JP3450280B2 - Compressed audio signal playback device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compressed audio signal reproducing device, and more particularly to a compressed audio signal reproducing device for reproducing a compressed audio signal having a high compression rate.

[0002]

2. Description of the Related Art In recent years, the field of silicon audio in which compressed music data is held in a memory and reproduced is rapidly expanding. The compressed audio signal reproducing device used in the silicon audio field is not limited to an audio player, but is beginning to be mounted on a mobile phone or a wristwatch, and not only a simple reproducing function but also a function such as fast-forwarding is strongly required. As the compression format of the audio signal, MP3 (MPEG Audio Layer-) is currently used.
Although the compression format called 3) is the mainstream, AAC (MPEG2 Advanced Audio) with a high compression rate is used.
It is expected that compression formats such as Coding) will expand the market in the future.

According to the AAC standard, ADIF (Audi
o Data Interchange Formata
t, hereinafter referred to as ADIF) format and ADTS (A
audio Data Transport Stream
m, hereinafter referred to as ADTS) format. In each format, the length of one frame is variable, but since the ADTS format has frame information including the frame length at the beginning of each frame, at the time of fast-forwarding, if the frame length is traced, the frame can be quickly transmitted. It is possible to skip.

[0004]

However, since the ADIF format does not have a frame length as frame information, at the time of fast-forwarding, unless the compressed audio signal is analyzed, the start address of the next playback frame cannot be known, and skipped at high speed. There is a problem that you can not do.

For example, FIG. 9 is a flow chart showing a procedure of frame-by-frame reproduction processing in a conventional compressed audio signal reproducing apparatus. The frame-by-frame reproduction processing in this conventional compressed audio signal reproducing apparatus is performed by the program execution in the reproduction processing unit of the computer configuration, and in step S1, the compressed audio signal is read in the address order and the frame bit information is segmented and acquired. ,
In step S2, it is determined whether there is a fast-forward instruction,
If there is a fast-forward instruction, the process returns to step S1, and if there is no fast-forward instruction, in step S3, PCM data conversion is performed based on the information segmented in step S1, and further reproduced by a PCM sound source.

The reproduction processing for each frame in this conventional compressed audio signal reproducing apparatus is sequentially performed from the first frame of a music piece, and when the subdivision processing for one frame in step S1 is completed, the next frame is first reproduced. The start address is known. Therefore, at the time of fast-forwarding, step S
It is necessary to repeat the subdivision processing of one frame bit information. To subdivide this frame bit information,
About 1/2 of the entire reproduction time is required, and the fast-forward speed is only about twice as fast as the normal reproduction, and it cannot be said that it can be used.

Further, if the start address of the reproduction frame after fast-forwarding is not determined and the reproduction is started from the middle of the frame after fast-forwarding, no music is heard.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a compressed audio signal reproducing apparatus for performing fast forward reproduction of a compressed audio signal of AAC standard DIF format at high speed.

[0009]

Therefore, according to the present invention, a compressed audio signal reproduction is performed in which a compressed audio signal compressed and recorded in a variable length frame having no frame length as frame information is read in an address order and reproduction processing is performed in frame units. In the device, during the first reproduction process of the compressed audio signal, the frame number and the start address of the reproduction frame are held as frame position information in the frame position information table, respectively, and in response to the fast-forward instruction during the second and subsequent reproduction processes, The read start address of the compressed audio signal after the fast-forward instruction is determined by referring to the frame information table.

The frame bit information subdivision means for reading the compressed audio signal in the order of addresses and subdividing the frame bit information, and the current address at the end of the subdivision processing during the first reproduction processing are The frame position information table is held as the start address of the reproduction frame, and the frame position information table is referred to in response to the fast-forward instruction at the end of the subdivision processing during the second and subsequent reproduction processes, and the fast-forward instruction is followed. Fast-forwarding means for determining the reading start address of the compressed audio signal,
PCM data conversion means for performing PCM data conversion based on the information subdivided by the frame bit information subdivision means in response to no fast-forward instruction at the end of the subdivision processing.

In addition, at the end of the subdivision processing, the fast-forwarding unit holds the current address as the start address of the next reproduction frame in the frame position information table in correspondence with the holding of the frame position information. Position information holding means, a fast-forward instruction acquisition means for determining whether or not the frame position information is held and a fast-forward instruction is determined in response to a fast-forward instruction at the end of the subdivision processing, and a fast-forward instruction acquisition value, and after the fast-forward instruction Read start address determining means for determining a destination frame number after fast forwarding corresponding to the fast forward instruction value and referring to the frame position information table to determine a read start address of the compressed audio signal after the fast forward instruction. .

