JP3552955B2 - Digital signal recording / reproducing device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a digital signal recording / reproducing device for recording / reproducing a video signal, and more particularly to a device for performing post-record editing of an audio signal.
[0002]
[Prior art]
2. Description of the Related Art In a VTR (video tape recorder) for recording and reproducing a video signal, a digital VTR capable of performing recording and reproduction with almost no deterioration in image quality and sound quality has been proposed.
A digital VTR converts a video signal and an audio signal into digital data, adds parity for error correction and auxiliary data indicating various information such as video and audio, and records the data on a magnetic tape. The operation of the VTR is controlled based on the recorded auxiliary data to obtain a reproduced video signal. As one of such digital VTRs, there is a DV standard agreed in 1994 by the HD Digital VCR Conference.
The outline of this standard is described below.
[0003]
FIG. 4 shows a recording tape pattern on a magnetic tape according to the DV standard. In the 525/60 system represented by the NTSC system, one frame is composed of ten tracks. On one track, four ITI sectors, an audio sector, a video sector, and a subcode sector are recorded, each separated by a gap.
[0004]
FIG. 5 shows the configuration of the audio sector.
The audio sector is composed of nine sync blocks containing audio data and the like and five sync blocks containing outer parity, each of which has a sync area of 2 bytes and an ID code of 3 bytes. In the former 9-byte sync block, in addition to audio data obtained by digitizing an audio signal, AAUX indicating audio auxiliary data, outer parity, and inner parity used for error correction are stored. At the time of reproduction, audio processing is controlled based on information on audio signals stored in the AAUX.
[0005]
FIG. 6 shows the structure of 6-byte data called a source pack in AAUX. PC0 is called a pack header and has a value of 50 (H), indicating that this pack is a source pack. AF SIZE (audio frame size) in the PC 1 is data indicating the number of audio samples in one frame. The CHN and AUDIO MODE in the PC 2 and the SMP and KU in the PC 4 are data indicating information such as an audio sampling frequency and the number of channels.
In the DV standard, a DV terminal conforming to the communication protocol IEEE1394 is prepared as an optional standard as a digital interface capable of high-quality editing dubbing without deterioration of image quality and sound quality. It is actually installed in VTR devices conforming to the DV standard issued by various companies, and has become a mainstream digital interface in consumer digital VTRs and peripheral devices.
[0006]
[Problems to be solved by the invention]
As in the case of the analog VTR, in the digital VTR as described above, the post-record editing of the audio signal on the already recorded magnetic tape is performed. At that time, when performing post-record editing on a part of the recorded audio data, it is necessary to control the frame size of the audio signal to be post-recorded based on the frame size of the audio data already recorded on the magnetic tape. is there.
When dubbing an analog audio signal, the audio signal is digitized by an A / D converter using a clock that is PLL-controlled based on the frame size of the recorded audio data, thereby controlling the frame size. To enable post-record editing.
[0007]
On the other hand, in the case of audio data input from the digital interface as described above, since the digital data has already been converted to digital data and frame size control cannot be performed, there is a difference between the recorded audio data and the audio data to be dubbed. There is no guarantee that the frame size is managed. Particularly, in a consumer digital VTR, an unlock mode in which clock synchronization between a video signal and an audio signal is not guaranteed is often used, and there is a high possibility that a frame size between audio data in post-record editing is different. Become.
Therefore, in such a case, the digital post-record editing itself is abandoned, or the input digital data is returned to an analog signal by the D / A converter once, and the A / A is again used by using the PLL-controlled clock. This is realized by adopting a method of performing digital conversion by D conversion and controlling the frame size. However, in the above-described method, signal degradation due to analog signal processing and increase and complexity of analog signal processing circuits such as A / D / D / A converters and PLL circuits are unavoidable.
[0008]
SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problems. It is possible to perform digital data reproduction on audio data input from a digital interface and perform post-record editing with the digital data as it is. An object of the present invention is to provide a digital recording / reproducing apparatus.
[0009]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided a digital recording / reproducing apparatus capable of recording and reproducing a plurality of audio signals as digital signals on a recording medium, the apparatus being provided with a function of post-record editing a part of the audio data. A frame size information extracting unit for audio data recorded on a recording medium, a frame size information extracting unit for audio data to be post-record edited, and a post-record editing based on both information extracted from the both frame size information extracting units. Control means for controlling the frame size of the audio data recorded by the computer, and processing means for processing information on the frame size of the audio data recorded by post-record editing , wherein the control means Using the audio error code specified in It is obtained to perform the frame size control.
[0012]
With the above configuration, the present invention performs post-record editing of digital audio data by controlling the frame size of the audio data to be post-recorded, so that the audio signal waveform at the time of reproduction has discontinuities without an increase in analog peripheral circuits. In addition to preventing the generation of noise due to the generation, it is possible to perform digital post-record editing without aural deterioration in sound quality.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the digital signal recording / reproducing apparatus of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing one embodiment of the digital signal recording / reproducing apparatus of the present invention.
