JPH09214891A - Moving image compression recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the number of components by using one system each of a compression section and an expanding section and supplying or outputting odd or even number field image information alternatively to the compression section or from the expanding section. SOLUTION: One system each of a compression section and expanding section 800 is provided and data from odd/even fields (ODD/EVEN) forming one frame are fed to the compression section and expanding section 800 via a switch 27. In this case, when a switching signal is at a high level (ODD1) in the ODD system, the data are written and read is conducted by using an inverted switching signal. When the inverted signal is at a high level, the data are read at a double speed (2f). Thus, the data of the same field are read twice for this period. Thus, preliminary scanning is made and compression processing is conducted. Furthermore, this is similar to the EVEN system and the preliminary scanning and compression processing of odd and even number fields are conducted alternately to process all the fields.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for compressing and recording image information.

[0002]

2. Description of the Related Art Recently, a method of compressing a digitized video signal using a high-efficiency coding technique and recording the data on a magnetic tape, a disk, a semiconductor memory or the like has become popular. As a typical compression method, there are MPEG, JPEG, SDVTR standards, etc., but each method uses a method in which the amount of data after compression is constant regardless of the pattern. this is,
This is because the aim is to ensure a certain recording time depending on the capacity of the recording medium, and there is a limit to the capacity (recording rate) that can be recorded per unit time depending on the recording medium. JPEG and SDVTR without time axis compression
As a standard, a technique that has been widely used recently as a compression algorithm for performing intra-field or intra-frame compression is a method of performing DCT (discrete cosine transform), further quantizing, and then entropy encoding. DCT is a so-called orthogonal transformation that transforms a spatial coordinate axis to a frequency coordinate axis so that a video signal converted into digital data can be easily coded. Quantization omits a component having a small frequency energy (high frequency component). The technique, entropy coding, is a technique in which short codes are assigned to high-frequency data and long codes are assigned to low-frequency data.

When such DCT, quantization, and entropy coding are performed with a constant quantization coefficient, the amount of data after compression changes depending on the pattern. That is, the amount of data after compression is large for a fine pattern such as a forest or a hand-knitted sweater, and the amount of data after compression is small for a pattern with few high frequency components such as a smooth white wall. When moving images are compressed continuously, there is no problem when the amount of data is small, but when the amount of data is large, there is a limit to the capacity (recording rate) that can be recorded per unit time depending on the recording medium, as described above. Therefore, the compressed data that continuously appears cannot be recorded within a predetermined time, that is, overflow occurs.

There are various methods for avoiding this, but as a general method, a process of estimating the amount of data after the compression is performed before the actual compression is performed, and then the quantization is performed so that the data size falls within a target data size. A method is used in which actual compression is performed by changing the coefficient and encoding settings.

Hereinafter, a few conventional examples will be shown and further description will be given. First, as a first conventional example, a configuration example of a feed-forward type compression unit will be shown and described. FIG. 3 shows a block diagram. In this example, since the code amount calculation is performed before compression, the compression / expansion unit 200 is provided with a hatched field memory 260 and a calculation unit 270. FIG.
Is an example in which the number of parts is increased, the circuit is enlarged, and the entire device is enlarged.

The flow of signals will be described below with reference to FIG. First, the A / D unit 100 converts the luminance signal Y and the color signals Cr and Cb from analog signals into digital signals. The video signal of one frame is stored in the odd and even field memories, and writing and reading are performed by the read / write control unit (not shown). Note that the read / write unit is omitted here.

In the compression / expansion unit 200, preprocessing for reducing redundancy is performed, but here, DCT (DESCRET C
OSINE TRANSFORM) is used. The video signal whose redundancy is reduced by the DCT is quantized and encoded to compress the data amount and recorded in the recording unit. Compression / expansion unit 2
A buffer memory 600 is provided between the 00 unit and the recording unit 700.
Is provided, data is temporarily stored in the buffer memory 600, and then recorded in the recording unit 700.

Quantization / inverse quantization unit 220 and encoding
The control of the inverse coding unit 230 is performed by feedforward, the redundancy is calculated from the output data of the DCT and the inverse DCT unit 210, and the quantization control unit 240 is based on this.
The control information is transferred to the encoding control unit 250 to determine the compression rate. In this example, while calculating the code amount,
Since the compression process cannot be performed, the field memory 260 needs to be provided in front of the quantization / inverse quantization unit 220. In other words, since the entire compression / expansion section must be synchronized, a delay element must be provided. Therefore, the field memory 260 for delay and the arithmetic unit 270 for calculating the compression ratio are required, and the number of parts increases.

A feedback type compression / expansion unit 800 is conceivable as one measure for improving this problem. A configuration of the feedback type compression unit 800 is shown in FIG. 4 as a second conventional example.

Description will be made with reference to FIG. First, the A / D unit 100 converts the luminance signal Y and the color signals Cr and Cb from analog signals into digital signals. A video signal of one frame is stored in odd (ODD) and even (EVEN) field memories, and writing and reading are performed by a read / write control unit (not shown). The processing is performed in two systems, an odd number and an even number, and the odd part is described as ODD and the even part is described as EVEN.
Since the left and right channels have the same configuration, only the ODD route will be described. This field memory 1
The data from 20 is compressed and recorded in the recording unit 700.

