JP4254960B2 - Audio data encoding apparatus and audio data reproducing apparatus - Google Patents

Description

  The present invention relates to recording and reproduction of audio data, and more particularly to a recording and reproduction technique for reducing processing load during reproduction of audio data including a loop portion.

  In an information processing apparatus having a digital voice data playback function such as a personal computer, a game machine, a music playback device, etc., encoded voice data is converted into analog voice data during playback and output as voice.

  The encoded audio data may be uncompressed like a music CD, but most of the encoded audio data is read in a compressed state, decompressed during reproduction, and output as audio.

  Various methods have been proposed and put to practical use as audio compression methods, but sample data arranged in time series is divided into a plurality of blocks, and orthogonal transformation, for example, DCT (Discrete Consine Transform), MDCT (Modified Discrete) is performed. A method of performing compression by applying (Consine Transform) is widely known. At this time, in order to increase the continuity of the speech waveform, a plurality of adjacent blocks are grouped and sequentially compressed while overlapping the blocks. A typical example of such a compression method is ATRAC (Adaptive TRans form Acoustic Coding) employed in a so-called minidisc (MD) (see Patent Document 1).

  FIG. 7A is a diagram illustrating a state in which audio data is compressed in units of blocks. In this figure, sample data arranged in time series is divided every predetermined number to generate blocks (original blocks) “A0” “A” “B” “C” “D” “D0”.

  Then, an encoding block is generated by performing compression processing with two consecutive blocks as a set and overlapping the blocks. Here, an encoding block “X1” is generated from the original blocks “A0” and “A”, and an encoding block “X2” is generated from the original blocks “A” and “B”.

At the time of reproduction of audio data, a decode block “a” is generated from the encode blocks “X1” and “X2”. Since the decoded block “a” corresponds to “A” of the original block, the sample of the decoded block “a” can be D / A converted to reproduce the sound. Similarly, since the decoded blocks “b”, “c”,... Can be obtained, the sound is continuously reproduced.
JP-A-8-287612

  By the way, there is a case where audio data is desired to be reproduced in a loop. For example, as shown in FIG. 7B, the sound from the predetermined position (LS) to the predetermined position (LE) of the sample data is repeatedly reproduced until a certain condition is satisfied. Here, it is assumed that LS that is the start position of the loop is included in the original block “A”, and LE that is the end position of the loop is included in the original block “D”.

  In this case, as shown in FIG. 7C, when reproduction is performed up to the position corresponding to LE of the decoded block “d”, reproduction is continued from the position corresponding to LS of the decoded block “a”. Will do.

  The decode block “d” is generated from the encode blocks “X4” and “X5”, but since the encode block “X4” has already been read when the decode block “c” is generated, “X5” is read. It's enough if you do the process. On the other hand, the decode block “a” is generated from the encode blocks “X1” and “X2”, but when returning in a loop, both the encode blocks must be read and processed. For this reason, the load of the decoding process temporarily increases.

  Further, in the loop, the decoded block “a” reproduced subsequent to the decoded block “d” must be generated before the reproduction of the decoded block “d” is completed. However, the decoded block “d” is reproduced only up to the position of LE without reproducing the entire block. For this reason, the decode block “a” must be generated in a shorter time, and the processing load described above is further increased.

  The increase in processing load at the time of the loop is a problem particularly in an audio data reproducing apparatus in which portability is important and a processing speed is restricted like a portable game machine and a portable music reproducing apparatus.

  An object of the present invention is to reduce the processing load at the time of reproducing audio data including a loop portion.

In order to solve the above problems, according to the first aspect of the present invention,
An audio data encoding device that encodes audio data including a loop portion in which a loop start position and a loop end position are specified,
A block dividing means for dividing the audio data into blocks;
Encoding means for encoding a set of a plurality of consecutive blocks as a set,
The encoding means further comprises:
There is provided an audio data encoding apparatus characterized in that encoding is performed by combining a block including a loop end position and a block including a loop start position.

Moreover, in order to solve the said subject, according to the 2nd aspect of this invention,
An audio data reproducing device for reproducing audio data including a loop portion in which a loop start position and a loop end position are designated,
Decoding means for sequentially reading encoded audio data in units of blocks and decoding a plurality of consecutive blocks as a set to generate audio data;
Determination means for determining the presence or absence of a loop,
The decoding means includes
If the audio data to be generated includes a loop end position and the determination means determines that there is a loop, the block including the loop end position and the block including the loop start position are used instead of the block to be read next. An audio data reproducing apparatus is provided that reads and decodes a block encoded as a set.

Here, the decoding means includes
If the audio data to be generated includes a loop end position, and the determination means determines that there is a loop, the encoding block used for generating the next block of the audio data including the loop start position Can be read and decoded.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing an outline of the configuration of an embodiment of the present invention. As shown in the figure, in this embodiment, the audio data reproducing apparatus 200 performs a process of decoding and reproducing the audio data encoded by the audio data encoding apparatus 100.

  Specifically, the audio data encoding apparatus 100 reads the audio data 11 to be recorded, performs a process such as compression using the encoding processing unit 110, and converts it into encoded data 20. Here, it is assumed that the audio data 11 is sampled at a predetermined rate in advance. Of course, analog audio data may be input to the audio data encoding device 100 and A / D converted by the audio data encoding device 100.

  In the present embodiment, the audio data 11 includes a loop portion, and a loop start position and a loop end position are designated in advance. The loop start position and the loop end position are indicated by, for example, an address or a sample number in the audio data 11 and are read together with the audio data 11 as loop information 12. Note that the loop information 12 may be added to the header portion or the like of the audio data 11 or may exist separately from the audio data 11.

  When the audio data reproduction apparatus 200 reproduces the audio data 11, the loop portion determines whether or not there is a loop according to a predetermined condition.

  If it is determined as a result of the loop presence / absence that a loop is to be performed, the loop is performed according to the loop information 12. That is, when the playback is performed up to the loop end position, the playback is resumed up to the loop start position. On the other hand, when it is determined that the loop is not performed, the loop is not performed regardless of the loop information 12. That is, when the playback is performed up to the loop end position, the subsequent playback of the audio data 11 is continued.

  A plurality of loop portions may be included for one audio data 11. In this case, a loop start position and a loop end position are designated as loop information for each loop portion. The plurality of loop portions can be determined whether or not there is a loop under different conditions.

  The developer can arbitrarily determine which range of the audio data 11 is the loop portion based on the contents of the audio data 11.

  The encoding processing unit 110 of the audio data encoding apparatus 100 divides the audio data 11 into a plurality of blocks, performs encoding using orthogonal transform (for example, MDCT) with a predetermined number of consecutive blocks as a unit, and blocks Are sequentially encoded to generate encoded data. Note that specific processing of the encoding processing unit 110 will be described later.

  The encoded data 20 is recorded on a recording medium 300 such as a CD-ROM together with a control program 30 that controls the loop processing of the audio data 11. The recording process on the recording medium 300 may be performed by the audio data encoding apparatus 100 or may be performed by another apparatus.

  Note that the encoded data 20 and the control program 30 may be recorded on separate recording media 300. The recording medium 300 is not limited to a CD-ROM, and may be an optical disc such as a DVD-ROM, a magnetic disc, a semiconductor recording device, or the like. Alternatively, the encoded data 20 may be output from the audio data encoding apparatus 100 to the audio data reproducing apparatus 200 via a communication line such as the Internet.

  The control program 30 is a program executed by the audio data playback device 200. Based on the control program 30, the audio data reproducing apparatus 200 determines whether or not there is a loop of audio data (hereinafter “audio data 11 a”) that is reproduced by decoding the encoded data 20 in accordance with an operation from the user, for example. decide. As a specific example, the loop portion of the audio data 11a is repeatedly reproduced until a predetermined operation such as key input is received from the user, and when the predetermined operation is received, the loop reproduction is terminated and the audio data after the loop portion is received. 11a is mentioned.

