JPH0480467B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to high-speed playback, low-speed playback, and reverse playback including high-speed and low-speed playback of digital audio signals in an apparatus for recording and reproducing video signals and digital audio signals. .

Conventional configuration and its problems Below is a rotating head helical scan video tape recorder (hereinafter abbreviated as VTR) that records video signals and digital audio signals on the same track.
We will explain the problems when playing back digital audio signals at variable speed. In the VTR, as shown in FIG. 1, following a video signal V for one field, a digitized audio signal A corresponding to a period of one field of the video signal is compressed in time and recorded on the same track. In standard reproduction (1x speed) of the signal recorded in this manner, the reproduction head sequentially traces the signal along the center of the track. In high-speed playback, the tape is fed faster, so that the playback head traces the tracks diagonally, as shown in FIG. 2a, and when it crosses between tracks, noise is generated in the playback signal. To prevent this noise from occurring, VTRs equipped with an automatic scan tracking (hereinafter abbreviated as AST) mechanism detect the servo control signal recorded at the edge of the tape and the envelope of the playback signal. By moving the playback head, which is mounted on a piezoelectric element that utilizes a piezo effect or the like, from side to side, the playback head is controlled to trace a single track from low-speed playback to several times faster. Figure 2b shows the state of the AST function using 1.25x speed as an example.The broken line in Figure 2a is the trace of the playback head under no control, and the dashed line in Figure 2b is the trace of the playback head under AST control. This is a trace line, and one trace will not span multiple tracks during AST control.
However, in this case, the playback head performs track skipping playback, and if you look at this situation in Figure 2b, the track in Figure 2b is skipped and the second track is skipped.
Following the track shown in Fig. 2b, the track shown in Fig. 2b is played back. Therefore, when a digital audio signal is played back at high speed, as shown in Figure 4, which shows the connection status of the audio signal, there will be a difference in the audio level at the part where the track jumps out, and E-Ro in Figure 4. There is a problem in that clicking noise will occur if this occurs and is played back as is. In low-speed playback, as shown by the broken line in Figure 3a, taking 0.5x speed as an example, the tape feed speed becomes slower, so the playback head crosses the tracks diagonally, and the playback head is placed between the tracks. Noise occurs in the reproduced signal when the signal crosses the In this case as well, the playback head is controlled by the AST circuit so that it does not trace across multiple tracks.
As shown by the dash-dotted line in FIG. 2B, during low-speed playback, the playback head advances while tracing the same track several times. In other words, tracks will be played back repeatedly. Therefore, when a digital audio signal is reproduced at a low speed, the audio for one field is reproduced several times at a time as shown in FIG. 4, making it very difficult to hear and producing unnatural sounds. Also, when repeating the same track signal,
Differences in the level of sounds such as chi, lin, and rouo occur, causing click noise. During reverse playback, including high-speed and low-speed playback, the head feed direction is the same as during standard playback, but the tape feed direction is reversed. Therefore, although the signal within one field is correctly reproduced, there is a problem that the order of the fields to be reproduced is reversed and the audio connection is lost. Then,
When using the special playback mode for editing or the like, when an audio signal is required, the conventional method is inconvenient for searching for editing points.

Purpose of the invention The present invention solves the above problems,
When the playback head skips tracks during high-speed playback of a digital audio signal, noise at discontinuous tracks is removed, and when the playback head performs track overlap playback during low-speed playback of digital audio, the noise is removed. The purpose is to prevent duplication and to reproduce a digital audio signal with continuity as audio even when reproducing high-speed and low-speed digital audio signals in reverse.

Structure of the Invention The present invention provides a magnetic recording and reproducing apparatus equipped with a so-called AST mechanism, which is designed to trace on the same track by giving a control signal to the reproducing head when the reproducing head passes over the tape surface. If the playback head skips tracks during high-speed playback, the end of the digital audio signal block before the skip should be faded out, and the end of the digital audio signal block after the skip should be faded in to connect. If the playback head plays the same track repeatedly, it stores only the first block of the continuous digital audio signal in memory and expands the time axis until the next track signal is played to prevent duplication of the playback audio signals. Also, when reproducing a digital audio signal in reverse, including during high-speed and low-speed playback, the digital audio signal can be varied by reversing the reading order sample by sample from the memory in which one field's worth of audio signals is written. It realizes regeneration.

