KR100762572B1 - Method and Apparatus for converting Advanced Audio Codec file into MPEG-4 Audio file - Google Patents

Abstract

The present invention parses an AAC file into headers and data, sets channel and frequency information using the classified header information, generates and initializes an ATOM basic structure, and parses the parsed AAC file. The frame size is obtained for each frame of the AAC file, the ATOM information required for each frame update is updated, and each ATOM information is combined with the corresponding frame data to be converted into an MP4A file.There is no header between frames like the ADIF header. Even if the content is not available, the mobile terminal can convert the MP4A file to the MP4A file in the course of transmission, and the additional sound quality can be prevented because the encoding is not required.

AAC file, MP4A file

Description

Method and Apparatus for converting Advanced Audio Codec file into MPEG-4 Audio file

1 is a block diagram schematically showing the configuration of an apparatus for converting a conventional AAC file into an MP4A file.

2 is a block diagram showing an apparatus for converting an AAC file into an MP4A file according to the present invention;

3 illustrates an MP4A file format in accordance with the present invention.

4 is a flowchart illustrating a method of converting an AAC file into an MP4A file according to the present invention.

5 is a diagram illustrating an ATOM generated when converting an AAC file into an MP4A file according to the present invention.

6 is a flowchart illustrating a method of converting an AAC file having an ADTS header into an MP4A file according to the present invention.

7 is a flowchart illustrating a method of converting an AAC file having an ADIF header into an MP4A file according to the present invention.

<Explanation of symbols for main parts of the drawings>

100: AAC decoder 110: AAC encoder

120, 210: MP4A file format converter 200: AAC parsing unit

The present invention relates to a method and apparatus for converting an AAC file into an MP4A file, which converts an AAC file into an MP4A (MPEG-4 Audio) file for AAC (Advanced Audio Codec) reproduction in a portable device.

Digital audio, which has been developed since the beginning of CD, has been developed to reduce the storage capacity by compressing audio in order to effectively transmit or store large amounts of data. Since 1992, the audio encoding method has been internationally standardized under the leadership of MPEG, and Dolby, Sony and AT & T have developed their own audio encoding methods.

MP3, which is most widely used among audio encoding methods, refers to MPEG 1 and 2 audio layer III. In general, MP3 requires more than 128Kbps of stereo data, which provides sound quality similar to CD. Recently, the trend of the audio encoding method is to develop a method of encoding to have less data while maintaining the sound quality.

These methods are preferentially adopted and used in the wireless environment where the transmission band should be used efficiently, and the range of their application is getting wider. For example, MPEG 2 and 4 AAC, which are widely used in VOD and AOD of wireless environment, providing sound quality similar to MP3 128Kbps with 96Kbps data, and products that support AAC have recently appeared for the recently released MP3 player. . One example is Apple's iPod.

The AAC file has an audio data interchange format (ADIF) and an audio data transport stream (ADTS) header as an interface format. Depending on the encoder, the AAC file may generate an AAC file in the form of a raw stream without these headers. In general, since ADTS has header information for each frame, it is easy to know the start position and size information of a frame. On the other hand, in the case of ADIF, since the header information is included only in front of the file, it is not easy to find the starting position of the next frame at any stream position.

Therefore, in the case of ADTS, it is relatively easy to provide a function of starting by moving frame by frame. However, in the case of ADIF, it is possible to search the stream according to the bit string structure in the case of FF, and in case of REW, the start position of the frame can be found by several attempts using the start position candidate group.

In the case of the iPod, instead of playing with the AAC file, it is supported by a file type called MP4A with side information providing additional time and size information. However, iTunes, a bundled program provided with iPod, converts and encodes CDs, WAVs, and MP3s into AAC, and converts them into MP4A file formats.

On the other hand, in the case of the existing aac file does not provide such a function, in order to put in the iPod as shown in Figure 1 AAC decoder 100 AAC decoding after AAC file, AAC encoder 110 to re- Through encoding, the MP4A file format converter 120 should change the format to MP4A. In addition to iPods, mobile phones are also expected to require this same type of conversion, as the importance of music players to the AAC file format is increasing.

