JP3375851B2 - Image recording device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image recording apparatus for converting a moving image signal into a compressed digital signal and recording the compressed digital signal on a recording medium. The present invention relates to an image recording device capable of changing the bit rate according to the situation.

[0002]

2. Description of the Related Art An image recording apparatus that digitizes a moving image signal, encodes it, and records it on a recording medium such as a magneto-optical disk, for example, MPE as a compression system.
In a device adopting G (Moving Picture Experts Group), methods such as prediction with motion compensation, orthogonal transform, and quantization are used.

When a moving picture signal is compressed and coded by these methods, a great difference occurs in the code amount after compression depending on the complexity of the moving picture signal and the type of the moving picture signal. Also,
Since the capacity of the buffer memory of the decoder for reproducing this compressed moving image signal is finite, the encoder must perform compression so that this memory does not overflow or underflow.

In the above-described coding system such as MPEG, more bits than the average are assigned to a moving picture signal having a high degree of difficulty for coding, and a moving picture signal having a low degree of difficulty is assigned a bit higher than the average. Try to allocate fewer bits,
There is a system called a variable bit rate coding system. Such a variable bit rate coding system is disclosed, for example, in "Technical Report of IEICE MR96-81 (1996-12)". As a result, the overall image quality of the video is improved within the limited code amount (bit amount).

FIG. 4 is a block diagram showing a configuration of an image / sound recording / reproducing apparatus including a conventional image recording apparatus. In this image / sound recording / reproducing apparatus, when an analog moving image / sound signal to be recorded is input, it is divided into an analog moving image signal and an analog audio signal, and an A / D converter 51 for an image signal and an audio signal, respectively. For A / D
It is converted into a digital moving image signal and a digital audio signal by the converter 52, input to the image compression / expansion circuit 53 and the audio compression / expansion circuit 54, and compressed.

The output bit rate (compression rate of the moving image signal) Vp in this image compression / expansion circuit is a variable rate, and is determined by the rate control circuit 65 according to the degree of difficulty of the input digital moving image signal. The bit rate Vp will be described later. The compressed digital moving image signal and the digital audio signal are multiplexed by the AV demultiplexing circuit 55 into a digital moving image audio signal, which is input to the signal processing circuit 56. The output bit rate of the digital moving image audio signal from the AV demultiplexing circuit 55 to the signal processing circuit 56 is Vd.

The signal processing circuit 56 includes data necessary for recording a digital moving image / sound signal on a recording medium.
For example, data such as at which address on the recording medium is recorded is added to the digital moving image audio signal and output to the driver circuit 57. In addition, the signal processing circuit 56
The buffer memory 66 is held.

The driver circuit 57 includes an amplifier 67,
The digital moving image audio signal received from the signal processing circuit 56 is processed so that it can be recorded in the recording medium 62, and is recorded in the recording medium 62 at the recording rate Vr. This recording rate V
r is a fixed rate determined by the characteristics of the image / audio recording / reproducing apparatus and the recording medium 62. Further, the servo circuit 59 controls the motor driver 60 to drive the motor 61 to rotate the recording medium at a constant speed.

The system microcomputer 58 includes the image compression / expansion circuit 53, the audio compression / expansion circuit 54, the AV demultiplexing circuit 55, the signal processing circuit 56 and the servo circuit 59.
It is a central part of the image / audio recording / reproducing apparatus for controlling.

The compression rate in this video / audio recording / reproducing apparatus will be described. Hereinafter, for simplicity, it is assumed that the bit rate Va of the compressed digital audio signal output from the audio compression / expansion circuit 54 to the AV demultiplexing circuit 55 is a fixed rate.

FIG. 5 is a graph showing an example of the time variation of Vd in the image / audio recording / reproducing apparatus. In this device, since the bit rate Va of the audio signal is fixed, this Vd depends on the compression bit rate Vp of the digital moving image signal determined by the rate control circuit 65. Therefore, the bit rate Vp is assigned according to the degree of difficulty of the moving image signal so as to improve the overall image quality of the digital moving image audio signal, and the level of Vp causes the level of Vd as shown in FIG. It is determined. That is, the rate control circuit 65 assigns Vp so that Vd is higher than the average bit rate Vm for a digital video signal having a high difficulty level, and assigns Vp so that Vd is higher than the average bit rate Vm. Vp is assigned so that Vd is lower than Vm.

