JP2957340B2 - Digital 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 a digital video recorder for recording a digital video signal subjected to image data compression processing on a magnetic tape or an optical disk.

[0002]

2. Description of the Related Art As a digital recording device for digitally recording a video signal such as a television signal, taking a digital VTR using a magnetic tape as an example, a D1 standard component digital VTR (D1-VTR) or a D2 standard composite VTR ( D2-VTR), which are used in the field of broadcasting and the like.

[0003] Also, Journal of the Institute of Television Engineers of Japan; Vol. 4
5, No. 7, pp. 813 to 819, "VTR coding technology" (1991), there is a method of reducing the amount of recording data by band compression or the like for the purpose of realizing a small home-use digital VTR. Among them,
Discrete Cosine Transform (DCT)
It is known that a method employing the above-described method and further using motion compensation inter-frame predictive coding is effective as a method having high compression efficiency.

[0004]

Generally, when recording an image on a VTR, in addition to the normal speed reproduction, the reproduction contents can be confirmed at the time of high-speed reproduction (hereinafter referred to as shuttle reproduction) so that the reproduction of the image can be confirmed. It is necessary to be able to perform cueing and the like. However, at the time of shuttle reproduction, signals are picked up in such a manner that the head traverses a video track recorded in a helical shape, so that it is impossible to obtain a regular reproduction signal in a time series. Therefore, if the inter-frame predictive coding that requires the information of the previous frame for decoding is applied to the VTR as it is, when the pixel block serving as the reference for decoding is not reproduced, the error spreads over several frames in a chain, and the image cannot be restored. It is possible, and the output image may be broken.

[0005] In particular, in order to realize a VTR in which video data from another moving image recording medium or a moving image communication medium which has been subjected to inter-frame prediction coding is directly recorded in the form of digital data, there is no possibility that the shuttle reproduction will fail. The challenge remains to be met.

[0006]

According to the present invention, in order to solve the above-mentioned problem, when an input digital video signal which has been motion-compensated for inter-frame prediction is input to a VTR, a part or all of the input digital video signal is once decoded, Means for re-encoding by a code completed in units of pixel blocks in a frame is V
Provided in the TR input process.

[0007]

By increasing the proportion of data using codes that can be decoded in data block units within a frame, the need to refer to the data of the previous frame is reduced.
During shuttle playback, it is not impossible to restore an image for a long time.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. Here, in each of the following embodiments, a VTR is described as an example. However, if the magnetic tape is replaced with an optical disk and the magnetic head is replaced with an optical head, the present invention can be applied to a VT.
It goes without saying that the present invention can be applied not only to R but also to, for example, an optical disk recorder.

FIG. 1 is a block diagram showing a first embodiment. An analog video signal and a digital video signal are input from input terminals 1 and 2, respectively. The analog video signal input from the input terminal 1 is converted into a digital signal by an A / D conversion circuit 4 and is subjected to an intra-frame compression encoding circuit. 5, and the digital video signal input from the input terminal 2 is transmitted to the intra-frame compression encoding circuit 5 as it is. Since the digital video signal supplied to the intra-frame compression encoding circuit 5 is uncompressed, it is necessary to perform compression utilizing characteristics of the image signal in order to record for several hours on a small cassette or the like. The intra-frame compression coding circuit 5 is a coding circuit that performs compression using only pixel data of the same frame. The compression ratio, that is, the data reduction effect is lower than that of the motion-compensated inter-frame prediction coding described later. The feature is that even if data of different frames is obtained in pieces during reproduction, each data block can be decoded. The image data compressed and encoded by the intra-frame compression encoding circuit 5 is supplied to a VTR transmission encoding circuit 6.

The above is the input path of the non-compressed image data. However, the present invention is not limited to this. In addition to the intra-frame compression encoding circuit 5, the inter-frame processing is used together with the input data of the image data. Compression may be performed. In short, the image data processed in the frame may be used.
It is sufficient that the ratio of data is large enough to perform shuttle regeneration.

On the other hand, there is also a use for recording digital image data compressed from a medium such as an output of another VTR or a broadcast without using signal processing as much as possible.
It is important as R. This is because the decoding and re-encoding of data involves image quality degradation due to truncation during calculation, rounding error and quantization noise.

The input terminal 3 is an input terminal for a compressed signal including inter-frame prediction as described above. In the compressed image signal including the inter-frame prediction input from the input terminal 3, first, header information attached to the image data is read by the header detection circuit 8, and the type of compression received by each pixel block, the position of the image, and the motion Information such as a compensation motion vector is interpreted. After detecting the header, the image data is decoded by the code conversion circuit 9 into an inter-frame prediction code, and is re-encoded by using a compression code only in the frame. The switch 10 is a switch for selecting and outputting one of the re-encoded image data and the image data bypassing the code conversion circuit 9. A control signal for selecting the switch 10 is supplied from the header detection circuit 8. For example, when the input data is compressed using inter-frame prediction, the upper side (INTER side) of the switch in FIG. By selecting the lower side (INTRA side), the ratio of intra-frame compression to all the compressed image data to be recorded can be increased.

The output of the switch 10 is sent to the VTR transmission coding circuit 6 like the output of the intra-frame compression coding circuit 5 and subjected to processing such as shuffling and error correction check bits. The information is recorded on the magnetic tape 11 via the magnetic head 7.

At the time of reproduction, data reproduced by the magnetic head 12 is subjected to processing such as deshuffle and error correction in a VTR transmission decoding circuit 13, and one of them is subjected to an inter-frame or intra-frame compression decoding circuit. (Interframe / intraframe compression / decoding circuit) 14 and the other to a dubbing output terminal 18. The image data sent to the inter-frame / intra-frame compression decoding circuit 14 undergoes expansion processing and error correction processing in the compression decoding circuit 14, and one of them is converted to an analog signal by the D / A conversion circuit 15. After that, it is output from the analog output terminal 16 to the outside,
The other is output from the digital output terminal 17 as an uncompressed digital signal.

The dubbing output terminal 18 is a terminal for supplying compressed image data to the outside, and is effective for duplicating compressed image data without image quality deterioration due to decoding and re-encoding.

As described above, in the present embodiment, in a digital VTR for recording a non-compressed input signal by compressing it in a frame and recording the compressed input signal, one of the inter-frame predictively coded data is applied to the compressed input signal. By converting part or all of the data to the intra-frame compression code and recording the data, the ratio of the intra-frame compression-encoded data to all the recorded data can be increased. As a result, during special reproduction such as VTR shuttle reproduction. The need to reference the data of the previous frame is reduced, and the probability of cascading propagation of errors is reduced.

Here, the intra-frame compression encoding circuit 5, the code conversion circuit 9, and the inter-frame / intra-frame compression decoding circuit 14, which are described as separate blocks in FIG.
Actually, the internal circuit can be shared, and the circuit scale can be reduced. Therefore, the connection when the internal circuit is also used will be described in detail with reference to FIG.

In FIG. 2, when an uncompressed image signal is inputted from the input terminal 1 or 2 and recorded, the switch 20 is selected at the upper side in the figure, and compression encoding processing in a frame is performed. First, a discrete cosine transform (DCT) circuit 21 defines a pixel block, and in the block, amplitude information is converted into coefficient information in a two-dimensional frequency domain. Next, each coefficient data is quantized by the quantization circuit 22 in different steps, and the number of bits to be allocated is reduced to compress the data. Further, the entropy encoding circuit 23
After the compression of the information without distortion using the occurrence probability of the bit pattern is performed, the data is sent to the buffer memory 24 for measuring the accumulated information amount for each recording track. The accumulated information amount is fed back to the quantization circuit 22, and a quantization step is determined in order to avoid an excessive or insufficient data amount per track. The DCT circuit 21
The path from to the buffer memory 24 corresponds to the intra-frame compression encoding circuit 5 in FIG.

The recording of a compressed signal including inter-frame prediction is processed according to the following path. The compressed signal from the input terminal 3 is first supplied to the switch 25. Here, the switch 25 is at the lower side (REC side) in the figure at the time of recording.
And one of its outputs is the entropy decoding circuit 26
Is converted to quantized DCT coefficient data. Further, the inverse quantization circuit 27 and the inverse DCT (IDCT) circuit 28 perform an operation opposite to that performed at the time of encoding, so that the data is expanded and amplitude data of the image is obtained.

The output of the switch 25 is also supplied to a header detection circuit 8, which generates a selection control signal for the switches 10 and 32 and outputs the header information to a motion vector information extraction circuit 31, which will be described later. .

When the compressed input data is intra-frame compression, the switches 32 and 10 are set to the lower side (INTR).
A) is selected, and the output of the IDCT circuit 28, that is, the image data of one independent block, is stored as it is in the frame memory 30 attached to the inter-frame prediction circuit 29.

On the other hand, the output of the IDCT circuit 28 is also supplied to an adder circuit 33. When the decoded data is compressed between frames, the switch 32 selects the upper side (INTER side) in the figure. doing. In the case of inter-frame compression, what is coded is the difference from the frame before and / or after the reference. Therefore, when the data stored in the frame memory 30 and the motion compensation processing are performed, The image cannot be restored unless the image data predicted by adding the motion vector data from the motion vector information extraction circuit 31 is used. Addition circuit 3
In 3, the image is restored by adding the difference data from the IDCT circuit 28 and the image data predicted between frames including the motion compensation, and the output is supplied to the inter-frame prediction circuit 29 via the switch 32, and the frame is restored. New reference data is stored in the memory 30.

Further, the restored image data is also supplied to the other input of the switch 20. The switch 20 selects the lower side in the figure when compressed data is input, and supplies the restored image data to the intra-frame compression encoding path (path from the DCT circuit 21 to the buffer memory 24).

In this way, the data which has been subjected to the inter-frame compression encoding can be converted into an intra-frame compression code and recorded on a tape.

As a secondary effect, since the output of the switch 32 can be monitored via the output terminals 16 and 17, a recording error can be avoided by checking the screen after decompression in recording the compressed digital data. .

Next, during reproduction, the switch 25 selects the upper side (PB side) in the figure, and the processing after the output of the switch 25 is the same as the processing of the compressed input data.

As described above with reference to FIG. 2, the effect is the same as that of FIG. 1, and a part or all of the data obtained by performing the inter-frame predictive coding on the compressed input digital signal is converted into the intra-frame compressed code. By performing the recording, the ratio of the intra-frame compression-coded data to all the recorded data can be increased, so that it is less necessary to refer to the data of the previous frame during special reproduction such as VTR shuttle reproduction. Thus, the probability of cascading propagation of errors is reduced.

Next, a second embodiment of the present invention will be described with reference to FIGS. In FIGS. 3 and 4, the processing blocks having the same functions as those in FIGS. 1 and 2 are denoted by the same reference numerals, and description thereof will be omitted to avoid duplication.

FIG. 3 is a signal processing block diagram in the present embodiment. Although the basic processing contents are the same as those in FIG. 1, there is a difference in a path for recording a compressed input signal from the input terminal 3. The switch 10 determines the ratio between the inter-frame compression and the intra-frame compression for the compression form of the recording signal. The selection is obtained not only from the header information from the header detection circuit 8 but also from the code conversion circuit 9. The feature is that data of the information generation amount is input to the information generation amount monitoring circuit 35, and control is performed in consideration of both.

Here, the information generation amount is the amount of data generated by encoding an input image, and is usually data necessary for determining a quantization step. If the recording capacity of the VTR has a sufficient margin with respect to the input data amount, the switch 10 is switched only by the header information, that is, information indicating whether the original compression mode is between frames or within a frame, and all the recording data is changed. What is necessary is just to convert into intra-frame compression. However, if the recording capacity on the VTR side has no margin, it is necessary to record data in the form of inter-frame compression having a high compression ratio.

At this time, the information generation amount monitoring circuit 35 receives the information generation amount indicating the margin for the recording capacity from the code conversion circuit 9, and controls the switch 10 so as not to exceed the capacity.
To increase the ratio of the inter-frame compression encoded data to the maximum. As a result, the probability of error propagation during shuttle playback can be minimized within a limited storage capacity.

FIG. 4 is a diagram showing an actual internal circuit block configuration in the second embodiment, similarly to FIG.
The information generation amount monitoring circuit 35 is supplied with information generation amount data from the buffer memory 24. This data is originally fed back to determine the DCT coefficient quantization step in the quantization circuit 22, and is calculated from the filling degree of the recording data in the buffer memory 24. The main signal processing is as described in FIG. The effect is the same as that described with reference to FIG. 3. The information generation amount monitoring circuit 35 receives the information generation amount indicating the margin for the recording capacity from the buffer memory 24, and switches the switch 10 so as not to exceed the capacity. The ratio of inter-compression data is increased to the maximum.
As a result, there is an advantage that the probability of occurrence of error propagation during shuttle reproduction can be minimized within a limited storage capacity.

In this embodiment, the digital VTR
When the recording capacity is small, the switch 10 is set to IN
The recording efficiency may be increased by using a mode in which the switch 32 is tilted to the INTRA side and operated on the TER side. That is, after decoding the image data of the intra-frame processing, the image data is compressed again by roughening the quantization parameter of the quantization circuit 22 in the intra-frame processing again. At this time, a path may be newly provided to bypass the DCT circuit 21 and the IDCT circuit 28 which are substantially ineffective.

Next, a third embodiment of the present invention will be described with reference to FIGS. This embodiment is also the first
Based on this embodiment, the control of the switch 10 for selecting an intra-frame code / inter-frame code is devised.
In addition to the form of compression from the header information output from the header detection circuit 8, the image position gate circuit 36 processes the screen position information indicating where the data to be recorded is on the screen, The data located in the center of the screen, which is usually considered to be important, is converted into an intraframe code at a high rate, and a gate is provided to provide high screen reproducibility during shuttle reproduction.
Is a selection control signal. As a result, even when the storage capacity on the VTR side is insufficient, the user can convert the compression to intra-frame compression in the screen area of interest and leave the inter-frame code in the other areas. This has the effect that the occurrence of error propagation during the shuttle can be eliminated to a specific area.

FIG. 6 is an internal block diagram of FIG. The image position gate circuit 36 switches from the header detection circuit 8 to the switch 1
0 is inserted in the path leading to the control terminal of 0, thereby achieving the same effect as the circuit in FIG. 5 described above. The main signal processing is as described in FIG.

As for the recording efficiency of image data with respect to the recording capacity of the VTR, it is clear that the combination of the second embodiment and the third embodiment is more effective.

FIG. 7 is a circuit block diagram showing a fourth embodiment. The block diagram in FIG.
The quantization selection circuit 40 is inserted in a feedback path of the information generation amount from the information generation circuit 4 to the quantization circuit 22, and the header information from the header detection circuit 8 is supplied to the circuit.

In the first embodiment, when the inter-frame / intra-frame code conversion is performed on the compressed input data from the input terminal 3, the quantization step in the quantization circuit 22 is determined by generating information from the buffer memory 24. Although the encoding is performed using only the amount data, in the present embodiment, the encoding with less redundancy and distortion is realized by using the quantization step information included in the header of the input signal at the time of inter-frame compression. A case where the quantization information selection circuit 40 is provided as an example and one of the two is selected will be described. The selection criterion may be, for example, as follows.

1) In the case of the step specified from the buffer memory> the quantization step of the header, there is no margin in the recording capacity, and it is necessary to suppress the information generation amount of the data amount by expanding the quantization step. The quantization information from the buffer memory 24 is prioritized.

2) In the case of the step specified from the buffer memory <the quantization step of the header In a case where the recording capacity has a margin and the quantization step may be set finely, a step before data is input is performed. Because the quantization step when inter-frame compression is performed is coarser than that, even if a new fine quantization is performed here, there is no guarantee that the information definition will increase, and the redundancy may increase. Is big.
Also, distortion may occur due to rounding errors during the calculation. Therefore, in this case, the information from the header detection circuit 8 is selected, and the margin of the recording capacity is allocated to another portion having a large data generation amount.

As a result, redundancy and distortion in intra-frame compression encoding can be avoided. In addition, effective use of the VTR recording capacity and improvement of image quality can be achieved as compared with the case where header information is not used.

Further, a quantization selection circuit 4 as shown in FIG.
As an extension of 0, by performing an appropriate operation on both quantization step information and performing fine quantization step control,
Further, the above effects can be increased.

[0043]

As described above, according to the present invention, a part or the whole of the input digital video signal which has been motion-compensated for inter-frame prediction compression coding is once decoded, and is decoded by a code which is completed in units of pixel blocks in the frame. Re-encoding means are provided in the input process of the VTR to increase the proportion of data using codes that can be decoded on a data block basis in the frame, thereby reducing the need to refer to the data of the previous frame. It is possible to reduce the probability of occurrence of chain propagation of errors during reproduction. Providing a digital dubbing output terminal for supplying the compressed image data to the outside is effective for duplicating the compressed image data without deteriorating the image quality due to decoding and re-encoding.

Further, the second and subsequent embodiments have the following effects in addition to the above effects. (Second Embodiment) A code conversion switch is switched so as not to exceed the capacity by using an information generation amount indicating a margin with respect to the recording capacity, and when the storage capacity on the VTR side is not sufficient, the inter-frame compression coding is performed. By increasing the data ratio to the maximum, the probability of error propagation during shuttle reproduction can be minimized within the limited storage capacity.

(Third Embodiment) A gate for always converting data at a specific screen position into an intra-frame code is provided as a selection control signal for a code conversion switch, so that the storage capacity on the VTR side is sufficient. In the case where there is no error, the occurrence of error propagation during shuttle can be eliminated to a specific area.

(Fourth Embodiment) In determining the quantization step in the quantization circuit in the intra-frame encoding circuit, the information generation amount data from the buffer memory and the inter-frame compression included in the header of the compressed input signal are used. By using the quantization step information, when the storage capacity on the VTR side has no margin, encoding with little redundancy and distortion can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a schematic configuration of a digital recording device according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing details of the configuration of FIG. 1;

FIG. 3 is a block diagram illustrating a schematic configuration of a digital recording device according to a second embodiment of the present invention.

FIG. 4 is a block diagram showing details of the configuration of FIG. 3;

FIG. 5 is a block diagram showing a schematic configuration of a digital recording device according to a third embodiment of the present invention.

FIG. 6 is a block diagram showing details of the configuration of FIG. 5;

FIG. 7 is a block diagram showing a configuration of a digital recording device according to a fourth embodiment of the present invention.

[Explanation of symbols]

 5 Intra-frame compression encoding circuit 6 VTR transmission encoding circuit 7, 12 Magnetic head 8 Header detection circuit 9 Code conversion circuit 10 Switch 11 Magnetic tape 13 VTR transmission decoding circuit 14 Inter-frame / intra-frame compression decoding circuit

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masaru Takahashi 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside Hitachi, Ltd. Video Media Research Laboratory (72) Inventor Kenshi Ichige 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa (56) References JP-A-1-314080 (JP, A) JP-A-4-14974 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) ) H04N 5/91-5/956 H04N 7/24-7/68 H04N 9/79-9/898

Claims (6)

(57) [Claims] An input means for inputting compressed image data obtained by compressing digital image data including a process between frames or fields of digital image data (hereinafter, these are simply referred to as frames); Means for converting part or all of the data subjected to inter-frame processing into image data subjected to intra-frame processing. 2. The apparatus according to claim 1, wherein said means for converting the compressed image data between frames into data for intra-frame processing comprises: means for decoding and expanding compressed image data between frames; A digital video recorder characterized by comprising compression means. 3. The digital and / or uncompressed (uncompressed) digital and / or uncompressed data according to claim 1 or 2,
Alternatively, a digital video recorder is provided, which comprises means for inputting an analog image signal, compresses the image data using at least the image data compressing means by the intra-frame processing, and then performs recording. 4. The data of image data to be recorded as to whether or not to perform data conversion by means for converting the compressed image data by the inter-frame processing into image data of an intra-frame processing according to claim 1. A digital recording device controlled by an amount. 5. The apparatus according to claim 1, wherein means for converting the compressed image data obtained by the inter-frame processing into image data for the intra-frame processing controls whether or not to perform the data conversion based on the screen position of the image data. A digital recording device. 6. The compressed image subjected to inter-frame processing, according to claim 1, further comprising quantization means for controlling an amount of image data to be recorded in the means for compressing image data by the intra-frame processing. When converting data into image data for intra-frame processing, a quantization parameter of the quantization means is determined based on an amount of image data to be recorded and a quantization parameter used in the inter-frame processing. A digital recording device characterized in that: