JP2005045698A - Device for creating data for special reproduction - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that data for special reproduction sometimes exceed the data size of an area TPA which is allocated as a recording area for data for special reproduction when the data for special reproduction is recorded on magnetic tape. <P>SOLUTION: An image data converting circuit 21 selects parts of an image to be displayed as a special reproduction image from input image data, and fills the rest of the image with image data which does not generate code amount. Specifically, it fills the rest of the image with monochromatic image data such as white and black. An image TP data creating circuit 22 encodes the converted image data as an I picture. A code amount judging circuit 23 judges whether the code amount of the encoded image data does not exceed a specified code amount. If it exceeds the specified code amount, the image data converting circuit 21 is controlled so as to perform conversion of the image data so that the number of pixels filling the black part is increased by a certain number with respect to that of the last time, according to the judgment signals from the code amount judging circuit 23. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a special reproduction data creation apparatus, and more particularly to a digital VCR (video cassette recorder) that records and reproduces MPEG2 (Moving Picture Experts Group 2) data, which is an international standard for image compression, on a recording medium such as a magnetic tape. 3), a special reproduction data creating apparatus for creating special reproduction data for reproduction at a speed different from that at the time of recording separately from normal reproduction data.

  In a digital VCR that records and reproduces a digital information signal on a recording medium such as a magnetic tape, a digital information signal obtained by compressing and encoding the information signal by MPEG2 is recorded and reproduced. Here, as is well known, encoding by MPEG2 employs motion compensation prediction, DCT (discrete cosine) conversion, and entropy encoding, and transmits encoded data in units of frames called pictures.

  The above pictures are classified into three types: I pictures, P pictures, and B pictures. An I picture is an intra-frame encoded image that is encoded in the same order as the original image, and can be reconstructed into a single frame by the I picture alone. A P picture is an inter-frame forward prediction encoded image that is predicted from a temporally previous (past) I picture or P picture. A B picture is an interframe bi-directional predictive encoded image that is predicted from a temporally later (future) and earlier (past) I picture or P picture.

  The above three types of pictures are appropriately combined to form a GOP (Group of Picture) and transmitted. Here, GOP is a unit of random access, and as shown in FIG. 4, one GOP includes one I picture, and includes a plurality of pictures including an I picture and a picture immediately before the next I picture. Composed. In one GOP, two B pictures are inserted between I pictures or P pictures in the example of FIG. The arrows in the figure indicate the direction of prediction, and in order to reconstruct the P picture and B picture, the data of the frame (picture) that is the basis of those predictions is necessary. A picture cannot be reconstructed alone. Also, since the encoded data amount of each picture is not fixed, the position on the tape to be recorded and the position of the image are not constant.

  Here, only the I picture encoding method will be briefly described together with a block diagram of an example of the encoding apparatus of FIG. The input original image is subjected to discrete cosine transform (DCT: Discrete Cosine Transform) by the DCT unit 1 in FIG. 5 and sent to the quantizer 2. The DCT-transformed coefficient is quantized by the quantizer 2 according to the value of the quantization scale and sent to a variable length coding (VLC) unit 3. The VLC unit 3 performs compression with variable statistical coding to reduce statistical redundancy by performing variable-length coding by assigning short codes to those with a high appearance probability among quantized DCT coefficients and assigning long codes to those with a low appearance probability. Generate and output data.

  Next, a format (HD digital VCR conference standard) for recording the compressed data (MPEG data) as described above on a digital VCR (DVCR: Digital Video Cassette Recorder) will be briefly described.

  FIG. 6 shows the recording format of the HD digital VCR conference standard. In the same figure, each track whose longitudinal direction is inclined with respect to the tape running direction is formed on the magnetic tape by a VCR which records and reproduces a digital signal with a rotary head on a running cassette type magnetic tape. Consists of an ITI area composed of insert information and track information, an audio data area, a video data area, and a subcode data area. Data such as audio and video is recorded in sync block units. However, MPEG data is recorded only in the video data area.

  As shown in FIGS. 6 and 7, the video data area is divided into a normal playback data area (NPA) and a special playback data area (TPA) such as high-speed playback. The reason why NPA and TPA are separated will be described. When there is no special reproduction data area (TPA), all the normal reproduction data is recorded in the video data area. In this case, when the reproduction is performed at a tape-head relative speed different from that for recording due to a request for fast-forward reproduction or the like, the first and second rotary heads straddle a plurality of recording tracks as indicated by HA and HB in FIG. Traveling with alternating scanning trajectories, of course, MPEG data can only be partially acquired.