Further, the read start address determining means is
The frame number closest to the jump destination frame number is searched from the frame position information table, and the head address corresponding to the searched frame number is read from the frame position information table and used as the read start address of the compressed audio signal.

Further, the frame position information holding means is
The frame position information is held in the frame position information table with the frame numbers having the preset set value intervals.

Further, the frame position information holding means is
The frame position information is held in the frame position information table in correspondence with the variables that are increased / decreased at the end of the subdivision processing and initialized with the set value.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a first embodiment of a compressed audio signal reproducing device of the present invention.

Referring to FIG. 1, the compressed audio signal reproducing apparatus of this embodiment comprises a frame bit information subdividing means 1, a fast-forwarding means 2 and a PCM data converting means 3 as a reproduction processing section of a computer configuration. Each of these means 1, 2 and 3 is a functional means realized by executing a program in a reproduction processing section of a computer configuration.

The frame bit information subdivision means 1 reads the compressed audio signal in the order of addresses, and subdivides the frame bit information.

The fast-forwarding means 2 holds the current address at the end of the subdivision processing in the frame position information table as the start address of the next reproduction frame during the first reproduction processing, and during the second and subsequent reproduction processings. In response to the fast-forward instruction at the end of the subdivision processing, the frame position information table is referenced to determine the read start address of the compressed audio signal after the fast-forward instruction.

The fast-forwarding means 2 further comprises a frame position information holding means 21, a fast-forwarding instruction acquisition means 22, and a read start address determining means 23, and the frame position information holding means 21 ends the frame at the end of the subdivision processing. The current address is held in the frame position information table as the start address of the next reproduction frame in correspondence with the holding of the position information. An example of this frame position information table is shown in FIG. Further, the fast-forward instruction acquisition unit 22 determines whether the frame position information is held and after the fast-forward instruction is received in response to the presence of the fast-forward instruction at the end of the subdivision processing, and obtains the fast-forward instruction value. After the fast-forward instruction, the jump destination frame number after the fast-forward is obtained corresponding to the fast-forward instruction value, the frame position information table is referred to, and the read start address of the compressed audio signal after the fast-forward instruction is determined.

The PCM data conversion means 3 performs PCM data conversion based on the information subdivided by the frame bit information subdivision means in response to no fast-forward instruction at the end of the subdivision processing.

FIG. 3 is a flow chart showing the procedure of frame-by-frame reproduction processing in the compressed audio signal reproducing apparatus of this embodiment. A frame-by-frame reproduction process in the compressed audio signal reproducing apparatus according to the present embodiment will be described with reference to FIG.

First, in step S1, the compressed audio signal is read in the order of addresses, and the frame bit information stored for each frame is subdivided and acquired.
The subdivision processing of the frame bit information is sequentially performed from the head frame of the music, and the head address of the next frame is not known until the subdivision processing for one frame is completed.

Next, in step S21, it is determined whether or not there is a fast-forward instruction, and if there is no fast-forward instruction, then in step S22 it is checked whether or not the file position information is held in the frame position information storage table. Only when there is no holding, frame position information holding processing is performed in step S23, and the frame number and start address of the next playback frame are held in the frame position information storage table as frame position information. Then, in step S3, PCM data conversion is performed on the basis of the subdivided information and further reproduced by the PCM sound source, and the reproduction processing of one frame ends.

If there is a fast-forward instruction in step S21, it is checked in step S24 whether file position information is held in the frame position information table. If not held, frame position information holding processing is performed in step S25, the frame position information is held in the frame position information table, and the process returns to step S1. Step S2
If it is held in step 4, in step S26, the fast-forward instruction determination is repeated until there is no fast-forward instruction, the fast-forward instruction value is acquired, and after the fast-forward instruction, the process proceeds to step S27.
The jump destination frame number after fast-forwarding is obtained corresponding to the fast-forwarding instruction value, the reading start address of the compressed audio signal is determined by referring to the frame position information table, the process returns to step S1, the reproduction process after fast-forwarding is restarted, and high-speed Fast forwarding processing is realized.

FIG. 4 shows steps 23 and 25 in FIG.
6 is a flowchart showing a detailed procedure of a frame position information holding process of FIG. Briefly, the frame number is incremented in step S41 of this frame position information holding processing, the frame number is held in the frame position information storage table in step S43, and the current address of the compressed data signal is held in step S44. , Is held in the frame position information table as the start address of the next reproduction frame.