  The audio data reproduction device 200 includes a program execution unit 210 that executes the control program 30 and the like, and a decode processing unit 220 that decodes the encoded data 20. The audio data reproduction device 200 has a function of reproducing the decoded audio data 11a and outputting the audio. As a result, the audio data reproducing apparatus 200 can decode and reproduce the encoded data 20 almost in real time. Specific processing of the decoding processing unit 220 will be described later.

  Note that the audio data encoding apparatus 100 can be configured using a personal computer, a workstation, or other general information processing apparatus having an audio processing function. Of course, a dedicated system specialized for recording audio data may be used.

  The audio data reproducing apparatus 200 can also be configured using a personal computer, a workstation, or other general information processing apparatus having an audio processing function. Of course, a dedicated system specialized for audio data reproduction may be used.

  Note that the present invention uses an information processing apparatus that places importance on portability and restricts processing speed, such as a PDA (Personal Digital Assistant), a portable game machine, and a portable music playback apparatus, as the audio data playback apparatus 200. It can be applied particularly effectively in cases.

  The information processing apparatus can function as the audio data encoding apparatus 100 or the audio data reproducing apparatus 200 when a central processing unit (CPU) executes an application program developed for recording audio data or reproducing audio data. . These application programs can be distributed in the market by being recorded on a recording medium such as a CD-ROM. It can also be distributed via a computer network such as the Internet.

  Next, audio data encoding processing in the audio data encoding apparatus 100 will be described with reference to the flowchart of FIG.

  First, the audio data encoding apparatus 100 reads the audio data 11 and the loop information 12 (S101). Here, as shown in FIG. 3A, the audio data 11 is sample data arranged in a time series, and the loop start (LS) position and the loop end (LE) position are determined by the loop information 12. It is specified.

  Next, the encoding processing unit 110 divides the audio data 11 into blocks (S102). The block division is performed, for example, by dividing every predetermined sample from the head of the audio data 11. Here, the number of samples in each block is constant, but may be variable according to a predetermined rule. FIG. 3B shows a state in which the audio data 11 is divided into blocks (original blocks). That is, the audio data 11 is divided into original blocks “A0” “A” “B” “C” “D” “D0”.

  In general, the loop portion and the block division position are determined independently. The loop start position and the loop end position are included in any one of the original blocks according to the relative position in the audio data and the number of samples included in each block.

  Here, it is assumed that the loop start position is included in the original block “A” and the loop end position is included in the original block “D”. It should be noted that which original block each includes the loop start position and the loop end position can be easily obtained from the number of samples included in each block.

  The encoding processing unit 110 performs audio compression (encoding) in units of continuous original blocks (S103). Here, the encoding process is performed for each of the original blocks arranged in time series regardless of the presence or absence of the loop information.

  In the encoding process, one encoded block is generated from two consecutive original blocks. However, each original block is overlapped and used to generate preceding and subsequent encoded blocks.

  That is, as shown in FIG. 3C, the encoding block “X1” is generated from the continuous original blocks “A0” and “A”, and the encoding block “X2” is generated from the original blocks “A” and “B”. To do. Similarly, encode blocks “X3”, “X4”, “X5”,... Are generated.

  As such a compression method, ATRAC (Adaptive TRans form Acoustic Coding) is typical, but the present invention is not limited to this. In addition, one encode block may be generated from three or more consecutive original blocks, or one decode block may be generated from three or more encode blocks during decoding.

  Next, the encoding process part 110 produces | generates the encoding block for loops (S104). Here, the encoding block for the loop is generated from the original block including the loop end position and the original block including the loop start position. At this time, at the time of the loop, since playback should be performed in the order from the loop end position to the loop start position, encoding is performed with the block including the loop end position in front and the block including the loop start position in the back.

