JP3225502B2 - Compressed data playback device for audio information - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for reproducing a recording medium such as an optical disk or a hard disk, and an apparatus for reproducing compressed audio data obtained through a communication line or the like.

[0002]

2. Description of the Related Art In recent years, audio data is compressed and recorded on a recording medium such as an optical disk or a hard disk.
Devices for expanding and reproducing it are becoming popular. The decoding process of such a device includes a decoder L for audio processing.
A device using SI (Large Scale Integrated circuit) and a general-purpose CPU (C
entral Processing Unit) and DSP (Digital Signal Pr
ocessor) to perform decryption processing.

In a device that performs decoding processing by a general-purpose CPU or the like, when system resources (CPU processing capacity, amount of memory, etc.) are lower than those required for audio decoding processing,
By setting the decoding accuracy based on system resources and reducing the decoding accuracy, the outflow speed is increased, and reproduction without sound interruption (real-time reproduction) is performed.

Here, the outflow speed, the decoding speed, and the decoding speed will be briefly described. The outflow velocity is defined by the decoder as D /
This is the supply speed of data to be supplied to an audio output device such as an A converter. In order to perform real-time reproduction, the above-mentioned audio output device operates at a fixed speed such as 44.1 kHz.
The outflow velocity must be the same as its fixed velocity in order to perform A conversion. When a buffer is provided between the decoder and the audio output device, the outflow speed may be higher than the fixed speed on average. The decoding speed is the speed at which the decoding process is performed, and is in direct proportion to the outflow speed. The decoding accuracy is the accuracy of the decoded data, and is in inverse proportion to the outflow speed. It is directly proportional to the amount of system resources required to decode one sample.

In an apparatus using a dedicated decoder LSI, reproduction without sound interruption can be performed based on system resources (power consumption, amount of memory, etc.).
I was designing an LSI.

[0006]

According to the above-described apparatus for performing a decoding process using a general-purpose CPU or the like, a method of setting the decoding accuracy in advance based on system resources is employed. I have. When the CPU is performing other processing (such as video decoding) in parallel, the setting is performed in advance based on system resources allocated to the audio decoding processing.

However, in this method and apparatus, since the setting of the decoding accuracy is fixed, if the system resources allocated to the audio decoding process are not constant, for example, the number of processes to be performed in parallel during reproduction and the number of exceptional processes increase. In such a case, the audio processing cannot be performed in time with the setting, and the sound is cut off. Further, since the setting of the decoding accuracy is fixed, the sound quality becomes constant.

Also, a dedicated decoder LSI as described above
In an apparatus using the system, since the LSI is designed based on predetermined system resources, when the system resources are insufficient, for example, when the battery is exhausted, the system is stopped. I will. Therefore,
The present invention has been made by paying attention to the above points, and has as its object to provide a compressed data reproducing apparatus for audio information without sound interruption.

In order to achieve the above object, a compressed audio data decoder for decoding compressed audio data and outputting audio decoded data, and temporarily storing the audio decoded data output from the compressed audio data decoder. What is claimed is: 1. An audio information compressed data reproducing apparatus, comprising: an output audio buffer memory; and an accumulation information output unit configured to output information on an accumulation amount of audio decoded data of the output audio buffer memory. And a compressed audio data decoder control means for changing the decoding accuracy and / or the decoding speed of the audio decoded data output by the compressed audio data decoder according to the accumulated amount information obtained from the audio information. To provide a compressed data reproducing apparatus. A compressed audio data decoder for decoding the compressed audio data and outputting audio decoded data; an output audio buffer memory for temporarily storing the audio decoded data output from the compressed audio data decoder; An audio information compressed data reproducing device comprising: an accumulation amount information output unit that outputs information on an accumulation amount of audio decoded data in an audio buffer memory, wherein the compressed audio data decoder detects a system resource amount allocated to the compressed audio data decoder. Means for detecting the amount of system resources to be output, and the audio decoding data output by the compressed audio data decoder in accordance with the storage amount information obtained from the storage amount information output means and the system resource amount obtained from the system resource amount detecting means. Compression data decoder control means for changing the decoding accuracy and / or decoding speed of the Providing compressed data reproducing apparatus of the audio information, characterized. Further, the system resource amount detecting means detects a system resource amount used by the compressed audio data decoder and / or a system resource amount required by the compressed audio data decoder, and accordingly, the compression 3. The apparatus according to claim 2, wherein the apparatus controls the amount of system resources allocated to the audio data decoder. 4. The apparatus according to claim 1, wherein the compressed audio data is compressed data according to the MPEG standard.

