JPH0787527A - Encoding device - Google Patents

Abstract

PURPOSE:To faithfully reproduce each input signals multiplexd with respect to time base by sampling plural continuously inputted analog signals in order at intervals of a prescribed time in accordance with rate of their required frequency bands and digitizing and encoding them. CONSTITUTION:A brightness signal Y is inputted from an input terminal 1 to an LPF 4, and a color difference signal CB is inputted from an input terminal 2 to an LPF 5, and a color difference signal CR is inputted from an input terminal 3 to an LPF 6. Signals which pass LPFs 4 to 6 are successively inputted to an A/D converter 11 through a switch 10, and encoded digital data is outputted from an output terminal 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coding device for time-domain multiplex coding of an analog signal such as an input video signal.

[0002]

2. Description of the Related Art PCM is one of the methods for converting analog signals such as audio signals and video signals into digital signals.
There is a technique called (Pulse Code Modulation). According to such a PCM technique, an input analog signal is input based on a sampling theorem (theorem that the original signal can be completely restored by sampling at a sampling frequency that is at least twice the highest frequency of the input signal). After passing through an LPF (a low-pass filter, which is provided to prevent the occurrence of aliasing distortion when converting an analog signal into a digital signal), sampling is performed at a sampling frequency that is at least twice the highest frequency of the signal, Further, it is quantized into a pulse train having discrete amplitude levels. Subsequently, this is code-converted into digital information represented by 1s and 0s. In this case, in order to improve the S / N ratio and match the characteristics of the magnetic recording system, A / D conversion is performed. Binary encoding is performed in the device. afterwards,
The digital data converted into the binary code is recorded and stored in a storage / recording medium (magnetic tape, CD, semiconductor memory, etc.). On the contrary, in order to return the recorded digital data to the original analog signal, the digital data is read from the storage / recording medium, D / A converted (digital / analog converted), and a pulse train having a discrete amplitude level is obtained. Then, the original analog signal is reproduced by passing the LPF again.

By the way, in a digital VTR device, a video signal is digitally recorded. In this case, in order to avoid aliasing distortion caused by sampling, the sampling frequency is usually 2.5 times the maximum frequency of the video signal. Sampling is performed with the above settings, and the A / D converter quantizes it with 8 bits to convert it into a digital code. in this case,
Since the video signal is a signal in which the luminance signal Y, the two types of color difference signals C _B and C _R , and other synchronization signals are frequency division multiplexed, each of these signals is used for encoding. After separating the components, each signal (Y, C _B C _R )
Is encoded. Therefore, normally, as many A / D converters as there are signals to be encoded are prepared.

On the other hand, when performing A / D conversion on a plurality of analog signals of two or more signals, when the maximum sampling frequency is four times or more the Nyquist frequency of the signal (half the sampling frequency), , It depends on how the frequency band of the required signal is selected (that is, when it is used in a frequency band lower than the Nyquist frequency. In such a case, the sampling frequency can be lowered by using the LPF. , It is possible to reduce the number of A / D converters used by using the technique of time-axis multiplex coding. It should be noted that such time-axis multiplex encoding technology uses information such as the PinP function (abbreviation of picture-in-picture, which is a function of displaying two screens on the same display screen) in a TV or VTR. This is a technique that has been widely used in the case of thinning out A.
Since the number of D converters can be reduced, the circuit cost can be significantly reduced.

FIG. 5 is a block diagram showing a configuration example of a conventional time-axis multiplex encoding apparatus for encoding a video signal.
In this device, the luminance signal Y is input from the signal input terminal 15 to the LPF 18, the color difference signal C _B is input from the signal input terminal 16 to the LPF 19, and the color difference signal C _R is input from the signal input terminal 17 to the LPF 20. Where LP
F18 to F20 are provided to prevent aliasing distortion that occurs when an analog signal that is continuously input is converted into a digital signal. That is, when an analog signal is converted into a digital signal, if there is an input signal with a frequency higher than the Nyquist frequency, the phenomenon of aliasing occurs and it becomes impossible to convert it into an accurate digital signal. In order to prevent this, a low-pass filter that passes only a frequency lower than the Nyquist frequency in the input signal is provided in the preceding stage of A / D conversion.

