KR101060490B1 - Method and device for calculating average bitrate of a file of variable bitrate, and audio device comprising said device - Google Patents

Abstract

The present invention relates to a method for calculating an average bitrate of a variable bitrate file. The present invention relates to a method of calculating an average bitrate of a variable bitrate file, and sets a location of a first file pointer with respect to a first block among a plurality of blocks included in a data area of the variable bitrate file. By extracting the header information of at least two frames included in the first block at the location of the file pointer, and calculating the average bit rate of a predetermined number of blocks of the plurality of blocks according to the comparison result of the extracted header information, The average bitrate can be calculated while reducing the preload time.

Description

Method and apparatus of calculating an average bitrate of a variable bitrate file, and audio device comprising the apparatus}

The present invention relates to a method of calculating an average bitrate of a file having a variable bitrate, and more particularly, a method and apparatus for calculating an average bitrate of a file having a variable bitrate without a header having an average bitrate value of the file, The present invention relates to an audio device including a computer-readable recording medium recording a program for executing the method of calculating the average bitrate of a file having a variable bit rate and an average bitrate calculating device of a file having a variable bit rate.

Bitrate represents the amount of data transmitted per second, and is divided into a fixed bitrate (CBR) and a variable bitrate (VBR). The fixed bitrate compresses according to a constant bitrate regardless of the amount of information input, so that a file of fixed bitrate includes frames of a fixed size.

On the other hand, the variable bitrate is a method of compressing by applying the bitrate variably according to the amount of information input, the file of the variable bitrate may include frames of different sizes. Variable bitrates can efficiently adjust the capacity allocated per unit bit, improving sound quality by allocating more bits where more data is needed and less bits where there is less data. You can.

In the case of the fixed bitrate, since the bitrate is constant, the total reproduction time can be calculated by dividing the overall file size by the bitrate. However, in the case of the variable bit rate, it is difficult to calculate the total reproduction time because the bit rate applied to each time point is different.

An object of the present invention is to provide a method and apparatus for calculating an average bitrate of a variable bitrate file that does not include a header having an average bitrate value of the file, and a method of calculating an average bitrate of a variable bitrate file. Disclosed is an audio device including a computer-readable recording medium having recorded thereon a program for execution and an apparatus for calculating an average bitrate of a variable bitrate file.

According to an aspect of the present invention, an average bitrate calculation method for a variable bitrate file sets a position of a first file pointer with respect to a first block among a plurality of blocks included in a data area of a file having a variable bitrate. Making; Extracting header information of at least two frames included in the first block at a location of the set first file pointer; And calculating an average bit rate for a predetermined number of blocks among the plurality of blocks according to the comparison result of the extracted header information.

The technical problem may include setting a location of a first file pointer with respect to a first block among a plurality of blocks included in a data area of a file having a variable bit rate; Extracting header information of at least two frames included in the first block at a location of the set first file pointer; And calculating an average bitrate for a predetermined number of blocks among the plurality of blocks according to the comparison result of the extracted header information. Achieved by a computer readable recording medium having recorded thereon.

In addition, the apparatus for calculating the average bitrate of the variable bitrate file according to the present invention for solving the above technical problem is to determine the first file pointer of the first block of the plurality of blocks included in the data area of the file of the variable bitrate A file pointer setting unit for setting a position; A header information comparison unit extracting header information of at least two frames included in the first block at the position of the set first file pointer and comparing the extracted header information; And an operation unit that calculates an average bit rate for a predetermined number of blocks among the plurality of blocks according to the comparison result of the extracted header information.

In addition, an audio device according to the present invention for solving the above technical problem comprises a memory for storing an audio file of a variable bit rate; Extract header information of at least two frames based on a location of a predetermined file pointer of a data area of the audio file, calculate an average bitrate of the audio file according to a comparison result of the extracted header information, and A control unit for modulating the file and providing the file as pulse code modulation (PCM) data; And a codec for decoding the PCM data provided from the controller.

According to the present invention, when the audio file does not include a header including the average bitrate value of the entire file, some data blocks of the audio file are selected, and some frames are also selected for the selected data block to obtain a bit rate. As a result, a relatively accurate average bitrate value can be obtained while reducing the preload time by reducing the amount of computation. As a result, the playback time of the audio file can be predicted, and thus time error or display error can be prevented.

