JP4770910B2 - Data recording method, recording medium, and reproducing apparatus - Google Patents

Description

  The present invention relates to a data recording method for recording variable-length data, and in particular, a data recording method for recording and reproducing a character string on a recording medium as subtitle information, and the data recording method The present invention relates to a playback device for playing back a recording medium.

  A reproducing apparatus represented by a DVD (Digital Versatile Disc) is widely used. In the DVD, subtitle information can be recorded at the same time in addition to the content of the main body, and the subtitles can be combined with the video and displayed as necessary. In these playback apparatuses, data in a graphic format is used for displaying subtitles. However, the graphic subtitle information has a drawback that the amount of data increases.

  On the other hand, in text broadcasting, digital broadcasting, etc., a method of transmitting subtitle information in a text format is considered. If text data is used, the amount of data can be reduced.

  By the way, as described in Patent Document 1 and Non-Patent Document 1, a method of recording video data and audio data in the MPEG packet format has been proposed. The MPEG packet format is also used for data transmission of digital broadcasting, and it can be considered that it is spread along with digital broadcasting.

JP 2003-123389 A

133 pages of the Nikkei Electronics July 21, 2003 issue (Nikkei BP)

  In the conventional playback device, the use of subtitles in the text format has not been considered. Therefore, there is no disclosure about a method for recording subtitle information in text format.

  When recording in the packet format, it can be handled in the same way as an MPEG packet. However, it is necessary to record useless data, and processing for extracting data from the packet is required, so that the efficiency is low.

  An object of the present invention is to provide a data recording method capable of efficiently recording text format data and having compatibility with conventional packet format data.

In order to solve the above problem, the present invention uses the configuration described in the claims as an example .

According to the present invention, since the recording data is recorded so as to be an integral multiple of the predetermined number of bytes, the text format data can be handled in the same manner as the packet format data. Further, it is not necessary to record unnecessary data as compared with the case of actually recording in the packet format, and efficient data recording can be performed.

Hereinafter, a method for recording subtitle data in a text format will be described as an embodiment to which the present invention is applied.
FIG. 1 is a diagram illustrating a data structure of subtitle data in a text format.
In FIG. 1, PTS 101 is display start time information indicating the display start time, DUR 102 is display period information indicating the display period, LEN 103 is subtitle character string length information indicating the length of the subtitle character string, text 104 is a subtitle character string, and null105. Is invalid data.

  At the head of each caption data, PTS 101 is recorded as display start time information indicating the display start time. At the time of subtitle display, according to the PTS 101, the text 104 that is a subtitle character string is displayed. In each caption data, DUR 102 is also recorded as display period information indicating a display period. The DUR 102 indicates the time from the start of the display of the text 104 to the end of the display. When this display period is over, the subtitle is deleted.

  Next, LEN 103 is recorded as caption character string length information, and text 104 is recorded behind the LEN 103. The text 104 is displayed on the screen in a predetermined format.

  After the text 104, null 105 is recorded as invalid data. This null 105 is stuffing data and fills the gap so that the data length of each caption data is a multiple of 192 bytes. Specifically, the contents of the stuffing data may be filled with a value of 00h indicating that there is no data.

FIG. 2 shows a block diagram of the reproducing apparatus of the present embodiment.
In FIG. 2, 201 is a disk device, 202 is an output control unit, 203 is an audio decoder, 204 is an audio output terminal, 205 is a video decoder, 206 is a video synthesis unit, 207 is a video output terminal, 208 is a caption display unit, 209 Is a system controller, and 210 is a remote control receiver.

Hereinafter, the operation during reproduction will be described.
First, the user turns on the power of the playback device and sets an optical disc (not shown) in the disc device 201. The disk device 201 detects the insertion of the optical disk and notifies the system control unit 209. The system control unit 209 recognizes that the optical disk has been set, and reads file management information in the optical disk. Here, the file management information is recorded at a predetermined position on the optical disc in accordance with, for example, a file management system represented by UDF (Universal Disk Format). File management information manages each piece of information recorded on the optical disc as a file. Specifically, the file identifier (file name), recording start sector number, file length, additional information, etc. of each file are recorded.

  After the file management information is read, the system control unit 209 reads a file necessary for reproducing the optical disk and sequentially analyzes it.

A file as shown in FIG. 3 is recorded on the optical disk to be reproduced.
In FIG. 3, reference numeral 301 denotes an info. File in which information such as the number of playlists and file names in the DVR directory is written. The dvr file 302 is a menu.menu. A tidx file (may be a menu.java file), 303 is a playlist file in which information such as video playback position, order and mark position is recorded, 304 is a playback start point on the stream file and its packet position, etc. 305 is a stream file in which information packets such as video and audio are recorded, and 306 is a caption information file in which caption information is recorded.

Here, the stream file 305 will be described.
Video information is recorded after being converted into a transport stream format by reducing the amount of data by MPEG (Moving Picture Experts Group) 2 which is one of image information compression techniques. MPEG2 can reduce the amount of data even for high-quality HD images represented by NTSC format and high-definition images, and reduces the data amount to about 1/10 to 1/50 of the original image. It can be reduced. For example, sufficient image quality can be obtained with a data amount of about 6 Mbps for NTSC format images and about 20 Mbps for HD images. Image compression by MPEG2 is widely used for image storage including DVD and digital broadcasting. Here, the MPEG2 format will be described as an example, but it goes without saying that data may be encoded using another image compression method.

  As with video, audio information is also compressed using an audio compression technique. There are various compression techniques such as MPEG1 audio and AAC format used in BS digital broadcasting. Also, since audio information has a smaller data amount than video information, it is possible to record data in a linear PCM format without compression.

  The video information and audio information encoded as described above are multiplexed as a transport stream and recorded as one file so that transmission and storage are easy. Specifically, each information is converted into a 188-byte packet. At this time, a PID (packet ID) for packet identification is added to each packet. By adding a single PID to a series of information, packets can be easily separated during reproduction.

In addition to video / audio, various information packets such as caption information, graphic information, and control commands can be multiplexed in the transport stream. Furthermore, packets such as PMT (Program Map Table) and PAT (Program Allocation Table) representing the relationship of each PID, and PCR (Program Clock Reference) representing time information are multiplexed. The transport stream on which information is multiplexed in this manner is recorded on the optical disc as a transport stream file.

Next, the clip information file 304 will be described.
The data structure of the clip information file 304 is shown in FIG.
In FIG. 4, PTS 401 is display start time information, and SPN 402 is packet recording position information. As described above, video information is recorded after MPEG2 format image compression. In the MPEG2 format, the data amount is reduced by using the correlation between successive images. Specifically, processing is performed in which the data of the immediately preceding image is used as it is without retransmitting the information of a portion that does not change between consecutive images. For this reason, image data in which only changes are encoded has a drawback that information on all pixels cannot be decoded from the data. Therefore, the only images that can be played back by fast-forwarding, skipping operation, or the like are images in which all pixels are encoded.

In general, image compression in the MPEG2 format is often performed by combining about 15 images. This set of images is called GOP (Group Of Pictures). If playback is performed from the beginning of this GOP, the image can be played back immediately.

In the clip information file 304, the packet recording position 401 at the tip of the GOP is recorded together with the display start time 402 (corresponding to the value of Presentation Time Stamp) of the image. Thereby, it is possible to easily search for a position where reproduction is started by searching or skipping.

  The clip information file 304 has a one-to-one correspondence with the transport stream file. 01000. Corresponding to a transport stream file called m2ts, 01000. If a clip information file called clpi is recorded, correspondence between files can be easily identified. Also, caption information is recorded in a one-to-one correspondence.

Next, the playlist file 303 will be described.
The playlist file 303 is a file in which information defining the playback order of the transport stream file is recorded. In the playlist file 303, one or more sets of information such as a file identifier, a reproduction start time, and a reproduction end time of a stream file to be reproduced are recorded as play item information. At the time of reproduction, the stream file is sequentially reproduced according to the play item information in the designated playlist file. In the play list file, sub play items that are reproduced in parallel with the stream file are recorded. The sub play item includes, for example, subtitle information recorded separately from the main stream, a dubbed audio stream, and the like. Further, the playlist file includes mark information indicating the skip position. By using the mark information, it is possible to easily know the reproduction start time of the next chapter, and it is possible to realize chapter skip by the user.

  At the start of playback, the system control unit 209 first starts the menu. The tidx file 302 is read and a menu is displayed. That is, a list of playlist files recorded on the optical disc is presented, and the user is requested to select a playlist. The user uses the remote control to select a desired playlist from the presented playlist.

  When one playlist is selected, the system control unit 209 downloads a playlist file corresponding to the selected playlist from the optical disc, and includes a play item and a sub play item included in the playlist file. Analyze the contents.

Here, for simplification of explanation, it is assumed that the play list file includes only “01000.m2ts” as a play item and “01100.sttl” as a sub play item. Of course, even when a plurality of play items are included, the same operation can be realized.

  When playback is performed from the top of the playlist, playback is started with a playback time of 0 seconds. First, the reproduction of data is started from the packet of the play item “01000.m2ts” at time 0 seconds. At this time, in order to obtain the packet position from the time information, “01000.clpi” which is a clip information file is used to obtain the play start reproduction packet position. From the reproduction start packet position and the file management information, the sector number on the optical disk of the “01000.m2ts” file to be reproduced is calculated.

  Specifically, the number of bytes can be obtained by multiplying the packet number by 192, and the sector number can be obtained by dividing by 2048. Further, the data start byte position in the sector can be obtained by the remainder divided by 2048.

  Reading of the stream data “01000.m2ts” is started from the sector number on the optical disk obtained by the above calculation. Specifically, data read from the optical disk is read as predetermined sector data by a signal processing circuit (not shown) in the disk device 201, and a video decoder and an MPEG2 stream packet are output by the output control unit 202. Input to the audio decoder.

  The video packet of the MPEG2 stream is decoded by the video decoder 205 and input to the video composition unit 206 as a video signal. The audio packet is decoded by the audio decoder 203 and output to the audio output terminal 204 as an audio signal.

On the other hand, the processing of the sub play item included in the playlist file is also performed in parallel with the reproduction of the main play item. Here, caption information “01100.sttl” is included as a sub play item.

  The sub play item also obtains the reproduction start position using the clip information file “01100.clpi” corresponding to the sub play item. Since the subtitle character string information in the sub play item is adjusted to the same 192 bytes as the packet length of the MPEG2 stream, the sector number and the data position in the sector are obtained by the same calculation as that for obtaining the sector number from the packet number. be able to.

Next, the system control unit 209 reads the information of subtitles to be displayed at a time from the reproduction start position and performs processing. As shown in FIG. 1, the caption data is divided and recorded for each caption to be displayed at one time, and each data includes PTS 101, DUR 102, LEN 103, text 104, and null 105. The text 104 in the read caption data is converted into graphic data by a predetermined decoding process, and is input to the caption display unit 208 together with information of the PTS 101 and the DUR 102.

  The caption display unit 208 displays the graphic data as a video signal only for a specified period in accordance with the PTS 101 and DUR 102 in the caption data.

  The video signal output from the caption display unit is combined with the video signal output from the video decoder 203 by the video synthesis unit 206 and output to the video output terminal 207.

  When subtitle decoding processing for one time is completed, subsequent subtitle information decoding processing is sequentially performed. Thereby, caption display is continuously performed.

  Through the processing as described above, predetermined subtitles are synthesized and output on the video recorded on the optical disc.

  When a skip operation is instructed by the user during playback or playback is performed from the middle of the stream, a value in the middle of the stream is designated as the playback time instead of the stream head. However, in this case as well, in the play item and the sub play item, the data reproduction start position can be obtained using the clip information file 304 in the play item and the sub play item, so that the data can be reproduced from the designated time. It is.

  Here, the caption data has a long display interval and usually has a display period of about several seconds. Therefore, the playback start time may correspond to outside the caption display period or in the middle of the caption display period. In this case, subtitle display processing is not performed until the next subtitle display period comes. That is, subtitle information having a display start time that is the same as or later than the designated playback start time may be decoded and controlled to be displayed.

In the caption data shown in FIG. 1, only characters are recorded, and information such as the display position, size, and color of characters is not included. Therefore, the characters are displayed in a predetermined size at a predetermined location on the screen. However, as a matter of course, there is a demand for displaying each subtitle character in a free position and in a free size. In this case, character modification information may be included in the character string data as a special character string such as <size = 20>. Of course, special character codes that are not normally used may be used to indicate the presence of character modification information. For example, an ESC code (27h) can be used.

  The data recording method of this embodiment can be applied not only to recording a character string but also to the case of recording data other than a character string when the special character code as described above is included. It is.

In the above embodiment, the length of each character string data is controlled to be a multiple of 192 bytes as shown in FIG. 1, but this is not limited. For example, since the sector length on the disk is 2048 bytes, conversion from a packet number to a sector number is facilitated by using a divisor of 2048 bytes such as 128 bytes or 256 bytes. For example, if the length of one subtitle character string is 128 bytes, the sector number can be obtained by dividing the packet number by 16.

  In the above embodiment, the subtitle display operation is performed by the program stored in the system control unit 209 in the playback device. For example, a subtitle display program is recorded on the optical disc, and This may be downloaded to the system control unit at the time of reproduction and controlled to be executed.

In the above embodiment, an example in which data is recorded on an optical disk has been described. However, the present invention is not limited to this. For example, the case of recording in a device such as a hard disk device or a semiconductor memory is also included. Furthermore, the present invention can be applied to an apparatus that transmits and displays data recorded in these via a network or broadcast radio waves, and various modifications are possible.

Diagram showing the data structure of caption data Block diagram of playback device Diagram showing file structure on optical disc Diagram showing the data structure of the clip information file

Explanation of symbols

101 Display start time information (PTS)
102 Display period information (DUR)
103 Character string length information (LEN)
104 Subtitle string (text)
105 Invalid data (null)
201 Disc Device 202 Output Control Unit 203 Audio Decoder 204 Audio Output Terminal 205 Video Decoder 206 Video Synthesis Unit 207 Video Output Terminal 208 Subtitle Display Unit 209 System Control Unit 210 Remote Control Reception Unit 301 Disc Information File 302 Menu Information File 303 Playlist File 304 Clip information file 305 Stream file 306 Subtitle information file 401 Display time information 402 Packet number

Claims (4)

  A recording method for recording a video data stream, an audio data stream, and a character string data stream on a recording medium,
  The video data stream is a fixed-length packet format stream including video data composed of a group of a plurality of images and display start time information indicating a display start time,
  The audio data stream is a stream of a fixed-length packet format including audio data and output start time information indicating an output start time,
  The character string data stream is a fixed-length packet-format stream including variable-length text-format character string data and display start time information indicating a display start time,
  The character string data stream includes variable length data including variable length text format character string data and display start time information indicating a display start time in an area in which data of a fixed length packet is stored. It is a stream of fixed-length packet format with invalid data added so that it becomes an integral multiple of the length,
  Recording the video data stream, the audio data stream, and the character string data stream on the recording medium;
  A clip information file including clip information indicating a correspondence between display start time information of a head image of a group of the plurality of images and a packet number indicating a position of a fixed-length packet including the head image; The steps to record in
  A recording method characterized by comprising:   A reproduction method for reproducing a video data stream, an audio data stream, and a character string data stream from a recording medium,
  The video data stream is a fixed-length packet format stream including video data composed of a group of a plurality of images and display start time information indicating a display start time,
  The audio data stream is a stream of a fixed-length packet format including audio data and output start time information indicating an output start time,
  The character string data stream is a fixed-length packet-format stream including variable-length text-format character string data and display start time information indicating a display start time,
  The character string data stream includes variable length data including variable length text format character string data and display start time information indicating a display start time in an area in which data of a fixed length packet is stored. It is a stream of fixed-length packet format with invalid data added so that it becomes an integral multiple of the length,
  The recording medium includes the video data stream, the audio data stream, the character string data stream, display start time information of the first image of a group of the plurality of images, and the first image. A clip information file including clip information indicating correspondence with a packet number indicating the position of a fixed-length packet is recorded;
  Playing back the video data stream, the audio data stream, the character string data stream, and the clip information file recorded on the recording medium;
  Outputting a reproduced video data stream with reference to the reproduced clip information file;
  A reproduction method characterized by comprising:   A recording medium on which a video data stream, an audio data stream, and a character string data stream are recorded,
  The video data stream is a fixed-length packet format stream including video data composed of a group of a plurality of images and display start time information indicating a display start time,
  The audio data stream is a stream of a fixed-length packet format including audio data and output start time information indicating an output start time,
  The character string data stream is a fixed-length packet-format stream including variable-length text-format character string data and display start time information indicating a display start time,
  The character string data stream includes variable length data including variable length text format character string data and display start time information indicating a display start time in an area in which data of a fixed length packet is stored. It is a stream of fixed-length packet format with invalid data added so that it becomes an integral multiple of the length,
  The video data stream;
  The audio data stream;
  The string data stream;
  A clip information file including clip information indicating the correspondence between the display start time information of the first image of the group of the plurality of images and the packet number indicating the position of the fixed-length packet including the first image;
  A recording medium on which is recorded.   A playback device for playing back a video data stream, an audio data stream, and a character string data stream from a recording medium,
  The video data stream is a fixed-length packet format stream including video data composed of a group of a plurality of images and display start time information indicating a display start time,
  The audio data stream is a stream of a fixed-length packet format including audio data and output start time information indicating an output start time,
  The character string data stream is a fixed-length packet-format stream including variable-length text-format character string data and display start time information indicating a display start time,
  The character string data stream includes variable length data including variable length text format character string data and display start time information indicating a display start time in an area in which data of a fixed length packet is stored. It is a stream of fixed-length packet format with invalid data added so that it becomes an integral multiple of the length,
  The recording medium includes the video data stream, the audio data stream, the character string data stream, display start time information of the first image of a group of the plurality of images, and the first image. A clip information file including clip information indicating correspondence with a packet number indicating the position of a fixed-length packet is recorded;
  The video data stream and the clip information file;
 Playback means for playing back the video data stream, the audio data stream, the character string data stream, and the clip information file recorded on the recording medium;
  Output means for outputting a reproduced video data stream with reference to the reproduced clip information file;
  A playback apparatus characterized by comprising:

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