However, the above-mentioned conventional process has a complicated disadvantage of converting an AAC file into an MP4A file.

Accordingly, an object of the present invention is to simplify the process of converting an AAC file into MP4A, thereby converting an AAC file into an MP4A file, which enables the conversion process to be performed in a process of transferring to a portable device, thereby enabling a more efficient audio playback function. To provide a conversion method and apparatus.

According to an aspect of the present invention, in order to achieve the above object, the AAC file is parsed and classified into header and data, the channel and frequency information is set using the classified header information, and the basic structure of ATOM is set. It generates and initializes, obtains a frame size for each frame of the parsed AAC file, updates ATOM information required for each frame update, and combines each ATOM information with the corresponding frame data to convert to an MP4A file. A method of converting an AAC file into an MP4A file is provided.

In obtaining a frame size for each frame of the parsed AAC file, if the header of the AAC file is ADTS, the frame size is obtained by using header information and boundary conditions of each frame.

Further, in obtaining a frame size for each frame of the parsed AAC file, if the header of the AAC file is ADIF, a bit stream of AAC data is parsed to obtain a frame size.

According to another aspect of the present invention, an AAC parsing unit for parsing an AAC file into a header and a data portion, and channel information using header information parsed by the AAC parsing unit. And an MP4A format conversion unit for acquiring the sampling frequency information and the size information of each frame, and constructing an ATOM and combining the AAC file with the AAC file to generate an MP4A file. A converter is provided.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a block diagram showing an apparatus for converting an AAC file into an MP4A file according to the present invention, and FIG. 3 is a diagram showing an MP4A file format according to the present invention.

Referring to FIG. 2, an apparatus for converting an AAC file into an MP4A file includes an AAC parsing unit 200 and an MP4A format converter 210.

The AAC parsing unit 200 parses the input AAC file into a header and a data part.

The MP4A format converter 210 obtains channel information, sampling frequency information, and size information of each frame from a header parsed by the AAC parser 200, and uses the obtained information to calculate ATOM. Configure.

Then, the MP4A format converter 210 combines the configured ATOM with an AAC file to generate an MP4A file.

That is, the MP4A format converter 210 obtains the AAC data size through a header and data parsing process using the information of the AAC file, and immediately configures an ATOM to enter the MP4A.

The MP4A file configured as described above is configured as shown in FIG.

Referring to FIG. 3, the MP4A file is composed of a File Type ATOM 300, a Media Data ATOM 310, and a Movie ATOM 320. That is, the MP4A file is a configuration in which a File Type ATOM 300 and a Movie ATOM 320 are added to an AAC file, and these information are configured by using channel information, sampling frequency information, and size information of each frame of the AAC.

That is, the MP4A file conversion apparatus reads the header for each frame of the AAC file and sets the sampling frequency and the channel information.

Then, the MP4A file conversion apparatus obtains a frame size for each frame, and configures ATOM for entering MP4A using the size information.

4 is a flowchart illustrating a method of converting an AAC file into an MP4A file according to the present invention, and FIG. 5 is a diagram illustrating an ATOM generated when converting an AAC file into an MP4A file according to the present invention.

Referring to FIG. 4, when an AAC file is input (S400), the MP4A file conversion apparatus parses the AAC file into a header and a data part (S402).

After performing step 402, the MP4A file conversion apparatus obtains channel and frequency information by using the classified header information, and generates and initializes a basic structure of each ATOM (S404). That is, the MP4A file conversion apparatus obtains channel and frequency information using the classified header information, and generates and initializes the basic structure of ATOM as shown in FIG.

After performing step 404, the MP4A file conversion apparatus updates ATOM information requiring frame update while adding an AAC stream every frame (S406).

That is, the MP4A file conversion apparatus adds an AAC stream every frame and updates ATOM information that needs to be updated for each frame as shown in the second classification of FIG. 5. A field updated in each ATOM data will be described with reference to FIG. 5.

The MDAT ATOM is codec data and refers to an AAC stream. Time to Sample Atom indicates information about how long the frame should be played and is configured using sampling frequency information.