In the compression / expansion unit 800, preprocessing for reducing redundancy is performed. Here, as in the above case, D
CT (DESCRET COSINE TRANSFER) is used. The video signal whose redundancy is reduced by the DCT is quantized and encoded to compress the data amount and recorded in the recording unit 700. A buffer memory is provided between the compression / expansion unit 800 and the recording unit 700, and data is temporarily stored in the buffer memory and then recorded in the recording unit 700.

The control of the quantizing unit and the encoding unit is performed by feedback, and the output data of the encoding is once fed back to the control units 240 and 250 to set the compression rate before the processing. Therefore, pre-scan is performed before compressing the data for one field, and then the data for one field is adaptively compressed (FIG. 5).
reference).

Note that FIG. 5A shows signals for switching between the odd field and the even field, and FIGS.
(D) shows the timing of read / write to the field memory of the odd field (ODD) and the output data from the compression unit. 5E to 5G show timings of read / write to the even-numbered field (EVEN) field memory and output data from the compression unit. Further, FIG. 5H shows output data of compressed data, and shows that compressed data of even and odd fields is sequentially output.

According to this structure, the pre-scan is performed before the actual compression to calculate the code amount, and the quantization coefficient and the encoding setting are redone based on the result, and the actual compression process can be performed. .

However, even with such a configuration, since two processing systems are required for even and odd fields, the number of parts increases and the circuit scale increases.
The problem of increasing the size of the device still remained.

[0016]

That is, the first conventional example has a drawback in that a calculation unit for calculating the code amount and a field memory for data delay are required, and the number of parts is increased.

Also in the second conventional example in which the feedforward is changed to the feedback to improve this, there are two systems for processing the even field and the odd field,
It was necessary and had the drawback that the number of parts did not decrease so much.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a compression recording apparatus capable of effectively reducing the number of parts and processing by only one system.

[0019]

In order to achieve the above-mentioned object, in the present invention according to claim 1, there are two systems for compression and decompression, which are two systems for an odd field and an even field, and one system for an odd field or an even field. The image information is selectively supplied to the compression unit or output from the expansion unit to reduce the number of parts. For example, it can be easily realized by providing a changeover switch in the path to the compression unit.

[0020]

FIG. 1 shows an embodiment of the present invention.
This will be described with reference to FIG. The configuration is the same as that of FIG. 4 except that a switch 127 is added and the compression / expansion unit 800 is used as one system. The same components as those in FIG. 4 are designated by the same reference numerals and will be described. The read / write section is omitted here,
Only write speed and read speed transfer speed (f)
It is written as.

The applicant of the present invention configures the compression / expansion unit 800 as one system, and supplies the data from the odd and even fields forming one frame to the compression / expansion unit 800 via the switch 127. Here, the changeover switch 127 is provided to supply to the compression / expansion unit 800, but a buffer or a selector may be used as long as it can be changed.

The signal flow will be described with reference to FIG. FIG.
(A) is a field switching signal, which is also used as a switch control signal. That is, the switch is switched using this signal so as to select the field memory of the odd field and the even field. 2 (b) and 2 (c) show the odd field (O
The read / write timing for DD) is (d)
(E) shows the read / write timing for the even field (EVEN), and (f) shows the timing for the output data (compressed image information) from the compression section.

The odd number is written as ODD, and the even number is written as E.
It is marked as VEN. Further, a number is added after ODD or EVEN so that the processing of the field can be understood.

In the ODD system, writing is performed when the switching signal is high (ODD1), and reading is performed as shown in FIG.
The switching signal of the reverse phase shown in (c), that is, the inverted signal of FIG. When this switching signal is high, the read speed is doubled (2f) to read. Therefore, the same field can be read twice during this period.
Therefore, prescan is performed and compression processing can be performed.

The same applies to the EVEN system, and processing of all fields is performed by alternately performing odd-numbered and even-numbered prescanning and compression processing. That is, the applicant has reduced the number of parts by configuring the system in this way.

With the above-mentioned configuration, the processing system can be configured as a single system without increasing the horizontal resolution and only by increasing the ratio of the writing speed and the reading speed to twice. Therefore, the compression process can be performed in real time, the image quality is not significantly affected, and the number of parts can be reduced.

[0027]

As described above, the processing for compressing the video information of each field constituting one frame is performed by one system to reduce the number of parts.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a compression method according to an embodiment of the present invention.

FIG. 2 is a timing chart for explaining the operation of FIG.

FIG. 3 is a diagram for explaining a conventional moving image compression method.

FIG. 4 is a diagram showing another conventional moving image compression method.

FIG. 5 is a timing chart for explaining the operation of FIG. 4;

[Explanation of symbols]

 100 ... A / D converter 110 ... D / A converter 120 ... Field memory 200, 800 ... Compression / expansion unit

Claims (1)

[Claims] 1. A compression unit for compressing image information by preprocessing the image information to reduce redundancy, quantizing the preprocessed image information, and further encoding the image information. Recording means for recording the compressed image information from the compression section on a recording medium, reproduction means for reproducing the image information recorded on the recording medium, and the compression section for the image information from the reproduction means. Is provided with a decompression unit for decompressing the image information by performing the opposite process, and at the time of recording, the image information for two fields consisting of one frame is selectively supplied to the compression unit and compressed by the compression unit. While the recorded image information is recorded on the recording medium by the recording means, at the time of reproduction, the image information recorded from the recording medium is reproduced by the reproducing means, and the image information for two fields expanded by the expansion unit is selectively selected. Output An image compression recording device characterized by the above.