In the figure, 1 is a reproduction signal processing unit, 16 is a reproduction AAUX data extraction unit, 17 is an AF size control unit, 18 is a recording AAUX data processing unit, 19 is a recording AAUX data extraction unit, and 20 is a recording signal processing unit. .
The operation will be described below.
[0014]
At the time of recording, the video signal and the audio signal input from the analog input terminals 30 and 32 are converted into digital data by A / D converters 21 and 27, and the video signal recording processing unit 28 and the audio signal recording processing unit 22 respectively. The digital processing such as encoding and shuffling is performed. This data is added with auxiliary data (AAUX data) from the recording AAUX data processing unit 18, an error correction parity is added in the error correction unit 23, and the channel coding unit 24 performs digital modulation for adapting to the digital recording / reproducing system. The recording is performed on a magnetic tape (not shown) by the recording head 29 through the recording amplifier 25.
[0015]
When the data to be recorded is digital input data input from the digital input terminal 31, the digital interface 26 performs the interface processing with the outside instead of the digital data conversion processing by the A / D converter. The same is true.
[0016]
At the time of reproduction, digital data recorded on a magnetic tape (not shown) is picked up by a reproduction head 12, amplified by a reproduction amplifier 11, equalized in waveform by an equalizer 10, and controlled in a stable manner by a PLL circuit 9. After being switched to the clock that has been set, the signal is demodulated by the channel coding unit 8. The demodulated digital data is subjected to error correction processing using the parity added at the time of recording, and the video signal reproduction processing section 3 and the audio signal reproduction processing section 6 perform processing such as deshuffling and decoding. The signals are converted into analog signals by the / A converters 2 and 5, and are output from the output terminals 13 and 15 as reproduced video signals and reproduced audio signals, respectively.
[0017]
At the time of post-record editing, the audio data recorded on the magnetic tape is processed up to the audio signal reproduction processing unit 6 as in the case of reproduction. The reproduced AAUX data is extracted from the data by the reproduced AAUX data extraction unit 16 and sent to the AF size control unit 17 and the recording AAUX data processing unit 18. On the other hand, digital audio data input via the digital interface 26 for post-record editing is sent to the audio signal recording processing unit 22 and the recorded AAUX data extraction unit 19. The recorded AAUX data extraction unit 19 extracts the data when AAUX is present in the digital data, and extracts the data containing the equivalent information when there is no AAUX itself. It is sent to the data processing unit 18. The AF size control unit 17 controls the frame size of audio data actually recorded on the magnetic tape by post-record editing based on the playback frame size and the recording frame size included in the playback AAUX data and the recording AAUX data, respectively. A control signal is generated and sent to the audio signal recording processing unit 22. The recording AAUX data processing unit 18 refers to both the reproduction AAUX data from the reproduction AAUX data extraction unit 16 and the recording AAUX data from the recording AAUX data extraction unit 19, and based on the information, actually performs the post-record editing to make the magnetic tape. Changes the content of the AAUX data recorded in. The contents of the change include information on the frame size controlled based on the frame size information inherent in the reproduced AAUX data. Then, the audio data from the audio signal recording processing unit 22 and the AAUX data from the recording AAUX data processing unit 18 are added with parity for error correction in the error correction unit 23, and are transmitted by the recording head 29 through the channel coding unit 24. Are recorded on a magnetic tape (not shown).
[0018]
FIG. 2 is a flowchart showing one embodiment of a processing method of audio frame size control according to the present invention.
Next, an embodiment of a frame size control method will be described with reference to this flowchart.
First, a comparison is made between the recording frame size (m) and the reproduction frame size (n) (step S1). If (m> n), p (≧ mn) sample data having a frame size difference (mn) or more is deleted from the recorded audio data (step S2). Next, q (= p- (mn)) sample data is replaced with an audio error code (step S3).
[0019]
The audio error code is a code defined by the DV standard, and is a code that defines that the sample data is invalid data. It is used when error correction cannot be performed due to a communication path error or when it is determined that the audio data itself is not reliable for some other reason. Incidentally, the audio error code defined by the DV standard is 8000 (H) for 16-bit audio encoded data and 800 (H) for 12-bit audio encoded data.
[0020]
Normally, when this audio error code is detected when playing an audio signal, data processing is performed based on the status of the data before and after the corresponding sample data, and it is determined that the reliability of the sample data before and after is high. If so, data interpolation processing is performed, and if it is determined that the reliability is low, mute processing or the like is performed.
[0021]
On the other hand, in the case of (m <n), the number of audio data samples is insufficient, so that the value of r (= nm) audio error codes of the difference (nm) of the frame size is included in the recorded audio data. Is added to the frame data (step S4).
[0022]
In the case of (m = n), it is not necessary to perform data replacement processing.
