JPS6218983B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronic editing method for a digital recorder, which eliminates data loss or duplication near the editing point when electronically editing and connecting tapes recorded by a digital recorder. This provides a method for connecting without error.

With a digital recorder that digitally encodes and records and plays back audio signals, when editing the recorded tape, if you apply the manual cutting of the tape used in conventional analog recorders, Errors at connection points may be dispersed over a long interval, and abnormal noises unrelated to the recorded data may also occur. Normally, the tape format for digital recording is divided into frames in order to synchronize the bits of the signal, and a frame synchronization code is placed at the beginning of each frame, and if an error occurs due to a dropout, etc., it is divided into frames. Detection, correction, etc. are performed. Therefore, when tapes that have been cut at arbitrary locations by hand-cut editing are spliced, not only will errors occur due to data discontinuity, but synchronization pull will be disrupted due to synchronization code discontinuity, and the data error section will be expanded. Ru. Furthermore, when editing by hand, it is necessary to fully consider the fact that the skill level of the operator is a major factor that affects accuracy. As mentioned above, when manually editing a digitally recorded tape, there is no guarantee that the editing will be accurate.

On the other hand, there is a concept of electronic editing in which editing is performed without cutting the tape. Conceptually, when two or more digital recorders are used and, for example, tapes A and B are to be edited and connected, a copy tape is created using tape A as the master. Next, tape B is set on the master side, and the previously copied tape is set on the slave side, and the two recorders are run in synchronization based on commands from the editing machine using control signals such as time codes. When the edit connection point comes, tape B on the master side
The content of is overwritten on the copy tape on the slave side. Finally, the contents of A+B are recorded on the copy tape, and the editing is completed. Specifically, in order to carry out the above-mentioned operation, there are various restrictions on the tape format used, the configuration of the recorder, the signal processing method, etc., and it is also necessary to devise measures. For example, when it comes to tape formats, when switching from playback mode to recording mode at an edit point during tape playback, the already recorded portion and the overwritten portion may have different bits due to wow and flutter while the tape is being played by the recorder. Since out-of-synchronization and therefore errors occur at the switching points, a method is needed that does not affect the final data. IBG (Inter
An effective method is to provide a blanking section called ``Block Gap'' and perform the above-described switching operation to the recording mode in that section. Furthermore, in order to perform the operations described above, the following functions are required in the configuration of the recorder. That is, it is necessary to make the spatial relationship between the means for reproducing and monitoring already recorded signals (reproducing head) and the means for additionally recording (recording head) correspond to the time sequence of the signals. In this case, it is necessary to provide a preceding playback head at a position that precedes the tape running, and to provide, for example, delay means for adjusting the time difference between the two heads in accordance with the elapse of time as the tape runs.

The present invention relates to a specific signal processing method and a configuration of a processing means for carrying out electronic editing work using the above-mentioned method, and is intended to realize a new method that does not cause loss of information data at editing connection points. be.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram centered on a digital recorder when performing electronic editing. In the figure, 1 indicates a recorder section, 1 is a tape which is a recording medium, 2 is a advance playback head, 3 is a recording head, 4 is a playback signal block, 5 is a delay memory, 6 is a recording block,
7 is a switch provided on the editing machine side, and 8 is an input terminal for signals additionally recorded at editing points. The signal recorded on the tape 1 is played back by the advance playback head 2, and the playback block 4 performs processing such as amplification and shaping of the playback signal, as well as demodulation, jitter absorption, error correction, etc., and then a switch on the editing machine side. Sent on 7th. A switch 7 on the editing machine side selects a signal to be additionally recorded. The signal selected by switch 7 is delayed by delay memory 5 for a certain period of time. The amount of delay in this case corresponds to the time required for the tape 1 to travel from the reproducing head 2 point to the recording head 3 point minus the time required for signal processing in the reproducing block 4 and recording block 6. Therefore, by inserting the delay memory 5, for example, when the switch 7 is turned on in the direction shown in FIG.
The signals arriving at the upper recording head 3 position match.

In the present invention, electronic editing is performed using a tape recording pattern with IBG. The signal played by the master recorder (corresponding to the signal input to terminal 8 in Figure 1) is transferred to the tape set in the slave recorder (corresponding to the recorder in Figure 1) from the editing point onwards. In the case of additional recording, the timing of the IBG signal detected from the signal reproduced by the preceding reproduction head is also adjusted in the delay memory 5 or the like in the same manner as in the case of the signal described above, so that the IBG signal coincides with the position of the recording head 3. In the IBG section where there is no music signal preceding the editing point (more specifically described later), the slave side recorder is switched from a simple playback state, the recording head is driven, and recording/recording is started.
Changes to playback mode. At this time, advance playback head 2
The signal played back is overwritten again. When an edit point (stored in advance as a time code address) is detected, switch 7 is switched and the reproduction signal of the master side recorder is continuously overwritten.

One reason why the switching point to the recording mode and the data switching point (editing point) are different is that the editing point does not coincide with the IBG, which is the recording mode switching point on the tape pattern. Editing accuracy is IBG
It doesn't matter if it's a unit, but if you want to increase it by a word, it won't match. Another reason is that generally, at an editing point, sounds with different levels are connected, so if the level difference is large, a click sound will be detected. Therefore, it is necessary to gradually increase or decrease the signal over time by fade-in/fade-out signal processing to make it less noticeable. Therefore, if crossfade signal processing is performed centering around the edit point, in the case described above, the edit point and recording switch point must be separated from each other in order to allow time for the crossfade signal processed playback signal to be overwritten again after the recording switch. .