  FIG. 4 is a diagram illustrating a state in which an encoding block for a loop is generated. In this example, since the loop end position is included in the original block “D” and the loop start position is included in the original block “A”, the loop encoding block “X” includes the original blocks “D” and “A”. Is generated. Therefore, the original blocks “D” and “A” are arranged as loop blocks. In the loop, when the portion corresponding to D1 of the block “D” is reproduced, the portion corresponding to A1 of the block “A” is reproduced.

  Here, the original blocks “D” and “A” can be used as they are for the data other than the portions D1 and A1 that are cut during the loop. By doing in this way, the continuity of a speech waveform can be improved. Of course, dummy data such as silence may be used.

  The audio data encoding apparatus 100 outputs the encoded blocks arranged in time series and the encoded block for loop as encoded data 20 (S105). At this time, the loop information is also output. The loop information may be output as a file different from the encoded data 20 or may be output by being added to the header portion of the encoded data 20. In any case, the encoded data 20 and the loop information are handled while maintaining the relevance. Further, the encode data 20 includes an encode delay (delay information) at the time of encoding as necessary.

  As described above, the encoded data 20 output from the audio data encoding apparatus 100 is recorded on the recording medium 300 together with the control program 30 and distributed to the market.

  Next, playback processing in the audio data playback device 200 will be described with reference to the flowchart of FIG.

  When reproduction of audio data recorded on the recording medium 300 is started based on a user operation or the like (S201), the audio data reproduction device 200 reads the first encoded block and loop information of the encoded data 20 (S202).

  First, reproduction when no loop is performed will be described. The case where the loop is not performed means that the block to be reproduced (block after decoding: decoded block) does not include the loop end position (S203: N), or even if the loop end position is included (S203). : Y), the case where no loop is performed (S208: N). Whether or not to perform the loop is determined by the program execution unit 210 according to the control program 30 as described above. Whether the decoded block contains a loop end position can be determined from the number of reproduced blocks, the number of samples included in the block, and loop information.

  When the loop is not performed, the next encoding block is read as usual (S205), and the decoding is performed using the continuous encoding block to generate the decoding block (S205).

  That is, as shown in FIG. 3D, a decode block “a” is generated from the encode blocks “X1” and “X2”, and a decode block “b” is generated from the encode blocks “X2” and “X3”. The decoded blocks “a”, “b”,... Are audio data corresponding to the original blocks “A”, “B”,.

  Audio data is reproduced by sequentially D / A converting the decoded blocks and outputting the audio (S206). The above processing is continued until the encoding block is completed (S207, S215).

  Next, reproduction when looping will be described. The case where the loop is performed is a case where the loop end position is included in the decoding block to be reproduced (S203: Y) and the state where the loop is performed (S208: Y).

  In this case, the audio data reproducing device 200 reads the loop encoding block instead of the next encoding block (S209). Then, a decode block is generated from the read encode block and the newly read loop encode block (S211).

  This process will be further described with reference to FIG. In this example, a loop occurs when the reproduction target is the decode block “d”. Since the encode block “X4” has already been read when the decode block “c” is processed, the encode block “X5” is read when there is no loop, but when the loop is performed, “X5” is read. ”Instead of the loop encoding block“ X ”.

  Then, as shown in FIG. 6A, a decode block “d” is generated from “X4” and “X”. Of the decoded block “d”, the portion to be reproduced is the portion of d1, so the audio data reproducing device 200 reproduces the portion of d1, and cuts after that (S211).

  The audio data reproducing device 200 reads the encode block to obtain the decode block “a” including the loop start position. Originally, in order to generate the decoded data “a”, the encoding blocks “X1” and “X2” must be read (see FIG. 3D), but here the encoding block “X” has already been read. It is sufficient to read and process the encoding block “X2” (S212).

  Then, as shown in FIG. 6B, a decode block “a” is generated from “X” and “X2” (S213). In the decoded block “a”, the portion to be reproduced is the portion a1, and therefore the audio data reproducing device 200 reproduces only the portion a1 (S214). This can be easily determined by referring to the loop information.

