Patent Application
20110077938
The present invention relates to a data reproduction method and a data reproduction apparatus for discontinuously reading data from a recording medium which stores compressed audio data therein and performing specific reproduction of the read data.
Some of data reproduction apparatus that reproduce audio data which are highly compressed by an MP3 (MPEG1 Audio Layer III) format can perform specific reproduction, such as double speed reproduction.
When such specific reproduction is performed, discontinuously concatenated data is existed at a boundary between the data extracted on a per-sector basis. However, the discontinuously concatenated data includes incomplete segmented frame data. Therefore, the discontinuously concatenated data is determined as error data and is not output as sound. However, when the data extracted on the per-sector basis are concatenated in a state that a trailing end of a frame and a leading end of a frame are accidentally coincided with a boundary between sectors, it may not be determined that the concatenated data is error data, so that the discontinuous frame is reproduced. Therefore, noise arises at the boundary of the concatenated extraction data.
To solve the problem, according to the technique disclosed in Patent Document 1, data are discontinuously extracted so that a trailing end of a frame and a leading end of a frame do not overlap each other at a concatenation boundary between the extracted data, whereby boundary data are forcefully detected as an error such as incomplete frame data, and the boundary data are not reproduced.
However, when a data size of the boundary data 6 accidentally matches a size of one frame as shown in
An object of the present invention is to provide a data reproduction method and a data reproduction apparatus that can completely avoid occurrence of noise during specific reproduction of compressed audio data read from a recording medium, which would otherwise be caused by boundary data obtained by concatenating data discontinuously read from the recording medium.
The present invention provides a data reproduction method including:
reading compressed audio data recorded in a recording medium discontinuously;
inserting dummy data between the read compressed audio data;
concatenating the dummy data and the read compressed audio data to generate data; and
performing specific reproduction of the generated data.
According to the data reproduction method, the specific reproduction is a fast-forward reproduction or a fast-backward reproduction.
According to the data reproduction method, the dummy data have a data size which is equal to or greater than a size of one frame in standards of the compressed audio data.
According to the data reproduction method, the dummy data have an arbitrary character string.
The present invention provides a data reproduction apparatus including: a data reading unit configured to read compressed audio data recorded in a recording medium; and a data insertion unit configured to insert dummy data between data to be concatenated and reproduces the data when performing a specific reproduction of data obtained by concatenating the data which are discontinuously read from the recording medium.
According to the data reproduction apparatus, the specific reproduction is a fast-forward reproduction or a fast-backward reproduction.
According to the data reproduction apparatus, the dummy data have a data size which is equal to or greater than a size of one frame defined in standards of the compressed audio data.
According to the data reproduction apparatus, the dummy data have an arbitrary character string.
According to a data reproduction method and a data reproduction apparatus of the present invention, it is possible to completely avoid occurrence of noise during specific reproduction of compressed audio data read from a recording medium, which would otherwise be caused by boundary data obtained by concatenating data discontinuously read from the recording medium.
An embodiment of the present invention is hereunder described by reference to the drawings. “Specific reproduction” described in the present embodiment signifies fast-forward reproduction and fast-backward reproduction, such as double-speed reproduction and so on.
The dummy data 10 are a data sequence having a character string 0x00 and assume, as a data size, a frame size of the dummy data 10 is the maximum size defined in the MP3 audio standards. The frame size of the MP3 audio data can be calculated from an MPEG format, a bitrate, and a sampling frequency.
A formula for calculating the frame size is provided below.
Frame size of MPEG1=144×bitrate/sampling frequency
Frame size of MPEG2 LSF=72×bitrate/sampling frequency
By reference to
As mentioned above, the data reproduction apparatus sequentially iterates data extraction processing, processing for concatenating the dummy data 10, and processing for skip reading of data. As a consequence, the dummy data 10 are inevitably inserted into the boundary data between the sets of reproduction data.
As mentioned above, according to the data reproduction apparatus and the data reproduction method of the present embodiment, when the MP3 audio data are subjected to specific reproduction, the dummy data having the maximum data size of the standards are inserted into the boundary data. Therefore, the data size of the boundary data does not match the size of one frame. Consequently, the boundary data obtained by concatenating data which are discontinuously read from recording data can be detected as an error, so that occurrence of noise, which would caused by reproduction of boundary data, can be avoided. Therefore, high grade reproduction can be accomplished.
For instance, if the data size of the dummy data 10 inserted between the extraction data is set to 1440 bytes that are the maximum frame size of the MP3 stream standards, it is possible to avoid occurrence of noise during specific reproduction of the MP3 audio data compliant with the standards, regardless of a constant bitrate and a variable bitrate. When the MP3 audio data having a constant bitrate are subjected to specific reproduction, a frame size conforming to the MP3 audio data to be reproduced can also be used.
The dummy data 10 are not limited to a data sequence consisting of a character string 0x00. Any arbitrary character string data can also be used, so long as the character string data do not coincide with a sync word existing in the frame of the MP3 stream. In any event, it is possible to avoid accidental detection of a sync word during reproduction of boundary data obtained by a discontinuous concatenation process in a retrieving a sync word of the next frame.
Reproducing procedures of the data reproduction method employed by the data reproduction apparatus of the present embodiment can be implemented by software and stored in a recording medium in the form of a computer program.
Although the present invention has been described in detail and by reference to a specific embodiment, it is apparent to those skilled in the art that the present invention will be susceptible to various alterations or modifications without departing the spirit and scope of the present invention.
The present patent application is based on Japanese Patent Application (Japanese Patent Application No. 2008-150699) filed on Jun. 9, 2008, the subject matters of which are incorporated herein by reference.
The data reproduction method and the data reproduction apparatus of the present invention are useful as a reproduction apparatus, a reproduction method, and the like, for subjecting compressed audio data to specific reproduction.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2008-150699 | Jun 2008 | JP | national |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP09/01805 | Apr 2009 | US |
| Child | 12962337 | US |