FIG. 5 is a flow chart showing a detailed procedure of the read start address determination processing of step 27 in FIG.
Briefly described, in step S51 of this read start address determination processing, the jump destination frame number after fast-forwarding is obtained corresponding to the obtained fast-forward instruction value, and in step S52,
The frame number closest to the jump destination frame number is searched from the frame position information table, and in step 53, the start address corresponding to the searched frame number is read from the frame position information table and set as the read start address of the compressed audio signal.

Next, the frame-by-frame reproduction processing in the compressed audio signal reproducing apparatus of the present embodiment will be specifically described with reference to the drawings. FIG. 6 is an explanatory diagram showing an example of a compressed audio signal, where the compressed audio signal is 3
It consists of 000 frames (about 1 minute) and about 50 per second.
Indicates that it is composed of frames. Also, FIG.
FIG. 6 is an explanatory diagram showing an example of updating the frame position information table. In the example 701 of updating, the frame number of frame 1
It indicates that initialized "1" and "0" are held as the head address. Furthermore, here, at first,
It is assumed that the reproduction process is performed to the end by the simple reproduction, and then the fast-forwarding instruction for 30 seconds is issued after 10 seconds from the beginning at the time of the second reproduction.

First, in step S1 of FIG. 3, the compressed audio signals of FIG.
The frame bit information stored in is subdivided and acquired. At the end of the subdivision processing of the frame bit information, it is determined in step S21 whether there is a fast-forward instruction. Since simple reproduction is assumed at first, there is no fast-forward instruction, and it is checked in step S22 whether the file position information is held in the frame position information table. Since there is no holding, the frame position information holding process of FIG. 4 is executed in step S23, and the frame 2 of FIG.
The frame number and the head addresses of "2" and "4" are held in the frame position information table, and the frame position information table becomes the update example 702 of FIG. Then, in step S3, PCM data conversion is performed on the basis of the subdivided information and further reproduced by the PCM sound source, and the reproduction processing of one frame ends.

The same processing is repeated 3000 times as many times as the number of frames as the first reproduction processing, and the frame position information table becomes update example 703 after processing frame 500 and update example 704 after processing frame 2000.
After processing the frame 2999, an update example 705 is obtained.

Next, the second reproducing process is started. Since it is assumed that a fast-forward instruction for 30 seconds is given after 10 seconds have passed from the beginning, up to 10 seconds after the start of the second reproduction process, that is, up to frame 500 (50 frames x 10 seconds),
In step S1 of FIG. 3, subdivision processing of frame bit information is performed, it is determined in step S21 that there is no fast-forward instruction, it is determined in step S22 that file position information is held, and PCM data conversion is performed in step S3. Reproduction processing is performed.

Next, step S for frame 500
At the end of the subdivision processing of step 1, it is determined that there is a fast-forward instruction in step S21, the process proceeds to step S24, it is determined that the file position information is retained in step S24, the process proceeds to step S26, and the fast-forward instruction is issued until there is no fast-forward instruction. The determination is repeated and the fast-forward instruction value for 30 seconds is acquired.

After the fast-forward instruction, the process moves to step S27,
Corresponding to the fast-forward instruction value for 30 seconds, the current frame number 501 and 30 seconds × 50 frames are added to obtain the jump destination frame number 2001 after fast-forwarding, and the frame number 2001 closest to the jump destination frame number 2001 is calculated. The corresponding start address "8000" is retrieved from the frame position information table and is determined as the read start address of the compressed audio signal, and the process returns to step S1 to reproduce the compressed audio signal after fast-forwarding. Is resumed.

That is, the fast-forwarding process from 10 seconds after the start of reproduction to 30 seconds ahead is instantly realized by referring to the frame position information table.

FIG. 8 is a flow chart showing the procedure of frame position information holding processing in the second embodiment of the compressed audio signal reproducing apparatus of the present invention.

The frame position information holding process in the compressed audio signal reproducing apparatus according to the present embodiment is the same as the frame position information holding process in the compressed audio signal reproducing apparatus according to the first embodiment shown in FIG.
S46 is added.

Step S4 of frame position information holding processing
1, the frame number is incremented, and step S
At 42, it is determined whether or not the preset set value and the variable match. If they do not match, the variable is increased or decreased at step S46.

If they match in step S42, the frame number is held in the frame position information storage table in step S43, and the current address of the compressed data signal is set as the start address of the next reproduction frame in step S44. The variables are held in the position information table, and variables are initialized in step S45.

As a result, in the frame position information holding process of this embodiment, the frame position information of all frames is not held in the frame position information storage table as in the first embodiment of FIG. The frame position information can be held in the frame position information storage table by the frame number.

The read start address determining process according to the present embodiment may be exactly the same as the read start address determining process according to the first embodiment shown in FIG. 5, and similar to the first embodiment, although an error occurs in the restart frame position after fast-forwarding. , Fast-forward reprocessing is performed at high speed.

Therefore, the compressed audio reproducing apparatus according to the present embodiment has a small frame position information table and is suitable for the purpose of cost reduction by using a small capacity memory.

[0041]

As described above, the compressed audio signal reproducing apparatus of the present invention can perform fast-forward reproduction of a compressed audio signal of AAC standard DIF format at high speed.

The reason is that, during the initial reproduction process of the compressed audio signal, the frame number and the start address of the reproduction frame are held in the frame position information table, respectively.
This is because the frame position information table is referred to in response to the fast-forward instruction during the reproduction processing after the first time, and the read start address of the compressed audio signal after the fast-forward instruction is instantaneously determined.

Further, by holding the frame position information at the frame numbers separated by the set value interval, the frame position information table can be made small, and the fast-forward reproduction can be speeded up without increasing the cost of the compressed audio signal reproducing apparatus. Has the effect of.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of a compressed audio signal reproducing device of the present invention.

FIG. 2 is an explanatory diagram showing an example of a frame position information table.

3 is a flowchart showing a procedure of frame-by-frame reproduction processing in the compressed audio signal reproducing apparatus of FIG.

FIG. 4 is a flowchart showing a detailed procedure of frame position information holding processing in steps 23 and 25 in FIG.

5 is a flowchart showing a detailed procedure of a read start address determination process of step 27 in FIG.

FIG. 6 is an explanatory diagram showing an example of a compressed audio signal.

FIG. 7 is an explanatory diagram showing an example of updating a frame position information table.

FIG. 8 is a flowchart showing a procedure of frame position information holding processing in the second embodiment of the compressed audio signal reproducing device of the present invention.

FIG. 9 is a flowchart showing a procedure of frame-by-frame reproduction processing in the conventional compressed audio signal reproducing apparatus.

[Explanation of symbols]

1-frame bit information subdivision means 2 fast-forwarding means 3 PCM data conversion means 21 frame position information holding means 22 Fast-forward instruction acquisition means 23 Read start address determination means S1-S27 steps

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Claims (6)

(57) [Claims] 1. A compressed audio signal reproducing apparatus for reading a compressed audio signal compressed and recorded in a variable length frame having no frame length as frame information and reproducing the compressed audio signal in frame units. The frame number and the start address of the reproduction frame are held in the frame position information table during the reproduction process, and the frame information table is referred to in response to the fast-forward instruction during the second and subsequent reproduction processes. A compressed audio signal reproducing apparatus, characterized in that a read start address of the compressed audio signal is determined. 2. The frame bit information subdivision means for reading the compressed audio signal in the order of addresses to subdivide the frame bit information, and the current address at the end of the subdivision processing during the first reproduction processing are The frame position information table is held as the start address of the reproduction frame, and the frame position information table is referred to in response to the fast-forward instruction at the end of the subdivision processing during the second and subsequent reproduction processes, and the fast-forward instruction is followed. Fast-forwarding means for determining the read start address of the compressed audio signal, and PCM for performing PCM data conversion based on the information subdivided by the frame bit information subdivision means corresponding to no fast-forwarding instruction at the end of the subdivision processing. The compressed audio signal reproducing apparatus according to claim 1, further comprising a data converting unit. 3. A frame in which the fast-forwarding unit holds the current address in the frame position information table as the start address of the next reproduction frame corresponding to the absence of holding the frame position information at the end of the subdivision processing. Position information holding means, a fast-forward instruction acquisition means for determining whether or not the frame position information is held and a fast-forward instruction is determined in response to a fast-forward instruction at the end of the subdivision processing, and a fast-forward instruction acquisition value, and after the fast-forward instruction Read start address determining means for determining a read start address of the compressed audio signal after the fast-forward instruction by obtaining a destination frame number after fast-forward corresponding to the fast-forward instruction value and referring to the frame position information table. Item 2. The compressed audio signal reproducing device according to item 2. 4. The read start address determining means searches the frame position information table for a frame number closest to the jump destination frame number, and a start address corresponding to the searched frame number is searched for in the frame position information table. 4. The compressed audio signal reproducing apparatus according to claim 3, wherein the read start address of the compressed audio signal is read. 5. The compressed audio signal reproducing apparatus according to claim 3, wherein the frame position information holding means holds each of the frame position information in the frame position information table at a frame number of a preset set value interval. 6. The frame position information holding means respectively holds the frame position information in a frame position information table in correspondence with a variable that is increased or decreased at the end of the subdivision processing and initialized by the setting. Item 5. The compressed audio signal reproducing device according to Item 5.