JP2776116B2 - Timecode conversion method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to devices having different time code frame periods (for example, VTR and DAT).
The present invention relates to a time code conversion method suitable for use in recording and reproducing a time code.

[0002]

2. Description of the Related Art As a time code conversion method, for example, there is a method described in Japanese Patent Application Laid-Open No. 1-264686. This is a method of converting a DAT time code into an SMPTE (Drop Frame) time code which is a standard time code for a VTR, and the procedure is as follows. a) Obtain the total number of frames of the DAT time code. b) dividing the total number of frames of the DAT time code by the ratio of the SMPTE frame period to the DAT frame period,
The total number of frames of the SMPTE time code is obtained. c) Obtain a predicted SMPTE time code from the DAT time code. d) Obtain the total number of frames of the predicted SMPTE time code. e) SM predicted from the total number of frames of SMPTE time code
The difference is obtained by subtracting the total number of frames of the PTE time code. f) adding the difference to the predicted SMPTE time code,
An SMPTE time code is required.

[0003]

In such a conventional time code conversion method, multiplication for obtaining the total number of DAT time code frames and multiplication and division for obtaining the total number of SMPTE time code frames are required. And
For real-time processing, there is a problem that the load on hardware and software increases. . Therefore, the present invention provides a new time code conversion method that reduces multiplication and division during conversion.

[0004]

In order to solve the above-mentioned problems, the present invention provides a time code having a first frame period (for example, an SMPTE time code having a drop frame) as shown in FIGS. Is the time code of the second frame period (for example, DAT time code)
Converting the time code of the first frame period into an approximation of the time code of the second frame period; 200, the time code of the first frame period, From the approximate value of the time code of the frame period of the first frame period and the phase difference Rj between the frame of the first frame period and the frame of the second frame period at the time of conversion (for example, the total number of frames and the frame period). And a step 201 of calculating a difference Ro) between the two frames, and until the difference between the two frames becomes smaller than the second frame period, the approximate value of the time code of the second frame period is obtained. Steps 202 and 20 for repeating addition or subtraction for one frame
3 is provided.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the configuration of a time code conversion apparatus using the present time code conversion method will be described. FIG.
Is a configuration diagram of a time code conversion device, and SMPTE (D
It performs time code conversion between a VTR (video tape recorder) having a rop frame (time code) and a DAT (digital audio tape recorder). The SMPTE time code is based on the American standard (C98.1).
This is a well-known code specified in 2).

[0006] The time code converter is a VTR for reproduction.
A time code reader 1 for reading the SMPTE time code from 100, a time code converter 2 for converting the read SMPTE time code to a DAT time code,
It comprises a format conversion unit 3 which interfaces with the recording medium 101 such as a DAT, a SCSI interface 4, and the like.

Reference numeral 5 denotes a time code conversion unit for converting a DAT time code read from the recording medium 101 such as a DAT into an SMPTE time code. It is configured to be output to the VTR 102.

Reference numeral 7 denotes a timing generation section for generating a timing clock of the converter based on a synchronization signal from an external VTR. The timing generator 7 generates a system clock Hs (for example, a sampling frequency of DAT of 48 KHz) and a DAT frame signal. Reference numeral 8 denotes a phase detection unit that detects a phase difference Rj between a DAT frame signal and a VTR frame signal (synchronization signal).

[0009] The time code conversion method described below is as follows.
Based on the phase difference Rj from the above-described phase detector 8,
SMPTE (Drop Fr) executed by the time code conversion unit 2
ame) This is a method of converting a time code (NTSC signal) into a DAT time code.

(Premise of Time Code Conversion Method) Next, the principle of the time code conversion method will be described. This time code conversion method has the following characteristics: a) SMPTE time code having a drop frame has a small error from real time,
The property that the T time code also has a small error from real time,
Therefore, the SMPTE (Drop Frame) time code is set to D
B) Phase difference between video frame and DAT frame at the time of conversion, and time code marker (phase difference between video frame and DAT frame at 00: 00: 00: 00) Relationship with SM
The time relationship between the PTE (Drop Frame) time code and the DAT time code is correlated. C) The time code marker (the phase difference between the video frame and the DAT frame at 00: 00: 00: 00) is greater than the DAT frame. It is a conversion method that uses small things.

(Principle of Time Code Conversion Method) a) As described above, the SMPTE time code having a drop frame has a small error from the real time, and the DAT time code has a small error from the real time. , SMPTE (Drop Frame) time code can be directly approximated as a DAT time code. So, DA
Assume an approximate value of the T time code as follows. SM
The PTE (Drop Frame) time code is Hs: Ms: Ss: Fs, the approximate value of the DAT time code is Hd: Md: Sd: Fd, and Hd = Hs, Md = Ms, Sd = Ss, Fd = Fs. I do.

B) Also, as is clear from the frame relationship in FIG. 2, the total number of frames × frame period of SMPTE time code + phase difference Rj = the total number of frames × frame period of DAT time code + phase difference Ro Because there is
From the SMPTE time code, the approximate DAT time code, and the phase difference Rj between the current video frame and the DAT frame, a difference Ro of “the total number of frames × frame period” of each of the video frame and the DAT frame can be calculated. SMP
Assuming that the total number of frames of the TE time code is i and the total number of frames of the DAT time code is j, i = 107892Hs + 1798Ms + 2INT (Ms / 10) + 30Ss + Fs ... j = 120000Hd + 2000Md + 33Sd + INT (Sd / 3) + Fd ... Given. Note that INT is a function that rounds down the decimal point and converts it to an integer.

