JP2000184376A - Video camera system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a video camera system where a load of a personal computer in the case of image expansion is relieved and a video image with less deterioration in image quality can be transmitted by approaching an image compression rate to a predetermined set value so that the required bandwidth is set within a bandwidth of a transmission line from a video camera to the personal computer. SOLUTION: The video camera system is provided with a storage means that stores image data obtained by picking up an image by a solid-state image pickup element 2 and subjected to image signal processing, a storage means 5 that applies quantization processing 7 by using a quantization table changeover means to select a quantization table to the image data and stores compressed image data after the image compression processing, an image data capacity detection means 10 that detects a capacity of the compressed image data stored in the storage means 5, an external I/F circuit including video signal conversion processing for display on a video display device and a transfer means to an external device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data amount after image compression irrespective of a data amount of video data which is connected to an external device such as a computer and obtained by a video camera or the like used for a videophone or a video conference. For a video camera system that keeps a constant.

[0002]

2. Description of the Related Art In recent years, a video camera is connected to a computer for use as a video conference or video phone, or a video from the video camera is recorded and compressed in the computer, and the video is exchanged as an e-mail. It is used as a video e-mail and the like, and a video camera has become popular with the spread of personal computers (hereinafter, referred to as PCs).

[0003] A video camera is connected to a PC,
There is a limit to the amount of data that can be transmitted. For example, USB (Universal Serial Bus), which is one of the serial I / F, has been used as a serial bus that replaces the conventional serial / parallel port. The advantage of this is that the data transfer speed is as high as 12 Mbit / sec. There is a certain thing. However, in recent years, when high-resolution video such as VGA size is required, the data amount of the input video becomes large,
When video data is transmitted to an external I / F such as C, it takes a very long time to transmit one image.

[0004] Therefore, recently, video cameras have been used for PCs.
If the bandwidth of the transmission path to
The system is configured so that high quality images can be obtained using image compression methods such as G, MPEG, and H.26X.

[0005]

Conventionally, when the bandwidth of a transmission path from a video camera to a PC is larger than the amount of information of a video signal to be transmitted, the bandwidth of the transmission path is adjusted to be within the bandwidth of the transmission path by using an image compression technique. Had designed the system. At this time, there is a difference in the amount of data after compression depending on the type of the input image (bright / dark / with or without complicated pattern).
However, the time required to decompress the compressed image did not change.

[0006] Recently, serial I / F which is becoming popular in PCs
USB, which is one of the devices, can connect up to 127 types of peripheral devices, but the amount of data that one peripheral device can transmit to the host PC is limited and the other peripheral devices occupy a large bandwidth Possibilities must also be considered.
Therefore, when designing the system, the compression rate must be increased in advance and the image quality must be sacrificed to some extent.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a video camera system capable of transmitting a video image with less deterioration in image quality at a compression rate according to a transmission band while reducing the load at the time of image expansion on the PC side.

[0008]

A video camera system according to the present invention has solved the above-mentioned problems.
In order to make the data amount of the compressed image data transmitted to the transmission path substantially constant, the invention described in (1) captures an image of a subject and converts the image into an electric signal, and processes the electric signal. A video signal processing means for converting the image data, a storage means for storing the image data subjected to the video signal processing, an image compression means for performing a quantization process by switching the image data by a quantization table by a quantization table switching means, Including storage means for storing compressed image data after image compression processing, image data capacity detection means for detecting the capacity of compressed image data stored in the storage means, and video signal conversion processing capable of being displayed on a video display device It has an external I / F circuit and a transfer means to an external device.

Further, the invention described in claim 2 is an external device.
In order to change a substantially constant amount of compressed image data to be output to the I / F, a video imaging unit that captures an image of a subject and converts it into an electric signal, and a video signal processing unit that processes the electric signal and converts it into a video signal Storage means for storing image data subjected to video signal processing, image compression means for performing quantization processing by switching the image data by a quantization table switching means, and compressed image after image compression processing Data storage means and a data capacity setting to keep the video (image) obtained by the image compression process almost constant regardless of the video data amount input from the video camera according to the instruction from the external I / F. Means for performing, a means for detecting the data capacity determined by the data capacity setting means, and an external I / O including a video signal conversion process which can be displayed on the video display device.
It has an F circuit and a transfer means to an external device.