  As described above, since MPEG data cannot be reconstructed by itself, the P picture and B picture data cannot be reconstructed alone. In the case of the above special reproduction, a special reproduction image can be obtained using only an I picture that can be decoded independently. The reproduced I picture data is not continuous on the screen and is fragmentary data. Moreover, since it is variable length encoded data, the position of the data on the screen does not correspond to the position on the magnetic tape. Therefore, it may not be possible to reproduce for a long time, and the specially reproduced image is very difficult to see as it is.

  Therefore, a position where the rotary head traces, that is, an area where data can be read, is always ensured in the track as TPA, and an I picture is recorded there as special reproduction data. The special reproduction data is created at the same time as the recorded MPEG transport stream is directly recorded on the NPA.

  Next, the MPEG transport stream will be briefly described with reference to FIG. With MPEG Transport Stream (MPEG-TS), it is possible to multiplex and transmit audio, text, etc. of various types of programs (programs) sent from each broadcasting station or images taken by various types of cameras. It is. This MPEG-TS program (program) designation method uses two-level pointers as follows.

  First, a program association table (PAT) included in a packet whose transport packet identification signal (PID) of the transport packet shown in FIG. 8A is PID = 0 is referred to. In this table, as shown in FIG. 8B, a table in which the program number indicating each program is associated with the PID of the transport packet including each PMT (program map table) is described.

  As shown in FIG. 8C, the PMT is a PID of a transport packet in which an elementary stream of each program (individual streams of images, sounds, character information, etc.) is transmitted or a PID of a packet including a clock. It is a table in which information such as is described. Therefore, when the program number of the desired program is designated with reference to the PAT, the PMT included in the PID of the program number is then referred to, and the PID in which each elementary stream of the desired program is transmitted is obtained. Images, sounds, character information, etc. of each program are obtained.

  Next, a conventional special reproduction data creation apparatus will be described with reference to the block diagram of FIG. First, a case where a specific program is recorded will be described. The MPEG-TS input from the input terminal 11 is supplied to the program extraction circuit 12, where data of a specific program to be recorded is extracted. The data of this specific program is data in which streams of images, sounds, character information, and the like are multiplexed as described in the method for acquiring a designated program from the transport stream. The data of this specific program is temporarily written in the NP buffer 13 for recording in the NPA as data for reproduction at the normal speed.

  On the other hand, the data of the specific program extracted by the program extraction circuit 12 is multiplexed with streams of images, sounds, character information, etc. as described above, so that only the image stream is extracted by the image stream extraction circuit 14. A stream including only an image signal of a specific program is output. The extracted image stream is decoded into an image signal by the image decoding circuit 15 and then temporarily stored in the image memory 16. The image data read out after being stored in the image memory 16 is generated into an encoded stream by the image TP data creation circuit 17 and written into the TP buffer 18 as special reproduction data (TP data).

  The NP and TP MPEG-TS written in the NP buffer 13 and the TP buffer 18 are read out and supplied to the track data creation circuit 19 where they are converted into a format to be written on the magnetic tape. Each data formatted by the track data creation circuit 19 is recorded at a predetermined position on the magnetic tape. That is, the data read from the NP buffer 13 is recorded in the normal reproduction data area NPA on the magnetic tape, and the data read from the TP buffer 18 is stored in the special reproduction data area TPA on the magnetic tape. To be recorded.

  When the input data is an image signal, the image signal is directly written from the terminal 10 to the image memory 16. The image TP data creation circuit 17 extracts image data from the image memory 16 at a predetermined timing. Subsequent processing is the same as described above.

  As described above, the special reproduction data area TPA has a limited area, and it is necessary to reduce the amount of data per recording time compared to the original amount of image data. For this reason, in general, only the I picture of the image data is extracted and then encoded so as to be smaller than the data amount writable to the TPA, thereby reducing the data amount.

  As a reduction method, a method of discarding other I pictures by using only a part of the I pictures in the I picture, a method of reducing the high frequency component of the image signal of the I picture, and reconstructing the image stream and again using MPEG An encoding method is conceivable.

  Here, the amount of encoded data of each picture in MPEG is not constant depending on the amount of high frequency components of the image, the speed of motion of the image, and the like. In general, since it is preferable to record normal reproduction with high image quality, a large amount of data is allocated and recorded in the normal reproduction data area NPA, and the special reproduction data area TPA is a sufficiently small data area compared to the NPA. It is desirable.

