JPH05144188A - Image signal recording/reproducing method - Google Patents

Abstract

PURPOSE:To execute recording and reproduction at a fixed transfer speed by prescribing time maximum value of the total information amount after in-frame and inter-frame compression encoding of plural pieces of image frames, and adding arbitrary data in the case being below the maximum value. CONSTITUTION:In a compression encoder 105, 1-6 frames and 7-12 frames constitute one group, respectively, and to the 1 and 7 frames, an in-frame compression encoding processing is executed, and to 2-6 frames and 8-12 frames, an inter- frame compression encoding processing is executed. Also, the total information amount after compression encoding of one group is subjected to compression encoding so as to become below 131072 bytes of the maximum value set in advance. In the case of this example, since the data capacity of one unit is 2048 bytes, a recording processor 106 divides them into 64 pieces of units of fixed length. Data of a 6-frame portion from the compression encoder 105 is data of a 61 unit and 1/2 unit portion, therefore, the remaining units are filled with arbitrary data, and the total data capacity is set to a fixed value of 131072 bytes. In such a manner, a data transfer speed becomes constant.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image signal recording / reproducing method, and more particularly to an image signal recording / reproducing method of digital data in which an image signal is compression-encoded.

[0002]

2. Description of the Related Art When an image signal is recorded and reproduced as digital data on a storage medium, it is very difficult to record and reproduce it in real time, especially with a moving image signal, because the amount of information is very large. For example, when an NTSC composite signal is quantized with a sampling frequency of 4 fsc (fsc is a color subcarrier frequency) of 8 bits, a transfer rate of about 120 Mbps is required. However, transfer rate 120M
Realizing a recording / reproducing system that achieves bps depends on the performance between the storage medium and the recording / reproducing head, and is technically extremely difficult. Therefore, when recording / reproducing information at a high transfer rate on a storage medium, real-time processing can be performed as a whole apparatus by a technique of using a plurality of recording / reproducing heads to reduce the transfer rate per recording / reproducing head. It was possible.

However, even if the real-time processing is enabled in this way, when considering the recording / reproducing time, it is not possible to record / reproduce all the moving image signal information as it is depending on the total capacity of the storage medium. Will be prescribed in. Therefore, in a recording / reproducing apparatus for a digitized moving image signal, the image signal is compression-encoded and recorded on a storage medium to such an extent that the deterioration of the information of the original signal is not noticeable, and the decoding process is performed during reproduction. A method for facilitating real-time processing of recording / reproduction and at the same time prolonging recording / reproduction has been considered.

As a method of compression coding, data of several frames are grouped into one group, and at least one frame of data is subjected to compression coding in a frame having a relatively low compression rate. The remaining frames are subjected to interframe compression encoding processing with a relatively high compression rate. By thus combining the intraframe and interframe compression encoding processing, the overall compression rate is improved and the image deterioration is relatively suppressed. When recording / reproducing this compression-encoded data on a storage medium, the compression-encoded data in the conventional frame and the compression-encoded data between the frames are arranged in time series, and a single recording / reproducing head is used. I was going.

[0005]

However, in the compression coding method as described above, the amount of coded data generally changes remarkably due to the difference in the correlation of the input image signals, and the data transfer rate greatly changes. There are cases. On the other hand, since the transfer rate of information between the conventional storage medium and the recording / reproducing head is generally determined by the performance of the storage medium, when the compression rate of encoded data is low, that is, when the amount of information after compression is large. However, the amount of encoded data increases the transfer speed of information between the storage medium and the recording / reproducing head, which may make it difficult to record / reproduce data in real time. Further, there is a problem that it is technically very difficult to record and reproduce by changing the transfer speed between the storage medium and the recording and reproducing head every moment.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a method for recording / reproducing a compression-coded variable-length digital image signal at a fixed transfer rate.

[0007]

In order to achieve this object, the present invention defines a plurality of image frames as one group, at least one frame in the group is subjected to intraframe compression coding, and the remaining frames are frame-coded. Perform inter-compression coding. Further, the maximum value of the total information amount of the intra-frame compression-encoded digital data and the inter-frame compression-encoded digital data of the group is defined. When the total amount of information of the compression-coded digital data is less than the maximum value, arbitrary data is added to the compression-coded digital data to realize recording / reproduction at a fixed transfer rate.

Further, by grouping a plurality of image frames, dividing the compression-encoded data into a plurality of fixed-length units, adding recognizable information to each unit, and recording it on a storage medium, it becomes easy. It is possible to find the beginning of the group.

