JP2010148042A - Recording device, recording method, and computer program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recording device which can easily practice an operation in units of frames while reducing an amount of data to be recorded, using a compression system not utilizing a correlation between frames. <P>SOLUTION: The recording device controls as follows. An optional frame in image data is set as a reference frame, and after the whole image data of the reference frame is encoded in an encoding portion, it is decoded and memorized in a memory portion, and a difference between the image data of the following frame of the reference frame and the image data of the reference frame memorized in the memory portion is obtained, and the difference data is encoded in the encoding portion, and when the encoded data satisfies the predetermined condition, the next frame also obtains the difference between the reference frame, and otherwise the next frame is controlled to be a reference frame. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a recording apparatus, a recording method, and a computer program.

  A hard disk video recorder is an apparatus that compresses an input video signal, converts it into digital video data, and records it on an HDD (Hard Disk Drive). Digital video data recorded on the HDD can be decoded into a video signal and reproduced. In order to realize such a function, the hard disk video recorder needs to control the HDD which is a storage device, and generally uses an OS (operating system) as a system for controlling the HDD. The OS controls the file system responsible for recording on the HDD, thereby controlling the recording or reproduction of the file when recording the digital video data on the HDD or reproducing the digital video data from the HDD.

  In such an OS, when the specification of a video signal handled by a hard disk video recorder is increased, the amount of data per unit time recorded on the hard disk drive increases as the specification improves. Improvements in specifications include, for example, changing the standard image quality to a high image quality, changing the screen resolution from the standard to HD (High Definition), and changing the frame rate from the standard to a high frame rate. Therefore, since the amount of data per unit time recorded in the HDD increases in the same manner, high-speed recording is required for the HDD.

  The HDD is a rotating recording medium, and the continuous recording speed has been increased by improving the rotational speed and increasing the density of magnetic recording by the head, and the recording speed of the data amount per unit time has improved, but there is still a limit. . In order to improve the performance of recording and reproducing digital video data, it is necessary to improve the recording speed and increase the recording capacity in order to cope with the increase in the amount of data per unit time in the HDD. However, there is a limit to the improvement in recording speed and the increase in recording capacity, which hinders data recording to the HDD exceeding the limit speed.

  Under such circumstances, when recording is performed in a field where fidelity is required for the content of the video recorded from the camera, the recorded video signal and the reproduced video signal are the same, lossless compression (lossless) It is necessary to perform recording and playback using a codec. Examples of such fields include the medical field, the art field, and the historical field. When recording is performed using the lossless compression codec, the capacity of the video data increases. Therefore, techniques for reducing the recording capacity are disclosed in, for example, Patent Documents 1 to 3.

JP-A-6-133305 JP 2005-101835 A JP 2001-128124 A

  In lossless recording / reproduction that performs faithful recording / reproduction in such fields, even if a codec that compresses data is used for recording / reproduction, the compression rate is not high and the data compression efficiency is not very good. For this reason, when recording and reproducing a high-quality video signal with a hard disk video recorder, the amount of data increases as the video specs increase. On the other hand, if faithful recording / reproduction is performed, the compression rate of the codec that compresses data is low, so the amount of data required for recording / reproduction increases per unit time, and the limit of the recording / reproduction speed per unit time to the HDD It will be close to or exceeding the point, which will interfere with recording and playback. In addition, if the amount of data required for recording / playback per unit time increases and the amount of data per unit time on the HDD increases, there is a problem that the recording file size of digital video data for the same time increases.

  On the other hand, the compression rate can be increased by using a codec having a high compression rate using intra-frame compression and inter-frame correlation. However, codecs with high compression ratios that use such intra-frame compression and inter-frame correlation generally use complex inter-frame correlations. There is a problem that becomes difficult. Specifically, in multiple-speed playback or reverse playback in trick play, it is possible to easily use an intra-frame compression-only codec that allows easy operation of skipping the target frame. However, it is difficult to use a codec having a correlation between frames when performing an operation of skipping a target frame. In codecs that use both intra-frame compression and inter-frame correlation, it is necessary to operate and play back frames that have undergone frame correlation in addition to operations that skip frames that are subject to trick play. There are complications.

  Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to use a compression method that does not use inter-frame correlation, while reducing the amount of data to be recorded and at the time of reproduction. It is an object of the present invention to provide a new and improved recording apparatus, recording method, and computer program capable of easily performing frame-by-frame operations.

  In order to solve the above problems, according to an aspect of the present invention, an encoding unit that encodes video data by an encoding method that does not use inter-frame correlation, and decoding video data encoded by the encoding unit A decoding unit, a storage unit that temporarily stores the video data decoded by the decoding unit, and a control unit that controls recording of the video data encoded by the encoding unit on a recording medium. Set an arbitrary frame as a reference frame, the entire video data of the reference frame is encoded by the encoding unit, then decoded by the decoding unit and stored in the storage unit, the video data of the subsequent frame of the reference frame, The difference between the reference frame and the video data stored in the storage unit is acquired, the difference data is encoded by the encoding unit, and if the encoded data satisfies a predetermined condition, the next frame is also compared with the reference frame. Get the difference If Tasa controls to the next frame and the reference frame, the recording apparatus is provided.