In practice, it is difficult to manufacture a filter having steep characteristics such that a signal passes or does not pass completely at a certain frequency. Therefore, the sampling frequency is set to be more than twice the input signal band. The LPFs 18 to 20 are all set to 400 nsec for the sake of easy understanding of the description.

Next, each signal that has passed through the LPFs 18 to 20 is sent to the respective signal output terminals 21 to 23 by the switch 24 (specifically, a multiplexer is used).
When it is connected to the A / D converter 25, it is input to the A / D converter 25. Here, the switch 24 has the signal output terminals 21 → 22 → 21 → 23 →
The connection with the A / D converter 25 is switched in the order of 21 → 22 →. As a result, the three signals of the luminance signal Y and the color difference signals C _B and C _R are multiplexed on the time axis and input to the A / D converter 25. Therefore, the A / D converter 25 sequentially performs binary encoding on the input multiplexed signal, and digital data is output from the data output terminal 26.

FIG. 6 is a waveform diagram of an input signal shown for explaining the encoding process of the video signal performed by the conventional time axis multiplex encoding device shown in FIG. (A) is a waveform diagram of an input video signal. The horizontal direction of this figure shows the passage of time, and the sampling time of each of the luminance signal Y, the color difference signal C _B , and the color difference signal C _R , which are the input signals, is →→
→ ············· Regarding the reference sampling time interval, the maximum sampling frequency of the A / D converter 25 is set to 10 MHz, and 100 nsec (1/10 MHz).
= 100 nsec).

The vertical direction in this figure shows the position of each signal input at the same time. The required frequency bands of luminance signal Y / color difference signal C _B / color difference signal C _R are 2.5 MHz / 1.25 MHz / 1.25 M, respectively.
Hz, and sampling of each signal is 2: 1:
It is supposed to be done at a ratio of 1. Further, in the figure, “● and ▲” indicate sampling points for the luminance signal Y (on the time axis, ...), and “■” indicate sampling points for the color difference signal C _B ( , Are shown on the time axis, and the sampling points (..., on the time axis) for the color difference signal C _R are shown by “x”.

FIG. 3B is a diagram showing a state in which the video signal time-multiplexed by the switch 24 is encoded by the A / D converter 25 and output as digital data. That is, the three signals of the luminance signal Y, the color difference signal C _B , and the color difference signal C _R are multiplexed on the time axis by the switch 24 and input to the A / D converter 25. Then, from the A / D converter 25, by repeating the sampling points “● → ■ → ▲ → ×” for each signal,
Digitally converted data is displayed at 100nsec intervals.
It is sequentially output from the data output terminal 26. In the figure,
“○, □, Δ, thinly displayed“ × ”” are signals discarded by the A / D converter 25 at the same sampling time for each of the luminance signal Y, the color difference signal C _B , and the color difference signal C _R. Shows the position of.

FIG. 3C is a waveform diagram in which the video signal encoded by the A / D converter 25 is reproduced by the D / A converter (not shown). In the figure, the alternate long and short dash line
The input waveforms of the color difference signal C _B and the color difference signal C _R shown in (A) are shown. Here, in the D / A converter, the sampling point “●” for the luminance signal Y
When reproducing the data of the color difference signal C _B and the color difference signal C _R input at the same time as the signal input in, the sampling points “■” and “X” are sampled at sampling time intervals with respect to the sampling point “●”, respectively. However, the data at the sampling points "■" and "×" are clearly different because of the difference. Therefore, in order to reproduce a signal input at the same time, there is no other way but to guess the corresponding data by calculation processing. Therefore, specifically, as shown in the drawing, for each of the color difference signal C _B and the color difference signal C _R , data at two adjacent sampling points is linearly interpolated to obtain the luminance signal Y. Approximate data is obtained for each of the color difference signals C _B and C _R input at the same time as the input time. However, the data thus obtained has a clear error from the actual signal level.