[0012]

However, in order to record the digital moving image audio signal in the recording medium 62,
The transfer rate Vd cannot be a bit rate higher than the recording rate Vr on the recording medium 62. Therefore, the rate control circuit 65 needs to control the compression bit rate Vp of the digital moving image signal so that this Vd does not exceed Vr. Therefore, since Vd is regulated to this Vr, Vp that Vd exceeds Vr cannot be assigned even to a digital video signal having a very high degree of difficulty. Therefore, the recording rate V to this recording medium is
There is a problem that the improvement of the overall image quality cannot be expected without being restricted by r.

[0013]

In order to achieve the above object, an image recording apparatus of the present invention is an image recording apparatus for compressing a moving image signal and recording the compressed moving image signal on a recording medium. A compression means for compressing a signal, a rate determination means for determining the difficulty level of the moving image signal, and a compression rate determined by the compression means according to the difficulty level, a storage means, and a compressed moving image. Recording means for recording the signal on a recording medium; first signal processing means for storing the compressed moving image signal in the storage means;
Second signal processing means for outputting the moving image signal stored in the storage means to the recording means at a constant rate ;
When the detection means for detecting the free space of the storage means and the moving image signal are input and the compression rate of the moving image signal is determined by the rate determining means, the compression means is controlled to perform the compression. Compress the video signal at a rate,
The first signal processing means is controlled to store the compressed moving image signal, and the second signal processing means is controlled to keep the compressed moving image signal stored in the storage means constant. and control means for outputting to said recording means at a rate, further, the control means, the detection means
To detect the free space of the storage means,
Based on the capacity, the rate determining means is provided with the compression means.
It is characterized by giving the upper limit of the compression rate .

According to the above arrangement, when a moving image signal is input, the rate determining means compresses a moving image signal having a high degree of difficulty at a high bit rate to obtain a moving image signal having a low degree of difficulty. The compression rate is determined according to the degree of difficulty of the moving image signal, such as compression at a low bit rate. The difficulty level of the moving image signal is the difficulty level of compression depending on the complexity and type of the moving image signal.
After that, the control unit controls the compression unit to compress the moving image signal at this compression rate. After that, the control means controls the first signal processing circuit to store the compressed moving image signal in the storage means such as a cache memory or a magnetic recording medium. Further, the control means is
The second signal processing circuit is controlled so that the compressed moving image signal stored in the storage means is output to the recording means such as a driver circuit at a constant bit rate. Then, the recording means records at the bit rate on a recording medium such as a magneto-optical disk.

As described above, since the compressed moving image signal is temporarily stored in the storage means and then recorded on the recording medium at a constant bit rate, the compression bit rate by the compression means is recorded on the recording medium. Can be momentarily larger than. As a result, a high compression rate can be assigned without being limited by the recording rate for compressing a moving image signal with a high degree of difficulty such as a scene change or a fade portion. Therefore, it is possible to improve the overall image quality of the recorded moving image signal.

[0016] Moreover, a detection means for detecting the free capacity of said storage means, said control means controls said detection means to detect the free capacity of said storage means, said on the basis of the-out capacity the air An upper limit of the compression rate by the compression means is given to the rate determination means .

That is, the control means obtains the free capacity of the storage means by the detection means. For example, when this free capacity is large, a very high compression rate upper limit is set in the rate detection means, and when the free capacity is low. Is set to the rate detection means with a not too high upper limit.

Thus, for example, even when moving picture signals having a high degree of difficulty are continuously input, the moving picture signals compressed at a high bit rate are not continuously stored in the storage means. Therefore, no trouble such as interruption or stop of the recording operation due to the overflow of the storage means is caused, so that the compression / recording can be reliably performed regardless of what moving image signal is input.

Furthermore, the upper limit of this compression rate is
By setting the output rate from the second signal means to the recording means or more, the capacity of the storage means can be utilized to the maximum extent, so that the overall image quality of the moving image signal to be recorded is surely ensured. Can be improved.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION As an embodiment of the present invention, an image / sound recording / reproducing apparatus will be cited and will be described below with reference to FIGS. 1 to 3. FIG. 1 is a block diagram showing a configuration of an image / audio recording / reproducing apparatus (hereinafter, this apparatus) according to the present embodiment. As shown in this figure, the present apparatus includes an A / D converter 11 for image signals, an A / D converter 12 for audio signals, and an image compression / expansion circuit (compression means).
13, an audio compression / decompression circuit 14, an AV demultiplexing circuit 15, a signal processing circuit (first and second signal processing means) 16, a memory (storage means) 17, and a system microcomputer (control means) 18. , Driver circuit (recording means) 1
9, a servo circuit 20, a motor driver 21 for driving the motor, and a motor 2 for driving the recording medium.
2, a recording medium 23 such as a magneto-optical disk, an image signal D / A converter 24, an audio signal D / A converter 25, and a rate control circuit (rate determining means) 26.
And a memory capacity detection circuit (detection means) 27.

An analog moving picture audio signal to be recorded is separately input to the apparatus from an analog moving picture signal and an analog audio signal from a moving picture sound signal source (not shown) such as a television tuner. The image signal A / D converter 11 is for converting an analog moving image signal input to the present apparatus from an analog signal to a digital signal to obtain a digital moving image signal. Similarly, the audio signal A / D converter 12 is for converting an analog audio signal from an analog signal to a digital signal to obtain a digital audio signal.

At the time of recording, the image compression / expansion circuit 13 converts the digital moving image signal converted by the image signal A / D converter 11 into MPEG2 (Moving Picture Experer).
ts Group Phase 2) method, variable bit rate Vp
It is for compressing and encoding with. Further, the image compression / expansion circuit 13 is for expanding the compressed digital moving image signal during reproduction. The rate control circuit 26 is for determining the bit rate Vp.

At the time of recording, the audio compression / expansion circuit 14 converts the digital audio signal converted by the audio signal A / D converter 12 into a fixed bit rate V.
It is for compression by a and encoding. The audio compression / expansion circuit 14 is for expanding the compressed digital audio signal during reproduction.

At the time of recording, the AV demultiplexing circuit 15 multiplexes the digital moving image signal and the digital moving image signal compressed and encoded by the image compressing / decompressing circuit 13 and the audio compressing / decompressing circuit 14 into a digital moving image / sound signal. It is for doing. Further, the AV demultiplexing circuit 15 is for separating the digital moving image audio signal into a digital moving image signal and a digital audio signal during reproduction.

The memory 17 is a memory controlled by the signal processing circuit 16. The signal processing circuit 16 is for temporarily storing, in the memory 17, the digital moving image and audio signals combined by the AV demultiplexing circuit 15 during recording. Further, the signal processing circuit 16 is for adding data necessary for recording the above-described image / audio signal to the recording medium 23, for example, address information on the recording medium 23, to the digital moving image / audio signal. Is. Further, at the time of reproduction, the signal processing circuit 16 is for storing a digital moving image signal output from a driver circuit 19 described later in the memory 17 and outputting it to the AV demultiplexing circuit 15. In addition, the memory capacity detection circuit 2
Reference numeral 7 is for detecting an available capacity of the memory 17 and transmitting it to the system microcomputer 18.

The servo circuit 20 controls the motor driver 21 to drive the motor 22 to rotate the recording medium at an appropriate speed. The driver circuit 19 includes an amplifier 28, receives the digital moving image audio signal stored in the memory 17 from the signal processing circuit 16 during recording,
The digital moving image audio signal is processed so that it can be recorded on the recording medium 23, and a recording unit (not shown) such as a magnetic head or an optical pickup is driven to record the signal on the recording medium 23. Also, at the time of reproduction, the recording medium 2
It is for amplifying the digital moving image audio signal reproduced from the signal No. 3 and transmitting it to the signal processing circuit 16.

The system microcomputer 18 controls the image compression / expansion circuit 13, the audio compression / expansion circuit 14, the signal processing circuit 16, the servo circuit 20, and the memory capacity detection circuit 27 to generate a moving image signal and It is the central part of this device that performs compression and recording of audio signals and expansion and reproduction. At the time of compression / recording, the system microcomputer 18 compresses the digital moving image signal in the image compression / expansion circuit 13 at a bit rate Vp according to the free space of the memory 17 and the difficulty level of the digital moving image signal. Information is supplied to the rate control circuit 26 to control the image compression / decompression circuit 13.