According to a third aspect of the present invention, an object is imaged in order to include information on the used quantization table in a header of the compressed image data to be transferred.
Image pickup means for converting the image data into an electric signal, image signal processing means for processing the electric signal and converting the image signal into a video signal, storage means for storing image data subjected to the image signal processing, and switching of the image data to a quantization table Image compression processing for performing quantization processing by switching a quantization table by means, storage means for compressed image data after image compression processing, and data capacity detection for detecting the capacity of compressed image data stored in the storage means Means for superimposing information on the quantization table used when compressing the image in the header of the compressed image data to be transferred, and an external I / F circuit including a video signal conversion process displayable on a video display device And a transfer means to an external device.

According to a fourth aspect of the present invention, in order to refer to a plurality of quantization tables, an image pickup means for picking up an image of a subject and converting the image into an electric signal, and processing the electric signal to obtain an image. Video signal processing means for converting to a signal, storage means for storing image data subjected to video signal processing, storage means for storing a plurality of quantization tables for quantization, and quantization table switching for switching quantization tables Means, means for storing image data after image compression processing, data capacity detection means for detecting the capacity of compressed image data stored in the storage means, and external I including a video signal conversion process which can be displayed on a video display device. / F circuit and means for transferring to an external device.

[0012] Further, the invention described in claim 5 is an embodiment of the present invention.
A video imaging unit that captures an image of a subject and converts it into an electric signal in order to change the quantization table in response to a request from the C side; a video signal processing unit that processes the electric signal and converts the electric signal into a video signal; Storage means for storing the processed image data, a plurality of quantization table storage means for quantization, quantization table switching means for switching the quantization table, and instructions on the PC side input from the external I / F Transmission means for transmitting, storage means for storing compressed image data after image compression processing, data capacity detection means for detecting the capacity of data of the compressed image stored in the storage means, and a video signal displayable on a video display device External I / O including conversion processing
It has an F circuit and a transfer means to an external device.

Further, according to the present invention, in order to preferentially use a quantization table which is frequently used, an image pickup means for picking up an image of a subject and converting it into an electric signal, , A video signal processing unit for converting the video signal into a video signal, a storage unit for storing the video signal processed image data, a unit for storing a plurality of quantization tables for quantization, and for switching the quantization table. Quantization table switching means, quantization table use frequency storage means for recording the history of used quantization tables, storage means for storing compressed image data after image compression processing, and storage means It has a data capacity detection means for detecting the capacity of compressed image data, an external I / F circuit including a video signal conversion process that can be displayed on a video display device, and a transfer means to an external device. Is shall.

According to a seventh aspect of the present invention, in the case where the input image of the subject is not output as compressed image data from the compression means, the subject is imaged and converted into an electric signal in order to output the image data. Video imaging means for processing, video signal processing means for processing the electric signal and converting it into a video signal, storage means for storing image data subjected to the video signal processing, and storing a plurality of quantization tables for quantization. Quantization table storage means, quantization table switching means for switching the quantization table, storage means for storing the compressed image data after the image compression processing, previously encoded data storage means, and storage in the storage means Data capacity detecting means for detecting the capacity of the compressed image data present, determining means for passing through the data capacity detecting means, and a video signal displayable on a video display device. An external I / F circuit including a conversion process,
It has a transfer means to an external device.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a video camera system according to the present invention will be described with reference to FIGS.

<First Embodiment> A first embodiment of a video camera system according to the present invention will be described in detail with reference to FIG.

FIG. 1 is a block diagram showing the configuration of a video camera system according to the present invention. The solid-state image sensor 2 converts an image from a subject condensed by a lens 1 into an electric signal and then performs A / D conversion. The analog video signal input to the circuit 3 is converted into digital image data. A digital signal in each image of the solid-state imaging device 2 output from the A / D conversion circuit 3 is stored in an image data storage unit 5 for DCT (Discrete Cosine Transfer) processing. After the DCT processing, the DCT transform coefficient calculated by the DCT processing unit 6 is quantized by the quantization processing unit 7 using the quantization table.

The Huffman coding processing unit 8 converts each quantized DCT transform coefficient into coded data. The encoded image data is sequentially stored in the storage unit 9. The amount of compressed image data stored in the storage unit 9 is detected by the capacity detection unit 10.

If it is determined that the compressed image data is compressed to a predetermined capacity (K) or within an allowable range (K-α to K + α) by the capacity detection unit 10, Via the external I / F circuit 12, the video signal is converted into a video signal that can be displayed on the video display device 13, and the video of the subject captured by the video display device 13 (CRT display or the like) can be displayed.

Next, the determination of the capacity detection unit 10 after compression will be described in detail.

The coding capacity stored together with the coded data in the storage unit 9 is compared with a target coding capacity set in advance by the capacity detection unit 10.
When the coding capacity output from the storage unit 9 is not within the target set capacity range, the coding capacity after compression is large.
In the case of (small), the capacity detection unit 10 sends a message to the quantization table switching unit 11 to increase (decrease) the compression ratio.