  As described above, according to the present invention, since the encoding block for the loop is prepared, the processing load at the time of the loop can be reduced.

  FIG. 6B shows this state. That is, when the loop is returned from the decoding block “d” to “a”, the encoding block “X” for the loop generated using the original blocks “D” and “A” is used. Thus, it is not necessary to read both the encoding blocks “X1” and “X2”. This is because “X” in FIG. 6B has already been read in the process of “d”, and therefore it is sufficient to read and process only “X2”.

Here, a brief description will be given of a case where an encoding method for generating encoded data of one block using three consecutive original blocks is used. When returning from the original block “D” to “A” as in the example shown in FIG. 4, two loop encoding blocks are generated with a set of “CDA” and “DAB”. Then, at the time of reproduction, encoding processing may be performed using these encoding blocks in the loop portion.
There is a compression method in which a delay occurs at the time of encoding and decoding. When such a compression method is used, output samples at the time of decoding are output with a delay. At this time, the desired reproduction can be performed by shifting the cutting position backward by the delayed sample.

It is a figure which shows the outline | summary of a structure of embodiment of this invention. 5 is a flowchart for explaining an encoding process in the audio data encoding apparatus 100. FIG. It is a figure explaining the block of the audio | voice data 11. FIG. It is a figure which shows a mode that the encoding block for loops is produced | generated. FIG. 10 is a flowchart for explaining playback processing in the audio data playback device 200. It is a figure explaining the process of the block unit in the case of a loop. It is a figure explaining the system which compresses audio | voice data by a block unit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Audio data 12 ... Loop information 20 ... Encoding data 30 ... Control program 100 ... Audio data encoding device 110 ... Encoding processing unit 200 ... Audio data reproduction device 210 ... Program execution unit 220 ... Decoding processing unit 300 ... Recording medium

Claims (13)