  According to such a configuration, the encoding unit encodes the video data by an encoding method that does not use inter-frame correlation, and the decoding unit decodes the video data encoded by the encoding unit. The storage unit temporarily stores the video data decoded by the decoding unit, and the control unit controls recording of the video data encoded by the encoding unit on the recording medium. The control unit sets an arbitrary frame as a reference frame, encodes the entire video data of the reference frame by the encoding unit, decodes the decoded data by the decoding unit, and stores the decoded data in the storage unit. The difference between the video data of the subsequent frame of the reference frame and the video data of the reference frame stored in the storage unit is encoded by the encoding unit, and if the encoded data satisfies a predetermined condition, the next frame Also, the difference from the reference frame is acquired, and if not satisfied, the next frame is set as the reference frame. As a result, it is possible to reduce the amount of data to be recorded while using a compression method that does not use inter-frame correlation. By recording video data in this way, it becomes possible to easily perform operations in units of frames during reproduction.

  The predetermined condition may be that a capacity of the difference data after being encoded by the encoding unit is equal to or less than a predetermined capacity. Further, the predetermined condition may be that the number of frames from which the difference is acquired is equal to or less than a predetermined number.

  The encoding unit may encode all the frames by a lossless compression method.

  The encoding unit may encode the video data of the reference frame using the lossless compression method, and may encode the video data of a frame other than the reference frame using the lossy compression method. .

  The encoding unit may encode all the frames using an irreversible compression method.

  The recording medium for recording the video data may be a medium that can be randomly accessed.

  In order to solve the above-described problem, according to another aspect of the present invention, a setting step for setting an arbitrary frame as a reference frame, and video data of the reference frame are encoded by an encoding method that does not use inter-frame correlation. An encoding step, a decoding step for decoding the video data encoded in the encoding step, a storage step for temporarily storing the video data decoded in the decoding step, and video data of a frame subsequent to the reference frame, The difference acquisition step for acquiring the difference from the video data of the reference frame stored in the storage step and the difference data acquired in the difference acquisition step are encoded, and if the encoded data satisfies a predetermined condition, The frame also includes a step of obtaining a difference from the reference frame and, if not satisfied, determining the next frame as the reference frame. Recording method is provided.

  In order to solve the above-described problem, according to another aspect of the present invention, a setting step for setting an arbitrary frame as a reference frame in a computer and an image of the reference frame by an encoding method that does not use inter-frame correlation An encoding step for encoding data; a decoding step for decoding the video data encoded in the encoding step; a storage step for temporarily storing the video data decoded in the decoding step; and a frame subsequent to the reference frame A difference acquisition step for acquiring a difference between the video data and the video data of the reference frame stored in the storage step; and the difference data acquired in the difference acquisition step is encoded, and the encoded data satisfies a predetermined condition. If the next frame also obtains the difference from the reference frame, and if the difference is not satisfied, the next frame is used as the reference frame. And flop, to the execution, the computer program is provided.

  As described above, according to the present invention, a compression method that does not use inter-frame correlation is used, and the amount of data to be recorded can be reduced, but the operation in units of frames can be easily performed during playback. In addition, an improved recording apparatus, recording method, and computer program can be provided.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

Further, preferred embodiments of the present invention will be described in detail according to the following order.
<1. Conventional hard disk recorder>
[1-1. Configuration of conventional hard disk recorder]
[1-2. Problems in conventional video data recording]
<2. Hard Disk Recorder According to One Embodiment of the Present Invention>
[2-1. Configuration of Hard Disk Recorder According to One Embodiment of the Present Invention]
[2-2. Video data recording method according to an embodiment of the present invention]
[2-3. Video data playback method according to an embodiment of the present invention]
[2-4. Modification of one embodiment of the present invention]
<3. Summary>

<1. Conventional hard disk recorder>
[1-1. Configuration of conventional hard disk recorder]
First, before describing the preferred embodiment of the present invention in detail, the configuration and operation of a conventional hard disk recorder will be described. FIG. 6 is an explanatory diagram showing the configuration of the conventional hard disk recorder 10.

  As shown in FIG. 6, the conventional hard disk recorder 10 includes a video input unit 11, a stream encoding unit 12, a system control unit 13, a file system 15, an HDD (Hard Disk Drive) 16, and stream decoding. A unit 17, a video synchronization unit 18, and a video output unit 19 are included.

  The video input unit 11 receives an input of a video signal generated outside the hard disk recorder 10 (for example, a video camera). When the video input unit 11 receives a video signal from the outside, the video input unit 11 generates a vertical synchronization signal, a horizontal synchronization signal, a clock signal, and the like used in the subsequent block from the received video signal under the control of the system control unit 13 described later. . The video data included in the video signal input by the video input unit 11 is sent to the subsequent stream encoding unit 12, and the vertical synchronization signal, horizontal synchronization signal, clock signal and other signals generated by the video input unit 11 are video. It is sent to the synchronization unit 18.

