JP3702505B2 - Digital information signal reproducing apparatus and digital information signal reproducing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for reproducing a digital information signal such as a digital video signal or a digital audio signal recorded on a magnetic tape. More specifically, the present invention relates to a reproduction output when detecting that no digital information signal is recorded. It relates to technology for muting.
[0002]
[Prior art]
In a magnetic recording / playback device that records and plays back video and audio signals on a magnetic tape, when playing back the unrecorded part, if the playback output is supplied to the monitor and speakers as they are, noise will appear on the entire monitor screen. In addition, annoying noise is generated from the speaker.
[0003]
Therefore, an envelope detection circuit for the reproduction RF output of the magnetic head is provided to detect the presence / absence of recording from the output level and to mute the video signal reproduction output and the audio signal reproduction output when reproducing the non-recording portion. It is done.
[0004]
[Problems to be solved by the invention]
However, the conventional mute control means requires a dedicated envelope detection circuit for detecting a non-recorded portion separately from the circuit used for normal recording / reproduction, which increases the circuit scale and increases the cost. There was a problem of doing.
[0005]
The present invention has been made in view of such problems, and provides a digital information signal reproducing apparatus and a digital information signal reproducing apparatus that do not require a dedicated detection circuit for detecting a non-recording portion. is there.
[0006]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, a digital information signal reproducing apparatus according to the present invention reproduces control data from each track of the magnetic tape and first means for reproducing a digital information signal from each track of the magnetic tape. The second means and the control data reproduced by the second means are received at the communication timing of the predetermined rotation cycle of the rotating drum, and it is determined whether mute is enabled according to the operation mode of the received control data. When it is determined that the mute is enabled, it is determined whether or not the track ID in the control data is an error. If it is determined that the error is detected, the error counter value is incremented, and the control data the track ID is specified number of times or more errors occur in succession, and peeling when the value of the error counter exceeds a predetermined value Third means determines that part, and a fourth means for muting the output of the first means under the control of said third means, said third means is a determination of the mute enable, If it is determined that the mute is not enabled, the error counter value is cleared .
[0007]
In order to solve the above-mentioned problem, the digital information signal reproducing method according to the present invention rotates the control data when reproducing a magnetic tape in which a digital information signal and control data are recorded on each track. It is received at a communication timing of a predetermined rotation cycle of the drum, it is determined whether or not mute is enabled according to the operation mode of the received control data, and when it is determined that mute is enabled, the track ID in the control data is It is determined whether there is an error. If it is determined that there is an error, the value of the error counter is incremented, and an error occurs continuously for a specified number of times in the track ID in the control data. There is determined that no recording portion when exceeding the predetermined value, mutes the playback output of the digital information signal, the Myu In determining bets enabled, if it is determined that it is not a mute enable is characterized in that for clearing the value of the error counter.
[0008]
The digital information signal reproducing apparatus and digital information signal reproducing method according to the present invention means an apparatus and method for reproducing at least a digital information signal. That is, an apparatus and method for recording / reproducing digital information signals are included.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 shows a track pattern on a magnetic tape reproduced by a magnetic recording / reproducing apparatus to which the present invention is applied. In this figure, the left end of the track is the head entrance (entry) side, and the right end is the head exit (separation) side. From the left end of the track, an ITI area, an audio data recording area, a video data recording area, and a subcode data recording area are provided. In the case of an NTSC television signal, one frame is divided into 10 tracks.
[0010]
Data is not recorded in the overwrite margin provided at the right end of the track and the IBG (interblock gap) provided between the data areas. In the amble areas (run-up and guard areas; here, the audio data recording area and the video data recording area are shown) added to both ends of the data recording area, for example, a frequency equal to the bit frequency of the data Are recorded and used to lock the PLL circuit for bit clock extraction during reproduction. The overwrite margin provided at the right end of the track is for dealing with jitter.
[0011]
The video data and audio data in FIG. 1 have a sync block structure with a unit of 90 bytes, and each block has an ID of 3 bytes. The audio and video pre-sync and post-sync have a sync block structure in units of 50 bits, and each sync block has a 3-byte ID. The contents of these IDs are the track ID in the frame, the continuous sync book number from the audio presync to the video postsync in the track, and the like.
