JP2687483B2 - Digital time code transmission system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A Field of Industrial Application The present invention relates to a digital time for digitally transmitting an analog time code signal known as so-called VITC which is address information for video signal editing and the like. A code transmission system, in particular, a digital interface format for time-division multiplex transmission of a digitally coded luminance signal and color difference signal of a television standard system video signal in a predetermined sequence alternately. At the specified scan line position during the vertical blanking period of the digital component video signal
The data word of the luminance signal forms a data string corresponding to the analog signal waveform of the time code with an odd number of samples per two consecutive bits of the time code, and the analog signal waveform of this time code is formed. The present invention relates to a digital time code transmission system for transmitting as a digital signal.

B. SUMMARY OF THE INVENTION The present invention is transmitted in a digital interface format for time division multiplex transmission of digitally coded luminance signals and color difference signals of a television standard video signal alternately in a predetermined sequence. At a predetermined scanning line position in the vertical blanking period of the digital component video signal, the data string corresponding to the analog signal waveform of the time code is formed at a predetermined scan line position in the vertical blanking period.
In a digital time code transmission system that forms an odd number of samples per bit and transmits the analog signal waveform of this time code as a digital signal,
When forming a level transition waveform of the analog signal of the time code by the data string such that a bit boundary of the analog signal waveform of the time code is located between two consecutive sample points of the data string,
The two data values that sandwich the bit boundary in the data string are smaller than the values corresponding to the high level of the time code analog signal waveform and are set to the low level of the time code analog signal waveform. If the level transition waveform is larger than the corresponding value and the level transition waveform changes with time from high level to low level, the value of the data of the preceding sample point of the above two sample points is the data of the sample point of the subsequent line. When the level transition waveform changes over time from a low level to a high level, the data value of the preceding sample point must be smaller than the data value of the following sample point. This ensures that the receiver can detect the timing edges of the digital time code and that the digit code is compatible with the time code of the analog video signal. Le Time code is obtained by allowing accurately reproduced.

C Conventional technology For example, in an analog VTR (video tape recorder) for broadcasting stations, a time code used as address information for tape editing is recorded on a cue track in the tape longitudinal direction.・
There are known a code (so-called LTC) and a time code (so-called VITC) which is recorded on a recording section in a vertical blanking period of a video track provided at an angle to the tape running direction.

On the other hand, in a digital VTR, recording such a time code signal in the longitudinal direction of the tape has been conventionally performed. The applicant of the present invention has previously proposed recording the time code signal on the inclined track in Japanese Patent Laid-Open No. 62-237876.
This prior application technology is based on the so-called 4: 2: 2 standard (or D-1).
The present invention relates to a recording method for recording a time code signal on an inclined track on a tape of a digital component VTR of the (standard). In the prior application, a plurality of inclined tracks are formed per field on a tape, and one inclined track has an audio track section in the middle of the head scanning direction and a video track section in the audio track section. The time code signal is recorded as a so-called ASTC (audio sector time code) at a plurality of portions of the audio track portion.

D Problem to be Solved by the Invention By the way, when converting a digital signal reproduced by a digital VTR as described above into an analog signal and using the same, compatibility with an analog video signal which has been conventionally used has to be ensured. It is preferable to keep the time code signal, and it is desirable that the time code signal also has a digital video signal format equivalent to the conventional analog VITC.

Here, as an interface format between a digital video signal recorded and reproduced by the digital VTR and an analog video signal, a digital component video signal interface format according to CCIR Recommendation 656 (or SMPTE RP-125). However, in the present situation, the format corresponding to VITC of an analog video signal is not defined in the format.

In view of such circumstances, the present applicant uses a time code such as VITC, which has been standardized as a time code of an analog video signal, in a digital component video signal interface such as the CCIR656 recommendation.・ As a digital time code transmission method that can be realized on the format, for time-division multiplex transmission of a digitally coded luminance signal and chrominance signal of a television standard video signal alternately in a predetermined sequence. At a predetermined scan line position in the vertical blanking period of the digital component video signal transmitted by the digital interface format, the data word of the luminance signal causes the time code as shown in A to H of FIG. Corresponding to various analog signal waveforms, for example, as shown in Table 1. Forming a digital data string of values, the digital time code transmission scheme, wherein transmitting the analog signal waveform of the time code as a digital signal proposed previously (Japanese Patent Application No. Sho
See 63-136826).

Numerical values of each data in Table 1 are hexadecimal numbers. For example, C0 is usually displayed as C0 _H and indicates the decimal number 192. However, H is omitted for the space of the table. Shows.