DESCRIPTION OF THE EMBODIMENTS An embodiment of the present invention will be described using as an example a VTR in which an audio digital signal corresponding to one field is time-base compressed and recorded on the same track following a video signal for one field. FIG. 5 is a block diagram of a VTR according to an embodiment of the present invention.
1 is an analog audio signal input terminal, 2 is a low-pass filter, 3 is an A/D converter, 4 is a time axis compression circuit, 5 is a frame configuration circuit, 6 is a modulation circuit,
7 is a recording/reproducing section, 8 is a demodulation circuit, 9 is an error correction circuit, 10 is a time axis expansion circuit, 11 is a fade-in/fade-out circuit, 12 is a D/A converter, 13 is a low-pass filter, and 14 is an analog audio output terminal. , 15 is an AST circuit, and 16 is a video signal input terminal.

The operation will be explained below. During recording, the analog audio signal is input to the low-pass filter 2 to remove frequency components outside the band, and the analog audio signal is input to the A/D converter 3.
convert it into a digital signal. Next, the time axis compression circuit 4 compresses the time axis in units of one field, and then the frame configuration circuit 5 performs an interleaving operation to add a synchronization signal and an error correction and detection code to form a frame. The framed digital audio signal is modulated by a modulation circuit 6, and recorded on a tape by a recording/reproducing section 7 in the recording pattern shown in FIG. On this occasion,
The video signal is also recorded before the digital audio signal, and FIG. 6 shows the relationship between the head and the tape in this recording method in one embodiment of the present invention. 6, 19 is the cylinder, 20 and 20' are the heads, and 2
1 is a recording tape, and 22 and 22' are capstans. The video signal is recorded alternately one field at a time by two heads 20 and 20' separated by 180 degrees on the cylinder in the area shown in Fig. 6, and the digital audio signal is recorded by the two heads 20 and 20' separated by 180° on the cylinder, and the digital audio signal is recorded in the area shown in Fig. 6. Record at the head in the section shown in Figure 6.

Next, regarding playback, in Figure 5, during variable speed playback, the AST circuit 1
Track skip playback, track overlap playback, etc. are performed using the signal No. 3, and the missing or duplicated digital playback signals are demodulated by the demodulation circuit 8.
Next, the error correction circuit 9 performs time axis correction and error correction, and the time axis expansion circuit 9 performs time axis expansion. Further, when track skipping reproduction is performed, the fade-in/fade-out circuit 11 performs the fade-in/fade-out. The signal that has gone through these processes is converted into analog by the D/A converter 12, and then passed through the low-pass filter 12.
is outputted to the analog audio signal output terminal 14 as an analog audio signal.

A detailed view of the portion shown in FIG. 518 is shown in FIG. In FIG. 7, 23 is an input terminal for the audio digital signal reproduced and demodulated from the VTR, 24 is a shift register, 25 and 26 are buffer memories, 2
7 is an error correction circuit; 28 is an output latch; 29 is a switch circuit for switching control and address signals for the memories 25, 26 and the error correction circuit 27; 30 is a write address counter; 31 is a clock input terminal to the write address counter;
32 is an address counter, 33 is a read address up/down counter, 34 is a data bus, 35
is a fade-in/fade-out circuit, and 36 is a fade-in/fade-out circuit.
AST circuit, 37 is a timing circuit, and 38 is an output terminal.

Next, its operation will be explained. During standard playback, a playback digital signal input field by field from the input terminal 23 is serial/parallel converted in sample units by the shift register 24 and output to the data bus 34. The signals on data bus 34 are
One field is alternately written in A25 and memory B26, one field at a time is read out in sample units, the error correction circuit 27 performs error correction, and the corrected digital signal is stored in the same memory in sample units.
Then, at the timing shown in the read cycle of FIG. 8, the signal is expanded and read from the memory, and the output latch 28 performs parallel/serial conversion on a sample-by-sample basis. FIG. 8 is a timing chart showing the timing relationship between the signals reproduced by the head and the write and read cycles of the memory in one embodiment of the present invention, where V ₁ , V ₂ , . . . V _o are video signals, A ₁ , A ₂ , ... A _o are digital audio signals.