The quantization table switching unit 11 outputs a quantization table with an increased (decreased) compression rate to the quantization processing unit 7, performs a quantization process, performs a Huffman encoding process, and stores the quantization table. The capacity is stored in the storage unit 9 and the capacity after compression is compared again by the capacity detection unit 10. As a result of the comparison, when the encoding capacity falls within the range of the set capacity, the encoded data is output to the external I / F circuit 12. If it is not within the range of the set capacity, the same processing is repeated until it falls within the range of the set capacity.

Next, the processing in the video display device 13 will be described in detail.

The image data compressed to a value substantially close to the capacity set in advance by the capacity detection unit 10 is inversely quantized by the decoding processing unit 14 and subjected to inverse DCT. The compressed image data is stored in the image data storage unit 15, and is converted from a digital signal to an analog signal by the D / A conversion circuit 16.

The operation unit 17 is operated by the user and means, for example, a keyboard, a mouse, and the like. The coding capacity of the capacity range set by the capacity detection unit 10 is changed via the external I / F 12.

For example, a change from the current set capacity can be instructed by inputting a setting menu, a capacity scroll bar, or the like displayed on the image with a mouse or a keyboard. When the capacity setting after compression or the setting range width is changed, the value of the changed setting is immediately input to the external device.
It is converted to the coding capacity via the I / F 12 and the capacity detection unit 1
The set value at 0 is changed to its coding capacity. The setting change becomes effective from the point in time when the capacity detection unit 10 is changed.

Further, after the compressed image data is compressed to a value substantially close to the capacity set by the capacity detection unit 10, when the compressed image data is transmitted to the external I / F circuit 12, a quantization process is performed. The information relating to the quantization table used for compression in the unit 7 is superimposed on the header of the compressed image data to be transferred. When the video display device 13 performs the decoding process, it performs the inverse quantization process using the quantization table used for compression.

At this time, the decompression process is executed by referring to the header of the transmitted compressed image data information and corresponding to the used quantization table. Even if the quantization table used for compression has changed, the decompression process can be executed according to the change, so that the load of the decompression process on the PC side is reduced.

<Second Embodiment> Next, a video camera system according to a second embodiment of the present invention will be described with reference to FIG.

FIG. 3 shows a configuration in which a quantization table storage unit 18 is added to the configuration of FIG. 1, and a plurality of quantization tables are stored in advance in the quantization table storage unit 1 as shown in FIG.
8 is stored. If the image has not been compressed to a value that is nearly equal to the capacity set by the capacity detection unit 10 after image compression,
A quantization table other than the quantization table is passed from the quantization table storage unit 18 to the quantization table switching unit 11,
Perform quantization processing.

The quantization table storage unit 18 stores a quantization table in which the quantization table is classified according to the input image data amount, the compressed image capacity, and the like, as shown in FIG. 2B. What contains a table column (column 1 to column n) may be stored.

For example, when a change is instructed from the current set capacity by inputting a mouse or a keyboard to a setting menu or a capacity scroll bar displayed on a video or the like, the changed value is immediately applied to the external input I / F 12. 2 included in the quantization table storage unit 18 via
The quantization table of FIG. 2A is changed based on the changed setting value, or another quantization table sequence using the quantization table sequence of FIG. 2B based on the changed setting value. Changes are made to

<Third Embodiment> Next, a third embodiment of the video camera system of the present invention will be described with reference to FIG.

FIG. 4 shows a configuration in which a quantization table use frequency storage unit 19 is added to the configuration of FIG. 3, and used quantization included in the header of the compressed image data transmitted to the external I / F circuit 12. The table is counted to determine the usage frequency, and based on the result, the quantization table of FIG. 2A or the quantization table sequence of FIG. 2B included in the quantization table storage unit 18 is quantized. The tables are made available to the quantization processing unit 7 in order of use frequency.

For example, the quantization table use frequency storage unit 1
9 stores each quantization table in the quantization table storage unit 18 or each quantization table in the used quantization table sequence, and each quantization table includes information on the frequency of use. In addition, the quantization tables are arranged in the order of high (low) use frequency. Therefore, referring to the information of the header included in the transmitted compressed image data, the used quantization tables are counted, and the tables are rearranged to those of high (low) use frequency.

Thereafter, the quantization tables arranged in the most frequently used (lower) ones are stored again in the quantization table storage unit 18, and the quantization tables from the most frequently used ones are stored in the quantization table switching unit 11. Delivery and quantization are performed.

<Fourth Embodiment> Next, a video camera system according to a fourth embodiment of the present invention will be described with reference to FIG.