By the way, in the digital time code transmission system as previously proposed by the present applicant, a data string corresponding to the analog signal waveform of the time code is sampled at an odd number of samples per two consecutive bits of the time code. Since it is formed by a number, the level transition waveform of the analog signal of the time code is set so that the bit boundary of the analog signal waveform of the time code is located between the sample points of two consecutive data of the data string. When forming the data string, the data string is formed by an odd number of samples for every two consecutive bits of the two pieces of data sandwiching the bit boundary, and the analog signal waveform of this time code is transmitted as a digital signal. In the digital time code transmission system, two consecutive data strings are used.
An object of the present invention is to enable the receiving side to accurately detect the timing of the bit boundary portion even when the bit boundary of the analog signal waveform of the time code is located between two data sample points. .

E Means for Solving the Problems In order to solve the above problems, the present invention alternately sets a digitally coded luminance signal and color difference signal of a television standard video signal in a predetermined sequence. An analog signal waveform of a time code by a data word of the luminance signal at a predetermined scan line position of a vertical blanking period of a digital component video signal transmitted by a digital interface format for time division multiplexing transmission. In the digital time code transmission system in which a data string corresponding to is formed by an odd number of samples per two consecutive bits of the time code, and the analog signal waveform of this time code is transmitted as a digital signal. Above between two consecutive sample points of data In forming the level transition waveform of the analog signal of the time code such that the bit boundary of the analog signal waveform of the time code is located by the data string, two data of the two data sandwiching the bit boundary in the data string are formed. The value is smaller than the value corresponding to the high level of the time code analog signal waveform, larger than the value corresponding to the low level of the time code analog signal waveform, and the level transition waveform is high. When changing from level to low level over time,
The data value of the preceding sample point of the above two sample points is larger than the data value of the following sample point,
When the level transition waveform changes with time from a low level to a high level, the value of the data of the preceding sample point is set to be smaller than the value of the data of the subsequent sample point.

In the digital time code transmission system according to the present invention, the data corresponding to the analog signal waveform of the time code is obtained by the luminance signal data word at the predetermined scanning line position in the vertical blanking period of the digital component video signal. Since the columns are formed, if this digital luminance signal is converted to an analog signal by D / A conversion, an analog time code such as VITC can be obtained as it is, and moreover, two consecutive data samples of the above data column can be obtained. Even when the bit boundary of the analog signal waveform of the time code is located between the points, the continuity of the analog waveform of the bit boundary portion is ensured and the timing of the bit boundary portion is accurately detected on the receiving side. can do.

G. Embodiment FIG. 1 is a schematic diagram for explaining an embodiment of a digital time code transmission system according to the present invention. VITC (vertical blanking period) of an analog video signal shown in FIG. 1A. Time code analog signal waveform (first
FIG. B) is represented by the data words of the luminance signal (Y) of the digital component video signal in the format as shown in FIG. 1C.

The format shown in FIG. 1C is, for example, as shown in FIG. 2, a luminance signal (Y) corresponding to a television standard analog video signal (FIG. 2A) and two color difference signals (C _B ≡B−Y, C _R ≡R−Y) are digitally coded at a sampling frequency of 13.5 MHz for the luminance signal and 6.75 MHz for each color difference signal to obtain Y as shown in FIG. 2B. It is a digital interface format in which C is a predetermined alternating sequence, that is, C _B , Y, C _R , Y, ... During this 1440T (T is 1 sample period of all video data) digital active line period in which the time division multiplexed video data is arranged, the analog video signal VITC
To form a data string corresponding to the analog signal waveform. The data string corresponding to this VITC is the original analog VITC.
In the same manner as above, they are arranged at the predetermined scanning line positions of the vertical blanking period of the video signal, that is, at 12th and 14th scanning lines.

Here, in this embodiment, the interface format of CCIR No. 656 recommendation (or SMPTE RP-125) for parallel transmission of 1 word 8 bits of a digital video signal is assumed, 1350T out of 1440T of the above digital active line is analog
It is used to form a VITC 90-bit signal waveform. That is, one bit of VITC corresponds to 15 words (15T) of the data words of the digital video signal as shown in FIG. 1C, and the data words of the luminance signal (Y) in these 15 words are used. , And a data string corresponding to the analog signal waveform of VITC. The 15 words may include 8 words or 7 words of the luminance signal word, and each of the 9 synchronization bits in the VITC may start with the data word of the luminance signal (Y). It is arranged in. Specifically, considering that the start timing of the analog VITC signal is specified to be at least 10.0 μs from the rise of the horizontal synchronization, as shown in FIG. 271T (= 10.04μ) from digital signal to digital time code
s), and the digital time code starts from the 28th luminance word (Y) in the active word after SAV (start of active video). The figures in Fig. 2 are all NTSC (52
The time in the case of the 5/60) method is shown in units of the sampling period T (≒ 37 ns), but for reference, PAL, SECAM (625/5
0) The time in the case of the method is shown in parentheses.

Next, a specific example of word data of the luminance signal (Y) for forming the analog VITC signal waveform will be described. In the example of FIG. 1C, when 8 words of the luminance signal (Y) are included in 15 words of the digital video signal corresponding to 1 bit of the analog VITC signal waveform, the data of these words are sequentially D ₁ , and _{D 2, D 3, D 4} , D 5, D 6, D 7, D 8, for the even blocks the luminance signal in the 15 word (Y) enters 7 words in the data D ₁ to D ₈ data D ₁ of the remaining 7 words disconnect the data _{D 4, D 2, D 3} , D 4, D 5, D 6, D 7, D
₈ shall be assigned sequentially.

Here, considering the continuity of the analog signal waveform, the waveform formed by the data string is optimized not only by the value of the relevant bit being “1” or “0” but also by the values of the bits before and after it. For this reason, as shown in FIGS. 3 and 4, the time code of the analog signal waveform is located between the sampling points of two consecutive data of the data string. When forming the level transition waveform of the analog signal by the data string, two data D ₈ and D ₁ that sandwich the bit boundary in the data string.
Is smaller than the value corresponding to the high level of the time code analog signal waveform, larger than the value corresponding to the low level of the time code analog signal waveform, and the level transition waveform is When the level changes from a high level to a low level over time, the value of the data D ₈ at the preceding sample point of the above two sample points is the data at the sample point of the subsequent line, as indicated by the ● in FIG. larger in than the value D _1, if the level transition waveform changes with time from a low level to a high level, as indicated by ◎ in Figure 3, the value of the data of the sample points above prior after the Defined as less than the value of the data at the sample point on the line.

FIGS. 4A to 4H show respective data and analog signal waveforms of odd-numbered blocks and even-numbered blocks in consideration of preceding and succeeding bits. For example, FIG. 4A shows the analog signal waveform of the bit “1” “0” at the center of the analog signal waveform changing from “0” to “1” through “0” to “1”. ,
This bit is expressed as (0) 10 (1) including the bits before and after. Similarly, FIG. 4B shows (1) 01 (0), that is, the signal waveform of the central bit “0” “1” when changing from “1” → “0” → “1” → “0”. 4C shows (0) 11.
(0), Fig. 4D shows (1) 00 (1), and Fig. 4E shows (1).
10 (0), FIG. 4F shows (0) 01 (1), FIG. 4G shows (1) 11 (1), and FIG. 4H shows (0) 00 (0). There is. Table 2 shows an example of specific numerical values representing the signal waveform of each bit by the above-mentioned 8-word (or 7-word) digital data string.

Numerical values of each data in Table 2 are all hexadecimal numbers. For example, C0 is usually displayed as C0 _H and indicates the decimal number 192. Shows. In this case the digital luminance signal, by representing each black level of the analog luminance signal _{(01RE) 16 (10 H)} , the white peak level _{(100IRE) 235 (EB H)} , the 192 (C0 _H ) Will correspond to the level of 801RE. This also takes into account the correspondence with analog VITC. The color difference signal word in the digital active line to which this time code is arranged may be set to 80 _H corresponding to the intermediate 0 level of the analog color difference signal.

Next, as an application example of such a digital time code transmission method, the above-mentioned 4: 2: 2 standard (or D-
ASTC (audio system) provided in the digital audio signal of the digital component VTR
An example in which the sector time code) is applied to the interface when it is taken out will be described with reference to FIG.

In FIG. 5, a component video signal, that is, a luminance signal (Y) and two color difference signals (C _B ≡B-Y, C _R ≡R-Y) are input in parallel to the input terminal 1. By the interface circuit (decoder) 2 of the so-called RP-125 described above, the luminance signal and the color difference signal are alternately converted into a format in which they are time-division multiplexed in a predetermined sequence in bit parallel as described above.
The digital video signal of 8 bits per word is sent to a recording head 6 via a video processing circuit 3, an adder 4, and a recording processing circuit 5, and is recorded on a magnetic tape 7. Here, the output from the decoder 2 is an 8-bit parallel digital video signal, but the video processing circuit 3, adder 4, and recording processing circuit 5 are 4-channel digital video signals.

A time code signal within the vertical blanking period of the digital video signal output from the decoder 2, so-called D-
The VITC signal is read by the D-VITC reader 11 and the selector
Sent to 12. The D-VITC signal includes a signal obtained by A / D converting the VITC in the original analog video signal as it is and a signal of the digital time code format of the above-described embodiment. This D-VITC
With the time code data read by the reader 11,
One of the external time code data from the terminal 13 is selected by the selector 12 and sent to the audio processing circuit 15 via the ASTC encoder 14. The digital audio signal from the terminal 16 is supplied to the audio processing circuit 15, and signal processing such as time code insertion into the user data area in the digital audio format is performed, and the adder is added. Sent to 4. Here, as described above, a plurality of inclined tracks are formed for one field on the magnetic tape 7, and one inclined track has an audio track portion in the middle of the head scanning direction and a video track portion. Are provided before and after this audio track portion, respectively. Therefore, the ASTC (audio sector time code) is recorded at a plurality of parts of the audio track portion.

Next, the digital video and audio signals reproduced by the reproducing head 21 from the magnetic tape 7 are divided into a video signal and an audio signal via a reproduction processing circuit 22, and the video signal is divided into a frame memory 23, an interpolation circuit 24 and the like. Is sent to the selector 25 via The audio signal is sent to an audio processing system and an ASTC decoder 27 via an audio memory 26, and is decoded by the ASTC decoder 27.
TC (audio sector time code) signal is D-
It is sent to the VITC encoder 28. This D-VITC encoder 28
Is the time code data from the ASTC decoder 27,
It is converted into a digital time code signal according to the format of the above-described embodiment of the present invention and sent to the selector 25.
In the selector 25, the predetermined line positions (12th and 14th) of the vertical blanking period of the digital video signal from the interpolation circuit 24 are replaced with the digital time code signal from the D-VITC encoder 28 as required. However, it is taken out from the output terminal 30 via the interface circuit (encoder) 29 of the so-called RP-125. Note that the frame number shift caused by the time delay associated with the signal processing in each circuit, that is, the shift in the correspondence between the time code data from the D-VITC encoder 28 and the actual frame of the playback output video signal is It is compensated by adding and subtracting the number of frames of time code data.

In the concrete example shown in FIG. 5, when the magnetic tape 7 is reproduced while being fed at high speed, the VI from the video signal is changed.
It is difficult to read TC (for example, so-called dynamic
ASTC from the audio signal can be used as VITC in the final reproduced video signal from the terminal 30 even if a tracking head is required). Also, VI
Since the TC is transmitted together with the video signal, the interface is simplified, and the delay in the unit of a frame generated by an intermediate device is the same as that of the video signal, so that the handling is easy.

The present invention is not limited to the above-described embodiment. In the above-described embodiment, the bit parallel interface format for transmitting 8 bits per word in parallel has been described. However, CCIR No. 656 recommendation (or SMP
It is also possible to easily apply the present invention to the serial transmission format in TE's RP-125). In addition, it goes without saying that various changes can be made without departing from the spirit of the present invention.

H According to the digital time code transmission system according to the present invention, the analog signal waveform of the time code is generated by the luminance signal data word at the predetermined scanning line position in the vertical blanking period of the digital component video signal. Since the data string corresponding to is formed, it is possible to perform digital time code transmission with high compatibility with VITC of analog signals. Therefore, a time code equivalent to VITC can be handled between digital devices, and this time code can be used.
Since the code is transmitted together with the video signal, the interface is easy and there is no adverse effect due to delay or the like. Moreover, in the digital time code transmission method according to the present invention, even when the bit boundary of the analog signal waveform of the time code is located between the sample points of two consecutive data of the data string, the bit boundary is Since the continuity of the analog waveform of the portion is ensured, the timing of the bit boundary portion can be accurately detected on the receiving side.

[Brief description of the drawings]

FIG. 1 is a diagram showing a transmission format of an embodiment of a digital time code transmission system according to the present invention, FIG. 2 is a timing chart for explaining the embodiment, and FIG.
FIG. 4 and FIG. 4 are waveform diagrams showing an example of 2 bits of the analog signal waveform of the time code, FIG. 5 is a block diagram showing an example in which the above embodiment is applied to a digital VTR, and FIG. 3 is a waveform diagram showing an example of one bit of a time code analog signal waveform in the digital time code transmission system proposed in FIG.

Claims (1)

(57) [Claims] 1. A digital interface format for time-division multiplex transmission of a digitally coded luminance signal and chrominance signal of a television standard video signal alternately in a predetermined sequence. At a predetermined scan line position in the vertical blanking period of the component video signal, a data string corresponding to the analog signal waveform of the time code is formed by the data word of the luminance signal, and the data string is continuous with the time code.
In a digital time code transmission system in which an analog signal waveform of this time code is transmitted as a digital signal by forming an odd number of samples per bit, the above-mentioned time is provided between two consecutive sample points of the above data string. When forming the level transition waveform of the analog signal of the time code such that the bit boundary of the analog signal waveform of the code is located by the data string, two data values sandwiching the bit boundary in the data string Is smaller than the value corresponding to the high level of the time code analog signal waveform, larger than the value corresponding to the low level of the time code analog signal waveform, and the level transition waveform is high level. To the low level over time, the data of the preceding sample point of the above two sample points is deselected. The data value of the preceding sample point is larger than the value of the data of the subsequent sample point, and when the level transition waveform changes from low level to high level with time, the data value of the preceding sample point is A digital time code transmission method characterized in that it is defined to be smaller than the value of point data.