Further, the system microcomputer 18 has the memory 1
The digital moving image audio signal stored in 7 is recorded on the recording medium 23 via the driver circuit 19. At the time of this recording, the system microcomputer 18 controls the servo circuit 20 so that the recording medium 23 is appropriately driven.

The image signal D / A converter 24 is for converting the digital moving image signal output from the image compression / expansion circuit 13 into an analog moving image signal during reproduction. In addition, the audio signal D / A converter 25
Is for converting the digital audio signal output from the audio compression / expansion circuit 14 into an analog audio signal during reproduction. Further, the D / A converters 24 and 25 output the analog moving image signal and the analog audio signal to an image / sound display device (not shown) such as a television receiver.

The compression / encoding processing of the analog moving image audio signal and the recording processing on the recording medium 23 in this apparatus will be described below. When an analog moving image / sound signal is input to this device, this signal is divided into an analog moving image signal and an analog audio signal by an input unit (not shown), and the image signal A / D converter 11 and the audio signal are respectively separated. It is transmitted to the A / D converter 12. Then, these analog signals are converted into digital signals by the A / D converters 11 and 12, and become digital moving image signals and digital audio signals, respectively.

Thereafter, the digital moving image signal and the digital audio signal are respectively transferred to the image compression / expansion circuit 1.
3 and the audio compression / decompression circuit 14. Then, the rate control circuit 26 determines the compression rate Vp of this digital moving image signal. After that, system microcomputer 1
8 controls the image compression / decompression circuit 13 to compress the digital moving image signal at the compression rate Vp determined by the rate control circuit 26 and transmit it to the AV demultiplexing circuit 15 and control the audio compression / decompression circuit 14. Then, the digital audio signal is compressed at the fixed rate Va and transmitted to the AV demultiplexing circuit 15.

After that, the system microcomputer 18 controls the AV demultiplexing circuit 15 to multiplex the compressed digital audio signal and digital moving image signal into one digital moving image audio signal, and to the signal processing circuit 16. Input. The transfer rate of the digital moving image audio signal transmitted from the AV demultiplexing circuit 15 to the signal processing circuit 16 is Vd.
And These Vp and Vd will be described later.

The system microcomputer 18 is the signal processing circuit 1
After controlling 6 to add the data necessary for recording to the recording medium 23 to this digital moving image audio signal, this digital moving image audio signal is temporarily stored in the memory 17. After that, the system microcomputer 18 controls the signal processing circuit 16 to output the digital moving image audio signal from the memory 17 to the driver circuit 1 at a constant bit rate Vr.
9 is transmitted. Then, the driver circuit 19 processes the digital moving image audio signal so that it can be recorded on the recording medium 23, drives a recording unit (not shown) such as an optical pickup and a magnetic head, and records at this bit rate Vr. It is recorded on the medium 23.

Here, the compression bit rate Vp of the digital moving image signal in the image compression / expansion circuit 13 and the transfer rate Vd from the AV demultiplexing circuit 15 to the signal processing circuit 16 will be described. This transfer rate Vd is a rate determined from Va and Vp described above. However, in this apparatus, since Va has a fixed rate, this Vd is a value determined from the value of Vp.

The system microcomputer 18 controls the memory capacity detection circuit 27 to detect the free capacity of the memory 17. Then, the system microcomputer 18 determines the upper limit of the transfer rate Vd in accordance with the free space and transmits it to the rate control circuit 26. This upper limit is Vdmax.
The system microcomputer 18 does not set this Vdmax to a value that exceeds the maximum mechanically transfer rate Vl of this device.

The rate control circuit 26, to which Vdmax has been transmitted from the system microcomputer 18, transfers the transfer rate Vd to Vdmax.
The compression bit rate Vp of each digital moving image signal is determined so as not to exceed max. After that, the system microcomputer 18 controls the image compression / expansion circuit 13 to compress the digital moving image signal by Vp determined by the rate control circuit 26.