[0010]

[0011]

[0012]

As described above, by controlling the decoding accuracy and the decoding speed during reproduction and outputting the data from the output data buffer memory 3 to the audio output device at a constant speed, the audio information of sound information without sound interruption can be obtained. It is intended to provide a compressed data reproducing device.

According to the present invention, as described above, since the apparatus itself variably controls the decoding accuracy and the decoding speed, it is possible to always reproduce without interruption of sound. Further, according to the present invention, reproduction can be performed with the highest decoding accuracy that can be reproduced with the system resources allocated at that time, that is, with sound quality.

[0015]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of an audio data compression data reproducing apparatus according to the present invention.
In the present embodiment, MPEG (Moving P
It adopts compressed audio data based on the “Icture Expert Group” standard (compliant with ISO 11172).

FIG. 1 is a block diagram of an MPEG decoding unit used in an embodiment of the audio data compressed data reproducing apparatus according to the present invention, and FIGS. 2 and 3 are diagrams showing an embodiment of the present invention. It is a flowchart of a decoding control process. Also,
Table 1 below shows an example of the setting of the decoding parameter in one embodiment of the present invention.

[0017]

[Table 1]

First, each block of the embodiment of the audio information compressed data reproducing apparatus of the present invention shown in FIG. 1 will be described in order below. The system resource amount detector 1 is an MPEG
The information on the system resource amount supplied to the audio decoder 2 is output to the MPEG audio decoder control unit 5.

The MPEG audio decoder 2 is supplied with compressed audio data, can set decoding accuracy and decoding speed in several stages, and can output the set audio decoded data. It is.

The output audio buffer memory 3 is MPEG
A buffer memory to which audio data decoded by the audio decoder 2 is supplied. The output audio buffer memory 3 is a FIFO (Fast In Fast Out) type buffer, and can output information on the amount of stored data.

The audio output device 4 is supplied with audio decode data output from the output audio buffer memory 3, and
The audio output device includes a D / A converter, an analog circuit, a speaker, and the like.

The MPEG audio decoder control unit 5 is adapted to the MPEG audio decoder 2 at that time based on the information obtained from the output audio buffer memory 3 and the information obtained from the system resource amount detector 1. The decoding accuracy parameter and the decoding speed parameter are set. Note that the system resource amount detector 1 shown in FIG. 1 is not used in the first embodiment.

(Embodiment 1) Next, referring to FIG.
A decoding control process according to the first embodiment of the audio information compressed data reproducing apparatus of the present invention will be described. MPEG here
The decoding accuracy and the decoding speed of the audio decoder 2 are the decoding accuracy L
OW and decoding accuracy HIGH, decoding speed LOW and decoding speed H
Each of IGH has two stages, and a CD disk is used as a recording medium.

As shown in FIG. 1, compressed audio data read from a CD disk as a recording medium is
It is supplied to the EG audio decoder 2. And this MPE
The G audio decoder 2 decodes the compressed audio data according to the set parameters supplied from the MPEG audio decoder control unit 5.

The audio data decoded by the MPEG audio decoder 2 is supplied to an output audio buffer memory 3.
The audio output device 4 reads data from the output audio buffer memory 3 and outputs audio.

As shown in the flowchart of the processing in FIG. 2, the MPEG audio decoder control unit 5
At regular intervals, information on the output data buffer usage is acquired from the output audio buffer memory 3 (step 201).

If it is larger than a certain threshold value, it is determined that the decoding process is ahead of the output, and if it is smaller than a certain threshold value, it is determined that the decoding process is behind the output (step 202).

If the decoding process has proceeded more than a certain threshold value, the combination (step 203) having a higher decoding accuracy than the decoding accuracy of the parameter currently set in the MPEG audio decoder 2 is set to the MPEG audio decoder control unit 5.
Is selected and set in the MPEG audio decoder 2 (step 205).

On the other hand, if the decoding process is slower than a certain threshold value, the outflow speed is faster than the outflow speed of the parameters currently set in the MPEG audio decoder 2 and the decoding accuracy of the outflow speed is higher than that. The MPEG audio decoder control unit 5 selects the highest combination (step 204) and sets it to the MPEG audio decoder 2 (step 20).
Five). By such control processing, the output data buffer amount in the output audio buffer memory 3 is controlled so that the audio output from the audio output device 4 is not interrupted.