Generally, editing work involves deleting unnecessary parts, connecting different tapes, inserting them in the middle, etc. In electronic editing, the recording mode is switched from the editing point, and the contents are rewritten by overwriting.
Alternatively, the recording mode is canceled from the editing point and the content is connected to the already recorded content. To explain this in an easy-to-understand way using drawings, Fig. 2A shows the case where recording is started midway, and B shows the case where recording is canceled midway. is overwritten and the edited tape A' shown in is obtained.
When a recording command is issued in IBG section A shown in FIG. 3, the switch 7 in FIG. 1 remains in the direction shown, so that the signal already recorded by the recording head 3 is overwritten again. . When the editing point RO is reached, the switch 7 is switched to the signal input terminal 8 to be connected, and new data is recorded. Second
Similarly, in the case shown in FIG. B, the signal switching is first completed at editing point C, and then the recording mode is canceled at IBG section D. The tape obtained in this way
A′ guarantees the continuity of data at the edit point and the continuity of the synchronization code at the recording change point.

Next, to explain in detail the reason for adopting the above method, in order to keep the tape running speed constant,
Servo control is applied to the travel drive motor. Servo control normally detects the clock component of a reproduced signal or the signal of a dedicated servo track and performs control, but wow and flutter components remain.
In reality, this varies depending on conditions such as tape speed and recording wavelength, but when servo control is performed on the advance playback head, there is a deviation of about 10 bits in the time axis as seen from the recording head position. Therefore, it is appropriate to switch the recording mode in a blanking section where no data exists.

On the other hand, the above-mentioned IBG must also be considered from a different perspective. That is, in order to perform recording at as high a density as possible, it is necessary to improve error correction capability while reducing redundancy. Therefore, it is not a good idea to provide frequent and long IBG sections. In the tape format used in the present invention, one block is subdivided into a plurality of frames as shown in FIG. ) with frame and IBG
Executes error detection and correction on a unit-by-unit basis. Although the data portion also includes a code for error detection and correction, it is effective to insert a second error correction code into the IBG section in order to further improve the correction ability. At this time, even if the second error correction code is lost, it does not have any effect on the normal error correction operation, and a code that simply reduces the correction ability is used.

To explain in more detail the case where electronic editing is performed using such a tape format, switching to or from the recording mode is performed in the IBG section shown in C of FIG. 3A. At this time, care must be taken to ensure that the switching point does not come to the position of frame synchronization code A and IBG frame synchronization code B due to wow and flutter.
When the edited tape is played back, the IBG (shown in Figure 3C) that has undergone the recording mode change is affected by wow and flutter, and as described above, the IBG is longer or shorter than the specified length by more than 10 bits. In the tape format shown in FIG. 3A, the omission of a frame synchronization code or the occurrence of a pseudo synchronization code has a great effect on data reproduction, and errors are spread not only to the frame concerned but also to the entire block. Therefore, in order to remove the pattern that matches the synchronization code contained in the normal data, a synchronization protection gate signal as shown in FIG. A method is used that does not cause code detection errors. The stricter the restriction conditions of the protection gate, the lower the probability that a detection error will occur. Since the generation of such a synchronization protection gate uses the equidistant property of the frame synchronization code shown in Figure 3C,
When an IBG that has switched the recording mode arrives, there is a possibility that the regular frame synchronization code at the beginning of the block cannot be detected. In the present invention, one method to improve this point is to use a non-cyclic pattern for the synchronization code as long as possible, and to set the timing of opening and closing of the synchronization protection gate in a region that is not affected by wow and flutter. That is, even if the synchronization code moves back or forth from the normal position due to recording mode switching, the protection gate is opened/closed with enough detection margin. Furthermore, this idea is further improved, and when the IBG frame synchronization code shown in FIG. In other cases, stricter measures may be considered.

If the recording mode switching point is detected by other means, for example, if a separate editing track is provided and a distinguishable signal is recorded at the same time as the recording mode is switched, the The same operation as above can be performed, and the loss of synchronization codes can be eliminated.

According to the present invention described above, the recording mode switching during editing and the switching and connection of information data are performed at different points, and the former is performed at a point that does not affect the information data, resulting in data loss, duplication, and errors. A complete editing connection can be made without any occurrence of .

Furthermore, when reproducing an edited tape, it is possible to eliminate frame synchronization code detection errors caused by the shadows of wow and flutter during tape running during editing.

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram of a digital recorder used in an embodiment of the present invention, FIGS. 2A and B are diagrams showing the state of the tape near the editing point during electronic editing, and FIGS. 3A to D are electronic FIG. 3 is a diagram showing a tape format used for editing and its synchronization code. 1...tape, 2...advance playback head, 3...
Recording head, 4... Reproduction signal block, 5... Delay memory, 6... Recording block, 7... Switch, 8... Input terminal.

Claims (1)

[Claims] 1 Converting an analog signal into a digital signal, dividing the digital signal into frames having a frame synchronization code, forming a block from a plurality of the frames, and converting the digital signal into a digital signal having a blanking section that does not contain information data. This is an electronic editing method in which a tape recorded using a recording method is used with two recorders, played back by a pre-play head, and additionally recorded by a recording head, and when editing is connected by additional recording at the time of editing. The recording mode is switched in the blanking section that precedes the editing point, and when editing is connected by stopping additional recording, the recording mode is canceled in the blanking section that is behind the editing point, and when the editing tape is played back, the recording mode is switched. An electronic editing system for a digital recorder characterized in that a protection gate for frame synchronization code detection is controlled to open and close at a timing that allows for fluctuations in the time axis of the tape when switching recording modes.