  Therefore, in the above-described conventional special reproduction data creation device, the special reproduction data amount written in the special reproduction data area TPA is used as the MPEG reproduction data amount per image written in the normal reproduction data area NPA. Compared to, the amount of data is extremely small. As a result, the image of the TPA MPEG stream (ie, the specially reproduced image) is significantly worse than the image of the NPA MPEG stream (ie, the normally reproduced image).

  Therefore, the present inventor has previously disclosed a special reproduction data creation device capable of improving the image quality of special reproduction data created when recording the transmitted MPEG-TS data on a recording medium (for example, patents). Reference 1). The conventional special reproduction data creation device described in Patent Document 1 is such that the image size is converted to the same or small with respect to the encoded image data compressed or encoded by the MPEG method or the decoded image data, and the image Image size conversion is performed so that the update rate is increased, and the image data after the image size conversion is composed of encoded image data encoded in the field or in the frame and N interframe forward prediction encoded image data. Special reproduction data is created.

JP 2003-37818 A

  Incidentally, the special reproduction data area TPA often has a certain data size, and it is desirable to use the data size of the TPA to the maximum in order to write the special reproduction image data to the TPA with high image quality. However, if special reproduction data created by a conventional special reproduction data creation apparatus is recorded on a magnetic tape, the data size of the TPA may be exceeded and may not fit within the TPA data size. When special reproduction is performed on a recording medium on which such special reproduction data is recorded, there may be a reproduced image in which the lower part of the screen is broken.

  The present invention has been made in view of the above points, and special reproduction data created when recording input MPEG2-TS data on a tape-shaped recording medium can be recorded within the data size of the writing area without image failure. It is an object of the present invention to provide a special reproduction data creation device that can be created to fit.

  In order to achieve the above object, the present invention provides special reproduction data to be reproduced from a tape-like recording medium at a tape-head relative speed different from that at the time of recording. In a special reproduction data creation apparatus for creating special reproduction data to be recorded in a different position from the recording area for the special data, a predetermined image portion of the first image data compressed and encoded by the MPEG method is used. Special data reproduction by image data conversion means for converting to second image data embedded with monochromatic image data and second image data output from the image data conversion means by intra-frame encoding or intra-field encoding The data generation means for generating data and the generated code amount of the special reproduction data output from the data generation means are equal to or less than the prescribed code amount that can be recorded in the predetermined area. If the generated code amount is larger than the prescribed code amount, the image data conversion means further expands the range of the predetermined image portion of the first image data and converts the expanded range to a single color. And a code amount determination unit that controls to fill with image data, and outputs the special reproduction data determined by the code amount determination unit to be equal to or less than a predetermined code amount.

  According to the present invention, since the generated code amount of the intra-frame encoded image or the intra-field encoded image which is the special reproduction data is set to be equal to or less than the specified code amount, the normal reproduction data is recorded on the tape-shaped recording medium. It is possible to store the special reproduction data, which is distributed in a different position from the area and recorded in the predetermined area, within the data size of the predetermined area without image failure.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a block diagram of a first embodiment of a special reproduction data creation apparatus according to the present invention. In the figure, the same components as those in FIG. 9 are denoted by the same reference numerals. In this embodiment, an image data conversion circuit 21 and a code amount determination circuit 23 are added to the conventional apparatus shown in FIG. 9, and the image TP data generation circuit 22 is different from the image TP data generation circuit 17 of the conventional apparatus. There is a feature in the point.

  In FIG. 1, MPEG-TS input through an input terminal 11 is extracted by a program extraction circuit 12 from a specific program to be recorded. The data of a specific program to be recorded is a multiplexed stream of images, sounds, character information, etc., and is temporarily written in the NP buffer 13 for recording in the NPA as normal playback data for playback at a normal speed. It is.

  On the other hand, the special reproduction data (TP data) is created as follows simultaneously with the normal reproduction data. Since the data (transport stream) of the specific program to be recorded output from the program extraction circuit 12 is multiplexed with streams of images, sounds, character information, etc. as described above, the image stream extraction circuit 14 Only the image stream is extracted from the data, and a stream including only the image signal of the specific program is output.

  The image stream of the specific program extracted by the image stream extraction circuit 14 is decoded into image data by the image decoding circuit 15, temporarily stored in the image memory 16, and then supplied to the image data conversion circuit 21. .

  The image data conversion circuit 21 selects an image portion to be displayed as a special reproduction image from the input image data, and fills the remaining image portion with image data that does not generate a code amount. Specifically, since it is known that the smaller the number of high frequency components of an image, the smaller the amount of generated code, it is filled with monochromatic image data such as white and black.

  For example, assuming that image data related to the image 25 shown in FIG. 2A having 720 pixels in the horizontal direction and 480 pixels in the vertical direction is stored in the image memory 16, the image data conversion circuit 21 is configured as shown in FIG. As shown in FIG. 8, black images 26a and 26b each having 8 pixels are embedded above and below the image 25 and converted into image data of 720 pixels in the horizontal direction and 480 pixels in the vertical direction (= 8 (black) + 464 + 8 (black)). At this time, if the unit of image data of the same value is 8 pixels in both the horizontal direction and the vertical direction, DCT used in MPEG or the like is performed in units of 8 pixels in both the horizontal direction and the vertical direction. Become.

  The image data converted as described above by the image data conversion circuit 21 is encoded by the image TP data creation circuit 22 as, for example, an I picture in the format of MPEG Video data, and then supplied to the code amount determination circuit 23. It is determined whether or not the code amount is within the prescribed code amount. If the code amount is within the prescribed code amount, the code is supplied to the TP buffer 18 and temporarily accumulated.

  On the other hand, when the code amount does not fall within the prescribed amount, the image data conversion circuit 21 converts the image data so that the number of pixels to be filled with black is increased by a certain amount from the previous time based on the determination signal from the code amount determination circuit 23. To be controlled. Whether the converted image data output from the image data conversion circuit 21 by this control is encoded again by the image TP data creation circuit 22 and then supplied to the code amount determination circuit 23 to be within a prescribed code amount. Please judge again.

  Thereafter, the above operation is repeated until the code amount determination circuit 23 falls within a predetermined code amount. In this way, image TP data having a prescribed code amount or less is extracted from the code amount determination circuit 23 as special reproduction data (TP data) and written into the TP buffer 18. The NP and TP MPEG-TS written in the NP buffer 13 and the TP buffer 18 are read out and supplied to the track data creation circuit 19 where they are converted into a format to be written on the tape-shaped recording medium.

  The data formatted by the track data creation circuit 19 is recorded at a predetermined position on the recording medium. That is, the data read from the NP buffer 13 is recorded in the normal reproduction data area NPA on the magnetic tape, and the data read from the TP buffer 18 is the special reproduction data on the tape-shaped recording medium. Recorded in area TPA.

  As described above, according to the present embodiment, the special reproduction data created when the input MPEG2-TS data is recorded on the tape-shaped recording medium can be recorded within the data size of the writing area TPA without image failure. Can fit.

  Next, a second embodiment of the present invention will be described. FIG. 3 is a block diagram showing a second embodiment of the special reproduction data creating apparatus according to the present invention. In the figure, the same components as those in FIG. In the present embodiment, a DCT coefficient reduction circuit 28 is provided in place of the image data decoding circuit 15 and the image memory 16 of the apparatus of the first embodiment shown in FIG. The feature is that the operation is different from that of the image data conversion circuit 21.

  In FIG. 3, the stream including only the image signal of the specific program output from the image stream extraction circuit 14 is supplied to the DCT coefficient reduction circuit 28, where the DCT coefficient of the image is checked for all blocks or a part of the blocks. And higher order components are made zero. Here, the DCT coefficient is a block unit of 0 × 8 pixels (in the case of a luminance signal) from the 0th pixel to the 63rd pixel (0: DC coefficient, 1 to 63: AC coefficient), and the AC coefficient is encoded. However, if the DCT coefficient of the higher-order component (other than the DC component) is set to 0 as described above, it is not necessary to transmit the DCT coefficient, and the amount of VLC (variable length code) code generation is reduced.

  On the other hand, if the luminance signal Y of the image information and the color difference signals Cb and Cr have the same value over a certain range, they appear visually as a single color. At this time, the frequency component of the image becomes small, and the higher order component becomes zero. In the image data conversion circuit 29, a DCT coefficient that becomes a single color (for example, black) is prepared in advance, and higher-order components (other than the DC component) of the luminance signal Y, the color difference signals Cb, and Cr of the image information are determined in advance. Replace with the original DCT coefficients of zero for a predetermined number of blocks.