When the free space of the memory 17 is large, the Vdmax set by the system microcomputer 18 is set to the recording medium 23.
The recording rate Vr is set to a value larger than the recording rate Vr. In this case, if the degree of difficulty of the digital moving image signal input to the image compression / decompression circuit 13 is very high, the rate control circuit 26 raises Vp for this signal,
The transfer rate Vd is the average transfer rate Vm and the recording rate Vr.
And increase it to a higher Vdmax. Therefore, V
Since d> Vr, the amount of digital moving image / sound signals stored in the memory 17 is larger than the amount of digital moving image / sound signals output from the memory 17. Therefore,
The free capacity of the memory 17 becomes smaller.

When a digital video signal having a low degree of difficulty is input to the image compression / decompression circuit 13, the rate control circuit 26 assigns a low Vp to this signal, so that the transfer transfer rate Vd is the average transfer rate. The rate Vm and the recording rate Vr become smaller, and Vd <Vr. Therefore, the amount of digital moving image audio signals stored in the memory 17 is smaller than the amount output from the memory 17. Therefore, the amount of digital moving image / sound signals stored in the memory 17 is smaller than the amount of digital moving image / sound signals output from the memory 17. Therefore,
The free capacity of the memory 17 increases.

FIG. 2A is a graph showing an example of the change of the transfer rate Vd with time (t), and FIG.
3 is a graph showing a change (t) in the usage amount of the memory 17 according to Vd shown in FIG. As shown in FIG. 2B, at times t1 and t3, the capacity of the memory 17 is small. Such times t1 and t
In 3, the system microcomputer 18 recognizes that the free space of the memory 17 is large, and assigns a high compression bit rate Vp to an image of high difficulty,
A high value Vdmax is set for the rate control circuit 26.

The rate control circuit 26 determines that this high value of Vd
Upon receiving max, the compression rate Vp higher than the recording rate Vr is assigned to the digital video signal having a high degree of difficulty, and as a result, the transfer rate Vd becomes the times t2 and t4.
In the vicinity of, the value exceeds the recording rate Vr of the recording medium 23.

Next, the reproducing operation of the digital moving image audio signal recorded on the recording medium 23 in this apparatus will be described. When a digital moving image audio signal recorded by the present apparatus is reproduced from the recording medium 23 by a reproducing unit (not shown) including an optical pickup and a magnetic head,
The driver circuit 19 amplifies this digital moving image audio signal and transmits it to the signal processing circuit 16. After that, the system microcomputer 18 controls the signal processing circuit 16 to process the digital moving image audio signal in the AV demultiplexing circuit 15 into a separable state and store it in the memory 17. The bit rate of the digital moving image audio signal from being input to the driver circuit 19 to being stored in the memory 17 is a reproduction rate from the recording medium 23 and is a fixed rate.
In the following, this reproduction rate is Vs.

The system microcomputer 18 is the signal processing circuit 1
6 is controlled so that the digital moving image audio signal is transmitted from the memory 17 to the AV demultiplexing circuit 15. This memory 17
The output rate from the signal processing circuit 16 to the signal processing circuit 16 is Vt. Then, the system microcomputer 18 uses the AV demultiplexing circuit 15
Is controlled to separate the digital moving image audio signal into a bit stream of a digital moving image signal and a digital audio signal.

Next, the system microcomputer 18 controls the image compression / expansion circuit 13 to expand the digital moving image signal and also controls the audio compression / expansion circuit 14.
Decompress the digital audio signal. After that, the expanded digital moving image signal is converted into an image signal D / A converter 2
4 is transmitted to an analog moving image signal such as NTSC, and the digital audio signal is transmitted to an audio signal D / A converter 25 and converted into an analog audio signal.

In the above processing, when the transfer rate Vs is equal to the above-mentioned Vr and the reproducing operation from the recording medium is not stopped halfway, the above-mentioned time change of Vt at the time of reproducing is the digital moving image required for reproducing. It is similar to the time change of Vd when the image / audio signal is recorded. Therefore, if the memory 17 at the time of reproduction has a capacity equal to or larger than the capacity of the memory 17 used when the reproduced digital video / audio signal is recorded, AV demultiplexing is performed. The digital moving image audio signal sent to the circuit 15 is not interrupted. Therefore, it is possible to reproduce the image signal and the audio signal without interruption.

