JP2010107767A - Method for reproducing of compressed audio file - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce memory capacity, concerning a method for reproducing of a compressed audio file. <P>SOLUTION: In the method, a data recording medium is accessed according to a reproducing request, and a plurality of data are reproduced in turn. Here, the compressed audio file in which header information is not set each data is stored in the data recording medium, and the compressed audio file has the plurality of data and a header including an offset value representing each address of the plurality of data. A first offset value being an offset value for the reproducing data among the plurality of data is stored in a memory. Also, the method includes: a step of calculating a calculated offset value representing an offset value, which is determined on the basis of the specified double speed and an elapsed time upon the reproducing of the data for the first offset value according to a request of rapid traverse and quick return including a specified double speed; and a step of playing back the data for the calculated offset value after the reproducing of the data for the first offset value among the plurality of data. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a compressed audio file reproduction method for executing a special reproduction function in a digital audio decoding system.

  In recent years, audio technology has been developed. In particular, the development of digital media technology is remarkable. Along with this, a large number of USB (Universal Serial Bus) audio players equipped with a high capacity HDD (Hard Disk Drive) and memory will be available, and the recording medium capacity of music files will be larger than CD (Compact Disc) etc. On the other hand. Therefore, various new compression formats are appearing one after another. This also allows the user to record one compressed audio file that is sufficiently long.

  In a system for reproducing a compressed audio file, a special reproduction function of fast forward / reverse while sound is required. In order to realize such a function, synchronization position information indicating the synchronization position is required as a place where decoding for outputting sound can be started, and information cannot be obtained if the frame delimiter cannot be easily calculated depending on the compression format. For the retention, a memory capacity proportional to the length of the target file is used.

  On the other hand, a processing apparatus for realizing an audio decoder system is manufactured with a minimum amount of resources as the set cost is reduced, and the LSI (Large-Scale Integrated circuit) is made into one chip and downsized. There are various requests for this function, and it is required to reduce the amount of memory used.

  Patent Document 1 is introduced as a conventional compressed audio file reproduction method (hereinafter referred to as conventional technology).

  In the prior art, when performing fast-forward playback of a compressed audio file such as MP3 (MPEG (Moving Picture Experts Group) Audio Layer-3), the target frame number is calculated as shown in FIGS. S11) A high-speed search for the target frame is executed (step S12). At this time, in the non-reproduction target frame area, the header portion of each frame is read (step S21), the head position of the subsequent frame is determined, and control is performed so that the frames are sequentially shifted (steps S22 to S24, S25-NO). ). Then, after the transition to the target frame (step S25-YES), the subsequent S frames are normally reproduced (step S13), and when fast-forward reproduction is continued (step S14-NO), the processing from step S11 is repeated. When the fast-forward reproduction is finished (step S14-YES), the process is terminated. In this way, it is possible to simply decode the frame header, calculate the position to the target frame to be played back, skip the unnecessary frame, and reduce the memory for holding synchronous position information is doing.

JP 2003-006992 A JP 2006-178179 A

  In the prior art, as shown in FIG. 3, when the compressed audio file is, for example, an MP3 file or an ATS (Advanced Audio Coding) file in ADTS (Audio Data Transport Stream) format as shown in FIG. There is a header portion, and by analyzing the header portion, the length can be obtained during the decoding of the frame. In such a case, as shown in FIG. 4, it is possible to skip to the next synchronization position as a target without performing the decoding of the frame (the output data creation process is not performed). It is not necessary to save the data in a certain memory, and the memory used can be reduced.

  However, as shown in FIG. 5, when the compressed audio file is an MPEG (Moving Picture Experts Group) -4 AAC (Advanced Audio Coding) file, a unit of one frame is configured by combining the header and the data. Does not have the concept of Therefore, if there is no header part in one block that can be decoded and the length of the file is indefinite, the skip operation cannot be performed during decoding. Therefore, as shown in FIG. 6, the result is stored and used for the synchronization position specification at the time of initial file / header analysis or analysis of all file data (see Patent Document 2). The necessity arises and there is a problem that a memory depending on the length of the file has to be secured.