In this process, while one memory is writing and error correction, the other memory is decompressing and reading. The reproduced digital signal that has undergone the above process is output to the output terminal 38 without being subjected to fade-in or fade-out.

AST circuit 36 during high speed playback and reverse playback
When the playback head performs track skipping playback under the control of the AST circuit 36, the timing circuit 37 generates the fade-in signal and fade-out signal shown in FIG. Then,
A reproduced digital signal block before a track jump is faded out, and a reproduced digital signal block after a track jump is faded in to prevent a difference in level of the audio signal from occurring before and after the track jump.

FIG. 9 is a time chart showing the timing of fade-in and fade-out in one embodiment of the present invention. In this embodiment, the head reproduction _audio signals _{A 1} , _{A 2 , .} Therefore, the timing of the fade-in and fade-out is at the track jump point, the second and third fields from c in FIG.

AST circuit 36 during low speed playback and reverse low speed playback
When the same track is played back multiple times under the control of Circuit 29 prevents the write address signal from being sent to either memory. Then, when playing back the next track's digital signal, a new digital signal is written to the other memory. When reading from memory, if the playback head traces the same track n times, the clock of the read address up-down counter 33 is set to 1/n and the time axis is extended to prevent the audio of the same track from being played back repeatedly. Make it. The timing of writing and reading from the memory is shown in the timing chart of FIG. In this case, the pitch of the reproduced signal will be slower, but
Audio level difference between overlapping signals,
Ni, ho-he, to, -chi, line, and ru-wo will no longer occur. During reverse playback including high-speed and low-speed playback, in addition to the fade-in/fade-out processing for track skipping playback and the time axis expansion processing for track overlap playback, the memory read address up/down counter 33 is down by the control of the timing circuit 37. Make it a counter. In this way, the reading order can be reversed sample by sample from the memory in which the audio signal was written, and the audio signal can be played back later by reversing the field playback order by reversing the tape feed direction. becomes.

Effects of the Invention The present invention provides a rotary head type helical scan VTR that records a video signal and a digital audio signal on the same track.A signal is generated from the AST circuit built in the VTR, and by controlling the signal, fade-in/fade-out operation and memory address By variable operation of the counter clock, it is possible to play back digital audio signals at high and low speeds in both forward and reverse rotation, eliminating the interference caused by clicking noises, which is highly effective when performing editing work.

[Brief explanation of drawings]

Figure 1 is a pattern diagram showing the recording pattern of video signals and digital audio signals on tape, Figure 2 is a pattern diagram showing trace lines of the playback head during high-speed playback, and Figure 3 is a pattern diagram showing the trace lines of the playback head during low-speed playback. 4 is a diagram showing the audio connection state of a conventional example, FIG. 5 is a block diagram of a VTR circuit in an embodiment of the present invention, and FIG. 6 is a reproduction diagram in an embodiment of the present invention. Figure 7 is a block diagram of the main parts of the same embodiment circuit; Figures 8, 9, and 10 are timing charts for standard playback, high-speed playback, and low-speed playback, respectively. .

Claims (1)

[Claims] Has an auto scan tracking mechanism,
Record and play back video signals and digital audio signals
On VTR devices, during high-speed playback, the auto
Under the control of the scan tracking mechanism, the digital audio signals of the fields before and after interlaced scanning are faded in and played back. During low-speed playback, the auto scan tracking mechanism controls the field to fade in and out the digital audio signals of the fields before and after the interlaced scanning. The signal of one field is written in the memory, read from the memory using a low-speed read clock corresponding to the number of repeated scans, and during reverse playback including high speed and low speed, the signal is read from the memory in units of samples in the reverse order of writing. A variable speed playback method for digital audio signals in a VTR device.