In the reproducing operation described above, the digital moving image audio signal reproduced at the bit rate Vs equal to the recording rate Vr is temporarily stored in the memory. The reason is as follows. In the following, the compressed digital moving image signal is referred to as a compressed digital moving image signal,
The expanded digital moving image signal is defined as an expanded digital moving image signal.

In order to expand the compressed digital moving image information compressed at the high bit rate Vp and obtain the expanded digital moving image signal to be sent to the image signal D / A converter 24, many compressed digital moving images are required. Image signal quantity is required. Therefore, if the digital moving image audio signal reproduced at the reproduction rate Vs and including the compressed digital moving image signal compressed at high Vp is directly processed without being stored in the memory 17,
The amount of compressed digital moving image signal for decompression in the image compression / decompression circuit 13 becomes insufficient. As a result, there is a gap in the output of the expanded digital moving image signal from the image compression / expansion circuit 13 to the image signal D / A converter 24, resulting in intermittent reproduction.

Therefore, in this apparatus, the system microcomputer 1
8 is a recording medium 2 so that the memory 17 is filled as much as possible.
The read amount from 3 is controlled. Since the bit rate at the time of this reading is Vs, which is constant, the memory 17
The above-described control of maximizing the number of times as much as possible means that reproduction is continued without stopping reading from the recording medium.
When such a control is performed, the recording rate Vr and the reproduction rate Vs change with time, and the Vd and Vt also change with time, so that the reproduction can be performed without interruption.

FIG. 3A shows the signal processing circuit 16 to AV
FIG. 3B is a graph showing an example of a time (t) change of the transfer rate Vt of the digital moving image audio signal to the demultiplexing circuit 15, and FIG. 3B corresponds to the transfer rate Vt shown in FIG. 9 is a graph showing a change in the amount of use of the memory 17 with time (t).

As shown in these figures, when Vt becomes larger than Vs, the usage amount in the memory 17 decreases and Vt becomes Vs.
When it becomes smaller than s, the usage amount in the memory 17 increases.
Further, A shown in FIG. 3B indicates a difference between the maximum amount and the minimum amount of the digital moving image audio signal accumulated in the memory 17. The memory 17 needs to have a capacity of A or more. Further, Vm shown in FIG. 3A is an average value of the transfer rate Vt.

Further, in this apparatus, the rotational speed of the recording medium is reduced to record the digital moving image audio signal, and this signal is reproduced at the normal rotational speed to obtain Vs ≧ Vtma.
It can be x. This Vtmax is the above Vt
Of the image compression / decompression circuit 13 and is mainly determined by the decompression capability of the image compression / decompression circuit 13.

As described above, when Vs ≧ Vtmax, it is not necessary to store as many digital moving image audio signals in the memory 17 as possible in the reproducing operation of the present apparatus described above. This is because the playback rate Vs is Vtmax
Therefore, even if a digital moving image audio signal including a compressed digital moving image signal compressed at a high compression rate Vp is reproduced, the compressed digital moving image signal amount in the image compression / expansion circuit 13 does not become insufficient. is there.

In this case, the recording medium 2 at the reproduction rate Vs
If reproduction from 3 is performed intermittently, the memory 17
Is used purely for the purpose of shock proof and prevention of intermittent regeneration, it is not necessary to hold the capacity indicated by A in FIG. 3 (b). Therefore, the capacity of the memory 17 used during reproduction is smaller than the capacity required for recording. Therefore, the digital moving image / audio signal recorded by this apparatus can be reproduced by a conventional image / audio recording / reproducing apparatus such as the image / audio recording / reproducing apparatus shown in FIG. 4 which does not have the memory 17.

In general, the power of the light beam used for recording on a recording medium such as a magneto-optical disk needs to be stronger than the power of the light beam used for reproduction. Therefore, it may be difficult to increase the number of rotations of the recording medium during recording to the same level as during reproduction. In such a case, if the present apparatus is used, even if the digital moving image audio signal is recorded while the rotation speed of the recording medium is reduced, as described above, normal reproduction at the normal rotation speed can be performed. Also, the reproduction of the digital moving image / sound signal thus recorded can be performed by the conventional image / sound recording / reproducing apparatus having no memory 17 as described above.