  The stream encoding unit 12 executes encoding processing (codec processing) on video data using video data sent from the video input unit 11 when recording video data on the HDD 16. The encoding process in the stream encoding unit 12 is executed under the control of the system control unit 13 described later. The video data is compressed by executing codec processing in the stream encoding unit 12. The video data compressed by the stream encoding unit 12 is recorded on the HDD 16 under the control of the system control unit 13.

  The system control unit 13 controls the operation of each unit of the hard disk recorder 10. The system control unit 13 includes a RAM (Random Access Memory) 14 for temporarily storing information used for controlling the operation of each unit of the hard disk recorder 10. The file system 15 controls recording of video data on the HDD 16 and operates under the control of the system control unit 13.

  In the HDD 16, the video data compressed by the stream encoding unit 12 is recorded under the control of the file system 15.

  The stream decoding unit 17 reads the video data from the HDD 16 and reproduces the decoding process corresponding to the encoding process in the stream encoding unit 12 when reproducing the video data recorded in the HDD 16. When reproducing the video data, the file read from the HDD 16 is managed by the file system 15. The decoding process in the stream decoding unit 17 is executed under the control of the system control unit 13. The video data decoded by the stream decoding unit 17 is sent to the video output unit 19.

  The video synchronization unit 18 generates a horizontal synchronization signal and a vertical synchronization signal necessary for reproducing video data recorded on the HDD 16. The synchronization signal generation process in the video synchronization unit 18 is executed under the control of the system control unit 13. The synchronization signal generated by the video synchronization unit 18 is sent to the video output unit 19 and is added to the video data subjected to the decoding process by the stream decoding unit 17 to become a video signal.

  The video output unit 19 generates a video signal by adding the horizontal synchronization signal and the vertical synchronization signal generated by the video synchronization unit 18 to the video data decoded by the stream decoding unit 17. . The video signal output from the video output unit 19 has the same waveform as the video signal input to the video input unit 11. The video signal generated by the video output unit 19 is sent to an external device such as a television, a display device, a projector, etc., and displayed as a video.

[1-2. Problems in conventional video data recording]
The configuration of the conventional hard disk recorder has been described above using the hard disk recorder 10 shown in FIG. 6 as an example. In the conventional hard disk recorder 10 having such a configuration, generally, the stream encoding unit 12 performs codec processing and encodes a video signal to reduce the amount of data. MPEG (Moving Picture Experts Group) is a widely used codec for the purpose of reducing the amount of data. MPEG is a codec that compresses data using intra-frame compression and inter-frame correlation. However, a codec such as MPEG, which is a popular codec, has a high compression rate, but is generally not lossless compression (lossless).

  Therefore, when JPEG (Joint Photographic Experts Group) or JPEG2000 is used in the lossless mode in order to perform lossless compression, the compression rate is low. Therefore, in order to perform high-fidelity recording and reproduction with lossless compression with a hard disk video recorder, there is a problem that the amount of recording and reproduction data required per unit time increases because the compression rate of the codec is low. Such a problem causes a problem that the limit of the recording / reproducing speed per unit time on the HDD is approached or exceeded. Further, when the amount of recording / playback data required per unit time increases and the amount of data per unit time on the HDD increases, there is a problem that the recording file size of digital video data for the same time increases.

  Further, when reproducing the video data recorded by the hard disk recorder 10 which has been encoded using the inter-frame correlation, an operation called FF (fast forward) or FR (fast reverse) is performed. And the signal processing operation becomes complicated. That is, it is necessary to read out frame data necessary for FF reproduction or FR reproduction while skipping frames. Therefore, when encoding using inter-frame correlation is used during FF playback or FR playback, when decoding a frame from data read while skipping the frame, It is necessary to read and process data. Therefore, when encoding using inter-frame correlation is performed, the FF playback processing and FR playback processing operations become complicated.

  On the other hand, when a codec that compresses video data using only intra-frame compression, such as JPEG 2000 or JPEG, video data can be easily decoded even in the case of FF playback or FR playback. Since such a codec does not use correlation between frames, the decoding process of continuous frames and the decoding process while skipping frames can be processed in exactly the same way, so that the process is not complicated.

  However, a codec that uses only intra-frame compression such as JPEG2000 does not use the correlation between frames of video data, and therefore generally has a low compression rate. In other words, if the correlation between frames of video data is used, it means that the data can be further compressed. Therefore, further compression is possible by adding the concept of inter-frame correlation to codecs that use only intra-frame compression, such as JPEG 2000, but adding the concept of inter-frame correlation allows decoding processing while skipping frames. It becomes difficult to respond.

  Therefore, in the present invention, when video data is encoded and recorded using an encoding method that does not use inter-frame correlation, a difference from the basic frame is acquired and encoded using a certain frame as a basic frame. If the encoded difference video data satisfies a predetermined condition, the difference video data is recorded. If not, the video data is recorded as a new basic frame instead of the difference. By recording video data in this way, it is possible to cope with decoding processing while skipping frames while reducing the compression rate. Hereinafter, preferred embodiments of the present invention will be described in detail.