  In the following, means for solving the problems will be described using the reference numerals used in the best modes and embodiments for carrying out the invention in parentheses. This reference numeral is added to clarify the correspondence between the description of the claims and the description of the best mode for carrying out the invention / example, and is described in the claims. It should not be used to interpret the technical scope of the invention.

The compressed audio file playback method of the present invention comprises:
A step (S00 to S01, S03 to S06) of accessing the data recording medium (00) in response to the reproduction request and reproducing a plurality of data in order, wherein the data recording medium (00) includes each data A compressed audio file in which header information is not set is stored, and the compressed audio file includes the plurality of data and a header portion including an offset value indicating an address of each of the plurality of data. ,
Storing in the memory (10) a first offset value that is an offset value for the reproduced data of the plurality of data (S02);
In response to fast-forward / fast-reverse requests including the specified double speed,
Calculating a calculated offset value representing an offset value determined based on the designated double speed and an elapsed time when data for the first offset value is reproduced (S07-No, S08; S11); ,
Regenerating the data for the calculated offset value after reproducing the data for the first offset value of the plurality of data (S08; S13);
It has.

  As described above, in the case of FIG. 6 which is a problem of the prior art, if all the information indicating the synchronization position (offset value) is held in the memory at the time of activation, it takes an analysis time. In addition, a memory capacity for storing all the synchronization positions is required.

  Therefore, according to the compressed audio file reproduction method of the present invention, at the time of the first header analysis, only the necessary position (offset value) is remembered, and the fast forward / reverse processing with sound is performed while using the position. Execute. Therefore, it is not necessary to save all the synchronization positions, and the memory capacity can be reduced.

  Hereinafter, a compressed audio file reproduction method according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

(First embodiment)
The present invention is applied to a compressed audio file in which header information is not set for each data. In the present embodiment, it is assumed that the compressed audio file is an MPEG (Moving Picture Experts Group) -4 AAC (Advanced Audio Coding) file.

  As shown in FIGS. 15 to 17, the MPEG-4 AAC file has a plurality of data from the first to the last (hereinafter referred to as music data) and a header portion. The header portion includes offset information (offset value) representing each address of the plurality of music data. For example, as shown in FIG. 8, when a plurality of music data is music data 1, 2,..., X, Y, Z, Z1,..., T, t1,. , Offset values P1, P2,..., PX, PY, PZ, PZ1,..., Pt, Pt1,. Here, X is an integer of 1 or more, and X, Y, Z, Z1, t, t1, and n are integers that satisfy X <Y <Z <Z1 <t <t1 <n.

[Operation image]
In the compressed audio file reproduction method according to the first embodiment of the present invention, the offset storage position (address A = H1) is first memorized at the time of header analysis immediately after the start of file reproduction (circle numeral 1 in FIG. 8). When there is a 10x fast-forward request during playback of music data at 1 second (circled number 2 in FIG. 8), a sound at 6 seconds is emitted after 0.5 seconds and 11 seconds after 1 second. It is sufficient that the music data at the location can be reproduced (circled numeral 3 in FIG. 8). First, in order to find the corresponding synchronization position immediately before 6 seconds, the value H1 stored first is used to return to the header section (FIG. 8). Circle number 4). Data is acquired directly from the header (circled number 5 in FIG. 8), and the offset value is compared and searched (circled number 6 in FIG. 8). Then, the music data is reproduced again (circle numeral 7 in FIG. 8). Next, in order to search for a synchronization position corresponding to 11 seconds, data is directly acquired from the address of the header part accessed earlier (circle numeral 8 in FIG. 8), and the search is repeated. If a value matching the condition is not found, the header is read again from the next access unit (circle numeral 9 in FIG. 8), and the search is continued. When the condition is satisfied (circle numeral 10 in FIG. 8), this is the next reproducible position and reproduction is performed (circle numeral 11 in FIG. 8).