Further, since the video frame and the DAT frame have the relationship of the equations (1) and (2),

[0014]

(Equation 1)

[0015]

(Equation 2)

Ro of “total number of frames × frame period” is Fs (when sampling at 48 KHz).
It is given by Ro = 1601.6 × i− (1440 × j−Rj). Here, Rj is the phase difference between the current (at j frames of DAT) video frame and the DAT frame, and is output from the phase detection unit 8 of the time code conversion device. Substituting the expression into the expression,
When calculating Ro, approximate DAT time code = SMPTE
It can be assumed to be a time code, and this is set again as H: M: S: F. Also, 900 frames of NTSC (29.97Hz) = DA
Since there is a condition of 1001 frames of T (33.3 Hz), the calculation can be simplified. Furthermore, to eliminate the decimal point operation,
When the equation is multiplied by 5 and summarized, 5Ro = 8008i- (7200j-5Rj) =-864 H-1616M + 2640S + 808F + 8008 × 2 × INT (M / 10) -7200INT (S / 3) + 5Rj.

By substituting the approximate DAT time code into the equation c) and calculating, 5Ro is obtained. The value of the approximate DAT time code is adjusted so as to satisfy the condition of 0 ≦ Ro <DAT total number of frames.

Specifically, in order to satisfy the condition of 0 ≦ 5Ro <1440 × 5... 1) In the case of 7200 ≦ 5Ro, 1440 × 5 is subtracted from 5Ro with the approximate DAT time code incremented. B) If 5Ro <0, decrement the approximate DAT time code and add 1440 × 5 to 5Ro

By repeating this, the DAT time code when 5Ro satisfies the expression is SMPTE (Drop Frame).
(Corresponding to FIG. 2).

In addition, Ro obtained by the above adjustment is obtained.
Is the phase difference between the video frame at time code 00: 00: 00: 00 and the total number of DAT frames. This is called a time code marker and is referred to during reproduction.

(Specific Procedure of Time Code Conversion Method) The specific procedure of the time code conversion method will be described with reference to the flowchart of FIG. [Step 200] An approximate value of the DAT time code is assumed. Hd = Hs, Md = Ms, Sd = Ss, and Fd = Fs. [Step 201] A difference Ro (5Ro) of (total number of frames × frame period) is calculated. [Steps 202 and 203] The value of the approximate DAT time code is adjusted so as to satisfy the condition of 0 ≦ Ro <DAT frame. [Step 204] A DAT time code and a time code marker are determined and calculated.

As described above, according to the present time code conversion, conversion is performed using the phase difference between the video frame and the DAT frame at the time of conversion, so that SMPTE (Drop Frame)
It is not necessary to calculate the total number of frames of the DAT time code and multiplication and multiplication by the conventional time code conversion method.
Division can be reduced.

The time code marker (00: 00: 00: 0)
Phase difference between the video frame at 0 and the total number of DAT frames)
Can be calculated simultaneously with the time code conversion. There is no need to determine by another means as in the past.

[0024]

As described above in detail, the time code conversion method according to the present invention is a method for converting a time code of a first frame period into a time code of a second frame period. Making the time code of the frame period an approximate value of the time code conversion of the second frame period; the time code of the first frame period; the approximate value of the time code conversion of the second frame period; Obtaining a difference between the two frames from the phase difference between the frames having the first frame period and the frames having the second frame period; and obtaining a difference between the two frames until the difference between the two frames becomes smaller than the second frame period. And repeating the addition or subtraction for one frame of the second frame period to the approximate value of the time code of
That is, since time code conversion is performed using the phase difference between the frame of the first frame period and the frame of the second frame period at the time of conversion, the total number of time code frames is calculated as in the related art. No need,
Therefore, the burden on hardware and software is small.

[Brief description of the drawings]

FIG. 1 is a flowchart showing one embodiment of a time code conversion method according to the present invention.

FIG. 2 is a diagram illustrating the principle of a time code conversion method according to the present invention.

FIG. 3 is a configuration diagram of a time code conversion device using the time code conversion method according to the present invention.

[Explanation of symbols]

2 Time code converter 8 Phase detector 200 Step of approximating DAT time code 201 Step of calculating difference Ro (5Ro) between both frames (total number of frames × frame period) 202, 203 Approximate DAT time code so as to satisfy the condition Steps to adjust the value of

Claims (2)

(57) [Claims] 1. A time code of a first frame period is set to a second time code.
A method of converting the time code of the first frame period into an approximate value of the time code of the second frame period; and a method of converting the time code of the first frame period into a time code of the first frame period. Determining the difference between the two frames from the approximate value of the time code of the second frame period, and the phase difference between the frames of the first and second frame periods at the time of conversion. Repeating the addition or subtraction of one frame of the second frame period to the approximate value of the time code of the second frame period until the difference between the two frames becomes smaller than the second frame period. A time code conversion method, comprising: 2. The time code conversion method according to claim 1, wherein the time code of the first frame period is an SMPTE time code having a drop frame.