[0009]

According to the present invention, with the above-described configuration, the maximum value of the total information amount after intra-frame and inter-frame compression encoding of a plurality of image frames is defined, and a plurality of frames are handled collectively, so that one frame The information amount can be averaged more than the maximum value of the information amount after compression, and the maximum value of the information amount can be lowered. Therefore, the maximum data transfer rate between the recording / reproducing apparatus including the recording / reproducing head and the storage medium can be lowered, which is advantageous in recording / reproducing compressed image information in real time. Further, by adding arbitrary data, the information processing speed of the recording / reproducing apparatus and the storage medium can be fixed, so that the entire apparatus can be simplified.

Further, the maximum information amount, which is obtained by combining the compression-encoded digital data and the added arbitrary data, is divided into a plurality of fixed information amount units, and each of the plurality of fixed information amount units is divided. By adding information that can recognize the unit and recording / reproducing on / from the storage medium, it is possible to easily access an arbitrary unit.

[0011]

An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 shows an image signal recording / reproducing method according to an embodiment of the present invention, in which a plurality of consecutive image frames are grouped and compression-encoded information is added with arbitrary data such as character information data to make a total. FIG. 6 is a schematic diagram showing division into a plurality of units at the time of recording / reproduction in accordance with a predetermined amount of information. The maximum total information amount of one group is 131072 bytes, and one group is divided into 64 units, and the information amount of one unit is 2048 bytes. FIG. 2 is a schematic diagram showing that six consecutive image frames are grouped in this embodiment, the first frame among them is the intra-frame coded frame, and the other remaining frames are the inter-frame coded frames. FIG. 3 shows a schematic block diagram of an image recording / reproducing apparatus according to an embodiment of the present invention.

As shown in FIG. 3, Y, U and V are externally applied.
(Y is a luminance signal, U and V are chrominance signals) The image signals analog input are quantized by the A / D converters 101, 102 and 103, and the Y signal has a sampling frequency of 13.5 MHz.
The z, U, and V signals are each quantized with 8 bits at a sampling frequency of 6.75 MHz, and the quantized data is stored in the memory 104. At this time, the total amount of data for one second is 216 Mbits. Further, an externally digitized image signal may be directly input to the memory 104. Memory 10
The image signal taken in 4 is sent to the compression encoder 5 and is subjected to compression encoding processing.

At this time, as shown in FIG. 2, the compression encoder 105 divides the data of 6 frames into one group,
Intra-frame compression coding is performed on the first frame,
The remaining 5 frames are subjected to interframe compression coding processing. The first to sixth frames and the seventh to twelfth frames shown in FIG. 2 are grouped into one group, and the first frame and the seventh frame are subjected to intraframe compression encoding processing, and the second to sixth frames and the eighth frame are processed. From the 12th frame to the 12th frame, interframe compression encoding processing is performed. The compression encoder 105 performs compression encoding so that the total amount of information after compression encoding of one group is equal to or less than a preset maximum value.

The data encoded as described above is sent to the recording processor 106. The recording processor 106 divides the data in group units into a plurality of fixed-length units. In this embodiment, the data capacity of one unit is 2048 bytes. When the maximum value of the total information amount of one group is 131072 bytes, it is divided into 64 fixed length units. As shown in FIG. 1, the compression-encoded 6-frame data sent from the compression encoder 105 is 6
Since the data is 1 unit and about 1/2 unit, the remaining unit (the portion shown by the shaded line) is filled with arbitrary data, and the total data capacity is set to a fixed value of 131072 bytes. The data divided for each unit is recorded by the recording processor 106.
After adding information indicating the beginning of the unit or information indicating the number of the unit, the optical pickup 10
Sent to 7. At this time, the transfer rate of the data sent to the optical pickup 107 is constant regardless of the amount of information encoded by the compression encoder 105. The intensity of the laser light is modulated according to the data sent to the optical pickup 107, and recorded on the optical disc 115 as digital data.

Regarding reproduction, the data reproduced from the optical disk 115 is detected by the optical pickup 108 in the reproduction processor 109. Further, the reproduction processor 109 performs data processing while recognizing the number of the unit of the group. Also, after the additional information data added by the recording processor 106 is removed, the reproduction data is sent to the compression decoder 110 together with the reproduction clock for decoding processing. The decoded image signal data is sent to the memory 111 and then stored in the memory 1 at a constant transfer rate.
11 and read from the D / A converters 112, 113, 1
It is output through 14 as an analog image signal to the outside.
The reading speed is set to 13.5 MHz for the Y signal and 6.75 MHz for the U and V signals according to the sampling frequency at the time of A / D conversion during recording. The data read from the memory 111 may be directly output as digital data to the outside.