  By repeating this process in the same procedure, a fast forward / fast reverse process is realized.

[Constitution]
FIG. 7 shows a compressed audio file reproducing apparatus as a system applied to the compressed audio file reproducing method according to the first embodiment of the present invention. The compressed audio file playback device includes a data recording medium 00, a driver 01, an input data buffering device 02, a decoder 03, an output device 04, a control unit 05, a display unit 06, an operation unit 07, a target position access device 08, The header unit analysis device 09, the memory 10, and a buffer (not shown) are provided. An example of the control unit 05 is a CPU (Central Processing Unit). Hereinafter, it is referred to as CPU05.

  The data recording medium 00 stores an MPEG-4 AAC file. The user uses the operation unit 07 to make a request such as playback, fast forward, fast reverse, and playback stop for the MPEG-4 AAC file stored in the data recording medium 00. In this case, the CPU 05 sends the driver 01, the input data buffering device 02, the decoder 03, the output device 04, the display unit 06, the operation unit 07, the target position access device 08, and the header unit analysis device 09 in response to the request. Control, execute playback, fast forward, fast reverse, stop playback, etc.

[Operation]
The compressed audio file reproduction method according to the first embodiment of the present invention will be specifically described.

[1]
In response to the reproduction request, the CPU 05 accesses the data recording medium 00 via the driver 01 and determines the format of the MPEG-4 AAC file (step S00 in FIG. 9). At this time, the CPU 05 analyzes the header part of the MPEG-4 AAC file (step S01 in FIG. 9).

In step S01, the CPU 05 searches for an atom (structural unit) called “stco” shown in FIGS. 15 to 17 at the header analysis timing at the start of audio file reproduction.
Here, the basic data unit of “˜.m4a” and “˜.mp4” which are MPEG-4 files is called Atom (see FIG. 14). Each Atom is composed of a size (including the field area of itself and type), a type, and information, and the Atom can be included in the Atom. In the “˜.m4a” file, music data in AAC RAW format (see FIG. 13) standardized by ISO / IEC 14496-1 is stored as audio data (audio data) in “mdat” Atom. ing. Various pieces of information are stored in a nested format in Atom before that.

[2]
The CPU 05 stores, in the memory 10, an offset value (first offset value) with respect to audio data to be reproduced among a plurality of audio data (step S02 in FIG. 9).

  In step S02, the CPU 05 holds only the head position (address A) where the offset value found in [1] is stored. It is not necessary to memorize all offset values.

[3]
The CPU 05 controls the input data buffering device 02 so as to buffer the audio data (step S03 in FIG. 9), and controls the decoder 03 so as to decode the audio data (step S04 in FIG. 9). , S05), and outputs the audio data as sound to the output device 04 (step S06 in FIG. 9). Thereby, music data 1, 2,..., X, Y, Z,..., T, t1,.

  In steps S03 to S06, the CPU 05 holds the offset value, and then decodes and reproduces the actual music data stored after ‘mdat’ Atom. When the CPU 05 finishes reproducing the music data n, the reproduction of the MPEG-4 AAC file ends (step S07-Yes in FIG. 9).

[4]
While the reproduction of the MPEG-4 AAC file is being executed, a fast forward / fast reverse request including the designated double speed is made (step S07-No). In this case, the CPU 05 executes a fast forward / fast reverse process in response to the fast forward / fast reverse request (step S08 in FIG. 9). In this fast forward / fast reverse process, the CPU 05 controls the target position access device 08 to determine the target position (step S11 in FIG. 10).

In step S11, the target position access device 08 represents an offset value determined based on the designated double speed included in the fast forward / fast reverse request and the elapsed time when data for the first offset value is reproduced. Calculate the calculated offset value.
Calculated offset value [Byte] = (Elapsed time [s] * Specified double speed) * (Average bit rate [bps] / 8) + Header size [Byte]
Here, in the case of 10 times speed, when 1 second elapses, a decoding position about 10 times ahead of the time of normal reproduction is obtained.

[5]
Next, the CPU 05 controls the target position access device 08 and the header part analysis device 09 to execute the synchronous position search process (step S12 in FIG. 10).
In this synchronous position search process, the target position access device 08 acquires an optimum offset position by header analysis (step S30 in FIG. 11).

  The header part analyzer 09 returns to the address A, acquires the offset value (first offset value) stored in the memory 10 and the next offset value (second offset value), and stores them in the buffer. Then, a comparison process for comparing the first and second offset values with the calculated offset value (third offset value) is executed (step S31 in FIG. 11). Here, the condition P is defined as the first offset value ≦ the third offset value <the second offset value.

As a result of executing the comparison process, when the condition P is not satisfied (step S32—No in FIG. 11), the header part analysis device 09 executes a data acquisition / update process (step S33 in FIG. 11). In this data acquisition / update process, the header part analysis device 09 accesses the header part of the file again, acquires the next offset value (fourth offset value) after the second offset value, The buffer is updated with the offset value of 4 as the first and second offset values, respectively.
The header part analysis device 09 executes data acquisition / update processing and comparison processing until the condition P is satisfied (S32-No, S33).

  When the condition P is satisfied as a result of executing the comparison process (step S32—Yes in FIG. 11), the target position access device 08 updates the buffer using the first offset value as an offset value that can be resynchronized ( Step S34 in FIG. 11). At this time, the address A is updated as the first offset value (step S35 in FIG. 11).

[6]
The CPU 05 resynchronizes based on the first offset value and continues the decoding process (step S13 in FIG. 10). That is, the input data buffering device 02 is controlled to buffer the audio data, the decoder 03 is controlled to decode the audio data, and the audio data is output to the output device 04 as sound. . Thus, after the music data for the first offset value is decoded and reproduced, the music data for the third offset value is decoded and reproduced.

  Here, normal processing can be continued by starting from the offset position of [5] where resynchronization is possible. After outputting the sound for a certain time, until there is a cancellation request, the process returns to [4] (step S14-No in FIG. 10), and steps S11 to S14 are repeated.

  The reason why the problems of the prior art are solved will be described.

When the header does not have frame length information and processing is performed while holding an offset value, the data necessary for obtaining the offset interval (obtained by analyzing 'stsc'Atom) is 4 in a maximum of one offset information. [Byte] +4 [Byte], the offset value itself is 4 [Byte], and 4 [Byte] is provided to hold the number of each. For example, if the offset points to the position at intervals of 0.5 seconds, considering a music file of 5 minutes,
300 [s] /0.5 [s] * (4 * 2 + 4) [Byte] + (4 + 4) [Byte] = 7208 [Byte]
That's okay. However, if the value called Sample Per Chunk (the number of chunks that can output 1024 samples) is 1,
(1024 [Sample] * 1) / (44100 [Sample / s]) ≈0.0232 [s]
So,
300 [s] /0.0232 [s] * (4 * 2 + 4) [Byte] + (4 + 4) [Byte] ≈156530 [Byte]
Is required.

Considering the same thing by ignoring the offset interval, if only the offset value is stored, it becomes 1/3, but still 300 [s] /0.5 [s] * 4 [Byte] + (4 + 4) [Byte] = 2404 [Byte]
300 [s] /0.0232 [s] * 4 [Byte] + (4 + 4) [Byte] ≈51732 [Byte]
Is required.

  Here, in the present invention, the minimum information is held in [2], and after that, it is only necessary to update and use the information while obtaining necessary information from the header portion in [5]. If there is street data, it will be enough. Since buffering can use the same area as that normally used for the header analysis unit, it is not necessary to prepare separately (in the case of a FAT file system, the sector size minimum value is equivalent to 512 bytes, and in the case of a CD file system, 2048 bytes). Etc.)