With respect to the embodiments of the present invention disclosed in the text, specific structural to functional descriptions are merely illustrated for the purpose of describing embodiments of the present invention, embodiments of the present invention may be implemented in various forms and It should not be construed as limited to the embodiments described in.

Hereinafter, with reference to the accompanying drawings, it will be described in detail a preferred embodiment of the present invention. The same reference numerals are used for the same constituent elements in the drawings and redundant explanations for the same constituent elements are omitted.

1 is a block diagram illustrating an audio device according to an embodiment of the present invention.

Referring to FIG. 1, the audio device 1 includes a memory 10, a controller 20, a codec 30, and an output 40. In one embodiment of the present invention, the audio device 1 may be embedded in a mobile device such as a mobile phone, a personal digital assistant (PDA), or the like.

When a request is received from the outside, the controller 20 may receive an audio file stored in the memory 10 in a stream data format. In one embodiment of the present invention, the control unit 20 may be a multimedia application processor.

As described above, the sizes of the frames included in the audio file of the variable bitrate are different from each other, and the bitrates according to viewpoints are also different. Therefore, in order to obtain the reproduction time of the audio file of the variable bit rate, it is necessary to obtain the average bit rate of the frames included in the audio file of the variable bit rate. In general, an audio file having a variable bit rate includes a header including attribute information of the entire file such as a VBRI header or an XING header at the front of the file. As a result, an average bitrate can be obtained by detecting a VBRI header or an XING header located at the front of the file.

However, with the recent popularization of user editing using various tools, some of the files edited by the user may not include a header containing attribute information of the entire file. In this case, the average bitrate of the audio file must be directly calculated in order to obtain the playback time of the audio file. If the average bitrate is obtained after obtaining the bitrates for all the frames included in the audio file, the preload time is long because the accuracy is high but the calculation amount is very large.

In an embodiment of the present invention, the controller 20 may include an average bitrate (ABR) calculator 21 for calculating an average bitrate of the audio file. Here, the average bitrate calculator 21 calculates an average bitrate by searching for a sync word in the middle of all sections of the audio file and extracting only some frames. Here, the sync word is a first field of the MPEG audio frame, also called a sync field, and is a sync signal indicating the start of the audio frame. For example, the sync word may consist of twelve "1s" (ie, OxFFF 1111 1111 1111). Here, Ox represents hexadecimal. The operation of the average bit rate calculator 21 will be described in detail with reference to FIGS. 2 and 3 below.

In addition, the controller 20 may further include an audio device interface (ADI) 22 for interfacing with the codec 30. Here, the audio device interface 22 may output pulse code modulation (PCM) data.

The codec 30 receives PCM data from the control unit 20 and decodes the audio file. The output unit 40 outputs the decoded audio file provided from the codec 30. In one embodiment of the present invention, the output unit 40 may be a speaker or an earphone.

FIG. 2 is a block diagram illustrating in detail the average bit rate calculator 21 included in FIG. 1.

3 illustrates an example of an audio file input to the average bitrate calculator 21 of FIG. 2.

Hereinafter, the operation of the average bit rate calculator 21 will be described in detail with reference to FIGS. 2 and 3. First, referring to FIG. 2, the average bit rate calculator 21 includes an attribute information detector 211, a file pointer setter 212, a header information comparer 213, and an operator 214.

2 and 3, an audio file includes an attribute information area and an audio data area. The audio data area may be divided into a plurality of blocks. In FIG. 3, the audio data area may be divided into N blocks. Each of the N blocks is composed of a plurality of frames.

The attribute information detector 211 receives an audio file input in the stream data format, and detects an area representing attribute information, that is, an attribute information region, in the file to obtain a size of the corresponding region. In one embodiment of the present invention, the attribute information may be an ID3 tag. Here, ID3 is a metadata format used in an MP3 file, and ID3 tag is a standard used to add information such as a title, a singer (musician), a record name, a song number, and the like to the MP3 file. Attribute information such as ID3 tag does not affect the playing time of the audio file. Therefore, the attribute information detector 211 excludes the size of the region obtained by detecting the region representing the attribute information when calculating the average bit rate.