(Embodiment 2) Next, referring to FIG.
A decoding control process according to the second embodiment of the present invention will be described. C
The compressed audio data read from the D disk is MPE
It is input to the G audio decoder 2. Then, the MPEG audio decoder 2 decodes the compressed data in accordance with the parameters set by the MPEG audio decoder control unit 5.

The decoded audio data is supplied to the next output audio buffer memory 3, and the audio output device 4 reads the data from the output audio buffer memory 3 and outputs the audio.

The MPEG audio decoder control unit 5 acquires information from the system resource amount detector 1 at regular intervals during audio reproduction (step 301), and determines the currently allocated system resource amount.

Also, information on the output data buffer usage is obtained from the output audio buffer memory 3 (step 30).
3) If it is larger than a certain threshold, it is determined that the decoding process is ahead of the output, and if it is smaller than a certain threshold, it is determined that the decoding process is behind the output (step 304).

If the decoding process has progressed from among the parameter combinations that can be processed with the current system resource amount, a combination having a decoding accuracy higher than the decoding accuracy of the parameters currently set in the MPEG audio decoder 2 If the decoding process is delayed, a combination having a higher outflow speed than the outflow speed of the parameters currently set in the MPEG audio decoder 2 and having the highest decoding accuracy among them is determined by the MPEG audio decoder controller 5. Is selected (steps 302, 305, 306) and set in the MPEG audio decoder 2 (step 307).

If the information obtained by the MPEG audio decoder control unit 5 is such that the system resource amount = medium, the output buffer amount> the threshold value, and the decoding accuracy of the parameter currently set in the MPEG audio decoder 2 is LOW, (Step
In 302), a combination of parameters that can be processed with the current system resource amount, and a combination of parameters in Tables 1 (2), 3), and 4) are selected as candidates, and in step 305, decoding accuracy is determined. Table 1 (3), which is HIGH, is selected.

Next, when the information obtained by the MPEG audio decoder control unit 5 is such that the system resource amount = large, the output buffer amount <the threshold value, and the outflow speed of the parameters currently set in the MPEG audio decoder 2 is slow. , (Step 20
In 2), a combination of parameters that can be processed with the current system resource amount and a combination of parameters in Tables 1 (1), (2), (3), and (4) are selected as candidates. Table 1 (1) having the highest decoding accuracy is selected from the above Tables 1 (1), 2) and 4). By such control processing, the output data buffer amount in the output sound buffer memory 3 is controlled so that the sound from the sound output device 4 is not interrupted.

In the second embodiment described above, the (step
In the processing of steps 305 and 306), priority is given to decoding accuracy, but if priority is given to saving of system resources and a combination of parameters which uses the least amount of system resources is selected, priority or elimination of other parallel processing can be achieved. It can be applied to electric power and the like.

(Embodiment 3) As Embodiment 3, Embodiment 2
As shown by the dotted line in FIG. 1, the MPEG audio decoder controller 5 outputs the system resource usage currently used by the MPEG audio decoder 2 to the system resource amount detector 1. As a result, of the system resources allocated to the MPEG audio decoder 2 by the system, the amount of unused system resources can be detected and recovered.

Also, the MPEG audio decoder control unit 5 in the second embodiment outputs the required amount of system resources required by the MPEG audio decoder 2 to the system resource amount detector 1 as shown by the dotted line in FIG. I do. For example, the MPEG audio decoder control unit 5 outputs a required amount of system resources required for higher-level decoding accuracy, and the system resource amount detector 1 detects the output and outputs the detected system resources to the system. With this information, the system allocates the system resources based on the information if the system resources have a margin.

The allocation of system resources will be described below with reference to Table 1. For example, the system resource usage in Table 1 is set to large = 7, medium = 5, and small = 3, respectively. It is assumed that the system resource amount currently allocated to the MPEG audio decoder 2 by the system detected by the system resource detector 1 is 4. From this value, the MPEG audio decoder control unit 5 gives the MPEG audio decoder 2 (4)
Set the parameters for The system resource detector 1 detects this information from the MPEG audio decoder control unit 5 and outputs it to the system. In this case, the value is 3. In addition, the system resource detector 1 detects the amount of system resources required for higher-level decoding accuracy from the MPEG audio decoder control unit 5 and outputs it to the system. In addition,
In this case, it becomes 5.