As described above, according to the present embodiment, the maximum value of the total information amount after intra-frame and inter-frame compression coding of a plurality of image frames is defined, and a plurality of frames are handled collectively, so that The information amount can be averaged more than the maximum value of the information amount after the compression for the frame, and the maximum value of the information amount can be lowered. Therefore, the maximum data transfer rate between the recording / reproducing apparatus including the recording / reproducing head and the storage medium can be lowered, which is advantageous in recording / reproducing compressed image information in real time. Further, by adding arbitrary data, the information processing speed of the recording / reproducing apparatus and the storage medium can be fixed, so that the entire apparatus can be simplified.

Further, it is possible to easily access an arbitrary unit by adding information for recognizing the unit to each unit of a plurality of fixed information amounts and recording / reproducing on / from the storage medium.

Although the recording / reproducing apparatus has been described in this embodiment, the recording apparatus or the reproducing apparatus may be independent. In addition, the optical pickup 107,
It does not matter even if 108 is common.

When the image frame is the image frame of the standard television signal, the information amount of a plurality of units is 204
8 bytes, the number of image frames in one group is 1
5 or less, and the number of units in the group may be 280 or less. When the image frame is an image frame of a high-definition television signal, the information amount of a plurality of units is 2
The number of image frames in one group may be 15 or less, and the number of units in the group may be 900 or less.

[0020]

As described above, according to the present invention, the image signals of a plurality of frames are grouped into one group, so that the amount of information is averaged and the maximum transfer rate can be lowered as a whole. Furthermore, the maximum value of the total information amount of the variable length data after compression encoding in the group is specified, and if the compression encoded information amount is less than or equal to the maximum value, arbitrary data is added. The transfer rate of information with the recording / reproducing head is fixed. Therefore, the recording / reproducing apparatus can always process data at a fixed speed, and the entire apparatus can be simplified.

In addition, by using the information that can be recognized for each unit,
Since you can easily access any position on the storage medium,
The cue of the group can be easily realized.

[Brief description of drawings]

FIG. 1 is a diagram showing an example in which six consecutive image frames are grouped and compression-encoded, arbitrary data is added to the information, and the total amount of information is adjusted to a predetermined amount. A schematic diagram showing that the data is divided into units of 64 fixed length (2048 bytes)

FIG. 2 is a schematic diagram showing intraframe coding of the first and seventh frames and interframe coding of the second to sixth frames and the eighth to twelfth frames in the present embodiment.

FIG. 3 is a schematic block diagram of a recording / reproducing apparatus according to an embodiment of the present invention.

[Explanation of symbols]

 101 A / D Converter 102 A / D Converter 103 A / D Converter 104 Memory 105 Compression Encoder 106 Recording Processor 107 Optical Pickup 108 Optical Pickup 109 Playback Processor 110 Compression Decoder 111 Memory 112 D / A Converter 113 D / A converter 114 D / A converter 115 Optical disk

Claims (6)

[Claims] 1. A digital image compression method in which a plurality of consecutive image frames are grouped into one group, at least one frame of the plurality of image frames is intra-frame compression coded, and the remaining frames are inter-frame compression coded. A method of recording / reproducing a signal, wherein the maximum value of the total amount of information of the intra-frame compression-encoded digital data and the inter-frame compression-encoded digital data of the group is defined, and the compression-encoded digital data of When the total amount of information is less than or equal to the specified maximum value, arbitrary data is added to any position of the compression-encoded digital data, and the digital image compression signal is recorded and reproduced at the specified maximum value of the total information amount. An image signal recording / reproducing method characterized by continuously recording / reproducing at a fixed transfer rate. 2. A maximum information amount, which is a combination of compression-encoded digital data and added arbitrary data, is divided into a plurality of fixed information amount units, and the divided plural fixed information amounts are divided into units. 2. The image signal recording / reproducing method according to claim 1, wherein recording / reproducing is performed by adding information capable of recognizing the unit for each unit. 3. The image signal recording / reproducing method according to claim 2, wherein the intra-frame compression-encoded digital data is arranged at the head of a group in which compression-encoded digital data and added arbitrary data are combined. .. 4. The image frame is an image frame of a standard television signal, the information amount of a plurality of units is 2048 bytes, the number of image frames in one group is 15 or less, and the number of units in the group is 280 or less. The image signal recording / reproducing method according to claim 2, wherein 5. The image frame is an image frame of a high-definition television signal, and the information amount of the plurality of units is 20.
3. The image signal recording / reproducing method according to claim 2, wherein the number of image frames in one group is 48 or less and the number of image frames in one group is 15 or less, and the number of units in the group is 900 or less. 6. The image signal recording / reproducing method according to claim 1, wherein the arbitrary data is character information data.