The file pointer setting unit 212 sets the position of the first file pointer in an area except the size of the area indicating the attribute information detected by the attribute information detection unit 211 in the entire file. In more detail, the file pointer setting unit 212 sets the position of the first file pointer in the first block among the plurality of blocks included in the audio data area, which is an area excluding the size of the area indicating the attribute information among all the files. Can be. In the file shown in FIG. 3, the position of the first file pointer is set in the first block B1 included in the audio data area portion excluding the attribute information area. Specifically, the file pointer setting unit 212 sets the position of the file pointer using the following equation (1).

[Equation 1]

P _d = I + (F _total -I) * d / N _D

Here, d is the B _1, B _2, ... in Fig. 3, (a That is, in the case of B1 d 1) indicates a sequence number of a plurality of blocks B, such as _N, P _d is the file pointer in each block Indicates a location. In addition, I represents the size of the attribute information area, F _total represents the size of the entire audio file, and N _D represents the number of blocks to be searched in the entire audio file.

The header information comparison unit 213 checks whether a header of the first frame valid at the position of the first file pointer set by the file pointer setting unit 212 exists. As mentioned above, the frame header includes a sync word, and in general, the frame header includes an identifier (ID) field, a layer field, a guard bit field, a bitrate index field, a sampling frequency field, a padding bit field, and a private field. It consists of a (private) bit field, a mode field, a mode extension field, a copy right field, an original / copy field, and an emphasis field. In one embodiment of the present invention, each frame header may include bitrate information, sampling rate information, padding information, layer information, and the like. For example, since an mp3 file means MPEG 1 or LAYER 3, the layer information indicates information about such a compression standard.

Hereinafter, the operation of the file pointer setting unit 212 and the header information comparison unit 213 according to whether the header of the first frame valid as a result of the check is present will be described in detail.

First, when the header of the first valid frame does not exist, the header information comparison unit 213 outputs a control signal for instructing the resetting of the file pointer to the file pointer setting unit 212. Accordingly, the file pointer setting unit 212 resets the position of the first file pointer. In detail, the file pointer setting unit 212 may reset the position of the first file pointer by moving the initial position of the first file pointer by a predetermined byte. For example, the file pointer setting unit 212 may reset the position of the first file pointer by moving 1 byte from the position of the initially set first file pointer. Accordingly, the header information comparison unit 213 checks whether a header of the first frame valid at the position of the set first file pointer exists again.

On the other hand, the header information comparison unit 213 extracts the first header information from the header of the first frame when there is a valid first frame header, and based on the extracted first header information, the size of the first frame. Calculate As described above, the header of the first frame includes bit rate information, sampling rate information, padding information, layer information, and the like, wherein the first header information includes bit rate information, sampling rate information, padding information, layer information, and the like. It includes. In detail, the header information comparison unit 213 may calculate the size of the first frame based on bit rate information, sampling rate information, and padding information among the first header information. Here, the size of the first frame can be obtained using Equation 2 below.

[Equation 2]

FL = 144 * BR / SR + P

Here, FL represents a frame size, BR represents a bit rate, SR represents a sampling rate, and P represents a size of a padded area. Here, 144 is a value divided by 8 to represent 1152, the number of samples, in bytes. Thus, 144 may vary depending on the embodiment.

Subsequently, the header information comparison unit 213 sets the second file pointer by moving the first file pointer by the calculated size of the first frame, and checks whether a header of the second frame valid at the position of the set second file pointer exists. Check it. Even in this case, the operation of the header information comparison unit 213 varies depending on whether or not a header of a valid second frame exists.

The header information comparison unit 213 outputs a control signal for instructing the resetting of the file pointer to the file pointer setting unit 212 when the header of the valid second frame does not exist. Accordingly, the file pointer setting unit 212 moves from the position of the second file pointer to the position of the first file pointer, and then moves the position of the first file pointer by a predetermined byte and resets it. At this time, the resetting operation of the position of the first file pointer is similar to that described above, and will be omitted.

On the other hand, the header information comparison unit 213 extracts the second header information from the header of the second frame when there is a valid second frame header, and compares the extracted first header information with the extracted second header information. do. For example, the header information comparison unit 213 may compare whether the first layer information included in the first header information and the second layer information included in the second header information match. As a result of the comparison, when the first layer information and the second layer information match, the header information comparison unit 213 outputs a control signal instructing the calculation unit 214 to calculate the average bit rate.