As described above, in the present apparatus, the digital moving image audio signal multiplexed by the AV demultiplexing circuit 15 is temporarily stored in the memory 17 and then recorded in the recording medium 23 via the driver circuit 19. is there. Then, the upper limit V of the transfer rate Vd from the AV demultiplexing circuit 15 to the memory 17 is set.
dmax is determined from the capacity of the memory 17.

Therefore, as long as the memory 17 has a free space, it is possible to instantaneously use the transfer rate Vd higher than the recording rate Vr for recording on the recording medium 23. As a result, since the analog moving image signal having a high degree of difficulty such as a scene change or a fade portion is digitally converted and compressed, a high compression rate Vd can be assigned without being limited to the recording rate Vr. Therefore, it is possible to improve the image quality of the entire recorded digital moving image audio signal as compared with the conventional image audio recording / reproducing device shown in FIG.

In this embodiment, the MPEG2 method is used as the method for compressing / encoding the moving image signal, but the present invention is not limited to this, and the present invention can be used regardless of the compression / encoding method. It is profitable. That is, the present invention can be applied to all apparatuses that digitally convert an analog moving image signal and compress it, and record it on a recording medium, or decompress and reproduce a compressed digital moving image signal.

Further, in this apparatus, the analog moving image audio signal is inputted, and after being converted into digital, compressed and recorded on the recording medium, but only the analog moving image signal may be inputted. In this case, the compression rate Vp is
Since it becomes equal to the transfer rate Vd, the compression rate Vp can be further increased. At this time, the system microcomputer 18 sets V in the rate control circuit 26.
The upper limit of d becomes the upper limit of Vp as it is.

Further, in this apparatus, the system microcomputer 18 sets the upper limit of Vp at the time of recording by the memory capacity detection circuit 2
7 is controlled to acquire the free space of the memory 17, and Vdmax is determined from this free space and transmitted to the rate control circuit 26, but the present invention is not limited to this. If the memory 17 has a very large capacity, this upper limit becomes the maximum mechanically transfer rate Vl in this device. In this case, the rate control circuit 26 receives V
If Vl is given in advance as the upper limit of d, it is possible to perform recording without being limited to Vr without using the memory capacity detection circuit 27.

In this embodiment, the upper limit of the transfer rate Vd given by the system microcomputer 18 to the rate control circuit 26 is determined from the free space of the memory 17, but the present invention is not limited to this. It may be determined from the maximum capacity.

Further, in the present embodiment, the recording rate Vr to the recording medium 23 and the reproduction rate Vs from the recording medium 23.
However, it is not limited to this,
It may be a variable rate based on the degree of difficulty of the digital moving image audio signal for recording or reproduction.

In this embodiment, an analog signal is input, but the present invention is not limited to this.
A digital signal may be input and compressed / recorded. In this case, the A / D converter 11
12 is unnecessary.

[0062]

As described above, the image recording apparatus of the present invention determines the compression means for compressing the input moving image signal and the difficulty level of the moving image signal, and determines the compression level based on this difficulty level. Rate determining means for determining the compression rate by means, storage means, recording means for recording the compressed moving image signal on a recording medium, and for storing the compressed moving image signal in the storage means First signal processing means, a second signal processing means for outputting the moving image signal stored in the storage means to the recording means at a constant rate, and a free capacity of the storage means. detection
Means and the moving image signal is input , and when the compression rate of the moving image signal is determined by the rate determining means, the compression means is controlled to compress the moving image signal at the compression rate, The first signal processing means is controlled to store the compressed moving picture signal, and the second signal processing means is controlled to control the compressed moving picture signal stored in the storage means at a constant rate. in a control means for outputting to said recording means, further said control means, on
The detection means is controlled to detect the free space in the storage means.
The rate determining means based on the free space.
This is a configuration that gives an upper limit of the compression rate by the compression means .

As a result, the compressed moving image signal is temporarily stored in the storage means and then recorded on the recording medium at a constant bit rate. Therefore, the compression bit rate by the compression means is set to be smaller than the recording bit rate on the recording medium. Can also be momentarily increased. Therefore, in order to compress video signals with high difficulty such as scene changes and fade parts,
Since a high compression rate can be assigned without being limited by the recording rate, it is possible to improve the overall image quality of the recorded moving image signal.