[0012]
Although specific numerical values are not shown in FIG. 1, a sync block number and a pilot frame indicating a servo system reference are recorded in the ITI area. In the subcode area, an FR flag indicating whether the track is the first half or the second half in one frame, a search ID, and the like are recorded.
[0013]
Hereinafter, in this specification, control data used for controlling various operations of the apparatus, which is data other than video data and audio data, will be referred to as system data.
[0014]
FIG. 2 is a block diagram showing a configuration of a main part of a magnetic reproducing apparatus to which the present invention is applied. This magnetic reproducing apparatus outputs magnetic heads H0 and H1 in accordance with magnetic heads H0 and H1 for reproducing digital data recorded on the magnetic tape 1 and a head switching pulse (SWP) output from a microcomputer 13 described later. Are alternately switched to provide a time series switch SW, and an RF reproduction amplifier 2 that amplifies the output of the switch SW. The magnetic heads H0 and H1 are provided at positions on the outer periphery of a rotating drum (not shown) opposed to each other by 180 degrees, and have different azimuth angles. Then, the digital data on the magnetic tape 1 are reproduced alternately by the magnetic heads H0 and H1.
[0015]
2 further includes an equalizer 3 that performs waveform equalization and level adjustment on the output of the RF reproduction amplifier 2, a PLL circuit 4 that generates a clock signal CLK from the output of the equalizer 3, and this An A / D converter 5 that digitizes the output of the equalizer 3 at the timing of the clock signal CLK; a channel decoder and ECC circuit 6 that performs demodulation and error correction processing of data output from the A / D converter 5; An audio decoding circuit 7 that deinterleaves the audio data separated in the channel decoder and ECC circuit 6 and a process such as data compression decoding on the video data separated in the channel decoder and ECC circuit 6 Output from the video decoding circuit 8 and a microcomputer 13 described later. An audio mute circuit 9 for muting the output of the audio decode circuit 7 according to the mute control signal, a video omute circuit 10 for muting the output of the video decode circuit 8 according to the mute control signal, and an output of the audio mute circuit 9 The system data separated by the D / A conversion circuit 11 for analogizing, the D / A conversion circuit 12 for analogizing the output of the video mute circuit 10, and the channel decoder / ECC circuit 6 have been subjected to errors for a predetermined number of times. A microcomputer (hereinafter referred to as a microcomputer) 13 for generating a mute control signal is sometimes provided.
[0016]
Since the present invention relates to the processing of reproduced audio data and reproduced video data, only the circuits related to the processing of audio data and video data are shown after the channel decoder and ECC circuit 6.
[0017]
Next, the operation of the magnetic reproducing apparatus shown in FIG. 1 will be described.
The RF signal reproduced alternately from the magnetic tape 1 by the magnetic heads H0, H1 passes through the head changeover switch SW, is amplified by the reproduction RF amplifier 2, and then is input to the equalizer 3. The equalizer 3 equalizes these RF signals so that they can be processed in the next stage and applies AGC to make the level constant.
[0018]
The output of the equalizer 3 is sent to the PLL circuit 4 and the A / D conversion circuit 5. The A / D conversion circuit 5 digitizes the output of the equalizer 4 and sends it to the channel decoder and ECC circuit 6. This digitization is performed at the timing of the clock signal CLK generated by the PLL circuit 4.
[0019]
The channel decoder and ECC circuit 6 records and demodulates the input data and performs error correction processing. Then, the audio data is separated and sent to the audio decoding circuit 7 and the video data is separated and sent to the video decoding circuit 8. The channel decoder and ECC circuit 6 further separates the system data and supplies it to the microcomputer 13. When the system data has an error and cannot be corrected, an error flag indicating that the system data is in error is set and sent.
[0020]
FIG. 3 shows a communication timing at which the channel decoder and ECC circuit 6 sends system data to the microcomputer 13. As shown in this figure, transmission of system data is performed in one rotation cycle of the rotating drum.
[0021]
In this embodiment, the microcomputer 13 detects that there is an error in the intra-frame track ID in the video data, and determines that there is no recording portion when it has continued for a prescribed number of times n times or more, for example 50 times or more. I do. The processing of the microcomputer 13 in this case is shown in FIG.