As a result of the comparison, when the first layer information and the second layer information do not match, the header information comparison unit 213 outputs a control signal instructing the file pointer setting unit 212 to reset the file pointer. Accordingly, the file pointer setting unit 212 sets the position of the first file pointer again after moving from the position of the second file pointer to the position of the first file pointer. At this time, the resetting operation of the position of the first file pointer is similar to that described above, and will be omitted.

The calculation unit 214 calculates a bit rate for some of the blocks included in the some blocks among the N blocks included in the audio data area of the audio file, and totals the calculated bit rates. The average bitrate of the audio file is calculated by dividing by the number of blocks used and the number of frames used.

In one embodiment of the present invention, the calculator 214 may divide the audio data area of the audio file into 40 to 50 blocks. For convenience of explanation, it is assumed that the calculator 214 divides the audio data area of the audio file into 40 blocks. In this case, the calculator 214 may extract the bitrates of the 10th to 30th blocks among the 40 blocks, and then calculate the average bitrate. In this case, the calculator 214 may select only 2 to 3 frames for the 10 th to 30 th blocks, and extract bitrates only for the selected frames.

Since a typical audio file starts a song in the previous week, if the bitrate is extracted only for the blocks at the beginning of the file, the average bitrate may be quite different from the average bitrate of the entire file. Therefore, by extracting bitrates for blocks in the middle part of the file, and calculating the average bitrate, a value similar to the average bitrate of the entire file can be obtained as the average bitrate.

In detail, the calculator 214 calculates an average bit rate of the audio file using the following equations (3) and (4).

&Quot; (3) "

Here, S _B represents the sum of bit rates for a predetermined number of frames in each block. In addition, N _B represents the number of frames to be searched in each block, and BR _b represents the bit rate in the b-th frame. In one embodiment of the invention, the operation unit 214 is N _B in the case of calculating the average bit rate for the 10 th to 30-th block may be 20 days.

&Quot; (4) "

Here, ABR represents the average bitrate of the audio file. In addition, N _D represents the number of blocks to search in the entire audio file, S _B represents the sum of bitrates for predetermined frames in each block, and N _B represents within each block. Indicates the number of frames to search. In one embodiment of the invention, the computing unit 214 is, N _B is 2, if the extracted bit rate only for the two frames in each block.

According to Equations 2 and 3, the calculation unit 214 obtains all bitrates for each frame included in each block, and then divides the average bitrate by dividing the number of used frames and the number of blocks used. Obtain However, in another embodiment of the present invention, the calculation unit 214 obtains the bitrate for each frame, then divides by the number of frames used to obtain the average bitrate in one block, and the operation By repeating for the blocks, the overall average bitrate may be obtained.

4 is a flowchart illustrating a method of calculating an average bitrate of a variable bitrate file according to an embodiment of the present invention.

Referring to FIG. 4, the method for calculating the average bitrate of the variable bitrate file according to the present exemplary embodiment includes steps processed in time series by the average bitrate calculator shown in FIG. 2. Therefore, even if omitted below, the contents described above with respect to the average bitrate calculator in FIG. 2 also apply to the method of calculating the average bitrate according to the present embodiment.

In step 400, the size of the attribute information area is detected. Herein, the attribute information area may be an area including an ID3 tag.

In step 410, the location of the first file pointer is set.

In step 420, it is determined whether the first header of the first frame exists effectively. If it is determined that the first header is valid, step 430 is performed. Otherwise, step 485 is performed.

In step 485, since the first header does not exist effectively, the position of the first file pointer is reset. In operation 420, it is determined whether the first header is valid at the position of the reset first file pointer.

In operation 430, since the first header is valid, first header information is extracted from the header of the first frame. More specifically, the size of the first frame may be calculated based on bitrate information of the first frame included in the first header information.

In operation 440, the device moves to the location of the second file pointer based on the extracted first header information. More specifically, the first file pointer may be moved to the position of the second file pointer based on the size of the first frame calculated from the first header information.

In operation 450, it is determined whether the second header of the second frame exists effectively. If it is determined that the second header is valid, step 460 is performed. Otherwise, step 480 is performed.