Sample To Chunk ATOM and Chunk Offset ATOM information is used to find where the AAC stream of the frame starts in the file. If the size information of the corresponding frame is known, the location of the current frame may be indicated by updating only the frame size information to the corresponding ATOM information of the previous frame.

Sample Size In the case of ATOM, this indicates the frame size, and this data is the value to be actually obtained.

Sync Sample Atom is needed to synchronize the sync when audio / video data is present at the same time. MP4A is not needed because it only includes audio.

As a result, in order to update the ATOM of the second classification, only ATOM information of the previous frame and size information of the corresponding frame can be updated. Therefore, in step 406, the process of obtaining the AAC frame size and updating the ATOM using the same are performed.

After performing step 406, the MP4A file conversion apparatus combines each ATOM information into one and converts the MP4A file into an MP4A file (S408). That is, the MP4A file conversion apparatus adds data of all frames, reflects the size and total reproduction time information of each ATOM, and combines each ATOM information into one. The ATOMs of the second classification of FIG. 5 are ATOMs including ATOMs updated every frame. In case of an ATOM having such a hierarchical structure, the ATOMs have a size including a size of a lower ATOM.

The ATOM generated through the above process will be described with reference to FIG. 5.

Referring to FIG. 5, ATOMs generated when converting an AAC file into an MP4A file are classified into three types.

The first classification is initially set to ATOM including the type (* .mp4 / * .mp4a, etc.) of the MP4A file to be generated, the codec type, and setting information (channel and sampling frequency information in the case of AAC) required by the codec decoder. When this happens, the field value does not change.

The ATOM corresponding to the first category includes a file type atom, an IOD atom, a handler atom, a media information header atom, a data information atom, a data reference atom, a sample description atom, and an ESD atom.

The second classification is an ATOM that has the same ATOM field entry no matter how many frames are included, but should be changed when only the corresponding field data is stored due to a change in the size or reproduction time of the included lower ATOM. These ATOMs are ATOMs that only need to be updated once after initializing required fields.

The ATOM corresponding to the second classification includes a movie atom, a track atom, a media atom, a media information atom, a sample table atom, a movie header atom, a track header atom, and a media header atom.

In the third classification, an entry of a field is added every frame, and an entry is added every frame, and the size of the ATOM is also changed. This ATOM is an ATOM that needs to be updated as an AAC frame is added.

The ATOM corresponding to the third classification includes MDAT Atom, Time to Sample Atom, Sample Size Atom, Sample to Chunk Atom, Chunk Offset Atom, and Sync Sample Atom.

6 is a flowchart illustrating a method of converting an AAC file having an ADTS header into an MP4A file according to the present invention.

Referring to FIG. 6, when an AAC file is input (S600), the MP4A converter reads header information of a first frame of the input AAC file and sets sampling frequency and channel information (S602). Since the header of the AAC file includes sampling frequency and channel information, the MP4A converter can set the sampling frequency and channel information by reading the header of the AAC file. The sampling frequency and channel information are not updated information.

After performing step 602, the MP4A conversion apparatus reads the corresponding data by the frame size indicated in the header information (S604), and determines whether the read data is read according to the frame boundary (S606).

If it is determined in step 606 that the read data has been read in accordance with the frame boundary, the MP4A converter stores frame size information and corresponding AAC data (S608).

The MP4A converter determines whether the above process is performed to the end of the entire AAC file (S610).

If the determination result of step 610 is made to the end of the input AAC file, the MP4A converter updates each ATOM data shown in FIG. 4 and stores it as an MP4A file (S612).

If the determination result of step 610 is not made to the end of the input AAC file, the MP4A converter reads the next frame header (S614) and performs the process again from step 604.

If it is determined in step 606 that the read data is not a frame boundary, the MP4A conversion apparatus finds a header and reads it to the frame boundary (S616).

7 is a flowchart illustrating a method of converting an AAC file having an ADIF header into an MP4A file according to the present invention.

