JPH04238164A - Device and method for digital video and audio recording - Google Patents

Abstract

PURPOSE:To switch plural compression modes with simple constitution and to efficiently execute multiple recording of video signals and audio signals with the digital video and audio recording device which records the video signals by compressing the code quantity thereof. CONSTITUTION:The compression ratio of video codes is changed by a data rate switch 21 and simultaneously the number of channels of the audio signals to be recorded is switched by a switch 22 for the number of recording channels. The recording patterns on a magnetic tape do not change if the ratio of the code quantities of the videos and sounds is set constant and, therefore, the dealing with plural modes with the simple constitution is possible. The max. possible recording region of the video signals is assured according to the number of the necessary audio channels, by which the high image quality is efficiently obtd.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a digital video and audio recording method and apparatus for compressing and recording the code amount of a video signal, and in particular to video and audio signals when a plurality of modes with different video code compression ratios are provided. The present invention also relates to a method and apparatus for efficiently multiplexing video signals and audio signals.

0002

[Background Art] Digital magnetic recording devices that compress and record the code amount of video signals are described in IE Transactions on Consumer Electronics, Vol. 34, No. 3 (1988), pp. 597 to 604. Page (IEEE Trans
actions on Consumer Elect
ronics, Vol. 34, No. 3 (1988),
pp 597-604). However, no consideration has been given to efficiently multiplexing and recording video signals and audio signals. In addition, since there is a trade-off between image quality and tape consumption depending on the compression ratio of the video code, it is conceivable to provide multiple modes with different compression ratios, but the above conventional technology did not take this point into consideration. .

0003

[Problems to be Solved by the Invention] An object of the present invention is to solve the problems that have not been taken into account in the above-mentioned prior art, and to switch between a plurality of modes with different video code compression ratios with a simple configuration to convert video and audio signals. The object of this invention is to multiplex record video signals and audio signals, and to efficiently perform multiple recording of video signals and audio signals.

0004

[Means for solving the problem] In order to switch between multiple modes with a simple configuration, the number of channels of the recorded audio signal is changed according to the mode, and the ratio of the code amount of the recorded video signal and the audio signal is kept constant. Try to keep it. Alternatively, the audio code is also compressed depending on the mode, so that the ratio of the code amounts of the video signal and the audio signal to be recorded is kept constant.

In addition, in order to multiplex video signals and audio signals efficiently, it is possible to set multiple types of the number of channels of audio signals to be recorded, and the video code compression ratio is changed according to the set number of channels. To keep the total amount of code recorded on a tape approximately constant.

[0006]

[Operation] By keeping the ratio of the code amount of the video signal and audio signal to be recorded constant, the video code and the audio code are multiplexed into one
Since the timing of code processing when creating recording codes for tracks is constant regardless of the mode, it is possible to support a plurality of modes with a simple configuration.

[0007] Furthermore, by changing the video code compression ratio according to the number of channels of the audio signal to be recorded so that the total amount of codes recorded on the magnetic tape is approximately constant, the maximum recording area can be obtained for the video signal. Since it is possible to estimate the amount of code, it is possible to efficiently obtain high image quality.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a block diagram of a signal processing section according to a first embodiment of the present invention that supports a plurality of recording modes. The signal input from the video signal input terminal 1 is sent to an AD converter 2, a discrete cosine transformer 3, a scalar quantizer 4, a variable length encoder 5,
The signal is supplied to a data multiplexer 8 via a buffer memory 6 and an outer correction encoder 7. Data rate controller 9 receives signals from buffer memory 6 and supplies signals to scalar quantizer 4 . On the other hand, a signal input from the audio signal input terminal 10 is also supplied to the data multiplexer 8 via an AD converter 11, a channel multiplexer 12, and an outer correction encoder 13. The output signal of the synchronization/ID generator 14 is also sent to the data multiplexer 8.
is being supplied to. The output signal of the data multiplexer 8 is supplied to a helical magnetic head 17 via an inner correction encoder 15 and a digital modulator 16. A signal is supplied from the recording mode setter 18 to a servo circuit 19, an operation clock generator 20, a data rate switch 21, and a recording channel number switch 22, and a signal is supplied from the operation clock generator 20 to a code recording processing section 23. A signal is supplied from the rate switch 21 to the data rate controller 9, and from the recording channel number switch 22 to the channel multiplexer 12.

Next, the operation will be explained. Video signal input terminal 1
A luminance signal and two baseband chrominance signals are input, and each is AD-converted to become a video code. The video code is subjected to discrete cosine transform, scalar quantization, and variable length coding to compress the code amount. At this time, the data rate controller 9 controls the scalar quantization table so that the code amount after compression does not exceed a predetermined recording capacity. On the other hand, four channels of audio signals from channel 1 to channel 4 are inputted from the audio signal input terminal 10, and each is AD-converted into audio codes. The four channels of audio codes are time-division multiplexed in a channel multiplexer 12. The compressed video code and audio code are each added with a first-stage error correction code, and then added with a synchronization code/ID code in the data multiplexer 8 and time-division multiplexed. After the multiplexed code is added with a second-stage error correction code, it is modulated by digital modulation into a code suitable for magnetic recording, and is recorded on the magnetic tape through the helical magnetic head 17.

Furthermore, the recording mode switching operation will be explained with reference to FIGS. 2 and 3 as well as FIG. 1.

FIG. 2 shows a recording pattern on a magnetic tape in the first mode according to the embodiment shown in FIG.
represents a recording pattern in the second mode. 24 is a magnetic tape, 25 is one track on the magnetic tape, 26 is a video code recording area, 27 and 28 are audio code recording areas, and the numbers written in the audio code recording area are recorded in these areas. This shows which channel the audio signal belongs to. In the mode shown in Figure 2, 4
The audio signal of the channel is recorded.

Now, when switching to the mode shown in FIG. 3, a control signal is first sent from the recording mode setter 18 to the servo circuit 19, the operation clock generator 20, the data rate switch 21, and the number of recording channels switch 22. . In response to this, the servo circuit 19 halves the cylinder rotational speed and tape running speed. At the same time, the code recording processing section 23
The operating clock frequency will also be halved. As a result, compared to the mode shown in FIG. 2, the recording density on the magnetic tape is the same, but the data rate of the recorded code and the amount of tape consumed are halved. The data rate switch 21 switches the control of the data rate controller 9 so that the code amount after compression becomes half of the mode shown in FIG. On the other hand, the recording channel number switch 22 sets the number of channels multiplexed in the channel multiplexer 12 to two channels, which is half of the mode shown in FIG. Through the above steps, the recording pattern shown in FIG. 3 is realized.

As can be seen by comparing FIG. 2 and FIG. 3, the sizes of the video code recording area and the audio code recording area are constant regardless of the mode, so the code recording processing section 23 changes the frequency of the operating clock. It is only necessary to change the code, and there is no need to change the timing when multiplexing codes. Therefore, according to this embodiment, a plurality of modes can be supported with a simple configuration.

FIG. 4 shows a block diagram of a signal processing section according to a second embodiment of the present invention in which a plurality of types of the number of audio signal recording channels can be set. Video signal input terminal 1, AD converter 2, discrete cosine transformer 3, scalar quantizer 4, variable length encoder 5, buffer memory 6, outer correction encoder 7, data multiplexer 8, data rate controller 9, Audio signal input terminal 10, A
D converter 11, channel multiplexer 12, outer correction encoder 13
, the synchronization/ID generator 14, the inner correction encoder 15, the digital modulator 16, the helical magnetic head 17, the data rate switch 21, and the code recording processing section 23 are the same as those in the embodiment shown in FIG. From the recording channel number setting device 29, a data timing switch 30 and a channel multiplexer 12 are connected.
A signal is supplied to the data rate switch 21 , and a signal is supplied from the data timing switch 30 to the code recording processing section 23 .

Next, the operation will be explained using FIG. 2 and FIG. 5 as well as FIG. 4. Recording channel number setter 29
When 4-channel audio recording is set, the operation is the same as in the first mode of the embodiment shown in FIG. 1, and the recording pattern on the magnetic tape is the same as that shown in FIG. Become. Next, when 2-channel audio recording is set by the recording channel number setting device 29, the audio signals multiplexed in the channel multiplexer 12 are limited to 2 channels, and the data timing switch 30 is used to change the video code, audio code, and synchronization. The timing at which the code and ID code are multiplexed is changed, resulting in a recording pattern as shown in FIG. That is, the recording area for audio codes is halved, and the recording area for video codes increases accordingly. Then, the data rate switch 21 switches the control of the data rate controller 9 so that the amount of compressed video code increases as the recording area increases.

Therefore, according to this embodiment, the recording area for video signals can be secured to the maximum extent according to the number of required audio signal channels, so that high image quality can be efficiently obtained.

The recording pattern on the magnetic tape when two-channel audio recording is set may be as shown in FIG. 6 or 7.

FIG. 8 shows a block diagram of a signal processing section according to a third embodiment of the present invention that supports a plurality of recording modes. Figure 1
An audio data compressor 31 and a sampling rate switch 32 are used instead of the recording channel number switch 22 in the embodiment shown in FIG.
and a quantization bit number switch 33, and the audio data compressor 31 is equipped with an AD converter 11 and a channel multiplexer 12.
The sampling rate switch 32 and the quantization bit number switch 33 are inserted between the recording mode setter 18 and the sampling rate switch 32 and the quantization bit number switch 33 respectively.
A signal is supplied from the audio data compressor 31 to the audio data compressor 31. The other configurations are the same as the embodiment shown in FIG.

Next, the operation will be explained using FIGS. 2 and 9 as well as FIG. 8. In the first mode, the operation is similar to that of the embodiment shown in FIG. 1, and the recorded pattern on the magnetic tape is the same as that shown in FIG. In the second mode as well, recording of the video signal is carried out in the same manner as in the embodiment shown in FIG. The audio signal is compressed to half the code amount of the first mode by switching the sampling rate and the number of quantization bits in the audio data compressor 31. For example, if the first mode had a sampling rate of 48 kilosamples per second and a quantization bit depth of 16 bits, the second mode would have a sampling rate of 48 kilosamples per second and a quantization bit depth of 12 bits.
If it is converted into bits, the amount of code is compressed in half. After this 4
The channel signals are multiplexed, and the recording pattern on the magnetic tape is as shown in FIG. In other words, the data of the code to be recorded
Although the tare rate is half that of the first mode, the recorded pattern on the magnetic tape remains unchanged.

Therefore, according to this embodiment, since the recording pattern on the magnetic tape is constant regardless of the mode, a plurality of modes can be supported with a simple configuration.

[0021]

Effects of the Invention According to the present invention, the sizes of the video code recording area and the audio code recording area can be reduced by changing the number of channels of the audio signal to be recorded depending on the mode or by applying compression to the audio code as well. Since it is constant regardless of the mode, it has the effect of being able to support multiple modes with a simple configuration.

[0022] Also, by securing the maximum recording area for video signals in accordance with the number of channels of the necessary audio signals, it is possible to efficiently obtain high image quality.

[Brief explanation of the drawing]

FIG. 1 is a signal processing block diagram showing a first embodiment of the present invention that supports multiple recording modes.

FIG. 2 is a recording pattern on a magnetic tape according to the first, second and third embodiments of the present invention.

FIG. 3 is a recording pattern on a magnetic tape when the recording mode is switched according to the first embodiment of the present invention.

FIG. 4: A second aspect of the present invention that allows setting the number of recording audio channels.
FIG. 2 is a signal processing block diagram of an embodiment of FIG.

FIG. 5 is a first recording pattern on a magnetic tape when the number of recording audio channels is changed according to the second embodiment of the present invention;
This is an example.

FIG. 6 is also a second example.

FIG. 7 also shows a third example.

FIG. 8 is a signal processing block diagram showing a third embodiment of the present invention that supports multiple recording modes.

FIG. 9 is a recording pattern on a magnetic tape when the recording mode is switched according to a third embodiment of the present invention.

[Explanation of symbols]

3... Discrete cosine transformer, 4... Scalar quantizer, 5... Variable length encoder, 8... Data multiplexer, 9... Data rate controller, 12... Channel multiplexer, 18... Recording mode setter,
21... Data rate switcher, 22... Recording channel number switcher, 29... Recording channel number setter, 30... Data timing switcher, 31... Audio data compressor.

Claims (6)

[Claims] Claim 1: A digital video and audio recording method in which a video signal and an audio signal are digitally encoded, the code amount of the video signal is compressed, and the video signal is recorded on a magnetic tape, in which a plurality of recordings with different compression ratios of the code amount of the video signal are provided. A digital video/audio recording method characterized in that the number of channels of an audio signal to be recorded is changed according to the recording mode, and the ratio of the code amount of the video signal to be recorded and the audio signal to be recorded is maintained constant. 2. A digital video and audio recording method in which a video signal and an audio signal are digitally encoded, and the code amount of the video signal is compressed and recorded on a magnetic tape, in which a plurality of recordings with different compression ratios of the code amount of the video signal are provided. A digital video and audio recording method comprising: a recording mode; and compressing audio codes to be recorded according to the recording mode, so as to maintain a constant code amount ratio of video signals and audio signals to be recorded. 3. A digital video and audio recording method for digitally encoding a video signal and an audio signal, compressing the code amount of the video signal, and recording it on a magnetic tape, in which a plurality of types of the number of channels of the audio signal to be recorded are set, A digital video and audio recording method characterized by changing the compression ratio of the code amount of a video signal according to the set number of channels, and keeping the total code amount recorded on a magnetic tape approximately constant. 4. A digital video and audio recording apparatus constructed by the digital video and audio recording method according to claim 1. 5. A digital video and audio recording apparatus constructed by the digital video and audio recording method according to claim 2. 6. A digital video and audio recording apparatus constructed by the digital video and audio recording method according to claim 3.