Image data compression or expansion method and apparatus, and image transmission system and monitoring system using the method and device

• US 6,493,466 B1
• Filed: 04/13/1999
• Issued: 12/10/2002
• Est. Priority Date: 04/13/1998
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Michikawa, Yuichi, Kuroda, Masayoshi, Takamoto, Koichi, Honda, Toyota, Imanishi, Shinya
• Primary Examiner(s): Johns, Andrew W.
• Assistant Examiner(s): Dang, Duy M.
• Application Number:
  US09/289,937
• Time in Patent Office: 1,337 Days
• Field of Search: 382/232, 382/233-236, 382/238, 382/244-246, 348/14.11, 348/14.12, 348/14.13, 348/14.14, 348/14.15, 348/384.1, 348/387.1, 348/390.1, 358/426.01, 358/426.02, 358/426.03
• US Class Current: 382/236
• 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 19/137 Motion inside a coding unit, e.g. average field, frame or block difference
• CPC Class Codes: H04N 19/142 Detection of scene cut or scene change
• CPC Class Codes: H04N 19/172 the region being a picture, frame or field
• CPC Class Codes: H04N 19/587 involving temporal sub-sampling or interpolation, e.g. decimation or subsequent interpolation of pictures in a video sequence
• CPC Class Codes: H04N 19/61 in combination with predictive coding

Abstract

Image data compression method and apparatus which improves image quality in a scene where image greatly changes and reduces the image data, and image transmission system and monitoring system using the method and apparatus. The image data compression apparatus which compresses input image data and outputs compressed image data comprises a detection unit which detects a motion or change of each scene, a determination unit which determines the detected motion amount or change amount, a switch circuit which controls a frame rate in accordance with the results of determination, and a compression encoding unit which compression-encodes the image data. The apparatus performs control such that an image having small motion amount and small change amount with respect to a predetermined image is not compression-encoded, so that the frame rate in a scene where the motion or change is large is higher than that in a scene where the motion and change are small.

Claims

1. An image data compression apparatus which compresses input image data and outputs compressed image data, comprising:

compression processing means for compression-processing input image data;

image change detection means for detecting a change in an image based on the input image data;

frame rate control means for controlling a frame rate of outputted compressed image data obtained by compression-processing image data; and

means for controlling the frame rate of outputted compressed image data such that the frame rate in a scene where the image change is small is lower than the frame rate in a scene where the image change is large, in accordance with the situation of the change in the image detected by the image change detection means;

wherein the frame rate control means includes switching control means for performing or not performing compression encoding on image data in one-frame units; and

wherein the frame rate control means does not perform compression encoding on image data having a small change amount or a small motion amount, by using the switching control means, in accordance with a result of detection by change amount detection means or a result of detection by motion amount detection means.

2. An image-data compression apparatus according to claim 1, further comprising synthesizing means for synthesizing information on the frame rate of the compressed image data, controlled by the frame rate control means;

wherein the information on the frame rate is added to the compressed image data, and the compressed image data is outputted.

3. An image data compression apparatus according to claim 2, wherein the information on the frame rate is information on a number of frames thinned out for reducing the frame rate or information on a time interval between thinned frames.

4. An image data compression method for compressing input image data and outputting compressed image data, comprising the steps of:

compression-processing input image data;

detecting a change in an image based on the input image data;

controlling a frame rate of outputted compressed image data obtained by compression-processing image data such that the frame rate in a scene where the image change is small is lower than the frame rate in a scene where the image change is large, in accordance with the situation of the detected change in the image;

performing or not performing compression encoding on image data in one-frame units; and

outputting the compression-processed image data;

wherein compression encoding is not performed on image data having a small change amount or a small motion amount in accordance with a result of detection by change amount detection means or a result of detection by motion amount detection means.

5. An image data compression method according to claim 4, further comprising the step of synthesizing information on the frame rate of the compressed image data, controlled in the frame rate controlling step;

wherein the information on the frame rate is added to the compressed image data, and the compressed image data is outputted.

6. An image data compression method according to claim 5, wherein the information on the frame rate is information on a number of frames thinned out for reducing the frame rate or information on a time interval between thinned frames.