When a tape on which the above-described frame size control processing has been performed is reproduced, it can be expected that discontinuous points of a waveform originally caused by a difference in frame size will be at a level that cannot be detected as noise by human hearing due to interpolation processing.
[0023]
FIG. 3 is a diagram for explaining an embodiment of a processing method of audio frame size control according to the present invention.
Next, an embodiment of the data replacement processing based on the frame size control will be described with reference to FIG.
In the NTSC system, when the audio encode mode is 32 KHz, the number of audio sample data per one frame (frame size) takes a value between 1053 and 1080 samples. Description will be made using a case where the frame size of audio data recorded on the magnetic tape is 1067 samples (FIG. 3A).
[0024]
As an example in the case of (m > n), consider a case where the frame size of audio data recorded by post-record editing is 1071 samples (FIG. 3B). That is, there is an excess of four samples. In this case, as illustrated in FIG. 3C, four samples from 1068 to 1071 samples are deleted, and data of 1067 samples is replaced with an audio error code. This is because if the data of 1067 samples is directly connected to the head data (one sample data) of the next frame data, noise is generated due to the discontinuity of the waveform, and this noise generation is prevented. It is.
[0025]
FIG. 3D shows an example of another processing method. In this example, four samples 1052, 1059, 1065, and 1071 are deleted, and four samples 1052, 1058, 1064, and 1070 are replaced with audio error codes. Incidentally, since the number of continuous audio error codes is smaller in the processing method of FIG. 3D than in the processing method of FIG. 3C, more advanced interpolation processing can be expected during reproduction.
[0026]
Conversely, as an example in the case of (m <n), consider a case where the frame size of audio data recorded by post-record editing is 1063 samples (FIG. 3E). In other words, there is an understate of four samples. In this case, as illustrated in FIG. 3F, virtual samples corresponding to four samples 1064 to 1067 are assumed, and the value of the sample data is used as an audio error code.
FIG. 3G shows an example of another processing method. In this example, four samples having an audio error code as a value are added after 1051 to 1052, between 1055 to 1056, between 1059 to 1060, and after 1063.
[0027]
In the example used in the above description, sample data to be added, replaced, or deleted is relatively close data, and samples to be processed are selected at equal intervals. However, the present invention is not limited to this, and various combinations of processing methods, such as selecting samples at unequal intervals, may be used, as well as dispersing them in frames.
In the above embodiment, the description has been made using the audio error code in the DV standard. However, when a similar code is prepared in another standard, frame control using the same code replacement as described above may be performed. It is possible.
[0028]
【The invention's effect】
As described above, according to the present invention, in a recording / reproducing apparatus for digitally recording a video signal, when post-editing digital audio data, by controlling the frame size of the audio data to be post-recorded, the audio signal at the time of reproduction is reproduced. It is possible to prevent the generation of noise due to the occurrence of discontinuity in the waveform, and to perform digital post-record editing without aural deterioration in sound quality.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an embodiment of a digital signal recording / reproducing apparatus according to the present invention.
FIG. 2 is a flowchart showing one embodiment of a processing method of audio frame size control according to the present invention.
FIG. 3 is a diagram illustrating an embodiment of a processing method of audio frame size control according to the present invention.
FIG. 4 is a diagram illustrating a tape track pattern of a DV standard digital VTR.
FIG. 5 is a diagram illustrating the configuration of an audio sector of a DV standard digital VTR.
FIG. 6 is a diagram illustrating the configuration of an AAUX (source pack) of a DV standard digital VTR.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Reproduction signal processing part, 2,5 ... D / A converter, 3 ... Video signal reproduction processing part, 4,26 ... Digital interface, 6 ... Audio signal reproduction processing part, 7,23 ... Error correction part, 8, Reference numeral 24: channel coding unit, 9: PLL circuit, 10: equalizer, 11: reproduction amplifier, 12: reproduction head, 16: reproduction AAUX data extraction unit, 17: AF size control unit, 18: recording AAUX data processing unit, 19 ... Recording AAUX data extraction unit, 20: recording signal processing unit, 21, 27: A / D converter, 22: audio signal recording processing unit, 25: recording amplifier, 28: video signal recording processing unit, 29: recording head.

Claims (1)

A digital signal recording / reproducing apparatus capable of recording / reproducing a plurality of audio signals as digital signals on a recording medium, the apparatus being provided with a function of post-record editing of a part of the audio data, which is recorded on the recording medium. Audio data frame size information extracting means, audio data frame size information extracting means for post-record editing, and audio data frames recorded by post-record editing based on both information extracted from the both frame size information extracting means. Control means for controlling the size; and processing means for processing information on the frame size of the audio data recorded by post-record editing , wherein the control means controls an audio error code defined by the DV standard for the audio data. Frame size control using Digital signal recording and reproducing apparatus, which comprises carrying out.

Images