In operation 480, the position shifts from the position of the second file pointer to the position of the first file pointer. In operation 485, the location of the first file pointer is reset. In operation 420, it is determined whether the first header is valid at the position of the reset first file pointer.

In operation 460, since the second header is valid, second header information is extracted from the second header of the second frame.

In operation 470, the first header information is compared with the second header information. Specifically, the first layer information included in the first header information is compared with the second layer information included in the second header information. As a result of the comparison, if the first layer information and the second layer information match, step 490 is performed; otherwise, step 485 is performed.

In step 485, the location of the first file pointer is reset. In operation 420, it is determined whether the first header is valid at the position of the reset first file pointer.

In step 490, the average bitrate of the audio file is calculated. More specifically, bitrates are obtained for some of the plurality of blocks included in the audio data area. In addition, a predetermined number of frames are selected from each of the some number of blocks to obtain bit rates for only the selected frames.

Specifically, bitrates may be obtained for M blocks among N blocks included in the audio data region. In addition, by selecting L frames in each of the M blocks, bitrates may be obtained only for the selected L frames. Here, one of ordinary skill in the art may understand that the number M of selected blocks and the number L of selected frames in each block may be changed.

In this case, the average bitrate of the audio file can be obtained by dividing the sum of the obtained M * L bitrates by M * L. On the other hand, by dividing the sum of the L bitrates obtained in each block by L, obtaining the average bitrate in each block, and then dividing the sum of the average bitrates in each block by N, the entire audio file The average bitrate of can be obtained.

In the above, the method of calculating the average bitrate of the file of the variable bitrate has been described as an example of the audio file, but the embodiment of the present invention is not limited to the audio file but can be applied to the video file and the video file.

As described above, although the present invention has been described by way of limited embodiments and drawings, the present invention is not limited to the above-described embodiments, which can be modified by those skilled in the art to which the present invention pertains. Modifications are possible. Accordingly, the spirit of the invention should be understood only by the claims set forth below, and all equivalent or equivalent modifications will fall within the scope of the invention.

In addition, the system according to the present invention can be embodied as computer readable codes on a computer readable recording medium. The computer-readable recording medium includes all kinds of recording devices in which data that can be read by a computer system is stored. Examples of recording media include ROMs, RAMs, CD-ROMs, magnetic tapes, floppy disks, optical data storage devices, and the like, and may also be implemented in the form of carrier waves (eg, transmission over the Internet). The computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion.

1 is a block diagram illustrating an audio device according to an embodiment of the present invention.

FIG. 2 is a detailed block diagram illustrating an average bit rate calculator included in FIG. 1.

3 illustrates an example of an audio file input to an average bit rate calculator of FIG. 2.

4 is a flowchart illustrating a method of calculating an average bitrate of a variable bitrate file according to an embodiment of the present invention.

Claims (22)

