JP2629836B2 - Digital time code transmission system - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital time code transmission system, and in particular, to a digital time code for digitally transmitting an analog time code signal known as a so-called VITC. -Regarding the code transmission system.

[Summary of the Invention]

The present invention relates to a digital time code transmission system for transmitting, as a digital signal, an analog signal waveform of a time code serving as address information for editing a video signal and the like, wherein luminance data and color difference data of a digital component video signal are transmitted. The analog video signal is formed by forming a data sequence corresponding to an analog signal waveform of a time code by luminance data at a predetermined scanning line position in a vertical blanking period of a format in which time-division multiplex transmission is performed alternately in a predetermined sequence. This realizes a digital time code that is compatible with the conventional time code.

[Conventional technology]

For example, in an analog VTR (video tape recorder) for a broadcasting station, a time code used for recording on a cue track in the longitudinal direction of a tape is used as a time code used as address information for tape editing.
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 recording of a time code signal on an inclined track has been proposed by the present applicant in Japanese Patent Application 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.

[Problems to be solved by the invention]

By the way, when a digital signal reproduced by a digital VTR as described above is converted to an analog signal and used, it is preferable to maintain compatibility with a conventionally used analog video signal. It is also desired that the signal be in a digital video signal format equivalent to the conventional analog VITC.

Here, as an interface format between the digital video signal and the analog video signal recorded and reproduced by the digital VTR, a digital component video signal interface format according to CCIR recommendation 656 (or SMPTE RP-125) However, at present, the format does not specify what corresponds to VITC of analog video signals.

The present invention has been made in view of such circumstances, and uses a time code such as VITC which has been conventionally standardized as a time code of an analog video signal.
An object of the present invention is to provide a digital time code transmission system that can be realized on a digital component video signal interface format such as the CCIR656 recommendation.

[Means for solving the problem]

In order to solve the problems described above, the digital time code transmission system according to the present invention uses a predetermined sequence of digitally encoded luminance signals and color difference signals of a television standard video signal. Digital interface for time division multiplex transmission
A data string corresponding to an analog signal waveform of a time code is formed by a data word of the luminance signal at a predetermined scanning line position in a vertical blanking period of a digital component video signal transmitted by the format. -It is characterized in that the analog signal waveform of the code is transmitted as a digital signal.

(Operation)

Since the data string corresponding to the analog signal waveform of the time code is formed by the luminance signal data word at a predetermined scanning line position during the vertical blanking period of the digital component video signal, this digital luminance signal is When converted to an analog signal by A conversion, an analog time code such as VITC can be obtained as it is.

〔Example〕

FIG. 1 is a schematic diagram for explaining an embodiment of a digital time code transmission system according to the present invention. FIG. 1A shows a VITC (vertical blanking period time code) of an analog video signal shown in FIG. 1A. ) 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 first format shown in FIG. C, for example as shown in FIG. 2, the television standard method of the analog video signal luminance signal corresponding to the (Figure 2 A) (Y) 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, and Y and C as shown in FIG. Is a digital interface format in which time division multiplex transmission is performed in an alternate predetermined sequence, that is, in the order of C _B , Y, C _R , Y,. A data sequence corresponding to an analog signal waveform representing VITC of an analog video signal within a digital active line period of 1440T (T is one sample period of all video data) in which the time-division multiplexed video data is arranged. To form
The data sequence corresponding to this VITC is arranged at predetermined scanning line positions in the vertical blanking period of the video signal, that is, at the 12th and 14th hours, similarly to the original analog VITC.