[0022]
First, after fetching the system data sent from the channel decoder and ECC circuit 6, it is determined in step S1 whether mute is enabled. Whether the mute is enabled is determined by looking at the operation mode of the magnetic reproducing apparatus. Although it is enabled in the playback mode, it is not enabled in the stop mode, for example. If not enabled, the error counter is set to 0, the mute flag is set to 0, and the process ends (steps S2 and S3).
[0023]
When enabled, it is determined whether or not the intra-frame track ID in the system data, here video data, is an error (step S4). If the result of determination is an error, the value of the error counter is incremented by 1 (step S5). If the result of determination is that there is no error, the error counter is set to 0, the mute flag is set to 0, and the process ends (steps S2 and S3).
[0024]
After the error counter is incremented by 1 in step S5, it is determined whether or not the value of the error counter exceeds n. If it exceeds n, the mute flag is set to 1 (steps S6 and S7). When the mute flag becomes 1, a mute control signal is sent to the audio mute circuit 11 and the video mute circuit 12.
[0025]
The audio mute circuit 9 and the video mute circuit 10 mute the digital outputs of the audio decode circuit 7 and the video decode circuit 8, respectively, according to the mute control signal. The digital signals that have undergone the mute processing are converted into analog signals by the D / A conversion circuits 11 and 12, respectively.
[0026]
In the above embodiment, muting is performed by looking at the error of the track ID in the frame in the video data. However, muting may be performed by looking at the error of other system data. In the embodiment, the digital signal is muted, but the analog signal after D / A conversion may be muted.
[0027]
【The invention's effect】
As described above in detail, according to the present invention, when the control data recorded on the magnetic tape continuously becomes an error, it is determined that there is no recording portion, and mute is performed. Therefore, it is not necessary to provide a dedicated circuit for detecting this.
[Brief description of the drawings]
FIG. 1 is a diagram showing a track pattern on a magnetic tape reproduced by a magnetic recording / reproducing apparatus to which the present invention is applied.
FIG. 2 is a block diagram showing a configuration of a main part of a magnetic reproducing apparatus to which the present invention is applied.
FIG. 3 is a diagram illustrating a timing at which a microcomputer receives system data.
FIG. 4 is a flowchart showing processing of a microcomputer.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Magnetic tape, 6 ... Channel decoder and ECC circuit, 9 ... Audio meet circuit, 10 ... Video mute circuit, 13 ... Microcomputer, H0, H1 ... Magnetic head

Claims (3)

First means for reproducing a digital information signal from each track of the magnetic tape;
Second means for reproducing control data from each track of the magnetic tape;
When the control data reproduced by the second means is received at the communication timing of the predetermined rotation cycle of the rotating drum, it is determined whether or not mute is enabled according to the operation mode of the received control data. If it is determined, it is determined whether or not the track ID in the control data is an error. If it is determined that there is an error, the value of the error counter is incremented, and the track ID in the control data is incremented by a specified number of times. A third means for determining a non-recording portion when errors occur continuously and the value of the error counter exceeds a predetermined value ;
And a fourth means for muting the output of the first means under the control of the third means,
3. The digital information signal reproducing apparatus according to claim 3, wherein the third means clears the value of the error counter when it is determined that the mute is not enabled when the mute is enabled .   The digital information signal reproducing apparatus according to claim 1, wherein the digital information signal is a digital video signal and a digital audio signal time-divided in each track. When reproducing a magnetic tape in which a digital information signal and control data are recorded on each track, the control data is received at a communication timing of a predetermined rotation cycle of the rotating drum, and the operation mode of the received control data Whether or not the mute is enabled. If it is determined that the mute is enabled, it is determined whether or not the track ID in the control data is an error. When the error continuously occurs in the track ID in the control data for a predetermined number of times and the error counter value exceeds a predetermined value, it is determined that there is no recording portion, and the digital information signal is reproduced. Mute the output ,
A digital information signal reproduction method characterized by clearing the value of the error counter when the mute enable is determined not to be mute enabled .

Images