JP2012019256A - Data recorder and data recording method - Google Patents

Abstract

When file management information Moov does not fit in a fixed-length area and management information needs to be divided, video data can be reproduced without omission without using extended management information Moof with few compatible devices. An object of the present invention is to provide a data recording apparatus and a data recording method.
When the recording area of management information Moov is exhausted, it is divided into a new file without using extended management information Moof with a small number of compatible devices, so that it is a highly compatible MP4 file, which is necessary at the time of division. Accordingly, the video data can be reproduced without omission by duplicating and recording the minimum video data.
[Selection] Figure 4

Description

  The present invention relates to a data recording apparatus and a data recording method using a file format for recording digital data such as video and management information thereof together.

  In a data recording apparatus using a file format for recording an image capturing apparatus such as a camera or a file input and recording digital data such as video and its management information together, moving image information and audio information, and synchronization information thereof MP4 file format (hereinafter referred to as MP4) defined by the MPEG-4 (Moving Picture Experts Group Phase 4) standard is one of the formats for multiplexing video data comprising text information and related text information and storing it as a file. It is done.

  MP4 is a set of basic units called “boxes”. The minimum unit for managing video data is called “sample”, management information such as the size of each sample and decoding / display time is stored in a box called “movie box” (hereinafter referred to as “Moov”). It is stored in a box called “media data box (hereinafter referred to as Mdat)”.

  The arrangement order of Moov and Mdat in a file is not defined in the standard, but for convenience in accessing a file via a network, a method of arranging Moov in advance is generally used. Also, depending on the playback device, if the Moov is not arranged in advance, it may not be handled as a playback target.

  The amount of management information stored in the Moov increases or decreases depending on the amount of information related to the video data compression method and the number of samples of the video data, so it is not determined until the attributes and length of the video data to be recorded are determined. .

  Therefore, as described above, when recording is performed using the method in which the Moov is arranged in advance, recording is performed in the following procedure with the file structure shown in FIG.

  First, at the start of recording, an area 501 for recording Moov is secured at the beginning of the file. The capacity of the area secured at this time is a value calculated by rough estimation from the recordable time of the video data.

  Next, video data is sequentially recorded behind 502 of the secured area. Finally, when the recording of the video data is completed, the Moov is recorded in the area 501 secured at the start of recording, and the remaining area of the capacity 504 is recorded as padding data (free box (hereinafter referred to as “Free”)). , MP4 storage is completed.

  In the above procedure, the capacity of the area 501 secured at the start of recording becomes a point. If the area 501 is secured large, the file storage will not be affected even if the recording capacity 503 of the Moov slightly increases than expected, but if it falls within the expected range, the surplus capacity 504 will increase, resulting in a file size of It will increase in vain.

  If the area 501 is secured in a small amount, the possibility that the file size is increased unnecessarily is reduced, but depending on the video data to be recorded, the recording capacity 503 of the Moov increases and cannot be stored in the recording area 501.

  In order to solve this problem, a method has been proposed in which management information is divided and recorded at a plurality of locations in a file (Patent Document 1).

  In the method of Patent Document 1, when the management information does not fit in the area reserved in advance, the management information is divided and stored in a box called extended management information “movie fragment box (Moof)” and recorded. Record behind the data area.

  A basic format in Patent Document 1 is shown in FIG. In this format, the Moov area at the beginning of the file is determined to be a predetermined size in advance, and recording is started with a fixed Mdat writing offset on the file (basic recording mode).

  In this case, when the user performs recording for a long time, the size of the Moov that increases with time may exceed a predetermined size. At that time, the recording is transferred to the format shown in FIG. 6B (extended recording mode).

  That is, it is possible to cope with long-time recording by repeatedly adding a pair of the Moof and Mdat areas following the Moov and Mdat of the basic area.

JP 2007-6140 A

  However, there are not a few players that do not support the reading of Moof, and these players are treated as having no video data whose management information is included in the Moof.

  That is, at the time of video playback, a part of the video is lost and played back.

  The present invention has been made in order to solve the above-described problems, and uses the Moof with a small number of compatible devices when the file management information does not fit in the fixed-length area and the file needs to be divided. It is another object of the present invention to provide a data recording apparatus and a data recording method that can reproduce video data without omission.

  In order to solve the above problems, a data recording apparatus and a data recording method of the present invention perform recording in a file format having a data area for recording data such as video and a management information area for recording data management information. A data recording device, a video buffer for buffering input video data, an audio buffer for buffering input audio data, and a multiplexing for multiplexing video data and audio data according to a standard And a management information buffer for buffering management information of video data and audio data required in the process of multiplexing. The multiplexing control unit includes a variable length first data area, Recording video data, audio data, and management information in a first file having a fixed-length first management information area corresponding to the first data area, When it is determined that the management information to be recorded in the file exceeds the fixed length, the recording to the first file is terminated, and the remaining management information, video and audio data are stored in the second fixed length of the second file. And a part of the video data or audio data are recorded in the first file and the second file in a duplicated manner. It is.

  As a result, Moof is not used, it is divided into new files and recorded as MP4 files with high playback compatibility. At the time of division, video is recorded by duplicating and recording minimum video data as necessary. Data can be reproduced without loss.

  Since the data recording apparatus and the data recording method according to the present invention use only the most basic components in the standard when recording video data management information, the data can be reproduced with more reproduction devices without loss of information. There is an advantage of becoming.

The figure which shows the structure of the data recording device in one embodiment of this invention The figure which shows the operation | movement flow of the data recording device in one embodiment of this invention. The figure which shows the structure of the data recording device of one embodiment of this invention The figure which shows the data structure of the file of the data recording device of one embodiment of this invention The figure which shows the data structure of the file of the conventional video data The figure which shows the data structure of the file which divided the conventional picture data

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 shows the configuration of a data recording apparatus according to an embodiment of the present invention.

  In the figure, a data recording apparatus 100 includes a video input 101 and an audio input 102 of video data having an input device such as an imaging device such as a camera or a file input, and a video buffer 103 for buffering the input video / audio data. , An audio buffer 104, a multiplexing control unit 105 that multiplexes video and audio in accordance with the MP4 standard, and management information for buffering MP4 video data management information required in the process of multiplexing And a buffer for recording data in the MP4 file 107 according to the MP4 file format.

  FIG. 2 shows an operation flow of the data recording apparatus of the present embodiment.

  To start recording a file, the data recording apparatus 100 first determines the size of the Moov recording area (S201).

  In the present embodiment, means for determining the capacity of the Moov recording area is not defined. For example, when there is a guideline for the recording time of the video (for example, when the longest recording time is determined, transcoding of an existing video, etc.) In the case where the total video playback time is known), the maximum capacity of the management information can be calculated based on the length.

  Next, the output file is opened (S202), and seek is performed for the size calculated in S201 to secure the Moov recording area, or arbitrary data is written to the file (S203).

  Next, the video data is output from the video buffer (video / audio input buffer) 103 to a file (S204). At this time, in accordance with the MP4 standard, a file is output for each appropriate unit (chunk) of video and audio.

  The management information of the video determined in S204 is added to the Moov stored in the management information buffer 106 (S205).

  When all the videos are output, the size of the Moov stored on the management information buffer 106 exceeds the threshold set smaller than the size of the Moov recording area (S206), or the data in the video buffer 103 is lost (S207). Until S204 and S205 are repeated.

  When the video output is completed or the Moov size exceeds the threshold, the file output position is sought to the top of the Moov recording area (S208).

  Next, the Moov is output to a file, and the remaining area of the recording area is padded with Free (S209). Thereafter, the file is closed and the output of one file is terminated (S210).

  When all the video has been output, the recording is completed (S212). When video data remains (that is, when the size of the Moov exceeds the threshold), recording from S201 to the next file is performed. Continue (S211).

  When recording video from the second file onward, the video data is stored redundantly with the end of the previous file as necessary in order to store the video data without omission. As a specific example, the video data format is H.264. FIG. 3 shows an example in which H.264 / AVC and audio data are compressed by MPEG-4 AAC.

  H. Moving images compressed in the H.264 / AVC format can be collected in a compression unit called GOP. In particular, in the case of a Closed GOP, the video of GOP #m does not depend on the video of the preceding GOP # m-1, so that even if the file is divided, no video is lost. On the other hand, when a file is divided at a GOP boundary of a moving image, an audio recording boundary does not always exist at the same time.

  Therefore, by recording the audio recording unit related to the dividing boundary of the moving image so as to overlap both the front and rear files, video and audio information is not lost in both files. However, since only this includes extra audio, the reproduction range is designated by management information (edit box (Edits)) for designating the reproduction range of MP4.

  In the case of the example in FIG. 3, in the file 301, the beginning of the video and the audio coincide with each other, and there is a surplus section at the end of the audio. Therefore, the playback length (Segment-duration) of Audio Set to match playback length.

  In the file 302, since there is a surplus section at the beginning of the audio, the length of the surplus section is set in the start position information (Media-time) in the Audio Edts, and the playback length is set to the same value as the Video as in the file 301. Set to match playback length.

  By performing the above processing at the time of file division, video data can be reproduced without excess or deficiency in both the front and rear files.

  FIG. 4 shows the data structure of a file recorded according to this embodiment. By the above-described recording method, the files 301 and 302 include the minimum necessary duplicate data 303 so that video data can be reproduced without excess or deficiency in each file.

  In addition, when a file is divided at a place where the moving image and audio recording boundaries described with reference to FIG. 3 completely coincide with each other, duplicate data becomes unnecessary and is not included in each file.

  As described above, according to the data recording apparatus of the present embodiment, when video / audio data is divided and recorded into a plurality of files, the rear end of the continuous front file and the top data of the rear file are recorded. By overlapping a part, video / audio data can be reproduced without excess or deficiency.

  A data recording apparatus and a data recording method according to the present invention use video / audio data as management information, such as a data recording apparatus for recording digital data such as video using an imaging device such as a camera or a file input as an input source. In addition, the present invention can be applied to all devices using a file format to be recorded.

DESCRIPTION OF SYMBOLS 100 Data recording device 101 Video input 102 Audio input 103 Video buffer 104 Audio buffer 105 Multiplexing control unit 106 Management information buffer 107 MP4 file 301, 302 file 303 Duplicate data

Claims (4)

A data recording apparatus for recording in a file format having a data area for recording data such as video and a management information area for recording management information of the data,
A video buffer for buffering input video data; an audio buffer for buffering input audio data; a multiplexing control unit for multiplexing the video data and the audio data in accordance with a standard; A management information buffer for buffering management information of the video data and the audio data required in the process of multiplexing;
The multiplexing control unit adds the video data and the audio to a first file having a variable length first data area and a fixed length first management information area corresponding to the first data area. Record the data and the management information,
When it is determined that the management information to be recorded in the first file exceeds the fixed length, the recording to the first file is terminated, and the remaining management information, video and audio data are transferred to the second file. In the fixed length second management information area and the variable length second data area,
A data recording apparatus, wherein a part of the video data or the audio data is recorded in the first file and the second file in an overlapping manner. 2. The data recording apparatus according to claim 1, wherein the duplicated data is recorded at an end of the first file and a head of the second file. 2. The data recording apparatus according to claim 1, wherein the overlapping data is at least a difference between recording boundaries of video data and audio data at a division position. A data recording method for recording in a file format having a data area for recording data such as video and a management information area for recording management information of the data,
Video data, audio data, video data, and audio data in a first file having a variable-length first data area and a fixed-length first management information area corresponding to the first data area Record management information,
When it is determined that the management information to be recorded in the first file exceeds the fixed length, the recording to the first file is terminated, and the remaining management information, video and audio data are transferred to the second file. In the fixed length second management information area and the variable length second data area,
A data recording method, wherein a part of the video data or the audio data is recorded in the first file and the second file in an overlapping manner.

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