JP2776144B2 - 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 a time code conversion method suitable for use when recording and reproducing time codes between devices (for example, VTR and DAT) having different time code frame periods. In particular, the present invention relates to a non-drop frame time code conversion method.

[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 a 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]

The above conventional time code conversion method uses a DAT time code and an SMPTE
(Drop Frame) This is a conversion method with time code, not SMPTE (Non-Drop Frame) time code. However, SMPTE (Non-Drop Frame) time code is 108 frames / real time.
Since there is a difference of H (hour), the conventional time code conversion method has a problem that an error of 2592 frames occurs at worst. Accordingly, the present invention provides a time code conversion method suitable for use in DAT time code and SMPTE (Non-Drop Frame) time code conversion.

[0004]

According to the present invention, a non-drop frame time code (for example, SMPTE (Non-DropFrame) time code) is converted to a drop frame time code (for example,
A method of converting the non-drop frame time code into an approximate value of the drop frame time code (SMPTE (Drop Frame) time code).
03) obtaining the total number of frames of the non-drop frame time code; obtaining the total number of frames of the drop frame time code; and calculating the difference between the total number of frames of the non-drop frame time code and the total number of frames of the drop frame time code. (Step 104), and adding the approximate value of the drop frame time code (Step 105).

A non-drop frame time code of a first frame period (for example, SMPTE (Non-
(Drop Frame) time code) to a time code of a second frame period (for example, DAT time code), wherein the non-drop frame time code of the first frame period is converted to a time code of a first frame period. Making the approximate value of the drop frame time code (steps 100 to 103); obtaining the total number of frames of the non-drop frame time code of the first frame period; Calculating the total number of frames; and calculating the difference between the total number of frames of the non-drop frame time code of the first frame period and the total number of frames of the drop frame time code of the first frame period (step 104). Frame period drop frame Add to the approximate value of the imcode,
The step of obtaining the drop frame time code of the first frame cycle (step 105) and the step of obtaining the time code of the second frame cycle from the drop frame time code of the first frame cycle (shown in FIG. 2) , Steps 200 to 204).

[0006]

According to the above time code conversion method, the non-drop frame time code of the first frame period is equal to the first time code.
Is converted to a drop frame time code of the first frame period, and the drop frame time code of the first frame period is further converted to a time code of the second frame period.

[0007]

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 block diagram of the time code conversion device T,
(Non-Drop Frame) Time code conversion between a VTR (video tape recorder) 10 having a time code and a DAT (digital audio tape recorder) 12 is performed. The SMPTE time code is a well-known code defined in the American standard (C98.12).

[0008] The time code conversion device T includes a VT for reproduction.
SMPTE non-drop frame from R10 (Non-Dro
p Frame) Time code reader 1 for reading time code, non-drop frame time code for reading
It comprises a first time code converter 2a for converting an MPTE drop frame (Drop Frame) time code to a second time code converter 2b for converting the converted drop frame time code to a DAT time code. . Reference numeral 11 denotes an interface with a recording medium 12 such as a DAT.

On the other hand, reference numeral 3a denotes a DAT time code from the recording medium 12 such as DAT, which is an SMPTE drop frame.
(Drop Frame) A time code conversion unit for converting the time code into a time code, and 3b converts the converted drop frame time code into an SMPTE non-drop frame.
e) A time code conversion unit for converting to a time code.
This converted output is transmitted through the time code generator 4 to S
It is configured to be output to the recording VTR 13 as an MPTE time code.

Reference numeral 5 denotes a timing generator for generating a timing clock for the converter based on a synchronization signal from an external VTR. The timing generator 5 generates a system clock Fs (for example, a sampling frequency of DAT of 48 KHz) and a frame signal for DAT. Reference numeral 6 denotes a phase detection unit that detects a phase difference Rj between a DAT frame signal and a VTR frame signal (synchronization signal).

As is apparent from the configuration of FIG. 1, this time code conversion is performed by a VTR (Video Tape Recorder) 10 having an SMPTE (Non-Drop Frame) time code,
At the time of time code conversion with an AT (Digital Audio Tape Recorder) 12, an SMPTE non-drop frame (Non-Drop Frame) time code is temporarily set to SM
It is converted to a PTE drop frame (Drop Frame) time code, and finally converted to a DAT time code. As a result, as will be described later, conversion is performed accurately with a configuration in which the burden on hardware and software is small.

(Conversion from Non-Drop Frame to Drop Frame) First, the first time code conversion unit 2a converts the SMPTE (Non-Drop Frame) time code to the SMPTE (Drop Frame) time code. The conversion operation (steps 100 to 105 in FIG. 1 described later) will be described. Non-drop frame (Hn: Mn: Sn:
Fn), the total number of frames is Inon, the drop frame (Hd:
Assuming that the total number of frames of Md: Sd: Fd is Idrop, Inon = 108000Hn + 1800Mn + 30Sd + Fd... Idrop = 107892Hd + 1798Md + 2INT (Md / 10) + 30Sd + Fd ... = Inon, Hn: Mn: Sn: Fn ≤Hd:
Md: Sd: Fd.