[0012]

As described above, when the conventional time-axis multiplex coding technique is used, the problem that the sampling data of each multiplexed input signal is non-simultaneous remains. Will end up. That is, it is impossible to sample each signal multiplexed on the time axis at the same time, and a time difference is always generated between each sampling signal. As a result, when reproducing the encoded signal, a calculation error may occur in the digital signal processing, and the input analog signal may not be faithfully reproduced.

The present invention has been made in view of the above circumstances, solves the problem of non-simultaneousness with respect to sampling data of each time-division multiplexed input signal, and ensures faithful reproduction of the input signal. It is an object of the present invention to provide an encoding device that enables the above.

[0014]

In order to achieve the above object, the present invention according to claim 1 provides a plurality of continuously input analog signals on a time axis in a required frequency band of each signal. Is a coding device that sequentially samples at predetermined time intervals according to the ratio of, and digitally converts each sampled signal to perform coding, wherein one of the analog signals is a reference signal for sampling. As
A signal delay means for delaying the input time of the other signal by the sampling time interval of the reference signal and the other signal is provided, and the plurality of analog signals input at the same time are sampled for the sampling time of each signal. It is characterized in that it is configured to be encoded in.

According to a second aspect of the present invention, the signal delay means is provided for each signal of the plurality of analog signals that are continuously input and has a predetermined delay time. It is characterized by being configured as. In the invention according to claim 3, the signal delay means is added to a band limiting low-pass filter provided for signals other than the reference signal.
It is characterized by being configured as a delay element having a predetermined delay time.

Further, in the invention according to claim 4, when the plurality of analog signals continuously input are already band-limited, the signal delay means outputs signals other than the reference signal. It is characterized in that it is configured as a delay element provided corresponding to the above and having a predetermined delay time.

[0017]

According to the above configuration, the plurality of analog signals continuously input by the encoding device are
The signals are sequentially sampled at a predetermined time interval according to the ratio of the required frequency band of each signal, and each sampled signal is digitally converted and encoded.

Further, according to the configuration of the invention according to the first aspect of the present invention, one signal of the plurality of analog signals continuously input is used as the reference signal for sampling, and the reference is provided by the signal delay means. The input time of the other signal is delayed by the sampling time interval between the signal and the other signal. As a result, a plurality of analog signals input at the same time are encoded at the sampling time for each signal.

Further, according to the configuration of the invention according to claim 2, the signal delay means has a predetermined delay time provided for each of the plurality of analog signals that are continuously input. It is configured as a bandpass low pass filter. Further, according to the configuration of the invention according to claim 3, the signal delay means adds a predetermined delay time to a band-limiting low-pass filter provided for signals other than the reference signal. Is configured as a delay element having

Further, according to the configuration of the present invention according to claim 4, the signal delay means is provided with a signal other than the reference signal when the plurality of analog signals continuously input are already band-limited. Provided for other signals in
It is configured as a delay element having a predetermined delay time. Therefore, according to the present encoding device, it is possible to cover the time lag due to sampling of another signal with respect to the reference signal by delaying the input time by a predetermined time.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be specifically described below with reference to the drawings. 1 is a block diagram showing the configuration of a first embodiment of an encoding apparatus according to the present invention. In this device, the luminance signal Y is input from the signal input terminal 1 to the LPF 4, the color difference signal C _B is input from the signal input terminal 2 to the LPF 5, and the color difference signal C _R is input from the signal input terminal 3 to the LPF 6. Next, the signals that have passed through the LPFs 4 to 6 are
When the signal output terminals 7 to 9 are connected to the A / D converter 11 by the switch 10 (specifically, a multiplexer is used), the A / D converter 1
Input to 1. Here, the switch 10 outputs signal output terminals 7 → 8 → 7 → 9 → 7 → 8 → ... at predetermined time intervals.
・ Each connection is switched in the order of. As a result, the three signals of the luminance signal Y and the color difference signals C _B and C _R are multiplexed on the time axis and input to the A / D converter 11. Therefore, the A / D converter 11 sequentially encodes the input multiplexed signal, and the encoded digital data is output from the data output terminal 12.