FIG. 5 shows a case where the previous compressed image data is stored in the configuration of FIG. 1 together with the encoded data and the encoding capacity.
When the input image data is not substantially compressed to the set capacity, the data storage unit 20 and the pass determination unit 21 that determines whether the data has passed the capacity detection unit 10 are added. The encoded data and the encoded capacity of the immediately preceding compressed image are stored in the data storage unit 20. However, in the initial case, the encoded data and the encoding capacity of the previous compressed image data are stored.

If a timer is used and the image data has not passed through the passage determination unit 21 within a certain time (no compressed image data is input), the previous data storage unit 20
The previous compressed image data is transmitted to the external I / F circuit 12.
When passing through the passage determination unit 21, the previous compressed data transfer is stopped, and the mode is immediately switched to the compressed data transmission mode within the set capacity range.

In this way, when the compression capacity of the image data cannot be set or when it takes time until the image is compressed in the initial state, the previous image is transmitted and the image data is displayed on the video. This prevents the image from being displayed on the device 13.

[0041]

According to the video camera system of the present invention, a PC
It is possible to provide a system capable of transmitting a video with less deterioration in image quality at a compression rate according to a transmission band by reducing the load at the time of image expansion on the side.

According to the first aspect of the present invention, a substantially constant data amount is output regardless of the image data amount input by the video camera, so that even high-resolution image data can be output in one second. The ratio (frame rate) to be sent becomes almost constant, and the frame rate is guaranteed.

According to the second aspect of the present invention, the external
Since the PC can change the almost constant data amount to be output to the I / F from the PC side, it becomes possible to change the amount of compressed image data to be transferred according to the performance of the PC and the transferable bandwidth of the external I / F.

Further, according to the third aspect of the present invention, the information about the used quantization table is included in the header of the transfer image data because the decoding process can be performed using the quantum table. The burden on the decompression process on the side is reduced.

Further, according to the invention as set forth in claims 4 to 6, a plurality of quantization table columns are used by changing a setting such as a capacity of image compression from a PC by using a plurality of quantization tables. The delay in the quantization processing unit can be reduced by changing the quantization table from the one with the highest frequency of use by changing the frequency of use of the quantization table or counting the frequency of use of the quantization table.

Further, according to the invention, when the input image of the subject is not output as the compressed image data from the compression means, the image data of the previous compression is output to display the image data. An image can be prevented from being displayed on the device.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a video camera system according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing an arrangement of a quantization table in a quantization table storage unit of the present invention.

FIG. 3 is a block diagram showing a configuration of a video camera system according to a second embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of a video camera system according to a third embodiment of the present invention.

FIG. 5 is a block diagram showing a configuration of a video camera system according to a fourth embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 lens 2 solid-state imaging device 3 A / D conversion circuit 4 memory control circuit 5 image data storage unit 6 DCT processing unit 7 quantization processing unit 8 Huffman coding processing unit 9 storage unit 10 capacity detection unit 11 quantization table switching unit 12 External I / F circuit 13 Video display device 14 Decoding processing unit 15 Image data storage unit 16 D / A conversion circuit 17 Operation unit 18 Quantization table storage unit 19 Quantization table use frequency storage unit 20 Previous data storage unit 21 Passage determination Department

Claims (7)

[Claims] 1. An image pickup means for picking up an image of a subject and converting it into an electric signal, a video signal processing means for processing the electric signal and converting it into a video signal, and a means for storing image data by the video signal processing means. An image compression unit for performing a quantization process by switching the image data by a quantization table by a quantization table switching unit; an image data storage unit and a data capacity detection unit after the image compression unit; and an external I / F. To the image data amount detection means, regardless of the amount of data,
A video camera system, wherein a video (image) obtained by the image compression means is kept substantially constant. 2. The video camera system according to claim 1, wherein a substantially constant amount of compressed image data to be output to the external I / F can be changed from the external I / F. 3. The video according to claim 1, wherein the transfer unit to the external I / F includes information on a quantization table used in a header of the compressed image data to be transferred. Camera system. 4. A video as claimed in claim 1, wherein said image compression means includes a storage means for storing a plurality of quantization tables and a quantization table switching means. Camera system. 5. The video camera system according to claim 2, wherein said quantization table can be automatically changed by a request from an external device. 6. The video camera system according to claim 4, further comprising a quantization table switching unit that counts the frequency of use of the quantization table and switches the quantization table from the one with the highest frequency of use. 7. The video camera system according to claim 6, further comprising means for outputting previously compressed image data when the input image data is not substantially compressed to the set capacity.