Time code arithmetic apparatus

Details Time code arithmetic apparatus Time code arithmetic apparatus

2000-10-06

2004-12-14

Tran, Thai (Department: 2616)

Motion video signal processing for recording or reproducing

Local trick play processing

With randomly accessible medium

C386S349000

Reexamination Certificate

active

06832038

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a time code arithmetic apparatus for calculating the time code written with the video signal of recording media.
BACKGROUND ART
The editing work of the video tape for broadcasting or the nonlinear editing work using the hard disk is carried out accurately based on the absolute address signal recorded in one-to-one relation to the video signal for each frame on the recording-medium (video tape or hard disk). This absolute address signal is called the SMPTE (Society of Motion Picture and Television Engineers)/EBU (European Broadcast Union) time code (hereinafter referred to as the time code) standardized by SMPTE and EBU.
The television transmission system is roughly divided into the NTSC scheme in which a picture for one second configured with 30 images (30 frames) and the PAL and SECAM schemes in which a picture for one second is configured with 25 images (25 frames). The NTSC scheme is employed in Japan, U.S.A. etc., while the PAL and SECAM schemes are used in European countries. The NTSC scheme employs the SMPTE time code reference, and the PAL scheme employs the EBU time code reference.
The unit of the SMPTE/EBU time code is expressed in hours, minutes, seconds and frames, each in two digits for a total of eight digits. The digits of hours, minutes and seconds are counted the same way as the 24-hour clock. The frame digit represents the count 30 for the NTSC scheme, and 25 for the PAL and SECAM schemes, with digits carried up or down to the second digit. Among the TV transmission systems, the NTSC scheme covers 30 frames per second (30 images constituting a picture of one second). Exactly, however, one frame has 33.3 milliseconds, 30 frames per second, and 29.97 Hz per frame (30 Hz: 1000 msec=xHz: 33.3 msec×30 frames). Therefore, the step of the time code is deviated from the real time, though little by little. This deviation, simply calculated, is 108 frames (3.6 sec) per hour, and the long editing work poses the problem of the deviation from the real time. In the PAL or SECAM scheme, the number of frames is 25 per second (25 images constitute a picture for one second). In these television transmission systems, therefore, the real time is coincident with the time code step.
In the NTSC scheme, two modes are specified as the standard for the time code step.
The first mode is called the drop mode, in which in order to obviate the deviation between the real time and time code step for a long time (one minute or longer), two frames (00 frame and 01 frame, hereinafter referred to as the drop frames) from the start of each minute on the minute except for 0, 10, 20, 30, 40 and 50 minutes are skipped (in other words, the frame
29
is followed by not frame
00
but frame
02
) thereby to step the time code. In this mode, two drop frames are skipped 54 times per hour, so that 108 frames are skipped per hour in keeping with the real time. Also, in the drop mode, the picture is continuous, but frame
00
and frame
01
are skipped (absent) as the time code corresponding to the picture in one-to-one relation.
The second mode is called the non-drop mode, which is a method based on the assumption that there is a deviation between the real time and the step of the time code o'clock. In this mode, the time code step is not accompanied by any skip of the frame unlike in the drop mode. Only the non-drop mode is employed for the PAL scheme and the SECAM scheme.
Conventionally, a time code arithmetic apparatus for performing the arithmetic operation in time code of drop mode according to the NTSC scheme (hereinafter referred to as the DF time code o'clock) is disclosed in JP-A-7-203345.
For these two types of DF time code o'clock, there are two methods of add/subtract arithmetic operations. One is, as described in prior art of the time code arithmetic apparatus of JP-A-7-203345, is such that the two input time codes counted in drop mode are converted into the time code in non-drop mode (hereinafter referred to as the NDF time code o'clock), respectively, before add/subtract arithmetic operation, and the NDF time code o'clock constituting the calculation result is reconverted to the DF time code o'clock (hereinafter referred to as the drop mode calculation method
1
).
The other method is performed by the time code arithmetic apparatus of JP-A-7-203345, in which two input time codes counted in drop mode are not converted into the NDF time code o'clock but the DF time code o'clock itself is used for calculation with the drop frames added thereto (hereinafter referred to as the drop mode calculation method
2
).
Now, the arithmetic relation between the DF time code o'clock and the NDF time code o'clock below.
DFt
1
: DF time code o'clock providing a reference of add/subtract arithmetic operation.
DFt
2
, DFt
3
, DFt
4
: DF time code o'clock
NDFt: NDF time code hour
If DFt
2
<DFt
1
<DFt
3
, DFt
4
, then
 
DFt
1
−
DFt
2
−&agr;=
NDFt
  Equation 1
DFt
1
−
NDFt−&agr;
2
=
DFt
2
  Equation 2
DFt
1
+
NDFt+&agr;
1
=
DFt
3
  Equation 3
DFt
1
+
DFt
2
+&agr;
3
=
DFt
4
  Equation 4
where
&agr;: the number of drop frames skipped from DFt
2
o'clock to DFt
1
hour
&agr;
1
: the number of drop frames generated upon the lapse of NDFt o'clock from DFt
1
o'clock
&agr;
2
: the number of drop frames generated after returning by NDFt time in the case where the time upon the lapse of the time NDFt from DFt
2
o'clock is DFt
1
.
&agr;
3
: two frames in the case where a new drop frame is generated in the calculation process of (time DFt
1
+DFt
2
time) and 0 frame in the case where no new drop frame is generated in the same process.
Equation 1 is the relational equation for calculating the NDF time code o'clock corresponding to the number of frames in real time from the difference of two DF time code o'clock. This equation is used for calculating the duration (real editing time) between the edit start time point and the edit end time point in editing on an editing apparatus.
The value &agr; in this equation 1 can be calculated by simply subtracting the number of drop frames skipped during the time from 00:00:00.00 o'clock to DFt
2
o'clock from the number of drop frames skipped during 00:00:00.00 o'clock to DFt
1
o'clock.
Therefore, this &agr; is the total number of frames dropped in the case where one frame is added each from DFt
2
o'clock to DFt
1
o'clock.
Also, during the time lapse from Dft
2
o'clock to Dft
1
o'clock frame by frame in the case where the result of addition corresponds to a drop frame, +2 frames are skipped and the number of counts is replaced by time data, and then it coincides with the NDFt o'clock.
Equation 2 is the relational equation for calculating the DF time code o'clock obtained when subtracting the NDF time code o'clock representing the number of frames corresponding to an arbitrary real time from DFt
1
o'clock. Equation 2 is used, for example, for calculating the DF time code o'clock at the edit start time point before an arbitrary real time after determining the editing end point in editing on an editing apparatus like in equation 1.
The value &agr;
2
in this equation 2 is theoretically the total number of frames dropped when subtracting frame by frame until the number of frames becomes zero during the time NDFt from DFt
1
o'clock.
This &agr;
2
, when an attempt to be made to calculate the DFt
2
o'clock from the information of DFt
1
o'clock and NDFt o'clock, cannot be easily calculated in view of the fact that a new drop frame may occur in the process of calculation, thereby complicating the calculation.
Equation 3 is the relational equation for calculating the DF time code o'clock when adding the NDF time code o'clock representing the number of frames corresponding to an arbitrary real time from the DFt

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