Here, in this embodiment, eight bits of one word of the digital video signal are transmitted in parallel.
It assumes the interface format of CCIR Recommendation 656 (or SMPTE RP-125), and converts 1350T of 1440T of the above digital active line to 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 converted to D _1. , D ₂ , D ₃ , D ₅ , D ₆ , D ₇ , D _8, and when the luminance signal (Y) is included in 7 words in the 15 words, the data D ₄ in the data D _{1 to} D ₈ is omitted. data D ₁ of the remaining 7 _{words, D 2, D 3, D} 4, D 5, D 6, it is assumed that sequentially allocates the D _7, D _8. Here, in consideration of the continuity of the analog signal waveform, the waveform formed by the data string is determined not only by whether the value of the bit is “1” or “0” but also by the values of the bits before and after the bit. . That is, FIGS. 3A to 3H show analog signal waveforms in consideration of the preceding and succeeding bits. For example, the third
FIG. A shows an extracted analog signal waveform of a bit of “1” at the center of an analog signal waveform that changes from “0” to “0” via “1”. (0) 1 (0). Similarly, FIG. 3B shows the signal waveform of (1) 0 (1), that is, the central bit “0” when changing from “1” → “0” → “1”. Is (0) 1 (1), FIG. 3D is (1) 0 (0), FIG. 3E
Is (1) 1 (0), FIG. 3F is (0) 0 (1), FIG. 3G is (1) 1 (1), and FIG. 3H is (0) 0 (0). Are respectively shown. The signal waveform of each of these bits is converted into the above-mentioned 8-word (or 7-word) digital
Table 1 shows an example of specific numerical values represented by data strings.

The numerical value of each data in Table 1 indicates a hexadecimal number. For example, C0 is usually indicated as C0H and indicates 192 in decimal, but H is omitted for convenience of space in the table. ing. In the digital luminance signal, the black level (0IRE) of the analog luminance signal is represented by 16 (10H) and the white peak level (100IRE) is represented by 235 (EBH). Level. This also takes into account the correspondence with analog VITC. Note that 7 of the luminance signals are included in the 15 words.
As described above, when words are arranged, the seven data obtained by removing the _fourth data D4 are sequentially used. The digital code to which this time code is assigned
The color difference signal word in the active line may be set to 80H 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 present invention is applied to an interface for taking out a sector time code (external data) will be described with reference to FIG.

In this Figure 4, the input terminal 1 is input component video signals, i.e. the luminance signal (Y) and two color difference signals _{(C B ≡B-Y, C} R ≡R-Y) , for example in parallel The above-described interface circuit (decoder) 2 of the RP-125 converts the luminance signal and the color difference signal into a format in which the luminance signal and the chrominance signal are alternately time-division multiplexed in a predetermined sequence in the bit parallel manner 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 in the vertical blanking period of the digital video signal output from the decoder 2, so-called D code
The -VITC signal is read by the D-VITC reader 11 and sent to the selector 12. The D-VITC signal is a signal obtained by directly A / D converting VITC in the original analog video signal.
It also includes code format signals. This D
One of the time code data read by the VITC reader 11 and 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. Audio processing circuit
A digital audio signal from a terminal 16 is supplied to a terminal 15, which performs signal processing such as insertion of a time code into a user data area in the digital audio format and sends the signal to the adder 4. Can be 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 above-mentioned ASTC
(Audio sector time code).

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
-Sent to the VITC encoder 28; The D-VITC encoder 28 converts the time code data from the ASTC decoder 27 into a digital time code signal according to the above-described embodiment of the present invention, and sends the digital time code signal to the selector 25. In the selector 25, a predetermined line position (12H and 14H) in the vertical blanking period of the digital video signal from the interpolation circuit 24 is replaced with a digital time code signal from the D-VITC encoder 28 as necessary. And
It is taken out from an output terminal 30 via an interface circuit (encoder) 29 of a so-called RP-125. In addition,
A frame number shift caused by a time delay due to signal processing in each circuit, that is, a shift in the correspondence between the time code data from the D-VITC encoder 28 and the actual frame of the reproduced output video signal is caused by the encoder 28 and the like. time·
Compensation is performed by adding and subtracting the number of frames of code data.

In the specific example shown in FIG. 4, when the magnetic tape 7 is reproduced while being fed at a high speed, the VI
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
The present invention can be easily applied 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.

〔The invention's effect〕

According to the digital time code transmission method according to the present invention, data corresponding to an analog signal waveform of a time code is provided by a luminance signal data word at a predetermined scanning line position during a vertical blanking period of a digital component video signal. Since the columns are formed, digital time code transmission that is highly compatible with VITC of analog signals can be performed. 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.

[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 is a waveform diagram showing an example of one bit of a time code analog signal waveform. FIG.
It is a block circuit diagram showing an example applied to R.

Claims (1)

(57) [Claims] 1. A digital signal transmitted by a digital interface format for time-division multiplex transmission of a digitally encoded luminance signal and color difference signal of a television standard video signal in a predetermined sequence. At a predetermined scanning 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 analog signal waveform of the time code is formed. Digital time signal transmission as a digital signal
Code transmission method.