Here, the frame difference assuming that the approximate value of the time code of the drop frame time code is (Hn: Mn: Sn: Fn) = (Hd: Md: Sd: Fd) is g (this is an approximate value). G = 108Hn + 2Mn-2INT (Md / 10)... From the equation.

The result of converting the frame difference g into minutes / seconds / frame by the rule of the drop frame is expressed as Mg: Sg: Fg.
Then, (Hd: Md: Sd: Fd) = (Hn: Mn: Sn: Fn) + (Mg: Sg: Fg). If the time code obtained by the formula is the frame value 00,01 which should be dropped, it is corrected to 02, and the rule of the drop frame (the minute frame 00, except for 00,10,20,30,40,50) 01 drop). This is an approximate drop frame time code.

Finally, an accurate frame difference d between the non-drop frame time code and the approximate drop frame time code is obtained and added and corrected. That is, the frame difference between the non-drop frame time code and the approximate drop frame time code is d. d = Inon-Idrop ... The number of frames is obtained from the equation. The frame difference d accurately calculated from the equation is added to the approximate drop frame time code. The addition at this time is performed according to the rule of the drop frame. Thereby, a drop frame time code is obtained. Based on this drop frame time code, it is finally converted to a DAT time code as described below.

(Drop frame time code to DA
Next, the final conversion from the drop frame time code to the DAT time code will be described. In the time code conversion method described below, a drop frame (SMPTE (Drop Frame) time code) executed by the second time code conversion unit 2b based on the phase difference Rj from the phase detection unit 8 described above. From DA
This is a conversion method to T time code. First, the premise 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 drop frame time code can be directly approximated as the DAT time code. B) The phase difference between the video frame (drop frame) and the DAT frame at the time of conversion, and the time code marker (0
0: 00: 00: 00, the relationship between the video frame and the DAT frame) is that the time relationship between the SMPTE (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 a conversion method that utilizes the fact that it is smaller than the DAT frame.

Based on the above assumptions, time code conversion is performed in the order of a) to b). a) As described above, the drop frame time code has a small error from the real time, and the DAT time code has a small error from the real time. Therefore, the drop frame time code can be approximated as it is as the DAT time code. Therefore, an approximate value of the DAT time code is assumed as follows. Set the drop frame time code to Hs: Ms: Ss: F
s and the approximate value of the DAT time code is Hd: Md: Sd: F
d, and approximates Hd = Hs, Md = Ms, Sd = Ss, and Fd = Fs.

B) Also, as is clear from the frame relationship in FIG. 3, the total number of frames × frame period of the drop frame time code + the phase difference Rj = “the total number of frames × frame period” of the DAT time code + phase difference Ro Therefore, a difference Ro of “the total number of frames × frame period” of each of the video frame and the DAT frame can be calculated from the drop frame time code, the approximate DAT time code, and the phase difference Rj between the current video frame and the DAT frame. Assuming that the total number of frames of the drop frame 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 ... a j = 120000Hd + 2000Md + 33Sd + INT (Sd / 3) + Fd ... b.

The drop frame (video frame) and the DAT frame are given by the following equations (1) and (2).

[0020]

(Equation 1)

[0021]

(Equation 2)

The difference Ro between “the total number of frames × the frame period” is given by Ro = 1601.6 × i− (1440 × j−Rj) when the frame period is expressed by Fs (at the time of 48 KHz sampling). Where Rj is the current drop frame (video frame) (at j frame of DAT) and DA
The phase difference between T frames, which is output from the phase detector 8 of the time code converter. When Ro is obtained by substituting the a and b equations into the equation, it can be assumed that approximate DAT time code = drop frame time code, which is set again as H: M: S: F, and NTS
900 frames of C (29.97Hz) = 10 of DAT (33.3Hz)
Since there is a condition of 01 frame, the calculation can be simplified. Further, to eliminate the decimal point calculation, the expression is multiplied by 5 to summarize: 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 expression 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 frame period. Specifically, in order to satisfy the condition of 0 ≦ 5Ro <1440 × 5... A) In the case of 7200 ≦ 5Ro, the approximate DAT time code is incremented and 1440 × 5 is subtracted from 5Ro. B) When 5Ro <0, the approximate DAT time code is decremented and 1440 × 5 is added to 5Ro. This is repeated, and the DAT when 5Ro satisfies the expression is repeated.
The time code is an accurate DAT time code corresponding to the drop frame time code (the state satisfies the relationship of FIG. 3).

Further, Ro obtained by the above adjustment is obtained.
Is the phase difference between the drop frame (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.

According to such time code conversion, since the conversion is performed using the phase difference between the video frame and the DAT frame at the time of conversion, it is necessary to calculate the total number of frames of the drop frame time code and the DAT time code. No multiplication / comparison compared with 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.

