPC Class Codes: H04N 19/124 Quantisation
• CPC Class Codes: H04N 19/132 Sampling, masking or truncation of coding units, e.g. adaptive resampling, frame skipping, frame interpolation or high-frequency transform coefficient masking
• CPC Class Codes: H04N 19/14 Coding unit complexity, e.g. amount of activity or edge presence estimation H04N19/146 takes precedence
• CPC Class Codes: H04N 19/146 Data rate or code amount at the encoder output
• 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 19/18 the unit being a set of transform coefficients
• CPC Class Codes: H04N 19/186 the unit being a colour or a chrominance component
• CPC Class Codes: H04N 19/59 involving spatial sub-sampling or interpolation, e.g. alteration of picture size or resolution
• CPC Class Codes: H04N 19/61 in combination with predictive coding
• CPC Class Codes: H04N 19/85 using pre-processing or post-processing specially adapted for video compression
• CPC Class Codes: H04N 9/8047 using transform coding

Abstract

The image signal band compressing method employs a three-dimensional motion compensating technique, an intraframe and an interframe processes which are alternatively executed. The transfer rate of the intraframe to the interframe is set to 4:1 in a unit of fixed length. The intraframe process is defined such that the present frame image data is compressed in a variable length compressing manner by way of two-dimensional discrete coding transform. The interframe process is defined such that motion data is estimated by comparing the present frame and the preceding frame, the present frame is expected on the basis of the motion data and the difference data between the motion compensated image data and the present frame data.

Claims

1. An image signal band compressing system comprising:

a mode switching means for processing image data in a unit of block or macro block, the image data being produced from component image signals converted in a ratio of 4;

2;

0, and the component image signals having a brightness signal Y and color signals Cr and Cb set in a ratio of 4;

2;

2 in correspondence to an intraframe mode or an interframe mode;

a scrambling means for supplying surplus data of a fluctuating region of the image input and resorting the image input without using additional data, the picture quality-deteriorated portion of the image input being condensated at edges of the image;

a discrete coding transform means for transforming and coding the output of the scrambling means by using discrete coding transform factors;

a human visual unit for processing the output of the discrete coding transform means in correspondence to the sensitivity of the human visual system;

an activity calculating means for calculating an activity and an activity average of the output of the human visual unit in the intraframe process mode or interframe process mode;

a first quantization means for quantizing the output of the human visual unit in a unit of block or macro block, the quantized output having a step size determined by the activity and activity average corresponding to the intraframe or interframe processing mode;

a first adaptive scanning means for comparing the activities between two regions in four scanning areas of 4 pixels×

4 lines in a block of 8 pixels×

8 lines and executing any one of a horizontal scanning, a vertical scanning and a zigzag scanning;

a first variable length coding means for effecting a variable length coding of the output of the first adaptive scanning means and calculating a difference Beta between the amount of data produced by accumulating the variable length coded data in a unit of fixed length and a target amount of data;

a buffer for temporarily storing the output of the first variable length coding means;

a second quantization means for quantizing the output of the human visual unit in a unit of block or macro block at a step size decided on the basis of the difference β

from the first variable length coding means and the activity and activity average from the activity calculating means.

a second adaptive scanning means for comparing the activities between two regions of four scanning areas in the output of the second quantization means and effecting any one of horizontal scanning, vertical scanning and a zigzag scanning;

a second variable length coding means for executing a variable length coding to the output of the second adaptive scanning means and calculating a difference between the amount of data produced by the variable length coding process and a target amount of data;

a comparator for selecting the output of the first variable length coding means when an absolute value |β

-γ

| is equal to or less than the absolute value being obtained by subtracting the difference of the second variable length cosign means from the difference of the first variable length coding means and, contrarily, selecting the output of the second variable length coding means when the absolute value is not zero; and

,

a factor removing and stuffing-bit appending means for removing factors of data exceeding the fixed length when an overflow is generated on the basis of the difference from the comparator and, contrarily, appending a stuffing bit when an underflow is generated.