  The image data converted as described above by the image data conversion circuit 29 is encoded by the image TP data creation circuit 22, for example, as an I picture in the format of MPEG Video data, and then supplied to the code amount determination circuit 23. It is determined whether or not the code amount is within the specified amount. When the code amount does not fall within the prescribed code amount, the image data conversion circuit 29 sets the number of 8 × 8 pixel blocks of DCT coefficients that become a single color (for example, black) from the previous time based on the determination signal from the code amount determination circuit 23. Is also controlled to convert the image data so as to increase a certain number. Whether the converted image data output from the image data conversion circuit 29 by this control is encoded again by the image TP data creation circuit 22 and then supplied to the code amount determination circuit 23 to be within the prescribed code amount. Please judge again.

  Thereafter, the above operation is repeated until the code amount determination circuit 23 falls within a predetermined code amount. In this way, image TP data having a prescribed code amount or less is extracted from the code amount determination circuit 23 as special reproduction data (TP data) and written into the TP buffer 18. Also in this case, the reproduced image of the TP data is an image as shown in FIG.

  Note that the present invention is not limited to the above-described embodiment. For example, the image TP data generation circuit 22 performs encoding in order from the upper left to the lower right of the screen in units of 16 × 16 pixel macroblocks. When encoding macroblocks in order, a threshold is set before exceeding the code amount of the range where all remaining macroblocks can be stored in blocks with a small amount of generated code (dummy blocks). When the code amount determination circuit determines that the threshold value is exceeded, a dummy block may be replaced from the macroblock location exceeding the threshold value.

  In addition, although the image position that appears as a single color (for example, black) on the screen is two places, the upper part and the lower part of the screen, either one may be present, or both or one of the right and left in the middle of the image may be present. Further, the special reproduction data has been described as an I picture which is an intra-frame encoded image, but may be encoded as an I picture which is an intra-field encoded image.

  According to the present invention, when creating the special playback data, at least one of the vertical and horizontal image sizes, the picture code amount, the image update rate, and the image activity of the input video encoded data is used. By using the method of determining the image size and the image update rate of data, an appropriate image update rate and resolution of the special reproduction image can be obtained.

  For example, in order to stabilize the image quality, the image size can be reduced by a filter (in this case, the code amount per block can be reduced, the sense of resolution is lost, but block noise does not occur), and the image is updated. A method such as decreasing the rate (in this case, increasing the amount of code given to the I picture when the transfer rate is constant) is adopted.

  On the other hand, in order to increase the image update rate and increase the number of images so that they can be easily searched, even if the image size is reduced by a filter and the code amount given to the I picture is small when the transfer rate is constant, block noise Increase the update rate. A high image update rate is effective because the human visual sensitivity to resolution tends to be weak (the human eye cannot follow fast-moving objects).

  In addition, regarding the selection of whether the encoding structure is an interlace structure or a progressive structure, switching between normal reproduction data reproduction and special reproduction data reproduction is performed by selecting the one that matches the encoding structure of the NP stream. The resetting that occurs in the display is prevented, and the display switching time of the display device is shortened.

It is a block diagram of a 1st embodiment of the present invention. FIG. 2 is a block diagram of an embodiment of an image TP data creation circuit in FIG. 1. It is a block diagram of the 2nd Embodiment of this invention. It is a figure which shows the kind etc. of an MPEG picture. It is a block diagram of an example of the encoding circuit of I picture. This is a digital VCR recording format. This is a video data area of a digital VCR. It is a figure explaining an MPEG transport stream. It is a block diagram of an example of a conventional device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 MPEG transport stream input terminal 12 Program extraction circuit 13 NP buffer 14 Image stream extraction circuit 15 Image decoding circuit 16 Image memory 18 TP buffer 19 Track data creation circuit 21, 29 Image data conversion circuit 22 Image TP data creation circuit 23 Code Quantity determination circuit 28 DCT coefficient reduction circuit

Claims (1)

Special playback data to be played back from the tape-like recording medium at a different tape-to-head relative speed than when recording, and distributed on the tape-like recording medium at different positions from the normal playback data recording area. In the special reproduction data creation device for creating the special reproduction data to be recorded as
Image data conversion means for converting a predetermined image portion of the first image data compressed and encoded by the MPEG method into second image data embedded with monochrome image data;
Data creation means for creating the special reproduction data by intra-frame coding or intra-field coding of the second image data output from the image data conversion means;
It is determined whether or not the generated code amount of the special reproduction data output from the data creating means is equal to or less than a specified code amount that can be recorded in the predetermined area, and the generated code amount is the specified code When the amount is larger than the amount, a code amount determination is performed to control the image data converting means to further expand the range of the predetermined image portion of the first image data and fill the expanded range with the monochrome image data. Means for outputting the special reproduction data determined by the code amount determination means to be equal to or less than the specified code amount.

Images