The data configuration actually required in the present invention is as follows.
-Current offset, next offset: 4 bytes * 2
(Value used for condition determination in [5]; first and second offset values)
-Total file size up to the position being analyzed: 4 bytes
(Corresponds to address A obtained in [2] and [5])
-Buffer reference position: 2 bytes
(4 * 2) + 4 + 2 = 14 bytes

  Since the 14-byte information can be used to determine the synchronization position, it is possible to implement fast-forward / fast-reverse processing with a low memory even in a file configuration (FIG. 6) that could not be realized by the prior art. .

  Therefore, according to the compressed audio file playback method according to the first embodiment of the present invention, for example, when trying to cope with a 20-minute song, it is necessary to secure the size in consideration of about 10 kbytes to 600 kbytes. However, even if the file becomes longer, it can be handled as long as the above 14-byte memory size is secured. In this case, it can be reduced to about 1/730 or more (up to about 1 / 43,000 when the storage information is increased). Further, since the memory usage is fixed, there is no need to thin out information, and the time display can be performed accurately.

[effect]
As described above, in the case of FIG. 6 which is a problem of the prior art, if all the information indicating the synchronization position (offset value) is held in the memory at the time of activation, it takes an analysis time. In addition, a memory capacity for storing all the synchronization positions is required.

  Therefore, according to the compressed audio file reproduction method according to the first embodiment of the present invention, at the time of initial header analysis, only the necessary position (offset value) is remembered, and the sound is used while using the position. Perform fast forward / fast reverse processing. In parallel with this processing, the actual data is accessed every time to perform minimum header analysis and offset value update. Therefore, it is not necessary to save all the synchronization positions, and the memory capacity can be reduced.

(Second Embodiment)
In the compressed audio file reproduction method according to the second embodiment of the present invention, the description overlapping that of the first embodiment is omitted.

[Operation]
As shown in FIG. 18, every time one decoding is completed (after step S05), the header part analysis device 09 performs a synchronous position search process (the same process as the synchronous position search process (step S12) in FIG. 10). Step S09) is performed, and the search is performed from data based on the current position when a fast forward / reverse request is made by constantly updating during reproduction.

[Operation image]
When a fast-forwarding request is received after playing back for 6 seconds, the situation in the first embodiment is shown in FIG. 19, and compared with FIG. 20 showing the situation in the second embodiment in the same case, the circled numbers in FIG. By performing the processes 3, 4, 5, and 6, the processes of the circled numbers 6 and 7 and part of the process of the circled numbers 8 in FIG. 19 are omitted.

  [5] When a single decoding completion notification is received after [3] in the first embodiment, [5] the same processing is performed, but the data is actually adjacent to each other, so the target position must be determined. No, only a single value update is performed, which can be realized by simple processing.

[effect]
According to the compressed audio file reproduction method according to the second embodiment of the present invention, since the corresponding offset is updated in real time after reproducing one piece of data, the synchronization position after entering the actual fast forward / reverse operation is determined. Since the time required for the search process is always based on the current position, it is shorter than the first embodiment and is at a constant interval.
This is particularly effective when the video data or when one file is sufficiently long is being played normally until the end, and a fast forward / reverse request is made at the end.

(Third embodiment)
In the compressed audio file reproduction method according to the third embodiment of the present invention, the description overlapping with the first and second embodiments is omitted. Further, the third embodiment can be combined with the first and second embodiments.

[Operation]
In the first embodiment, the header analysis device 09 obtains the offset value (first offset value) stored in the memory 10 and the next offset value (second offset value) and stores them in the buffer. A comparison process is performed for storing and comparing the first and second offset values with the calculated offset value (third offset value) (step S31 in FIG. 11). Therefore, when the condition P (first offset value ≦ third offset value <second offset value) is not satisfied as a result of executing the comparison process (step S32—No in FIG. 11), the header part analysis device 09 Performs data acquisition / update processing (step S33 in FIG. 11). In this data acquisition / update process, the header part analysis device 09 accesses the header part of the file again, acquires the next offset value (fourth offset value) after the second offset value, The buffer is updated with the offset value of 4 as the first and second offset values, respectively. However, when it is necessary to analyze the cluster chain with the FAT file system, it is difficult to search in the reverse direction.