<2. Hard Disk Recorder According to One Embodiment of the Present Invention>
[2-1. Configuration of Hard Disk Recorder According to One Embodiment of the Present Invention]
FIG. 1 is an explanatory diagram showing the configuration of a hard disk recorder 100 according to an embodiment of the present invention. Hereinafter, the configuration of a hard disk recorder 100 according to an embodiment of the present invention will be described with reference to FIG.

  The hard disk recorder 100 records video data in a built-in HDD, reads the recorded video data from the HDD, and plays it back. As shown in FIG. 1, a hard disk recorder 100 according to an embodiment of the present invention includes a video input unit 102, a subtraction unit 103, a stream encoding unit 104, a system control unit 106, and a file size detection unit 110. A file system 112, an HDD 114, a stream decoding unit 116, a first frame memory 118, a second frame memory 120, an addition unit 121, a video synchronization unit 122, and a video output unit 124. Composed.

  The video input unit 102 receives an input of a video signal generated outside the hard disk recorder 100 (for example, a video camera). When the video input unit 102 receives a video signal from the outside, the video input unit 102 generates, from the received video signal, a vertical synchronization signal, a horizontal synchronization signal, a clock signal, and the like used in the subsequent block under the control of the system control unit 106 described later. . The video data included in the video signal input by the video input unit 102 is sent to the subsequent stream encoding unit 104, and the vertical synchronization signal, horizontal synchronization signal, clock signal and other signals generated by the video input unit 102 are video. It is sent to the synchronization unit 122. When the video signal input to the video input unit 102 is an analog signal, the analog signal is converted into a digital signal. At this time, an A / D conversion unit that executes A / D conversion processing may be provided inside the video input unit 102.

  When the video data is recorded on the HDD 114, the stream encoding unit 104 executes an encoding process (codec process) on the video data for each frame using an input signal. In the hard disk recorder 100 according to the present embodiment, JPEG 200 is used as a codec. JPEG2000 is a codec with no inter-frame correlation, and performs color space coordinate conversion on the input image signal as necessary, performs wavelet conversion (DWT) for each color of the signal, and codes the coefficients independently. It is to become. DWT includes an integer type filter with a relatively simple circuit configuration capable of reversible conversion, and a real number type filter that cannot perform reversible conversion but has better image quality than the integer type. In the present embodiment, a lossless compression (lossless) mode using an integer filter is used for wavelet transform.

  In JPEG2000, the DWT transform coefficient is decomposed into bit planes and divided into encoded blocks of a certain size (for example, 64 × 64) in each subband, and then binary arithmetic coding is performed. The transform coefficient value in each coding block is divided into sign bits (positive: 0, negative: 1) and absolute value information, and the absolute value is expressed in a natural binary system and encoded sequentially from the upper bit plane. When the entirety of each subband of the screen is close to black, all zero bit planes are continuous from the upper bit plane, so that encoding is efficient. Specifically, the number of all 0 bit planes from the upper plane excluding the sign bit plane is stored in the encoding header, and the encoding of all 0 bit planes is skipped. For this reason, the amount of recording / playback data required per unit time is reduced for an image whose screen is close to black. In this embodiment, this JPEG2000 encoding property is used.

  The encoding process in the stream encoding unit 104 is executed under the control of the system control unit 106 described later. By executing codec processing in the stream encoding unit 104, the video data is compressed. The video data compressed by the stream encoding unit 104 is recorded on the HDD 114 under the control of the system control unit 106. The stream encoding unit 104 subtracts an image signal stored in a first frame memory 118 (to be described later) from an image signal input to the video input unit 102 by a subtracting unit 103 according to a frame. The signal is encoded. Details of the encoding process in the hard disk recorder 100 will be described later.

  The system control unit 106 controls the operation of each unit of the hard disk recorder 100. The system control unit 106 includes a RAM (Random Access Memory) 108 as a work area at the time of controlling each unit of the hard disk recorder 100. The file system 112 controls the recording of video data on the HDD 114 and operates under the control of the system control unit 106. The HDD 114 is a recording medium that can be randomly accessed, and the video data compressed by the stream encoding unit 104 is recorded under the control of the file system 112.

  The file size detection unit 110 determines whether the video data encoded by the stream encoding unit 104 is less than a predetermined capacity. In this embodiment, the video data to be encoded is changed by the file size detection unit 110 determining whether the video data encoded by the stream encoding unit 104 is less than a predetermined capacity. It is characterized by.

  The stream decoding unit 116 reads the video data from the HDD 114 and executes the decoding process corresponding to the encoding process in the stream encoding unit 104 when reproducing the video data recorded in the HDD 114. When reproducing the video data, the file read from the HDD 114 is managed by the file system 112. The decoding process in the stream decoding unit 116 is executed under the control of the system control unit 106. The video data decoded by the stream decoding unit 116 is sent to the video output unit 124, and the video data of a reference frame (hereinafter also referred to as “base frame”) is stored in the first frame memory 118 and the second frame memory. 120.

  The first frame memory 118 and the second frame memory 120 are memories for storing base frame video data. The video data stored in the first frame memory 118 is for obtaining a difference from the video data input to the video input unit 102. The video data stored in the second frame memory 120 is used to generate video data of the frame by adding it to the video data of the frame recorded in the HDD 114 as a difference when reproducing the video. .

  The video synchronization unit 122 generates a horizontal synchronization signal and a vertical synchronization signal necessary for reproducing video data recorded in the HDD 114. The synchronization signal generation processing in the video synchronization unit 122 is executed under the control of the system control unit 106. The synchronization signal generated by the video synchronization unit 122 is sent to the video output unit 124 and is added to the video data subjected to the decoding process by the stream decoding unit 116 to become a video signal.

  The video output unit 124 generates a video signal by adding the horizontal synchronization signal and the vertical synchronization signal generated by the video synchronization unit 122 to the video data decoded by the stream decoding unit 116. . The video signal output from the video output unit 124 has the same waveform as the video signal input to the video input unit 102. The video signal generated by the video output unit 124 is sent to an external device such as a television, a display device, a projector, etc., and displayed as a video.

  The configuration of the hard disk recorder 100 according to the embodiment of the present invention has been described above. Next, a video data recording method using the hard disk recorder 100 according to an embodiment of the present invention will be described.

[2-2. Video data recording method according to an embodiment of the present invention]
FIG. 2 is a flowchart for explaining a video data recording method using the hard disk recorder 100 according to the embodiment of the present invention. Hereinafter, a video data recording method using the hard disk recorder 100 will be described with reference to FIG.

  When video data is recorded on the hard disk recorder 100, a video signal is first input to the video input unit 102 (step S102). When a video signal is input to the video input unit 102, a vertical synchronization signal, a horizontal synchronization signal, a clock signal, and the like are generated, and then the video data included in the input first frame video signal is reversibly compressed using the JPEG2000 method. Depending on the mode, the stream encoder 104 performs encoding (step S104).

  When the video data of the first frame is encoded by the stream encoding unit 104, the encoded video data of the first frame is recorded on the HDD 114 under the control of the file system 112 (step S106). Then, the video data of the first frame recorded in the HDD 114 is read under the control of the file system 112 and decoded by the stream decoding unit 116 (step S108). When the video data of the first frame is decoded by the stream decoding unit 116, the first frame is stored in the first frame memory 118 and the second frame memory 120 as the base frame (step S110). When the video data of the first frame is stored in the first frame memory 118 and the second frame memory 120, the system control unit 106 determines whether or not the frame encoded in step S104 is the last frame (step S112). . If the result of determination in step S112 is that the frame encoded in step S104 is the last frame, the video data recording process ends. On the other hand, if the result of determination in step S112 is that the frame encoded in step S104 is not the last frame, the video data of the subsequent frame is input to the video input unit 102 (step S114).

  When the video data of the subsequent frame is input to the video input unit 102, the subtraction unit 103 calculates the difference between the video data of the base frame stored in the first frame memory 118 in step S110 and the video data of the frame. Obtain (step S116). Then, the difference between the video data of the base frame and the video data of the frame is encoded by the stream encoding unit 104 in the JPEG2000 format lossless compression mode (step S118).

  After encoding in step S118, the encoded video data is recorded on the HDD 114 under the control of the file system 112 (step S120). Then, the system control unit 106 determines whether the frame is the last frame (step S122).

  If the result of determination in step S122 is that the frame encoded in step S118 is the last frame, the video data recording process ends. On the other hand, if the result of determination in step S122 is that the frame encoded in step S118 is not the last frame, it is determined whether or not the capacity of the video data encoded in step S118 is less than or equal to a predetermined capacity. (Step S124).

  As a result of the determination in step S124, if the capacity of the video data encoded in step S118 is less than or equal to a predetermined capacity, the process returns to step S114 and the video signal is input by the video input unit 102. Thereafter, the processing up to step S122 is repeated, and the encoding process for the difference video data is continued.

  On the other hand, as a result of the determination in step S124, if the capacity of the video data encoded in step S118 exceeds a predetermined capacity, the process returns to step S102, and the video signal of the next frame is received by the video input unit 102. input. Thereafter, the processing up to step S110 is executed, and video data is stored in the first frame memory 118 and the second frame memory 120 in order to newly set a frame input to the video input unit 102 as a base frame.

  In this way, the difference between the base frame and the frame is acquired and encoded in each frame, and whether or not the data capacity after encoding is equal to or less than a predetermined size is to continue acquiring the difference. Decide whether to set a new base frame.

  FIG. 3 is an explanatory diagram showing an example of video data recorded on the HDD 114 by the processing shown in FIG. In the example shown in FIG. 3, the video data recorded in the HDD 114 is obtained by adding header information before the video data of each frame.

  In the header information area 141a of the first frame, information indicating that the frame is a base frame (Header = 0xfffffff0), the data size of the video data of the frame (Frame Length = N1), and the data size up to the base frame (Base offset) = Offset) is stored. The actual video data is stored in the video data area 141b of the first frame.