Based on these information, if there is enough system resources, the system assigns 5 to the MPEG audio decoder 2
Assign to If there is no extra system resource, the surplus system resource = 1 is collected.
As described above, by outputting at least one of the information to the system, the system can always allocate an optimal system resource amount to the MPEG audio decoder 2.

As described above, if at least one of the above information is output to the system, the system can always allocate the optimal amount of system resources to the MPEG audio decoder 2.

Although the control in the first, second, and third embodiments is performed based on a certain threshold value, it is also possible to provide a plurality of threshold values to make the control adaptive. Examples of the method of controlling the decoding accuracy and controlling the outflow speed include the following (1) and (2). (1) According to the MPEG standard, output data is calculated by combining frequency band data called 32 subbands.
The number of sub-bands to be combined is changed to control the amount of calculation. (2) Change the bit precision during operation.

Examples of a method for controlling the decoding speed and controlling the outflow speed include the following (1) and (2). (1) Change the algorithm of memory usage (using a constant table, etc.). (2) Control the internal clock of the decoder.

Although the above embodiment employs the MPEG standard for the compressed audio data, the present invention can be applied to other audio compression methods.

[0046]

As described above, according to the audio data compressed data reproducing apparatus of the present invention, during audio reproduction, the amount of system resources allocated at that time and the decoding process proceed.
By judging the delay, changing the decoding accuracy and the decoding speed, and controlling the outflow speed of the decoded audio data to be output, the output data amount in the output audio buffer memory is controlled. The audio from the audio source is not interrupted, and the reproduction can be performed with the highest decoding accuracy, that is, the highest sound quality that can be reproduced with the system resources allocated at that time.

Further, by changing the priority item at the time of parameter selection from decoding accuracy to saving of system resources, the present invention can be applied to, for example, prioritizing power saving (long time) reproduction and other parallel processing. Can be done.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of a decoding unit of a compressed audio data reproducing apparatus of the present invention.

FIG. 2 is a flowchart showing the operation of the audio data compressed data reproducing apparatus according to the first embodiment of the present invention, which is performed by the audio decoder control unit 5 when decoding accuracy is controlled during reproduction.

FIG. 3 is a flowchart showing the operation of the audio information compressed data reproducing apparatus according to the second embodiment of the present invention, which is a process of the audio decoder control unit 5 when controlling decoding accuracy during reproduction.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 System resource amount detector 2 MPEG audio decoder 3 Output audio buffer memory 4 Audio output device 5 MPEG audio decoder control unit 31 Means for outputting information on the usage of output data buffer memory

Claims (4)

(57) [Claims] 1. A compressed audio data decoder for decoding compressed audio data and outputting audio decoded data, an output audio buffer memory for temporarily storing the audio decoded data output from the compressed audio data decoder, And a storage amount information output means for outputting information on the storage amount of the decoded audio data in the output sound buffer memory, wherein the storage amount obtained from the storage amount information output means is provided. An audio information compressed data reproducing apparatus, comprising: a compressed audio data decoder control means for changing decoding accuracy and / or decoding speed of audio decoded data output from the compressed audio data decoder according to information. 2. A compressed audio data decoder for decoding compressed audio data and outputting decoded audio data, and an output audio buffer memory for temporarily storing the decoded audio data output from the compressed audio data decoder. And a storage amount information output unit that outputs information on a storage amount of the decoded audio data in the output audio buffer memory, wherein the compressed audio data decoder includes a system resource allocated to the compressed audio data decoder. The compressed audio data decoder outputs in accordance with the system resource amount detecting means for detecting the amount, and the accumulated amount information obtained from the accumulated amount information output means and the system resource amount obtained from the system resource amount detecting means. A compressed audio data decoder control means for changing the decoding accuracy and / or the decoding speed of the audio decoded data; A compressed data reproducing apparatus for audio information, characterized in that: 3. The system resource amount detection means detects a system resource amount used by the compressed audio data decoder and / or a system resource amount required by the compressed audio data decoder. 3. The apparatus according to claim 2, wherein the apparatus controls the amount of system resources allocated to the compressed audio data decoder. 4. The apparatus according to claim 1, wherein said compressed audio data is compressed data according to the MPEG standard.