  Therefore, in the third embodiment, as shown in FIGS. 21 and 22, a data acquisition / update process (step S33 ′ in FIG. 21) is executed instead of the data acquisition / update process (step S33 in FIG. 11). In this data acquisition / update process (step S33 ′ in FIG. 21), the header analysis device 09 cannot search within the same buffer at the time of a fast return request (steps S40-Yes and S41-Yes in FIG. 22). The offset value stored in the buffer is cleared (step S42 in FIG. 22). Next, the header part of the file is accessed again to obtain the next offset value (fourth offset value) after the second offset value (step S43 in FIG. 22), and the second and fourth offset values are obtained. The buffer is updated as the first and second offset values, respectively (step S44 in FIG. 22). As described above, the header analysis device 09 searches again from the beginning by clearing (deleting) the information (offset value) when the search cannot be performed in the same buffer at the time of a fast reverse request.

[Operation image]
If it is difficult to calculate an address for obtaining the y-th data in the process of circled number 10 in FIG. 23, a process of clearing information is added in the process of circled number 11 in FIG. 23 (FIG. 24). Thus, it is possible to access the data by re-acquisition from the beginning.

In order to realize this fast reverse method, the following information is required in addition to the first embodiment. The values obtained in [5] of the first embodiment are cleared using the following data, respectively.
-First offset of music data, second offset: 4 bytes * 2
(Start of 'stco'Atom and next value, used to clear)
-Third offset storage address: 4 bytes
(Used to clear address A)
(4 * 2) + 4 = 12 bytes

[effect]
According to the compressed audio file reproduction method according to the third embodiment of the present invention, even in the case of a file system that is difficult to follow in the reverse direction by using a total of 26 bytes in addition to the 14 bytes of the first embodiment, It is possible to easily cope with the return.

(Fourth embodiment)
In the compressed audio file reproduction method according to the fourth embodiment of the present invention, the description overlapping with the first to third embodiments is omitted. The fourth embodiment can be combined with the first to third embodiments.

  The compressed audio file may be a WBR (Windows® Media Audio) VBR (Variable Bit Rate) file. Each of the plurality of data described above corresponds to a packet. Even in this case, as shown in FIG. 25, when VBR is detected by header analysis, the present invention is used to store and update the access position and offset value for the index information stored after the data. Thus, fast-forward / fast-reverse can be realized without storing all the synchronization positions in the memory 10.

[effect]
According to the compressed audio file playback method according to the fourth embodiment of the present invention, an audio file of one hour usually requires about 15 kbytes if all index information is held, and the memory is used at about 1/1000. The amount can be reduced.

[Summary]
As described above, according to the compressed audio file reproduction method of the present invention, the following effects are realized.
1. Almost no memory capacity is required, and a minimum amount of about 20 bytes is sufficient.
2. Prevents time deviation due to synchronization position thinning.
3. With the same file structure, fast forward / fast reverse can be realized regardless of the type.

FIG. 1 is a flowchart showing a fast-forward playback process according to the prior art (background art). FIG. 2 is a flowchart showing a frame search according to the prior art (background art). FIG. 3 shows an example of a data structure considered in the fast-forward playback of the prior art (background art). FIG. 4 shows an outline of the operation when the prior art can be used (background art). FIG. 5 shows an example of a data structure in which the prior art cannot be used (background art). FIG. 6 shows an outline of the operation when the prior art cannot be used (background art). FIG. 7 shows a compressed audio file playback apparatus as a system applied to the compressed audio file playback method according to the first to fourth embodiments of the present invention. FIG. 8 shows an operation image of fast-forward playback using the target file in the compressed audio file playback method according to the first embodiment of the present invention (when a 10 × fast-forward request at a 1 second point is received). . FIG. 9 is a flowchart showing a compressed audio file reproduction method according to the first embodiment of the present invention. FIG. 10 is a flowchart showing the fast forward / reverse processing of FIG. 9 in the compressed audio file reproduction method according to the first embodiment of the present invention. FIG. 11 is a flowchart showing the synchronization position search process of FIG. 10 in the compressed audio file reproduction method according to the first embodiment of the present invention. FIG. 12 shows a format image of AAC (ADTS format) (background art). FIG. 13 shows a format image of AAC (RAW format). FIG. 14 shows an MPEG-4 Atom configuration defined in “QuickTime File Format (March 27, 2001) APPENDIX C”. FIG. 15 is a header image showing the storage location of 'stco'Atom. FIG. 16 is an image showing how offset information is stored in 'stco'Atom. FIG. 17 is a header image showing the storage location of 'stsc'Atom. FIG. 18 is a flowchart illustrating a compressed audio file reproduction method according to the second embodiment of the present invention. FIG. 19 shows an operation image of fast-forward playback using a target file in the compressed audio file playback method according to the first embodiment of the present invention (10-times fast-forward at a 6-second point) for comparison with the second embodiment. In the case of receiving a request). FIG. 20 shows an operation image of fast-forward playback using a target file in the compressed audio file playback method according to the second embodiment of the present invention. FIG. 21 is a flowchart showing the synchronization position search process of FIG. 10 in the compressed audio file reproduction method according to the third embodiment of the present invention. FIG. 22 is a flowchart showing the data acquisition / update process of FIG. 21 in the compressed audio file reproduction method according to the third embodiment of the present invention. FIG. 23 shows an operation image of fast-reverse playback using a target file in the compressed audio file playback method according to the first embodiment of the present invention, compared with the third embodiment (immediately after FIG. 8, 11 (When a 10 × fast reverse request at a second point is accepted). FIG. 24 shows an operation image of fast-forward playback using a target file in the compressed audio file playback method according to the third embodiment of the present invention. FIG. 25 shows a usage image of the WMA file in the VBR in the compressed audio file reproduction method according to the fourth embodiment of the present invention.

Explanation of symbols

00 data recording medium,
01 driver,
02 Input data buffering device,
03 Decoder,
04 output device,
05 CPU,
06 Display section,
07 Operation part,
08 Target position access device,
09 header analysis device,
10 memory,

Claims (12)

A step of accessing the data recording medium in response to a reproduction request and reproducing a plurality of data in order; and a compressed audio file in which header information is not set for each data is stored in the data recording medium. The compressed audio file includes the plurality of data and a header portion including an offset value indicating an address of each of the plurality of data.
Storing a first offset value, which is an offset value for data to be reproduced, of the plurality of data in a memory;
In response to fast-forward / fast-reverse requests including the specified double speed,
Calculating a calculated offset value representing an offset value determined based on the designated double speed and an elapsed time when data for the first offset value is reproduced;
Replaying data for the calculated offset value after replaying data for the first offset value of the plurality of data;
A compressed audio file playback method comprising: Performing a synchronization position search process between the step of calculating the calculated offset value and the step of reproducing data for the calculated offset value;
Further comprising
The step of executing the synchronous position search process includes:
The first offset value stored in the memory and the second offset value that is the next offset value are stored in a buffer, and the first and second offset values and the calculated offset value are the first offset values. Performing a comparison process comparing the offset value of 3;
As a result of executing the comparison process, when the condition of the first offset value ≦ the third offset value <the second offset value is not satisfied, the second offset value, the second offset value Executing a data acquisition / update process for updating the buffer with the fourth offset value being the next offset value as the first and second offset values, respectively;
Performing the comparison process after executing the data acquisition / update process;
As a result of executing the comparison process, if the condition is satisfied, updating the buffer with the first offset value as an offset value capable of resynchronization;
Including
Reproducing data for the calculated offset value comprises:
Re-synchronizing based on the first offset value and regenerating data for the third offset value after regenerating data for the first offset value;
The compressed audio file reproduction method according to claim 1, comprising: The step of sequentially reproducing the plurality of data includes:
Decoding each of the plurality of data and executing the synchronous position search process;
Re-synchronizing based on the first offset value after performing the synchronization position search process, and reproducing the decoded data of the plurality of data;
The compressed audio file reproduction method according to claim 2, further comprising: The step of executing the data acquisition / update process includes:
Deleting the offset value stored in the buffer when searching in the buffer was not possible at the time of the fast reverse request;
Obtaining the fourth offset value next to the second offset value and updating the buffer with the second and fourth offset values as the first and second offset values, respectively;
The compressed audio file reproduction method according to claim 2 or 3, comprising: The compressed audio file is an MPEG (Moving Picture Experts Group) -4 AAC (Advanced Audio Coding) file.
The compressed audio file reproduction method according to any one of claims 1 to 4. The compressed audio file is a WBR (Windows (registered trademark) Media Audio) VBR (Variable Bit Rate) file,
Each of the plurality of data corresponds to a packet;
The compressed audio file reproduction method according to any one of claims 1 to 4. A data recording medium storing a compressed audio file in which header information is not set for each data, and the compressed audio file includes a plurality of data and an offset value representing an address of each of the plurality of data A header portion including
A controller that accesses the data recording medium in response to a reproduction request and reproduces the plurality of data in order;
Comprising
The controller is
Storing a first offset value, which is an offset value for data to be reproduced, of the plurality of data in a memory;
In response to fast-forward / fast-reverse requests including the specified double speed,
Calculating a calculated offset value representing an offset value determined based on the designated double speed and an elapsed time when data for the first offset value is reproduced;
Replaying data for the calculated offset value after replaying data for the first offset value of the plurality of data;
Compressed audio file playback device. The controller is
After calculating the calculated offset value, execute a synchronous position search process,
In the synchronous position search process,
The first offset value stored in the memory and the second offset value that is the next offset value are stored in a buffer, and the first and second offset values and the calculated offset value are the first offset values. A comparison process for comparing with the offset value of 3 is executed,
As a result of executing the comparison process, when the condition of the first offset value ≦ the third offset value <the second offset value is not satisfied, the second offset value, the second offset value A data acquisition / update process for updating the buffer with the fourth offset value, which is the next offset value, as the first and second offset values,
After executing the data acquisition / update process, execute the comparison process,
As a result of executing the comparison process, if the condition is satisfied, the first offset value is updated as an offset value that can be resynchronized, and the buffer is updated.
Re-synchronizing based on the first offset value and reproducing data for the first offset value, and then reproducing data for the third offset value;
The compressed audio file playback apparatus according to claim 7. The controller is
Decoding each of the plurality of data, and executing the synchronous position search process;
After executing the synchronization position search process, resynchronization is performed based on the first offset value, and the decoded data of the plurality of data is reproduced.
The compressed audio file reproduction apparatus according to claim 8. The controller is
If searching within the buffer was not possible at the time of the fast reverse request, delete the offset value stored in the buffer,
Obtaining the fourth offset value next to the second offset value, and updating the buffer with the second and fourth offset values as the first and second offset values, respectively.
The compressed audio file reproduction apparatus according to claim 8 or 9. The compressed audio file is an MPEG (Moving Picture Experts Group) -4 AAC (Advanced Audio Coding) file.
The compressed audio file reproduction apparatus according to any one of claims 7 to 10. The compressed audio file is a WBR (Windows (registered trademark) Media Audio) VBR (Variable Bit Rate) file,
Each of the plurality of data corresponds to a packet;
The compressed audio file reproduction apparatus according to any one of claims 7 to 10.

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