JPH05122655A - Compression signal recorder - Google Patents

Abstract

PURPOSE:To provide a compression signal recoder which can record variable- length encoding data the recording medium of a specified capacitance with efficiency and high quality. CONSTITUTION:The number of the time length of video information to be newly recorded is inputted in a compression rate setting circuit 105. A storage capacity detecting circuit 103, for example, detects the recording remaining amount of a tape T with the diameter of the tape of a reel and the compression rate setting circuit 105 calculates a target compression rate by comparing the recording remaining amount of the tape T and the numbers of time length of information to set it in a variable-length encoding circuit 104. The target compression rate is set to be that 'the remaining amount of a tape, which can be recorded' = 'information amount after compression' and the variable-length encoding circuit 104 executes compression with a parameter to be that 'the remaining amount of tape T, which can be recorded' >= 'information amount after compression' with the target compression rate as reference.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compressed signal recording apparatus for compressing an information signal by variable length coding and recording it on a recording medium.

[0002]

2. Description of the Related Art Generally, when compressing an information signal such as image data, a method of allocating a fixed-length code and coding and a method of allocating a variable-length code are known. The variable-length coding method of can assign a short code to data that frequently occurs,
The compression ratio can be improved as compared with the fixed length coding method. Therefore, in recent years, from the viewpoint of compression efficiency, development of a compressed signal recording device using the variable length coding method has been advanced.

[0003]

However, when an image data recording / reproducing apparatus such as a VTR (video tape recorder) is constructed by using such a variable length coding method, the amount of data after coding is not constant. Therefore, there is a problem in that when this coded data is recorded on a recording medium having a fixed capacity, inconvenience occurs.

That is, even if the compression parameter is set to a constant value, for example, when recording an image for one hour, the amount of data after encoding differs depending on the picture pattern of the image, so that the entire image is recorded on the recording medium. However, on the contrary, the recording medium has a large capacity, and therefore, by changing the compression parameter, it is possible to record with higher image quality, but the image quality is degraded. Become.

In view of the above-mentioned problems of the prior art, it is an object of the present invention to provide a compressed signal recording apparatus capable of efficiently recording variable-length coded data on a recording medium having a fixed capacity with high quality. To do.

[0006]

In order to achieve the above object, the present invention provides a compressed signal recording apparatus for compressing an information signal by variable length coding and recording the compressed information on a recording medium,
A variable length coding means for variable length coding an information signal, and a compression ratio of the variable length coding means according to the recordable recording capacity of the recording medium so that all the compressed data of the information signal is recorded on the recording medium. And a control means for controlling.

[0007]

According to the present invention, since the compression rate is controlled according to the recordable recording capacity of the recording medium so that all the compressed data of the information signal is recorded in the recording medium, the variable length encoded data can be stored in the recording medium. It is possible to record efficiently and with high quality on a recording medium having a fixed capacity.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a block diagram showing a schematic configuration of an embodiment of a compressed signal recording device according to the present invention, and FIG. 2 is a block diagram showing a configuration of an example of the variable length coding circuit of FIG.

FIG. 1 shows a digital VTR as an example, and the upper part shows a magnetic tape T obtained by variable length coding of an image signal.
Shows a compressed signal recording device for recording, and the lower stage shows the compressed signal reproducing device. First, when recording is performed, the number of hours of newly recorded video information is input to the compression rate setting circuit 105 via the input terminal 101. On the other hand, the storage capacity detection circuit 103 detects the recordable recording capacity by, for example, obtaining the remaining recording capacity of the tape T based on the tape diameter of the reel, and the compression rate setting circuit 105 inputs the remaining recording capacity of the tape T. The target compression rate is calculated by comparing the number of hours of information input via the terminal 101, that is, the amount of information to be recorded before compression, and the calculated target compression rate is set in the variable length coding circuit 104. To do.

Here, the target compression rate is a compression rate such that "the recordable recording capacity (remaining amount) of the tape" = "the amount of information after compression", which is used for the compression of the variable length coding circuit 104. This is a value for setting a parameter, and the variable-length coding circuit 104 makes “recordable recording capacity (remaining amount) of the tape T” ≧ “information amount after compression” on the basis of this target compression rate. The compression is performed with such parameters.

By the above operation, the recording operation is started after setting the target compression rate.

The image signal is input through the input terminal 100, converted into digital data by the A / D converter 102, and then encoded by the variable length encoding circuit 104 according to the above-set parameters and compressed. .. This encoded data is error-correction-encoded by the error-correction code adding circuit 106 as a countermeasure against errors that occur during recording and reproduction, and then the synchronization signal / identification signal (Syn).
c. The ID) adding circuit 108 adds a synchronizing signal and an ID signal for recording and reproduction. The ID signal includes an address of image information, a compression parameter, and the like. Then, in the modulation circuit 110, for example, 8-14
The data is subjected to modulation such as conversion or 8-8 conversion, which has the effect of suppressing low frequency components, amplified by the recording amplifier 112, and then recorded on the tape T by the recording head 114.

On the other hand, at the time of reproduction, the data recorded on the tape T is reproduced by the reproducing head 116, the reproduction signal is amplified by the reproduction amplifier 118, and then the demodulation circuit 120.
Demodulated by. This demodulated data is Syn
c. After the synchronization signal and the ID signal are detected by the ID detection circuit 122, the error correction circuit 124 corrects the error generated during recording and reproduction. Then, in the variable length code decoding circuit 126, Sync. The compressed data after error correction is decoded and expanded by the compression parameter in the ID signal detected by the ID detection circuit 122, and the restored image data is converted into an analog signal by the D / A converter 128 and output. It is output as an image signal via the terminal 130.

Therefore, according to the above embodiment, the storage capacity detecting circuit 103 detects the remaining recording amount of the tape T, for example, by the tape diameter of the reel, and the compression ratio setting circuit 105 detects the remaining recording amount of the tape T and the input terminal. The target compression ratio is calculated by comparing the number of times of the images input via 101, and the variable-length coding circuit 104 uses the target compression ratio as a reference for “the remaining recordable amount of the tape T” ≧ “compression”. Since the compression is performed by the parameter that becomes "the amount of information after", the variable-length coded data can be efficiently recorded with high quality on the tape T having a constant capacity.

In the above embodiment, the target compression rate is set once at the start of recording, but this operation is performed at a predetermined time interval during recording to correct the target compression rate at any time. You may.

FIG. 2 shows an example of a variable length coding circuit. This variable length coding circuit is configured to combine DCT (discrete cosine transform) and variable length coding for compression. Specifically, in order to perform compression closer to the target value within the target compression rate, a predetermined initial coefficient is set in the parameter that controls the compression rate, and the amount of compressed information after encoding at a predetermined time interval is set. Then, the coefficient is corrected at predetermined time intervals.
That is, based on the difference between the information amount when the previous coefficient is used and the target information amount, the next coefficient is determined, the information amount is recalculated, and finally the target compression ratio is close and the target value is set. The information amount data that does not exceed is compressed and encoded.

In FIG. 2, digital image data converted by the A / D converter 102 shown in FIG. 1 is input to an input terminal 140, and this image data is first converted from a raster scan data string in the blocking circuit 142. converted into a block sequence of i × j pixels, and then
The DCT circuit 144 performs discrete cosine transform and transforms into the frequency domain.

The converted data is quantized by a quantizer (Q) 148a and sequentially delayed by delay circuits 146a to 146d, and each delay data is quantized by a quantization table as described later. It is quantized by the units 148b to 148e. Here, the characteristics of the quantizers 148a to 148e are determined by the parameter S that controls the compression ratio. When the parameter S increases, the amount of information after compression decreases, and conversely, the parameter S decreases.
When becomes smaller, the amount of information after compression increases.

On the other hand, the initial coefficient generation circuit 156 receives the target compression rate from the compression rate setting circuit 105 shown in FIG. 1 via the input terminal 166, and sets the parameter S suitable for achieving this target compression rate. The initial value S0 is generated and supplied to the multiplication circuit 152a and the coefficient calculation circuit 158a. In addition, the quantization matrix generation circuit 150 generates each element Xij of the quantization matrix, and this element Xij is the multiplication circuit 152.
At a, the initial value S0 is multiplied (Xij × S0) and supplied to the quantizer 148a as a quantization table. The quantizer 148a quantizes the data transformed into the frequency domain by the DCT circuit 144 with this quantization table, and therefore, the compression rate can be controlled by controlling the quantization characteristic of the quantizer 148a. ..

The data quantized by the quantizer 148a is variable-length coded by the variable-length coder 154a, and the information amount Ba after this coding is calculated. The coefficient calculation circuit 158a stores the information amount Ba after the encoding,
Parameter S set by the initial coefficient generation circuit 156
Based on the initial value S0 and the target compression rate of S0, a coefficient S1 is calculated so that S0 <S1 when the information amount Ba is larger than the desired information amount and S0> S1 when the information amount Ba is smaller than the desired information amount. Stage multiplication circuit 152b and coefficient calculation circuit 158b
Supply to.

As a result, it becomes possible to compress the data into an information amount closer to the target compression rate in the encoding unit in the next stage.

In the multiplication circuit 152b, this coefficient S1 is multiplied by each element Xij of the quantization matrix (Xij × S).
1), the quantization table is supplied to the quantizer 148b.

The converted data delayed by the delay circuit 146a by a predetermined amount is quantized by the quantizer 148b by the quantization table, and the quantized data is variable-length coded by the variable-length encoder 154b. Further, the information amount Bb after this encoding is calculated. Coefficient calculation circuit 15
8b compares the encoded information amount Bb with the coefficient S1 set by the coefficient operation circuit 158a at the preceding stage, and when the information amount Bb is larger than the desired information amount, S1 <S
2 and conversely, if it is small, the coefficient S such that S1> S2
2 is calculated, and this coefficient S2 is supplied to the multiplication circuit 152c and the coefficient calculation circuit 158c in the next stage. In the multiplication circuit 152c, this coefficient S2 is multiplied by each element Xij of the quantization matrix (Xij × S2) and supplied to the quantizer 148c as a quantization table.

Similarly, the coefficient calculation circuits 158c and 15c
In 8d, the coefficients S3 and S4 are calculated, and the quantizers 148d and 1
The quantization table of 48e is calculated, and therefore the calculation of the coded information amount is repeated, and the compression rate is closer to the target compression rate.
The compression rate is controlled so that the encoded information amount is within the target information amount. That is, in this embodiment, the delay circuit 1
The compression rate is controlled for each time delayed by 46a to 146d.

At the final stage, the data quantized by the quantizer 148e is variable-length coded by the variable-length coder 154e, and this compressed data is stored in the buffer 160 at a predetermined recording rate and at a predetermined recording rate. Dummy data is added in order to adjust the rate, is then multiplexed with the final coefficient S4 in the multiplexing circuit 162, and is output to the error correction code adding circuit 106 shown in FIG. 1 via the output terminal 164. .. Therefore, according to this embodiment, since the compression rate is corrected at any time during recording, the compressed data can be recorded efficiently and with high quality on the recording medium having a fixed capacity.

In the above embodiment, the delay circuits 146a ...
Although the compression rate is modified only with the delay time of 146d as one unit, the occupancy rate of the compressed data in the buffer 160 is supplied to the compression rate setting circuit 105 shown in FIG. 1 as needed to further refine the target compression rate. By controlling, it is possible to record on the recording medium more efficiently and with high quality.

The present invention also provides a variable length coding circuit 154.
The number of stages is not limited to a to 154e, and
The present invention is not limited to the combination of DCT (discrete cosine transform) and variable length coding. Further, although the digital VTR has been described as an example in the present embodiment, it can be applied to a device for compressing other information signals by variable-length coding and recording them on a recording medium, and the magnetic tape T. Although the compression rate is changed according to the remaining amount of the recording medium, the compression rate may be changed according to the capacity of another recording medium.

[0028]

As described above, according to the present invention, in a compressed signal recording apparatus for compressing an information signal by variable length coding and recording the compressed information on a recording medium, a variable length code for variable length coding the information signal. Since the compression means and the control means for controlling the compression rate of the variable length coding means according to the recordable recording capacity of the recording medium so that all the compressed data of the information signal are recorded on the recording medium, The long coded data can be efficiently recorded with high quality on a recording medium having a fixed capacity.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a compressed signal recording device according to the present invention.

FIG. 2 is a block diagram showing an example of a variable length coding circuit in FIG.

[Explanation of symbols]

 103 recording capacity detection circuit 104, 154a to 154e variable length coding circuit 105 compression rate setting circuit 144 DCT (discrete cosine transform) circuit 148a to 148e quantizer T magnetic tape

Claims (3)

[Claims] 1. A compressed signal recording apparatus for compressing an information signal by variable length coding to record the information signal on a recording medium, wherein a variable length coding means for variable length coding the information signal and compressed data of the information signal A compressed signal recording apparatus comprising: a control unit that controls the compression rate of the variable length encoding unit according to the recordable recording capacity of the recording medium so that the entire recording medium is recorded. 2. The control means calculates the compressed data amount of the information signal at every predetermined time interval, and controls the compression rate of the variable length coding means at every predetermined time interval according to this compressed data amount. The compressed signal recording apparatus according to claim 1, wherein 3. The compressed signal recording apparatus according to claim 1, wherein the variable length coding means performs variable length coding on the data that has been discrete cosine transformed.