An audio data encoding apparatus that encodes audio data including a loop portion in which a loop start position and a loop end position are specified,
A block dividing means for dividing the audio data into blocks;
Encoding means for generating a first encoded block for each set by encoding a plurality of consecutive blocks as a set,
The encoding means further comprises:
An audio data encoding apparatus characterized in that a second encoded block is generated for a set of blocks by encoding a block including a loop end position and a block including a loop start position as a set. The audio data encoding device according to claim 1,
In the second encoding block, any data other than the data from the beginning of the block including the loop end position to the loop end position and the data from the loop start position to the end of the block including the loop start position is arbitrarily set. An audio data encoding apparatus characterized by allowing data. An audio data reproducing device for reproducing audio data including a loop portion in which a loop start position and a loop end position are designated,
In the audio data divided into predetermined blocks, each of the first encoded blocks encoded as a set of a plurality of continuous blocks is sequentially read, and the audio is obtained by decoding the plurality of continuous first encode blocks as a set. Decoding means for generating data;
Determination means for determining whether or not a condition for performing loop reproduction is satisfied,
The decoding means includes
When the audio data generated using the next first encoding block includes a loop end position and the determination means determines that the condition for performing loop reproduction is satisfied, In place of the first encoding block, audio data including the loop end position is obtained by reading and decoding the second encoding block encoded as a set of the block including the loop end position and the block including the loop start position. An audio data reproducing apparatus characterized by generating The audio data reproducing device according to claim 3,
The decoding means includes
After the audio data including the loop end position is generated by decoding the second encoded block, the first encoded block encoded as a set of the block including the loop start position and the next block is read. An audio data reproducing apparatus that generates audio data including a loop start position by performing decoding. A program for causing an information processing apparatus to function as an audio data encoding apparatus that encodes audio data including a loop portion in which a loop start position and a loop end position are specified,
In the information processing apparatus,
A block division function that divides audio data into blocks, and an encoding function that generates a first encoded block for each set by encoding a plurality of consecutive blocks as a set.
The encoding function further includes:
A program for generating a second encoded block for a set of blocks by encoding a block including a loop end position and a block including a loop start position as a set. The program according to claim 5,
In the second encoding block, any data other than the data from the beginning of the block including the loop end position to the loop end position and the data from the loop start position to the end of the block including the loop start position is arbitrarily set. A program characterized by allowing data. A program for causing an information processing apparatus to function as an audio data reproducing apparatus that reproduces audio data including a loop portion in which a loop start position and a loop end position are designated,
In the information processing apparatus,
In the audio data divided into predetermined blocks, each of the first encoded blocks encoded as a set of a plurality of continuous blocks is sequentially read, and the audio is obtained by decoding the plurality of continuous first encode blocks as a set. A decoding function that generates data and a determination function that determines whether the conditions for loop playback are satisfied,
The decoding function is
If the audio data generated using the next first encoding block includes a loop end position and the determination means determines that the condition for performing loop reproduction is satisfied, Instead of the next first encoding block, a second encoding block encoded as a set of a block including a loop end position and a block including a loop start position is read and decoded, so that audio including the loop end position is read. A program characterized by generating data. The program according to claim 7,
The decoding function is
After the audio data including the loop end position is generated by decoding the second encoded block, the first encoded block encoded as a set of the block including the loop start position and the next block is read. A program that generates audio data including a loop start position by performing decoding.   An information processing apparatus-readable recording medium on which the program according to any one of claims 5 to 8 is recorded. A recording medium readable by an information processing device,
Information for designating the loop start position and loop end position of the audio data;
For audio data divided into blocks, a first encoded block encoded as a set of a plurality of consecutive blocks;
For the audio data divided into blocks, a second encoded block encoded as a set of a block including the loop end position and a block including the loop start position is recorded,
The information processing apparatus is
A decoding step of sequentially reading the first encoding block from the recording medium and generating audio data by decoding a plurality of consecutive first encoding blocks as a set;
A determination step for determining whether or not a condition for performing loop playback is satisfied,
In the decoding step,
When it is determined that the loop end position is included in the audio data generated using the next first encoding block and the condition for performing the loop reproduction is satisfied in the determination step, the next Instead of the first encoding block, the second encoding block is read from the recording medium and decoded, thereby generating audio data including a loop end position ,
Recording medium characterized Rukoto said determining step is further a program for realizing the recording to the information processing apparatus. An audio data encoding method in an audio data encoding apparatus for encoding audio data including a loop portion in which a loop start position and a loop end position are specified,
The audio data encoding device is
A block dividing step for dividing the audio data into blocks;
Performing an encoding step of generating a first encoding block for each set by encoding a plurality of consecutive blocks as sets,
In the encoding step,
An audio data encoding method comprising: encoding a block including a loop end position and a block including a loop start position as a set to generate a second encoded block for the set of blocks. An audio data decoding method in an audio data reproducing apparatus for reproducing audio data including a loop portion in which a loop start position and a loop end position are designated,
The audio data decoding device comprises:
In the audio data divided into predetermined blocks, the first encoded block encoded as a set of a plurality of continuous blocks is sequentially read, and the audio data is decoded by decoding the plurality of continuous first encode blocks as a set. A decoding step to generate;
A determination step for determining whether or not a condition for performing loop playback is satisfied,
In the decoding step,
When it is determined that the loop end position is included in the audio data generated using the next first encoding block and the condition for performing the loop reproduction is satisfied in the determination step, the next Instead of the first encoding block, the second encoding block encoded as a set of the block including the loop end position and the block including the loop start position is read and decoded, so that the audio data including the loop end position is obtained. An audio data decoding method comprising generating the audio data. An audio data decoding method of claim 1 2,
The audio data decoding device, in the decoding step,
After the audio data including the loop end position is generated by decoding the second encoded block, the first encoded block encoded as a set of the block including the loop start position and the next block is read. An audio data decoding method comprising: generating audio data including a loop start position by performing decoding.

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