Furthermore, a detection means for detecting the free space of the storage means is further provided, and the control means controls the detection means to detect the free space of the storage means, and based on the free space. have adapted to provide an upper limit of the compression rate by the compression means to said rate determination means Te
Therefore, for example, moving image signals with high difficulty may be continuously input.
Video compressed at a high bit rate, even if compressed
The image signal is not continuously stored in the storage means.

Therefore, in addition to the above-mentioned effects, since the trouble of the recording operation is interrupted / stopped due to the overflow of the storage means, no matter what moving image signal is input, the compression / reduction is surely performed. There is an effect that recording can be performed.

Further, in the image recording apparatus of the present invention, in addition to the above configuration, the upper limit of the compression rate is equal to or higher than the output rate of the compressed moving image signal from the second signal means to the recording means. It is a certain structure.

As a result, in addition to the above effects, the capacity of the storage means can be utilized to the maximum extent, so that the overall image quality of the moving image signal to be recorded can be surely improved. .

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a video / audio recording / reproducing apparatus showing an embodiment of the present invention.

2 (a) shows an example of a change over time in a transfer rate of a digital moving image / sound signal transmitted from an AV demultiplexing circuit to a signal processing circuit in the image / sound recording / reproducing apparatus shown in FIG. 2B is a graph, and FIG.
6 is a graph showing a change over time in the amount of memory used in the device according to the transfer rate shown in FIG.

3 (a) is a graph showing an example of a temporal change of a transfer rate of a digital moving image / sound signal from a signal processing circuit to an AV demultiplexing circuit in the image / sound recording / reproducing apparatus shown in FIG. Yes, FIG. 3B is a graph showing the change over time in the amount of memory used in the device according to the transfer rate shown in FIG.

FIG. 4 is a block diagram showing a configuration of an image / audio recording / reproducing apparatus including a conventional image recording apparatus.

FIG. 5 is a graph showing an example of transfer rate time change of a digital moving image audio signal from a signal processing circuit to an AV demultiplexing circuit in the image audio recording / reproducing apparatus shown in FIG.

[Explanation of symbols]

13 Image compression / decompression circuit (compression means) 16 signal processing circuit (first and second signal processing means) 17 Memory (storage means) 18 system microcomputer (control means) 19 Driver circuit (recording means) 26 Rate control circuit (rate determining means) 27 Memory capacity detection circuit (detection means)

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-8-46907 (JP, A) JP-A-6-76470 (JP, A) JP-A-10-228728 (JP, A) JP-A-1- 200793 (JP, A) JP-A-6-141298 (JP, A) JP-A-6-343158 (JP, A) JP-A-8-205087 (JP, A) JP-A-8-340536 (JP, A) JP-A-9-18873 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04N 5/91-5/956 G11B 20/10 H04N 5/907, 7/24

Claims (2)

(57) [Claims] 1. An image recording apparatus for compressing a moving image signal and recording the moving image signal on a recording medium, a compression means for compressing an input moving image signal, and a difficulty level of the moving image signal, A rate determining means for determining a compression rate by the compression means according to the degree of difficulty, a storage means, a recording means for recording a compressed moving image signal on a recording medium, and a compressed moving image signal as described above. A first signal processing means for storing in the storage means, a second signal processing means for outputting the moving image signal stored in the storage means to the recording means at a constant rate, and an empty space in the storage means. a detecting means for detecting the capacity, the moving image signal is input, the compression rate of the moving picture signal is determined by the rate determining means, animal in the compression rate by controlling the compressing means The image signal is compressed, the first signal processing unit is controlled to store the compressed moving image signal, and the second signal processing unit is controlled to store the compressed image signal stored in the storage unit. And a control means for outputting the moving image signal to the recording means at a constant rate . Further, the control means controls the detection means to control the detection means.
The free space of the storage means is detected, and based on the free space
The rate determining means is provided with the compression rate of the compression means.
An image recording device characterized by giving an upper limit . 2. A moving image in which the upper limit of the compression rate is compressed.
Output of image signal from the second signal means to the recording means
The image recording apparatus according to claim 1, wherein the image recording apparatus has a rate equal to or higher than the rate .