Referring to FIG. 7, when an AAC file is input (S700), the MP4A converter reads header information of a first frame of the input AAC file and sets sampling frequency and channel information (S702). Since the header of the AAC file includes sampling frequency and channel information, the MP4A converter can set the sampling frequency and channel information by reading the header of the AAC file. The sampling frequency and channel information are not updated information.

After performing step 702, the MP4A conversion apparatus parses the bit stream of the AAC file to read the corresponding data (S704), and determines whether the read data is read according to the frame boundary (S706). Since the ADIF has header information only in front of the file, the ADIF parses the bit stream to determine the size of the corresponding frame, and reads data as much as the determined size. The MP4A conversion apparatus then determines whether the read data has been read at the frame boundary.

If it is determined in step 706 that the read data has been read in accordance with the frame boundary, the MP4A converter stores frame size information and corresponding AAC data (S708).

The MP4A converter determines whether the above process is performed to the end of the entire inputted AAC file (S710).

If the determination result of step 710 is made to the end of the input AAC file, the MP4A converter updates each ATOM data shown in FIG. 4 and stores it as an MP4A file (S712).

If the determination result of step 710 is not made to the end of the input AAC file, the MP4A converter performs the operation again from step 704 for each frame.

If the read data is not a frame boundary, the MP4A conversion apparatus searches up to a stream that meets the boundary condition and reads the corresponding data (S616).

As described above, even if the header does not exist between frames such as the ADIF header, the mobile terminal can immediately convert the content to an MP4A file during the transmission process.

The present invention is not limited to the above embodiments, and many variations are possible by those skilled in the art within the spirit of the present invention.

As described above, according to the present invention, it is easy to convert an AAC file into an MP4A file that can be easily supported from a mobile device to FF / REW.

In addition, according to the present invention, even if the content does not have a header between the frames, such as the ADIF header, the mobile terminal can be converted directly to the MP4A file during the transmission process, and also because the encoding does not need to be re-added, further reducing the sound quality. There is an effect that can be prevented.

Claims (9)

Parsing the AAC file into a header and data; Setting channel and frequency information using the classified header information, and generating and initializing a basic structure of ATOM; Obtaining a frame size for each frame of the parsed AAC file and updating ATOM information required for each frame update; and Combining each ATOM information with the corresponding frame data and converting it into an MP4A file Converting AAC file to MP4A file, characterized in that it comprises a. The method of claim 1, The basic structure of the ATOM is a file type ATOM, Media Data ATOM, Movie ATOM conversion method characterized in that the conversion to MP4A file MP4A file. The method of claim 1, In obtaining a frame size for each frame of the parsed AAC file, if the header of the AAC file is ADTS, the MP4A file of the AAC file is obtained by using the header information and boundary conditions of each frame. How to convert to. The method of claim 1, In obtaining a frame size for each frame of the parsed AAC file, if the header of the AAC file is ADIF, the MP4A file of the AAC file is obtained by parsing a bit stream of AAC data. How to convert to. The method of claim 1, The ATOM information has the same ATOM field entry regardless of how many frames are included in the first classification that does not change the field value when it is initially set, but the corresponding field data is changed due to the change of information on the size or playing time of the lower ATOM included. A method of converting an AAC file into an MP4A file, comprising: a second classification, which should be changed when only is stored, and a third classification, requiring updating as an AAC frame is added. The method of claim 5, The ATOM belonging to the first category is an MP4A file of an AAC file, comprising a File Type Atom, an IOD Atom, a Handler Atom, a Media Information Header Atom, a Data Information Atom, a Data Reference Atom, a Sample Description Atom, and an ESD Atom. Method of conversion. The method of claim 5, The ATOM corresponding to the second category is an MP4A file of an AAC file, which includes a movie atom, a track atom, a media atom, a media information atom, a sample table atom, a movie header atom, a track header atom, and a media header atom. Method of conversion. The method of claim 5, The ATOM corresponding to the third category includes an MDAT Atom, a Time to Sample Atom, a Sample Size Atom, a Sample to Chunk Atom, a Chunk Offset Atom, and a Sync Sample Atom. delete

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