  In the header information area 142a of the second frame, information indicating that the frame is a difference frame (Header = 0xfffffff1), the data size of the video data of the frame (Frame Length = N2), the base frame (that is, The data size (Base offset = offset) up to the first frame) is stored. The actual video data is stored in the video data area 142b of the second frame. Similarly, header information is stored in the header information area 143a of the third frame, and actual video data is stored in the video data area 143b of the third frame.

  The header information is also stored in the header information area 144a of the (M-1) th frame, and the actual video data is also stored in the video data area 144b of the (M-1) th frame. Here, it is assumed that the video data of the (M−1) th frame exceeds a predetermined capacity. Then, the next M-th frame does not take the difference and becomes a new base frame. Header information is stored in the header information area 145a of the Mth frame, and actual video data is stored in the video data area 145b of the Mth frame. Here, information (Header = 0xfffffff0) indicating that the frame is a base frame is stored in the header information area 145a.

  Subsequently, header information is stored in the header information area 146a of the (M + 1) th frame, and actual video data is stored in the video data area 146b of the (M + 1) th frame. The header information area 146a stores the data size up to the base frame, but the base frame here is not the top frame but the Mth frame. Similarly, header information is stored in the header information area 147a of the (M + 2) th frame, and actual video data is stored in the video data area 147b of the (M + 2) th frame.

  FIG. 4 is an explanatory diagram showing the state of video data recorded on the HDD 114 of the hard disk recorder 100 according to the embodiment of the present invention. First, a base frame is set, and a base frame file is recorded on the HDD 114. Subsequent frames take a difference from the base frame, and a difference frame file is recorded on the HDD 114. The base frame and the difference frame are combined and stored for M frames. If the difference data capacity exceeds the predetermined capacity, a new base frame is set and the base frame file is recorded in the HDD 114. .

  By recording data in the HDD 114 in this way, it is possible to reproduce the video data recorded on the HDD 114 without complicating the processing, not only when reproducing the video data normally but also when reproducing while skipping frames.

  The video data recording method using the hard disk recorder 100 according to the embodiment of the present invention has been described above. Next, a method for reproducing video data recorded on the hard disk recorder 100 according to an embodiment of the present invention will be described.

[2-3. Video data playback method according to an embodiment of the present invention]
First, a case where video data recorded on the HDD 114 is normally reproduced will be described. When reading of the video data compressed and recorded in the HDD 114 is started under the control of the file system 112, the system control unit 106 analyzes the header information stored in the header information area of the first read frame. Then, the header information is analyzed to determine whether the frame is a base frame or a difference frame.

  For example, when the first read frame is a base frame, the video data stored in the video data area of the frame is read and sent to the stream decoding unit 116. The stream decoding unit 116 decodes the video data and sends it to the video output unit 124, and sends the decoded data to the second frame memory 120 for storage. The video output unit 124 adds the synchronization signal generated by the video synchronization unit 122 to the transmitted video data, and outputs the video signal in the same waveform as the signal when input to the hard disk recorder 100. . If the hard disk recorder 100 is an apparatus that outputs an analog video signal, a D / A converter may be provided inside the video output unit 124 to convert it to an analog video signal.

  Subsequently, under the control of the file system 112, the header information area of the subsequent frame compressed and recorded in the HDD 114 is read. Then, the system control unit 106 analyzes the header information stored in the header information area to determine whether the frame is a base frame or a difference frame.

  When the system control unit 106 determines that the frame is a difference frame, for example, the video data stored in the video data area of the frame is read and sent to the stream decoding unit 116. The stream decoding unit 116 decodes and outputs the video data. The decoded video data is added by the adder 121 to the base frame video data stored in the second frame memory 120. The video data added by the adding unit 121 is sent to the video output unit 124. The video output unit 124 adds the synchronization signal generated by the video synchronization unit 122 to the transmitted video data, and outputs the video signal in the same waveform as the signal when input to the hard disk recorder 100. .

  As described above, the analysis of the header information and the decoding process of the image data are repeated, and when the difference frame is reproduced, the addition process with the video data of the base frame is executed, thereby the video compressed and recorded in the HDD 114. Data can be played back.

  Next, a case where playback is performed while skipping frames will be described. Here, when the video data compressed and recorded in the HDD 114 is reproduced halfway by the above-described reproduction method, processing such as FF (fast forward) reproduction and FR (fast reverse) reproduction which are special reproduction is performed. The start time will be described. The hard disk recorder 100, when performing special playback FF, FR, etc., is realized by continuously reading the data of a plurality of frames away from the current frame and further reading the data of a plurality of frames apart To do.

  A case where FF playback is performed by the hard disk recorder 100 will be described with reference to FIG. Here, a case where the current frame is the first frame and the Mth frame is reproduced next by FF reproduction will be described.

  First, the system control unit 106 reads the header information area 142a of the second frame next to the first frame, and acquires frame length information. In the header information area 142a, N2 is described as the data length of the second frame. Therefore, the data in the HDD 114 is sought for the data length. Then, since the data reading position is moved to the head of the header information area 143a of the third frame by the seek, the header information area 143a is read to acquire the frame length information. In the header information area 143a, N3 is described as the data length of the third frame. Therefore, the data in the HDD 114 is sought for the data length.

  In this manner, the acquisition of the header length and the seek of data in the HDD 114 are repeated until the target Mth frame. Then, the header information area 145a of the Mth frame is read, the header information of the Mth frame is acquired, and it is determined whether the Mth frame is a base frame or a difference frame.

  If the Mth frame is a base frame, the video data is read from the data area 145 b of the Mth frame, and the read video data is sent to the stream decoding unit 116. On the other hand, when the Mth frame is a difference frame, the Base offset information of the Mth frame is read from the header information area 145a. The base offset information of the Mth frame stores the start position of the base frame used for reproducing the Mth frame. Therefore, the data in the HDD 114 is sought to the beginning of the base frame based on the read Base offset information of the Mth frame.

  When the head of the base frame is reached, the header information area of the base frame is read and the data length of the base frame is acquired. Then, the video data corresponding to the acquired data length is read from the HDD 114 and sent to the stream decoding unit 116. The stream decoding unit 116 decodes the video data and sends it to the video output unit 124, and sends the decoded data to the second frame memory 120 for storage.

  When decoding of the video data of the base frame is completed, the reading position is returned to the Mth frame, and the data length of the Mth frame is obtained from the header information area 145a of the Mth frame. Then, the video data corresponding to the acquired data length is read from the HDD 114 and sent to the stream decoding unit 116. When the M-th frame video data is decoded by the stream decoding unit 116, the base frame data stored in the second frame memory 120 is added by the adding unit 121 and sent to the video output unit 124.

  When the video of the Mth frame is thus reproduced, the acquisition of the header length and the seek of the data of the HDD 114 are repeated until the next target frame, and the acquisition and decoding of the video data are executed. By controlling the reading of data from the HDD 114 in this way, the hard disk recorder 100 according to the present embodiment can cope with reproduction while skipping frames. Here, the case of FF playback has been described as an example, but it goes without saying that FR playback is also possible by controlling the reading of data from the HDD 114 in the case of FR playback as well.

  The method for reproducing the video data recorded on the hard disk recorder 100 according to the embodiment of the present invention has been described above. Next, a modification of the hard disk recorder according to one embodiment of the present invention will be described.

[2-4. Modification of one embodiment of the present invention]
FIG. 5 is an explanatory diagram showing the configuration of a hard disk recorder 100 ′ according to a modification of the embodiment of the present invention. In the hard disk recorder 100 according to one embodiment of the present invention, two frame memories are provided to cope with both recording and reproduction. In the hard disk recorder 100 ′ according to the modification of the embodiment of the present invention shown in FIG. 5, the frame memories are integrated into one frame memory 126. That is, the difference between the base frame video data stored in the frame memory 126 and the video data input to the video input unit 102 is acquired during video recording. Further, at the time of reproducing the video, the base frame video data stored in the frame memory 126 and the difference video data are added. By recording and reproducing the video data in this way, the burden on the apparatus can be reduced.

<3. Summary>
As described above, according to the hard disk recorder 100 according to the embodiment of the present invention, a base frame is set at the time of video recording, and subsequent frames are encoded by taking a difference from the base frame and sequentially recorded on the HDD 114. . Then, when the difference data and the base frame are encoded and the difference data capacity exceeds the predetermined capacity, the next frame is newly set as the base frame, and the subsequent frames are newly set. Get the difference from the set base frame.

  Further, at the time of video reproduction, a frame from which video data is read is determined based on header information added for each frame when video data is recorded. By recording and reproducing the video data in this way, it becomes possible to easily perform the operation in units of frames while reducing the amount of data to be recorded.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

  For example, in the above-described embodiment, when the difference data is encoded with the difference from the base frame, if the capacity of the difference data exceeds a predetermined capacity, the next frame is newly set as the base frame. However, the present invention is not limited to such an example. For example, when the number of difference frames reaches a predetermined number when recording video data, the next frame may be newly set as a base frame. If the base frame is not created for a long period of time, the time required for seeking the base frame when reproducing the video data may be increased. When the number of difference frames reaches a predetermined number, a next frame is newly set as a base frame, thereby making it possible to prevent an increase in time required for seeking the base frame.

  For example, in the above embodiment, the data size from the base frame is recorded in the header information area of each frame, but the present invention is not limited to such an example. For example, in addition to the data size from the base frame, the number of frames from the base frame may be recorded in the header information area of each frame. Recording the number of frames from the base frame in the header information area facilitates reading of video data during special playback such as FF playback and FR playback, and creation of index data from video data recorded in the HDD 114. .

  For example, in the above embodiment, the JPEG2000 lossless compression (lossless) mode is used as the codec for all frames, but the present invention is not limited to this example. For example, the base frame may be encoded in JPEG2000 lossless compression (lossless) mode, and the difference frame may be encoded in lossy compression mode. By reversibly compressing the base frame, the data of the base frame becomes the same at the time of input and at the time of output, and deterioration due to taking the difference can be suppressed. Also, the difference frame can suppress data deterioration due to difference processing from the lossy compression mode.

  For example, the base frame may be encoded in the lossy compression mode. By encoding the base frame in the lossy compression mode, the image quality deteriorates, but the amount of data recorded in the HDD 114 can be greatly reduced. Even when encoding is performed in the lossy compression mode, once the encoding process is performed by the stream encoding unit 104 and then the decoding is performed by the stream decoding unit 116, the accuracy of the difference data can be improved. Become.

  In the above embodiment, the HDD is used as a recording medium for recording video data. However, the present invention is not limited to such an example. The recording medium for recording the video data may be an HDD medium, for example, an optical disk such as a CD (compact disk) or a DVD (digital multipurpose disk), as long as random access is possible. In addition to the optical disk, a flash memory or other nonvolatile semiconductor memory may be used.

  The present invention is applicable to a recording apparatus, a recording method, and a computer program.

It is explanatory drawing shown about the structure of the hard-disk recorder 100 concerning one Embodiment of this invention. It is a flowchart explaining the recording method of the video data using the hard-disk recorder 100 concerning one Embodiment of this invention. 4 is an explanatory diagram illustrating an example of video data recorded on an HDD 114. FIG. FIG. 4 is an explanatory diagram showing a state of video data recorded on an HDD 114. It is explanatory drawing shown about the structure of the hard disk recorder 100 'concerning the modification of one Embodiment of this invention. It is explanatory drawing shown about the structure of the conventional hard disk recorder.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Hard disk recorder 11 Video input part 12 Stream encoding part 13 System control part 14 RAM
15 File system 16 HDD
17 stream decoding unit 18 video synchronization unit 19 video output unit 100 hard disk recorder 102 video input unit 103 subtraction unit 104 stream encoding unit 106 system control unit 108 RAM
110 File Size Detection Unit 112 File System 114 HDD
116 Stream decoding unit 118 First frame memory 120 Second frame memory 121 Adder unit 122 Video synchronization unit 124 Video output unit

Claims (9)

An encoding unit that encodes video data using an encoding method that does not use inter-frame correlation;
A decoding unit for decoding the video data encoded by the encoding unit;
A storage unit for temporarily storing the video data decoded by the decoding unit;
A control unit for controlling recording of the video data encoded by the encoding unit on a recording medium;
With
The controller is
An arbitrary frame is set as a reference frame, the entire video data of the reference frame is encoded by the encoding unit, and then decoded by the decoding unit and stored in the storage unit,
Obtaining difference data between video data of a frame subsequent to the reference frame and video data of the reference frame stored in the storage unit, and encoding the difference data by the encoding unit;
A recording apparatus that controls the next frame to obtain a difference from the reference frame if the encoded data satisfies a predetermined condition, and controls the next frame as a reference frame if the encoded data does not satisfy the predetermined condition.   The recording apparatus according to claim 1, wherein the predetermined condition is that a capacity of difference data after being encoded by the encoding unit is equal to or less than a predetermined capacity.   The recording apparatus according to claim 1, wherein the predetermined condition is that a number of frames from which a difference is acquired is equal to or less than a predetermined number.   The recording apparatus according to claim 1, wherein the encoding unit encodes all frames by a lossless compression method.   The encoding unit encodes video data of a reference frame using a lossless compression method when encoding video data, and encodes video data of a frame other than the reference frame using an irreversible compression method. The recording apparatus according to 1.   The recording apparatus according to claim 1, wherein the encoding unit encodes all frames by an irreversible compression method.   The recording apparatus according to claim 1, wherein the recording medium is a randomly accessible medium. A setting step for setting an arbitrary frame as a reference frame;
An encoding step of encoding the video data of the reference frame in an encoding method that does not use inter-frame correlation;
A decoding step of decoding the video data encoded in the encoding step;
A storage step of temporarily storing the video data decoded in the decoding step;
A difference acquisition step of acquiring difference data between video data of a frame subsequent to the reference frame and video data of the reference frame stored in the storage step;
The difference data acquired in the difference acquisition step is encoded, and if the encoded data satisfies a predetermined condition, the next frame also acquires a difference from the reference frame, and if not, the next frame is determined as the reference frame. A determination step, and
A recording method comprising: On the computer,
A setting step for setting an arbitrary frame as a reference frame;
An encoding step of encoding the video data of the reference frame in an encoding method that does not use inter-frame correlation;
A decoding step of decoding the video data encoded in the encoding step;
A storage step of temporarily storing the video data decoded in the decoding step;
A difference acquisition step of acquiring difference data between video data of a frame subsequent to the reference frame and video data of the reference frame stored in the storage step;
The difference data acquired in the difference acquisition step is encoded, and if the encoded data satisfies a predetermined condition, the next frame also acquires a difference from the reference frame, and if not, the next frame is determined as the reference frame. A determination step, and
A computer program that executes

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