delete Setting a position of a first file pointer with respect to a first block among a plurality of blocks included in a data area of a file having a variable bit rate; Extracting header information of at least two frames included in the first block at a location of the set first file pointer; And Calculating an average bit rate for a predetermined number of blocks among the plurality of blocks according to the comparison result of the extracted header information; Extracting header information of at least two frames included in the first block Extracting first header information when a header of a first frame exists among the at least two frames at a location of the first file pointer; Moving to a location of a second file pointer based on the first header information; Extracting second header information when a header of a second frame among the at least two frames exists at the location of the second file point; And And comparing the extracted first and second header information. The method of claim 2, The first header information includes first bitrate information and first layer information for the first frame, and the second header information includes second bitrate information and second layer for the second frame. A method for calculating the average bitrate of a variable bitrate file comprising information. The method of claim 3, The extracting of the first header information includes calculating a size of the first frame based on the first bitrate information. 5. The method of claim 4, Moving to the position of the second file pointer comprises moving the first file pointer by the size of the calculated first frame. The method of claim 2, Moving the position of the first file pointer by a predetermined area when the header of the first frame does not exist at the position of the first file pointer, Extracting header information of at least two frames included in the first block is performed based on the position of the first file pointer moved by the predetermined area. . The method of claim 2, Moving the position of the first file pointer by a predetermined area when the header of the second frame does not exist at the position of the second file pointer, Extracting header information of at least two frames included in the first block is performed based on the position of the first file pointer moved by the predetermined area. . The method of claim 3, Moving the location of the first file pointer by a predetermined region when the first and second layer information do not match as a result of comparing the first and second header information; Extracting information of at least two frames included in the first block is performed based on a position of a first file pointer moved by the predetermined area. The method of claim 2, Calculating an average bit rate for a predetermined number of blocks of the plurality of blocks As a result of comparing the first and second header information, when information on the compression standard of the file included in each of the first and second header information is identical, each of a predetermined number of blocks of the plurality of blocks Calculating bitrates of at least two frames for; And And calculating the average bitrate by dividing the calculated sum of the bitrates by the number of blocks and the number of frames. The method of claim 2, The setting of the position of the first file pointer with respect to the first block may be performed by subtracting the size of the attribute information area from the total size of the file and dividing the subtraction result by the number of blocks. How to calculate the average bitrate of a bitrate file. delete delete A file pointer setting unit that sets a position of a first file pointer with respect to a first block among a plurality of blocks included in a data area of a file having a variable bit rate; A header information comparison unit extracting header information of at least two frames included in the first block at the position of the set first file pointer and comparing the extracted header information; And A calculation unit configured to calculate an average bit rate of a predetermined number of blocks among the plurality of blocks according to a comparison result of the extracted header information; The header information comparison unit extracts first header information when a header of a first frame exists among the at least two frames at a location of the first file pointer, and extracts first header information based on the first header information. Move to a location of a pointer, extract second header information when a header of a second frame exists among the at least two frames at a location of the second file point, and extract the first and second header information. Apparatus for calculating the average bitrate of the variable bitrate file, characterized in that for comparing. The method of claim 13, The first header information includes first bitrate information and first layer information for the first frame, and the second header information includes second bitrate information and second layer information for the second frame. And an average bitrate calculation device for a variable bitrate file. The method of claim 14, The header information comparison unit calculates a size of the first frame based on the first bitrate information, and moves the first file pointer by the size of the calculated first frame. Average bitrate calculation device. The method of claim 14, The header information comparison unit, when the header of the first frame does not exist at the position of the first file pointer, when the header of the second frame does not exist at the position of the second file pointer or the first and the first And outputting a control signal for instructing resetting of the file pointer to the file pointer setting unit when the two layer information does not match. The method of claim 13, The calculation unit may determine a predetermined number of blocks among the plurality of blocks when information on a compression standard of the file included in each of the first and second header information matches as a result of comparing the first and second header information. Calculating the bitrates of at least two frames for each block, and calculating the average bitrate by dividing the sum of the calculated bitrates by the number of blocks and the number of frames. Device for calculating average bitrate of rate file. The method of claim 13, An attribute information detector for detecting a size of the attribute information region of the variable bit rate; The file pointer setting unit subtracts the size of the attribute information area from the total size of the file, and sets the position of the first file pointer by dividing the subtraction result by the number of blocks. Average bitrate calculation device. A memory for storing an audio file of variable bit rate; Extract header information of at least two frames based on a location of a predetermined file pointer of a data area of the audio file, calculate an average bitrate of the audio file according to a comparison result of the extracted header information, and A control unit for modulating the file and providing the file as pulse code modulation (PCM) data; And It includes a codec for decoding the PCM data provided from the control unit, The control unit A file pointer setting unit that sets a position of a first file pointer with respect to a first block among a plurality of blocks included in the data area; A header information comparison unit extracting header information of at least two frames included in the first block at the position of the set first file pointer and comparing the extracted header information; And A calculation unit configured to calculate an average bit rate for a predetermined number of blocks among the plurality of blocks according to a comparison result of the extracted header information; The header information comparison unit, Extracts first header information when the header of the first frame exists among the at least two frames at the location of the first file pointer and moves to the location of the second file pointer based on the first header information. And extracting second header information when the header of the second frame exists among the at least two frames at the location of the second file point, and comparing the extracted first and second header information. Audio device. delete The method of claim 19, The control unit An attribute information detector for detecting a size of an attribute information region of the audio file; And the file pointer setting unit sets the position of the first file pointer by subtracting the size of the attribute information area from the total size of the file and dividing the subtraction result by the number of blocks. The method of claim 19, And an output unit for outputting data decoded by the codec.

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