The above block structure is substantially the same as the structure shown in FIG. 5, but the delay time characteristic of the low-pass filter used in the present encoding apparatus is LPF4.
Is 400 nsec, LPF5 is 00 nsec,
The difference is that the LPF 6 is set to 700 nsec (the reason will be described later). 2 is shown in FIG.
FIG. 6 is a waveform diagram of an input signal shown for explaining a process of encoding a video signal performed by the encoding device shown in FIG. (A)
[Fig. 4] is a waveform diagram of an input video signal. Similar to FIG. 6, the horizontal direction of this figure shows the passage of time, and the sampling time of each signal of the luminance signal Y, the color difference signal C _B , and the color difference signal C _R , which are the input signals, is →→→ It is assumed that the time passes in the right direction in the order of. Regarding the reference sampling time interval, the maximum sampling frequency of the A / D converter 25 is set to 10 MHz, and 1
It is set to 00 nsec (1/10 MHz = 100 nsec). Further, the vertical direction of this figure shows the position of each signal input at the same time, and regarding each required frequency band of the luminance signal Y / color difference signal C _B / color difference signal C _R , respectively. 5 MHz / 1.25 MHz / 1.25 MHz, and sampling of each signal is performed at a ratio of 2: 1: 1.

Further, in the figure, the sampling points for the luminance signal Y are represented by "● and ▲" (on the time axis,
,,, ...) are shown. Further, “” shown in the waveform diagrams of the color difference signal C _B and the color difference signal C _R respectively indicate sampling points for the signals delayed by passing through the LPF 5 and the LPF 6.

Here, the luminance signal Y is used as the reference of the sampling time, and the sampling time difference between the luminance signal Y and the color difference signal C _B is 100 nsec. This is L
The delay time characteristic of PF4 is 400 nsec,
Since that of LPF5 is 500 nsec, it is a result that is naturally derived as the difference. The delay time of the color difference signal C _{B in} the LPF 5 is 400 + 100 =
It is 500 nsec. The sampling time difference between the luminance signal Y and the color difference signal C _R is 300 nsec. This is because the delay time characteristic of the LPF 4 is 400 nsec and that of the LPF 6 is 700 nse.
Since it is c, the result is naturally derived as the difference. The delay time of the color difference signal C _{R in} the LPF 6 is 400 + 300 = 700 nsec.

The solid lines this way, in the figure, the actual waveform of each signal of the color difference signals C _B and a color difference signal C _R indicating the one-dot chain line, connecting each sampling point of the color difference signals C _B and a color difference signal C _R Will move to the waveform indicated by.
(B) is a diagram showing a state in which the video signal time-axis multiplexed by the switch 10 is encoded by the A / D converter 10 and is output as digital data. That is, the three signals of the luminance signal Y, the color difference signal C _B , and the color difference signal C _R are multiplexed on the time axis by the switch 10 and input to the A / D converter 11. Then, from the A / D converter 11, the digitally converted data is sequentially output from the data output terminal 12 at 100 nsec intervals by repeating the sampling points “● → ● → ▲ → ●” for each signal. . In the figure, "○, □,
Δ, thinly displayed “x” indicates the position of the signal that is discarded by the A / D converter 10 at the same sampling time for each of the luminance signal Y, the color difference signal C _B , and the color difference signal C _R. .

(C) is coded by the A / D converter 10.
The converted video signal to a D / A converter (not shown)
Therefore, it is a waveform diagram reproduced. As shown in the figure,
Issue C _BAbout LPF5 compared to the luminance signal Y
Since it is delayed by 100 nsec, when sampling
The luminance signal Y is covered by the difference of 100 nsec between the intervals.
At the same time (at the time indicated by ,, ... in the figure)
Is played. Similarly, the color difference signal C_RAbout the luminance signal
Compared to No. Y, it is delayed by LPF6 by 300 nsec.
Therefore, the sampling time interval difference is 300 nse.
c at the same time as the luminance signal Y (also,
(Time indicated by middle, ...,). This
Simultaneous sampling data for each signal, such as
And the input signal waveform shown in Fig. 6 (A) is faithful.
Is reproduced.

