JP2001292417A - Digital image signal recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a digital image signal recorder that can generate and record special reproduction data at a high compression rate with higher resolution. SOLUTION: A black/white image data (data being a source of special reproduction data) read from a memory 5 are fed to a code quantity calculation section 7 and a DCT coefficient reduction circuit 6. The code quantity calculation section 7 decides a degree (n) so that a code quantity of the special reproduction data generated by the DCT coefficient reduction circuit 6 reaches a prescribed object code quantity or below. The DCT coefficient reduction circuit 6 deletes DCT coefficient data of a luminance block of black/white image data from a code word equivalent to a coefficient of the (n+1)th degree or over to a code word just before an EOB code or from a code word equivalent to a coefficient of the (n+1)th degree or below to the code word just before the EOB code (that is, the circuit 6 deletes the DCT coefficient data of high-degree luminance data) on the basis of the degree (n) and supplies the result to a packet re-synthesis section 8 as a special reproduction video stream.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a digital image signal recording apparatus for recording a digital image signal compressed and encoded by orthogonal transformation. In particular, it is an object of the present invention to provide a digital image signal recording apparatus capable of generating and recording special reproduction data having a higher resolution and a high compression ratio.

[0002]

2. Description of the Related Art A digital VTR (Video Tape Recorder) for recording image data compressed and encoded by using orthogonal transform, such as the MPEG system which is a standard method of color moving image compression and encoding, on a magnetic tape is used. In some cases, special reproduction data to be reproduced at the time of special reproduction in which the tape feed speed is made faster than that during normal reproduction in the forward or reverse direction is recorded at a predetermined position on the magnetic tape separately from the normal data. Such special reproduction data is usually prepared as dedicated data created by performing an operation such as increasing the compression ratio.

On the other hand, since the image signal transmitted in digital television broadcasting or the like does not include data for special reproduction, the above-described special reproduction cannot be performed only by recording such an image signal as it is.

[0004] As a digital image signal recording apparatus for recording a digital image signal containing no data for special reproduction so that it can be specially reproduced, Japanese Patent Laid-Open No. 10-1912 discloses a digital image signal recording apparatus.
There is 56. According to JP-A-10-191256,
Special reproduction by separating intra-frame data (independently coded data within an image) from input digital image data and deleting codewords corresponding to coefficients higher than (degree n + 1) among orthogonal transform (DCT) coefficients Data can be created. The code amount per intra frame after the deletion processing is CF (n), and the target code amount recordable in the frame period of the special reproduction data to be recorded is C
, The frame period and the target code amount C of the special reproduction data to be recorded are set such that the code amount CF (nmin) ≦ C corresponding to the minimum value nmin of the order n is satisfied.
When the code amount CF (nmin) corresponding to the minimum value nmin exceeds the target code amount C, at least data of the next intra frame is not recorded.

[0005]

In the above recording apparatus,
In order to secure a sufficient compression rate and suppress the target code amount, it is necessary to set the order n to a small value to some extent. However, reducing the order n leads to a decrease in the resolution of the special reproduction image. The code amount CF (nmin) corresponding to the minimum value nmin
Exceeds the target code amount C, the next intra-frame data is not recorded, so that the intra-frame period of the special reproduction data changes, and the special reproduction image becomes unnatural. . The present invention
It is an object of the present invention to provide a digital image signal recording apparatus capable of generating and recording special reproduction data having a higher resolution and a high compression ratio.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides the following digital image signal recording apparatus. [1] Digital image data compressed by inter-picture predictive encoding using orthogonal transformation is input, and intra-data separating means for separating intra-image data from the digital image data, and separated by the intra-data separating means. Color conversion means for removing color difference data from intra image data, inserting color difference data with zero DC error into the removed color difference data to generate monochrome image data, and the monochrome image data generated by the color conversion means And the monochrome image data is read out from the storage unit at an image cycle determined by the reproduction speed during special reproduction, and corresponds to the coefficient of the orthogonal transform block of the luminance data in the read monochrome image data of n + 1 or higher order. Code from the code word to be executed to immediately before the end of block code The natural number n is determined so that the code amount of the read black-and-white image data is within a predetermined target code amount, and the code word is deleted for the read black-and-white image data based on this n. A special reproduction data generating means for generating the special reproduction data by performing the special reproduction data generation, and converting the generated special reproduction data into the same format as the input digital image data to the intra data separation means. Signal recording means for generating a recording signal by synthesizing the recording signal in time series, and recording means for recording the recording signal on a recording medium. [2] Digital image data compressed by inter-picture prediction coding using orthogonal transformation is input, and intra-data separating means for separating intra-image data from the digital image data, and separated by the intra-data separating means. Color conversion means for removing color difference data from intra image data, inserting color difference data with zero DC error into the removed color difference data to generate monochrome image data, and the monochrome image data generated by the color conversion means A black-and-white image data read from the storage unit at an image cycle determined by a reproduction speed during special reproduction, and a code word representing a coefficient of an orthogonal transformation block of luminance data in the read black-and-white image data. , From the (n + 1) th code word to the end-of-block code By deleting up to the codewords up to, a natural number n is determined so that the code amount of the read monochrome image data is within a predetermined target code amount. Based on this n, the natural number n is determined for the read monochrome image data. A trick play data generating means for deleting code words and generating trick play data, and after converting the generated trick play data into the same format as the input digital image data to the intra data separating means, A digital image signal recording apparatus, comprising: recording signal generating means for generating a recording signal by synthesizing time-series with input digital image data; and recording means for recording the recording signal on a recording medium. [3] In the digital image signal recording apparatus according to claim 1 or 2, the special reproduction data generating means sets an image cycle N for reading out the black and white image data from the storage means as a reproduction double speed in the special reproduction. A digital image signal recording apparatus, wherein N = F · S, where S is the number and F is the display holding number of one image during the special reproduction. [4] The digital image signal recording apparatus according to claim 3, wherein the special reproduction data generating means compensates for (F-1) motions for the number of display holdings F of one image during the special reproduction. None, the forward prediction image data with no prediction error is generated, and this (F-1) forward prediction image data is added after each of the black-and-white image data from which the codeword has been deleted to perform special reproduction. Digital image signal recording apparatus for generating application data.

[0007]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing the configuration of an embodiment of a digital image signal recording apparatus according to the present invention. In the figure,
An MPEG2 transport stream obtained by packetizing a video stream compressed and encoded in accordance with MPEG2 is input as an input signal. While the input signal is input to the recording format conversion unit 1, it is supplied to an intra data separation circuit 2 to separate only I picture (intra frame) data. The separated I picture data is supplied to the color data removal circuit 3, where all the DCT (orthogonal transform) coefficient data of the chrominance block is removed and supplied to the zero coefficient addition circuit 4. The zero coefficient adding circuit 4 inserts the color difference data with zero DC error into the DCT coefficient portion of the color difference from which the supplied data has been removed to obtain monochrome image data, and stores the monochrome image data in the memory 5.

FIG. 2 specifically shows the operation of the color data removing circuit 3 and the zero coefficient adding circuit 4. The upper part shown in FIG. 2 is one screen of I picture data supplied to the color data removing circuit 3. From the I picture data, the color difference block D
Black and white image data shown in the lower part of FIG. 2 (output of the zero coefficient adding circuit 4) is obtained by removing all CT coefficient data and inserting color difference data with zero DC error in the removed part.
It is. Note that EOB in the drawing is an end code: End of
Block (end of block).

Returning to FIG. 1, the monochrome image data read from the memory 5 is supplied to a code amount calculation unit 7 and a DCT coefficient reduction circuit 6. The code amount calculation unit 7 determines the order n such that the code amount of the special reproduction data generated by the DCT coefficient reduction circuit 6 is equal to or less than a predetermined target code amount.
The DCT coefficient reduction circuit 6 determines n among the DCT coefficient data of the luminance block of the monochrome image data based on the order n.
From a code word corresponding to a coefficient of order +1 or higher to a code word immediately before an EOB (end of block) code, or n + 1
The packet re-synthesizing unit deletes the code word from the first code word to the code word immediately before the EOB (end of block) code (that is, deletes DCT coefficient data of higher-order luminance data) as a video stream for special reproduction. 8

[0010] The special reproduction video stream supplied to the packet resynthesizing unit 8 is packetized as the same MPEG2 transport stream as the input signal input to the intra data separation circuit 2. Thus, special reproduction data is generated. In this embodiment, the method of reducing the DCT coefficient data is the same as the conventional example.

The generated special reproduction data is supplied to a recording format converter 1. The recording format converter 1 records the input signal and the special reproduction data at predetermined positions on the magnetic tape.

Here, in the DCT coefficient data, n +
The code words corresponding to the first-order and higher-order coefficients and the (n + 1) th and subsequent code words will be briefly described. In encoding such as MPEG, a series of coefficients obtained by scanning DCT coefficients by zigzag scanning or the like is subjected to run-length encoding (a coefficient value (level) other than 0 and the number of 0 coefficients (run) therebetween). Represented by For example, the sequence of coefficients after scanning is d1, d2, d
3, 0, 0, d6, 0, d8. . . Then, in run-length encoding, the codeword is represented as (run, level)
(0, d1), (0, d2), (0, d3), (2, d
6), (1, d8). The codeword (2, d6) is the fourth codeword, and is a codeword corresponding to a sixth-order coefficient.

Next, in the present embodiment, the frame period N of the monochrome image data read from the memory 5 for generating the special reproduction data is changed to the special reproduction multiple speed S so that the intra frame period of the special reproduction data does not change. And the number F of display holding frames of one frame of the special reproduction image, N = F
It was a fixed value represented by S. This will be described with reference to FIG. For example, in the case of generating quadruple speed reproduction data (F = 4, S = 4) that reproduces one frame at a time every four frames, the frame period N is N = 4 × 4 = 16, and the input to the apparatus is The monochrome image data is read from the memory 5 once every 16 frames of the signal.

On the other hand, the monochrome image data is stored in the memory 5 in the intra cycle of the input signal. When an MPEG2 transport stream or the like generated by an encoding device that performs scene change detection is used as an input signal, the intra cycle of the input signal may change. However, in the present embodiment, the period for reading the monochrome image data from the memory 5 for generating the special reproduction data is constant, and is not affected by the intra period of the input signal. Therefore, even if the intra-cycle of the input signal changes, the intra-frame cycle of the special reproduction data does not change, and the special reproduction image does not become unnatural due to the change of the intra-cycle of the input signal.

In this case, there are data such as black-and-white image data (indicated as I4 in the figure) generated from the intra-frame I4 in FIG. 3 which are not recorded on the magnetic tape as special reproduction data. In some cases, black and white image data generated from the same intra-frame may be recorded twice consecutively as special reproduction data.

Next, in the case of quadruple-speed playback, after one intra-frame of black-and-white image data, no motion compensation is performed, and a black-and-white image previously encoded as a P picture (forward predicted image) with no prediction error. Special reproduction data may be generated by inserting three frames of image data. In this case, the frame rate at the time of reproducing the special reproduction data can be made equal to the frame rate of the normal reproduction data. Therefore, the reproducing apparatus at the time of reproduction can reproduce the data by the same reproducing means without considering whether it is the data for normal reproduction or the data for special reproduction.

[0017]

As described above, the digital image signal recording apparatus of the present invention deletes the color difference data when the special reproduction data is generated. Compared with data, the code amount is reduced, and recording at a low rate is possible. Further, in the present invention, the code amount of the color difference data can be allocated to the luminance data for the same code amount as the special reproduction data including the color difference data, and the code amount is equal to or less than the target code amount. Since higher-order DCT coefficients can be left as compared with the conventional example, it is possible to generate special reproduction data having a higher resolution. Further, the digital image signal recording apparatus has a read-out cycle N for reading black-and-white image data from the storage means in the special reproduction data generation means.
Where N = FS (S: playback speed during special playback, F: display holding number of one image during special playback), even if the intra-image period of the input digital image data fluctuates. It is possible to prevent the trick-play image from becoming unnatural.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment.

FIG. 2 is a diagram for explaining a black-and-white image data creation method in one embodiment.

FIG. 3 is a diagram showing an intra-image cycle of an input signal, a frame cycle of black-and-white image data, and special reproduction data in one embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Recording format conversion part 2 Intra data separation circuit 3 Color data removal circuit 4 Zero coefficient addition circuit 5 Memory 6 DCT coefficient reduction circuit 7 Code amount calculation part 8 Packet resynthesis part

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) FG23 GK08

Claims (4)

[Claims] 1. An apparatus for receiving digital image data compressed by inter-picture predictive encoding using orthogonal transform, and for separating intra image data from the digital image data, Color conversion means for removing color difference data from the extracted intra image data, inserting color difference data with zero DC error into the removed color difference data to generate black and white image data, and the black and white generated by the color conversion means Storage means for storing image data; and reading out the black-and-white image data from the storage means at an image cycle determined by a reproduction speed during special reproduction, and a coefficient of order n + 1 or higher of an orthogonal transformation block of luminance data in the read black-and-white image data. From the code word corresponding to , A natural number n is determined so that the code amount of the read monochrome image data is within a predetermined target code amount. Based on this n, the natural number n is determined for the read monochrome image data. A special reproduction data generating means for deleting words to generate special reproduction data; and converting the generated special reproduction data into the same format as the digital image data input to the intra data separation means. A digital image signal recording apparatus, comprising: recording signal generation means for generating a recording signal by synthesizing the digital image data in a time-series manner; and recording means for recording the recording signal on a recording medium. 2. Intra-data separating means for receiving digital image data compressed by inter-picture predictive encoding using orthogonal transformation, and separating intra-image data from the digital image data; Color conversion means for removing color difference data from the extracted intra image data, inserting color difference data with zero DC error into the removed color difference data to generate black and white image data, and the black and white generated by the color conversion means A storage unit for storing image data, and a code word representing coefficients of an orthogonal transformation block of luminance data in the read monochrome image data, wherein the monochrome image data is read from the storage unit at an image cycle determined by a reproduction speed during special reproduction. From the (n + 1) th codeword to the end of block By deleting up to the code word immediately before the symbol, a natural number n is determined so that the code amount of the read black-and-white image data is within a predetermined target code amount. On the other hand, a trick play data generating means for deleting the code word to generate trick play data, and the generated trick play data is converted into the same format as the input digital image data to the intra data separating means. Digital image signal recording, comprising: recording signal generating means for generating a recording signal by combining the input digital image data with the input digital image data in time series; and recording means for recording the recording signal on a recording medium. apparatus. 3. The digital image signal recording apparatus according to claim 1, wherein said special reproduction data generating means sets an image cycle N for reading said monochrome image data from said storage means, and A digital image signal recording apparatus characterized in that when the reproduction speed is S and the number of display holdings of one image during the special reproduction is F, N = FS. 4. The digital image signal recording apparatus according to claim 3, wherein said special reproduction data generating means is configured to generate one or more of the special reproduction data.
For the display holding number F of the image, forward prediction image data of (F-1) frames without motion compensation and no prediction error is generated, and the forward prediction image data of (F-1) frames is generated. A special reproduction data which is added after each of the black-and-white image data from which the codeword has been deleted to generate special reproduction data.