JPH05158499A - Compressing and recording device for signal - Google Patents

Abstract

PURPOSE:To provide the device for securing required accuracy while decreasing the number of bits required for recording. CONSTITUTION:Digitized data are stored in a buffer memory 2 as they are, and the maximum and minimum values of the data stored in the buffer memory 2 are stored by a maximum value detection circuit 3 and a minimum value detection circuit 4. Based on these values, the maximum change amount and DC component of the stored data are calculated, and the number of bits for storing the change component and the number of bits for storing the DC component are decided by a bit number change circuit 9. Then, recording is executed to a recording medium 6 with the number of bits.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal compression recording apparatus for digitally compressing / decompressing a signal which varies with time but does not vary significantly with respect to a recording medium.

[0002]

2. Description of the Related Art Conventionally, various methods for recording an analog signal have been proposed, but many of them have a problem in reproduction accuracy. If an attempt is made to improve the accuracy of the analog signal itself, the structure becomes complicated and the economy becomes poor. Become. If you want to record with good cost and accuracy, first of all, analog signal A
There has been proposed a method in which a signal converted into a digital signal is recorded on a recording medium by sampling with a / D converter and digitizing.

[0003]

However, in order to record a digital signal, a recording medium of an amount determined according to the number of resolution bits at the time of digitization is required, and if accuracy is required, a large recording capacity is required. There was a problem to say.

The present invention has been made in view of the above circumstances, and provides an apparatus for ensuring accuracy while reducing the number of bits required for recording.

[0005]

In order to solve such a problem, the present invention provides an A / D converter for converting an analog signal into a digital signal, and a buffer for storing the digital signal at a sampling timing for a predetermined time. A memory and a maximum value detection circuit that stores the maximum value within a predetermined time,
A minimum value detection circuit that stores the minimum value within a predetermined time, a bit number conversion circuit that determines the number of bits required to store the variation and the DC component from the difference between the maximum value and the minimum value, and the determined number of bits And a multiplexer for selecting a change component and a direct current component in the buffer memory and recording them on a recording medium.

[0006]

The digitized data is stored in the buffer memory as it is, and the maximum value and the minimum value of the data stored in the buffer memory are stored by the maximum value detection circuit and the minimum value detection circuit. Based on this value, the maximum amount of change in the stored data and the DC component are obtained, and the bit number conversion circuit determines the number of bits for storing the variation and the number of bits for storing the DC component. Then, recording is performed on the recording medium according to the number of bits.

[0007]

[Embodiment] Not only audio signals but also video signals and the like have a strong correlation with signals before and after a certain time. If the direct current component and the changed component can be recorded separately by utilizing this property, information having a large data size can be recorded even on a recording medium having a small recording capacity. An example will be described with reference to FIG. It is assumed that there is a signal that changes with time and sampling is performed every time Ts until time Ta (Ta = Ts × 24).

8-bit strength resolution (256 levels)
When sampling up to Ta, the number of bits written to the recording medium is 8 × 24 = 192, and this numerical value is uniquely determined.

For example, the value of B is 240 and the value of A is 190.
When (= DC component), BA = 50 (maximum change amount), and if only the change amount is recorded, it can be expressed by 6 bits. DC, maximum change, T
The change data for each s are arranged as follows.

190, ← ---- DC component ... 8 bits 6, ← ---- Minimum number of bits including maximum change ... 3
Bits 31, 28, 26, 27, 35, 35, 24, 19, 17, 29, 34, 33, 20, 7, 7, 0, 21, 18, 21, 39, 50, 45, ... 6 each
Bits 38, 23, 28 ← ---- 24 pieces of change data

When the constituent bits are summed up, 8 bits corresponding to 190, 3 bits corresponding to 6 and 6 bits corresponding to 19 to 28 are summed up to 155, respectively.
The number of bits is smaller than that of the conventional 192 bits. This method is effective as the correlation between the front and rear of the signal is large, that is, the change is small.

FIG. 1 is a block diagram for realizing this processing. The analog signal input to the A / D conversion circuit 1 is converted into a digital signal and supplied to the buffer memory 2, the maximum value detection circuit 3, and the minimum value detection circuit 4. Data for a predetermined period, for example, the period Ta shown in FIG. 2, is recorded in the buffer memory 2, and the old data is sequentially output.

The maximum value detection circuit 3 stores the maximum value of the supplied signals, and the minimum value detection circuit 4 stores the minimum value of the supplied signals. For example, 221
(190 + 31), 218 (190 + 28), 216
(190 + 26), 217 (190 + 27), 225
If (190 + 35) data is sampled, first, 221 is written in the maximum value register. Then 22
1 (X) and 218 (Y) are compared, and if X is larger, the contents are rewritten, and if Y is larger, the register contents are rewritten.

Next, 221 (X) and 218 (Y) are compared, 221 (X) and 225 (Y) are compared, and then 225.
It becomes (X). The same is done so that the smallest minimum value remains. In this case, the stored value is held for Ta time, cleared after writing to the recording medium, and held for another value for the next Ta time. In order to do this in real time, two buffer memories 2 shown in FIG.

The output of the maximum value detection circuit 3 and the output of the minimum value detection circuit 4 are supplied to the subtraction circuit 7, and the difference is supplied to the bit number conversion circuit 8. The bit number conversion circuit 8 finds the number of bits required to express the data of the difference between the maximum value and the minimum value, and supplies it to the multiplexer 5.

The output of the buffer memory 2 is supplied to the multiplexer 5 with only the changed amount by subtracting the minimum value, that is, the direct current component in the subtraction circuit 9. The output of the minimum value detection circuit 4 is also supplied to the multiplexer 5. The DC component is defined as the minimum value within Ta time.

Next, an example of the effect of this method will be described. Now that you have an answering machine that uses IC memory,
The operating condition is A / D conversion bit number 12 bits, A / D
The D conversion speed is 20 KHz, the memory used is 1 Mbit DRAM (2000 yen), and the recording time is 5 minutes.

When the number of memories required to satisfy the above conditions is calculated by the conventional method (calculation is simply performed by the capacity without considering the calculation algorithm etc.), the time that can be recorded per memory is as follows. become. 1048576 bits / 12 bits / 20 KHz = 4.37 seconds

Therefore, the required number in 5 minutes is as follows. 300 seconds ÷ 4.37 seconds = 69 (138,000 yen) Depending on the person, a loud voice, a low voice, a person who speaks upright, a person who speaks at intervals, etc.
There are various types, and the amount of compression cannot be uniquely determined because the factors related to this method vary greatly.

When actually examined, the silent period in a normal conversation is about ⅕, the volume of voice is ½ on average, and it is compressed to ⅕ as a whole. Then, if you have the same amount of memory, you can record 2.5 times as much as 12.5 minutes. Also, if the recording time is 5 minutes, the memory capacity is 28, which is 2/5 (56,000 yen), which is less than half. Therefore, the required space is about half even if the buffer memory and the circuit for maximum value detection are included.

[0021]

As described above, according to the present invention, since the variation and the DC component are separated and recorded, even if the number of bits is small, it is possible to perform the compression recording without impairing the signal quality. It is possible.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a graph showing an input waveform

[Explanation of symbols]

 1 A / D conversion circuit 2 Buffer memory 3 Maximum value detection circuit 4 Minimum value detection circuit 5 Multiplexer 6 Recording medium 7, 9 Subtractor 8 bit number converter

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Claims (1)

[Claims] 1. An A / D converter for converting an analog signal into a digital signal, a buffer memory for storing a digital signal for each sampling timing over a predetermined time period, and a maximum value detection circuit for storing a maximum value within the predetermined time period. A minimum value detection circuit that stores the minimum value within the predetermined time, and a bit number conversion circuit that determines the number of bits required to store the variation and the DC component from the difference between the maximum value and the minimum value, A signal compression recording apparatus comprising a multiplexer for selecting a change component in a buffer memory and a direct current component according to the number of bits and recording it on a recording medium.