FIG. 3 shows a second encoding device according to the present invention.
3 is a block diagram showing the configuration of the embodiment of FIG. This encoding device uses a delay time (40 in this case) of an LPF used for each signal of a luminance signal Y, a color difference signal C _B , and a color difference signal C _R.
0 nsec), but the color difference signal C _B is passed through the delay element DL13 (having a delay time of 100 nsec here) provided in the preceding stage of the LPF, and the color difference signal C _R is also Similarly LPF
Of the delay element DL14 (300 ns here)
ec) (with a delay time of ec). By adopting such a configuration, it becomes possible to maintain the same time property of the sampling data when the time axis multiplexed signal is encoded, as in the encoding device shown in FIG.

FIG. 4 shows a third encoding device according to the present invention.
3 is a block diagram showing the configuration of the embodiment of FIG. In this encoding device, the LPF is not used, the luminance signal Y is input to the switch unit as it is, and the color difference signal C _B is passed through the delay element DL13 (here, the delay time is 100 nsec). Further, regarding the color difference signal C _R , the delay element DL14 (here, 3
(With a delay time of 00 nsec). And by taking such a configuration,
Similarly, similar to the encoding device shown in FIG. 1, it is possible to maintain the same time property of the sampling data when encoding the time-axis multiplexed signal.

[0029]

As described above, according to the present invention, it is possible to easily solve the problem of non-simultaneity with respect to the sampling data of each multiplexed input signal in the conventional time-axis multiplex coding apparatus. That is, by delaying each signal by the difference of the sampling time interval, it is possible to secure the same time property of the sampling data, and an arithmetic error will not occur during digital signal processing.
As a result, during reproduction, it is possible to faithfully reproduce a plurality of analog signals such as video signals and audio signals that are continuously input.

Further, according to the present invention, since the sampling signals of the respective signals can be handled as those arranged in a grid pattern, there is a side effect that the encoding process can be easily performed.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a first embodiment of an encoding device according to the present invention.

FIG. 2 is a time chart of each input signal shown for explaining a coding process performed by the coding apparatus shown in FIG.

FIG. 3 is a block diagram showing a configuration of a second embodiment of an encoding device according to the present invention.

FIG. 4 is a block diagram showing a configuration of a third embodiment of an encoding device according to the present invention.

FIG. 5 is a block diagram showing a configuration example of a conventional time-axis multiplex encoding device that encodes a video signal.

FIG. 6 is a waveform diagram of each input signal shown for explaining a process of encoding a video signal performed by the conventional time-axis multiplex encoding device shown in FIG.

[Explanation of symbols]

10 switch 11 A / D converter Y luminance signal Y C _B color difference signal C _R color difference signal LPF low-pass filter DL delay element

Claims (4)

[Claims] 1. A plurality of continuously input analog signals are sequentially sampled at predetermined time intervals according to the ratio of the required frequency band of each signal on the time axis, and each sampled signal is digitally sampled. An encoding device for converting and encoding, wherein one signal of the analog signals is used as a reference signal for sampling, and a sampling time interval between the reference signal and another signal An encoding device comprising signal delay means for delaying a signal input time, wherein the plurality of analog signals input at the same time are encoded at a sampling time for each signal. 2. The signal delay means is configured as a band limiting low-pass filter having a predetermined delay time, which is provided for each of the plurality of analog signals continuously input. The encoding device according to claim 1. 3. The signal delay means is configured as a delay element having a predetermined delay time, which is added to a band limiting low-pass filter provided for signals other than the reference signal. The encoding device according to claim 1. 4. The signal delay means is a predetermined delay provided for signals other than the reference signal when the plurality of analog signals continuously input are already band-limited. Coding device according to claim 1, characterized in that it is configured as a delay element with time.