(Specific Procedure of Time Code Conversion Method) The specific procedure of the time code conversion method will be described with reference to the flowcharts of FIGS. Steps 100 to 105 in FIG. 1 are conversion steps from a non-drop frame to a drop frame. [Step 100] Frame difference g (g = 108Hn + 2M)
n-2INT (Md / 10)) is calculated. [Step 101] The frame difference g is converted into minutes / seconds / frames according to the rule of a drop frame. [Step 102] An approximate drop frame time code is calculated. [Step 103] Correction is performed based on the rule of the drop frame to obtain an approximate drop frame time code. [Step 104] An accurate frame difference d between the non-drop frame time code and the approximate drop frame time code is obtained. [Step 105] The frame difference d is added to the approximate drop frame time code. Drop frame time code is required.

Steps 201 to 205 in FIG.
Is a conversion step from a non-drop frame to a drop frame. [Step 201] An approximate value of the DAT time code is assumed from the drop frame time code obtained in step 105. Hd = Hs, Md = Ms, Sd = Ss, and Fd = Fs. [Step 202] A difference Ro (5Ro) of (total number of frames × frame period) is calculated. [Steps 203 and 204] The value of the approximate DAT time code is adjusted so as to satisfy the condition of 0 ≦ Ro <DAT frame. [Step 205] A DAT time code and a time code marker are determined and calculated. The non-drop frame time code is finally converted to a DAT time code.

As described above, according to the present time code conversion, it is not necessary to calculate the total number of frames of the time code as compared with the conventional time code conversion method.
The number of divisions is greatly reduced, and the load on hardware and software is reduced, and non-drop frame time code can be accurately converted to DAT time code.

[0030]

As described above in detail, the time code conversion method according to the present invention is a method for converting a non-drop frame time code of a first frame period into a time code of a second frame period. Obtaining a drop frame time code of a first frame period from the non-drop frame time code of the first frame period; and obtaining a time code of a second frame period from the drop frame time code of the first frame period. , So that the hardware and software load is less than that of the conventional time code conversion method, and the non-drop frame time code is accurately converted to the DAT time code. be able to.

[Brief description of the drawings]

FIG. 1 is a flowchart showing one embodiment of a time code conversion method according to the present invention, showing conversion from a non-drop frame time code to a drop frame time code.

FIG. 2 is a flowchart showing one embodiment of a time code conversion method according to the present invention, showing conversion from a drop frame time code to a DAT time code.

FIG. 3 is a diagram illustrating the principle of a time code conversion method (conversion from a drop frame time code to a DAT time code) according to the present invention.

FIG. 4 is a configuration diagram of a time code conversion device using the time code conversion method according to the present invention.

[Explanation of symbols]

T Time code conversion device 2a First time code conversion unit 2b Second time code conversion unit 6 Phase detection unit 100 Step of calculating frame difference g 103 Step of calculating approximate drop frame time code 104 Exact frame difference d Determining step 105 adding the frame difference d to the approximate drop frame time code 200 calculating the approximate DAT time code value 201 calculating the difference Ro (5Ro) between both frames (total number of frames × frame period) 202, 203 Step of adjusting the value of the approximate DAT time code so as to satisfy the condition

Claims (4)

(57) [Claims] 1. A method of converting a non-drop frame time code into a drop frame time code, wherein the non-drop frame time code is an approximate value of the drop frame time code; Determining the total number of frames of the drop frame time code; and calculating the difference between the total number of frames of the non-drop frame time code and the total number of frames of the drop frame time code. Adding to an approximate value. 2. A method for converting a non-drop frame time code of a first frame period into a time code of a second frame period, the method comprising: converting the non-drop frame time code of the first frame period to a first frame period. Making the approximate value of the drop frame time code of the frame cycle; calculating the total number of frames of the non-drop frame time code of the first frame cycle; and calculating the total number of frames of the drop frame time code of the first frame cycle. Determining the difference between the total number of frames of the non-drop frame time code of the first frame period and the total number of frames of the drop frame time code of the first frame period by the drop frame time code of the first frame period. Is added to the approximate value of A time code conversion method comprising: obtaining a drop frame time code of a frame cycle; and obtaining a time code of a second frame cycle from the drop frame time code of the first frame cycle. 3. A method for converting a non-drop frame time code of a first frame period into a time code of a second frame period, comprising: Obtaining the drop frame time code of the first frame period; and setting the drop frame time code of the first frame period to an approximate value of the time code of the second frame period. Determining a difference between the two frames from a code, an approximate value of a time code of the second frame period, and a phase difference between the frames of the first and second frame periods at the time of conversion. And until the difference between the two frames becomes smaller than the second frame period. Repeating the addition or subtraction of one frame of the second frame period to or from the approximate value of the time code of the frame period. 4. A method for converting a non-drop frame time code of a first frame period into a time code of a second frame period, wherein the non-drop frame time code of the first frame period is converted to a first time code of a first frame period. Making the approximate value of the drop frame time code of the frame cycle; calculating the total number of frames of the non-drop frame time code of the first frame cycle; and calculating the total number of frames of the drop frame time code of the first frame cycle. Determining the difference between the total number of frames of the non-drop frame time code of the first frame period and the total number of frames of the drop frame time code of the first frame period by the drop frame time code of the first frame period. Is added to the approximate value of Obtaining a drop frame time code of a frame cycle; making the drop frame time code of the first frame cycle an approximate value of the time code of the second frame cycle; and a time code of the first frame cycle. 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: