JP4612436B2 - Audio decoding device - Google Patents

Description

  The present invention relates to an audio decoding apparatus that decodes a compressed stream, and in particular, reduces current consumption by appropriately detecting a state in which there is no work to be processed by a CPU even during operation and shifting to a sleep state. The present invention relates to an audio decoding device that can be used.

  With the widespread use of computer devices controlled by CPUs, attempts have been made to reduce power consumption.

  For example, based on the count of a counter placed in the microprocessor, the microprocessor power consumption is selectively adjusted by predicting the usage of the microprocessor and comparing the predicted usage with a threshold value. Has been proposed (for example, Patent Document 1).

  In addition, a printing apparatus has been proposed that controls the CPU to transition to a sleep mode or a power stop mode when a DMA transfer request signal is not output for a predetermined time or longer (for example, Patent Document 2).

Furthermore, in a software control system environment using a multitasking OS, it has been proposed to effectively reduce the power consumption of a processor when executing a plurality of tasks with time constraints and additional fluctuations (for example, patents). Reference 3).
Japanese Patent Laid-Open No. 11-161383 JP 2003-337713 A Japanese Patent Laid-Open No. 2001-180083

  However, the audio decoding apparatus is conventionally in the sleep mode only when it is not operating. As a result, even when the CPU is in operation and there is no work to be processed by the CPU, current is consumed only by going around the main loop.

  The present invention has been made in view of the above-described problems. Even when the CPU is in operation, the CPU appropriately detects a state where there is no work to be processed, and shifts to a sleep state. An object of the present invention is to provide an audio decoding device that can be reduced.

To solve the above problems, the audio decoding apparatus disclosed, a main task execution determining means for determining whether the main task of the said decoding is performed by the CPU to decode the compressed stream, the primary task is When it is determined that the main task is not executed, a sleep count unit that increments a sleep count, and when the sleep count is incremented by the sleep count unit, the number of times that the main task is continuously executed A maximum number of times determination means for determining whether or not the maximum number of times the main task has been executed, and the number of times that the main task has been continuously executed is determined to be greater than the maximum number of times that the main task has been continuously executed. If that, the maximum number assignment unit that assigns a該回number said maximum number, the primary task is If it is determined that the row, and the sleep count initialization means for zero-clearing the sleep count, the state at present even during the operation of the CPU, and is the primary task at the time of transition to a previous sleep state the continuously been executed the maximum number of times a sleep transition threshold, and a sleep judging means for the sleep count to determine whether it exceeds the sleep transition threshold, if the sleep count exceeds the sleep transition threshold, A sleep state transition means for transitioning to a sleep state; a buffer capacity determination means for determining whether or not a buffer for storing a decoded stream for audio output when the sleep state is canceled has a predetermined capacity or more; When the buffer has a predetermined capacity or more, the main task is continuously executed at the sleep transition threshold. Configured to have a threshold assignment means that assigns the maximum number of times.

  In such an audio decoding device, when the number of times that no main task is continuously executed exceeds a threshold, control can be performed so as to shift to a sleep operation of the CPU. Therefore, a reduction in current consumption can be realized.

  According to the present invention, it is possible to configure an audio decoding device with low current consumption by counting the number of times that a main task is not executed continuously and, when the value exceeds a threshold value, transitioning to a sleep operation of the CPU. is there. Furthermore, the number of times that the main task has been executed in succession can be counted, and the sleep transition threshold value can be dynamically determined based on this information. Therefore, it is possible to efficiently shift to the sleep operation.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram for explaining the principle of an audio apparatus according to the present invention. In FIG. 1, the audio device 100 includes a CPU (Central Processing Unit) and a main memory 110, a DMA transfer circuit 120, an SDRAM 130, a DMA transfer circuit and a PCM output circuit 140. As a hardware configuration, the DMA transfer circuit 120 and the DMA transfer circuit / PCM output circuit 140 are one. Further, in FIG. 1, a portion processed by the CPU firmware is shown as a task.

  Processing of the stream and data is as follows.

  First, an audio (audio) compressed stream is sequentially stored in the stream buffer 132 from the upper CPU. If a stream accumulates and there is one or more free space in a PES (Packetized Elementary Stream) buffer 112 configured as a bank buffer, the PES transfer task TSK1 is executed. This is a process of transferring a stream from the SDRAM 130 having a slow access time to a main memory that can be processed at high speed by the CPU.

  By this PES transfer task TSK1, data is transferred to the PES buffer 112 in units of 256 bytes. This task is a startup process to the DMA transfer circuit 120, and the actual transfer is performed by DMA transfer (DMA_DS).

  If there is one or more PES buffers 112 and there is a free ES (Elementary Stream) buffer 114 configured as one or more ring buffers, the ES extraction task TSK2 is executed. The ES extraction task TSK2 is a process of extracting Audio ES data from the PES stream.

  When the ES buffer 114 accumulates 1 ES or more and the PCM buffer 134 has one or more vacancy, the decoding process task TSK3 is executed. The decoding process task TSK3 is a process of the main body for decoding the encoded stream. The decrypted data is temporarily stored in the temporary buffer 116 configured as a single buffer, and the PCM transfer task TSK4 is executed in conjunction with it. The PCM transfer task TSK4 is an activation process to the DMA transfer circuit 120, and the actual transfer is performed by DMA transfer (DMA_ETC).

  If one or more pages exist in the PCM buffer 134, the PCM output task TSK5 is executed. The PCM output task 5 serially transfers the decoded data to the external terminal at a constant rate. The PCM output task 5 is an activation process to the DMA transfer circuit 120, and actual transfer is performed by DMA transfer (DMA_DP).

  Once the PCM output task TSK5 is executed and the PCM starts to be output, it is necessary to continue the above processing without delay so that the PCM buffer 134 is not exhausted. When the PCM buffer 134 is exhausted, the sound is cut off, which is not desirable. If eleven PCM buffers 134 are secured in the SDRAM 130 and the stream continues to be supplied, the decoding process is performed until the stream becomes full. By sufficiently storing the PCM buffer 134, the PCM output can be output without interruption even if the processing temporarily becomes heavy.

  As described above, since it is necessary to perform the decoding process at a fixed time, the process is divided by using a fixed processing unit as a task, and buffering is performed so that the processes can be performed in parallel before and after the divided process. The execution condition for each task is determined by the state of the input and output buffers.

  The state of these buffers is constant to some extent in the normal state, and the operation of the task can be expected accordingly. However, if there is an error in the stream buffer supply state, ES stream contents, or stream, Video (video) and lip Each buffer state changes due to any influence, such as when skip or repeat occurs in units of samples for synchronization, and the timing at which each task operates changes every moment.

  FIG. 2 is a flowchart for explaining processing executed by the CPU according to the present invention. In FIG. 2, processing executed by the CPU is roughly divided into main processing and interrupt processing.

  In the main process, after the initialization process (step S101), the sequence management task (step S102), the sleep operation detection task (step S103), the PES transfer task TSK1 (step S104), and the ES extraction task TSK2 (step S105) The decode processing task TSK3 (step S106), the PCM transfer task TSK4 (step S107), and the PCM output task TSK5 (step S108) are executed if the respective tasks are evaluated and the execution conditions are satisfied.

  As described above, whether to execute tasks TSK1 to TSK4 is determined by the buffer state. The PCM output task TSK5 is executed from the main process only once for the first time, and from the interrupt process for the second time and thereafter. This is because the end of the DMA transfer (DMA_DP) that performs PCM output is used as a trigger for starting the next DMA transfer (DMA_DP). That is, the PCM output is activated from the interrupt without interruption.

  The sequence management task (step S102) determines the state transition by determining the decoding start or instruction command from the host CPU. The acquisition or analysis of these commands from the host CPU is performed by interrupt processing, but the actual processing is executed by this task. Other interrupts include a PES transfer post-processing task that performs processing after completion of DMA transfer (DMA_DS).

  The sleep operation detection task (step S103) determines the processing status of the task, determines whether there is no work to be processed by the CPU and can shift to the sleep mode, and enters the sleep state if there is a condition. Normally, the loop of the main process shown in FIG. 2 is periodically repeated. However, since the CPU command stops when the sleep state is entered, the sleep operation detection task is completely stopped. As a result, a standby state with low current consumption is established. The return from the sleep state is when the interrupt signal is asserted, and can be recovered from the following conditions. There are a stream supply command notification from the host CPU, a DMA transfer (DMA_DS) transfer completion interrupt, and a DMA transfer (DMA_DP) transfer completion interrupt. This corresponds to the command acquisition or analysis task in interrupt processing (step S201), the PES transfer post-processing task (step S202), and the PCM output TSK5 (step S203). In addition to this, there is a decode start or stop instruction command from the host CPU that is notified at the VSYNC 16.6 ms interval of Video.

  FIG. 3 is a diagram showing a breakdown of processing time focusing on 1-frame decoding. In FIG. 3, processing is normally performed in the order of tasks TSK1 to 4. The ES extraction task TSK2 may be called a plurality of times when one frame is decoded depending on the stream. In the PCM output task TSK5, the processing in the firmware is only the activation processing to the hardware, and the contents of the PCM buffer 134 are simply DMA-transferred to the outside by the hardware, so that one-frame decoding processing is not affected at all. Therefore, since it can be ignored as the processing of the CPU, it is not described in the breakdown. At the same time, the sequence processing task in the main process (step S102), the sleep operation detection task (step S103), the command acquisition or analysis task in the interrupt process (step S201), and the PES transfer post-processing task (step S202) The amount of processing is sufficiently small compared to the above processing and can be ignored, so detailed description thereof will be omitted.

  This example is an example of processing time breakdown when 2ch audio decoding is performed. However, if 4ch audio decoding is performed, 11 ms × 2 = 22 ms is required. If these processes require 11 ms, one frame time requires 24 ms, so 13 ms is the remaining margin. In other words, this time is a period for which the CPU is idle and becomes a sleep target.

  FIG. 4 is a diagram illustrating processing time timings of a plurality of frames. In FIG. 4, immediately after decoding is started, if it is assumed that the stream is continuously supplied to the stream buffer, tasks TSK1 to 4 (11 ms) are continuously processed, and the CPU has no waste of processing time (empty). Processing continues until the PCM buffer 134 is full. When 11 frames are decoded and the PCM buffer 134 is full, dead time (empty) occurs.

  Further, depending on the state in which the supply of the stream is temporarily stopped, even when the PCM buffer 134 is not full, the CPU can be in a standby state waiting for the stream supply.

  Thus, the margin (free time) varies depending on each factor including the buffer state.

  In the present invention, instead of monitoring only a specific buffer state, the number of times that no main task is continuously executed is counted, and when it exceeds a threshold, the CPU is put into a sleep operation.

  In the main process shown in FIG. 2, a flag indicating whether or not the main tasks of tasks TSK1 to TSK3 have executed the task is prepared as one common variable. Here, since the PCM transfer task TSK4 is derived from the decode processing task TSK3, it is used together with the decode processing task TSK3.

  This task operation determination flag is cleared to zero immediately before the initial initialization process and the PES transfer task TSK1. Each task sets this flag to 1 if it is executed. Do nothing to be done. As a result, it is 1 if any of the three main tasks TSK1 to TSK1 is executed, and 0 if it is not executed at all. The task operation determination flag is referred to by the sleep operation detection task (step S103).

  FIG. 5 is a flowchart for explaining an example of processing by the sleep operation detection task. First, the current state is confirmed (step S131). If not in operation, the process proceeds to step S135. On the other hand, if it is in operation, the task operation determination flag is checked to check whether or not the main task has been executed (step S132). If the main task is being executed, the main task continuous non-execution count sleep_cnt is cleared to zero (step S133), and if not executed, it is incremented by one (step S134). Therefore, the number of times the main task has not been continuously executed is counted in the main task continuous non-execution count sleep_cnt.

  Next, it is confirmed whether or not the current state is stopped (step S135). If the current state is stopped, the CPU sleep command is unconditionally executed to enter the sleep state (step S137), and the state is changed from the sleep state. Immediately after the return, the main task continuous non-execution count sleep_cnt is cleared to zero (step S138), and the CPU returns from the processing by the sleep operation detection task.

  Further, when the current state is in operation and the number of continuous main task unexecuted sleep_cnt exceeds the threshold value 10, the CPU sleep command is executed similarly to enter the sleep state (step S137). Immediately after the return, the main task continuous non-execution count sleep_cnt is cleared to zero (step S138), and the CPU returns from the processing by the sleep operation detection task. On the other hand, if the main task consecutive non-execution count sleep_cnt does not exceed the threshold value 10, the CPU directly returns from the processing by the sleep operation detection task.

  The threshold for transitioning to the sleep state is set in consideration of this because the ES extraction task TSK2 may be called a plurality of times when decoding one frame depending on the stream. The reason is that the size of the PES buffer 112 is 256 bytes on one side, while the size of the ES buffer 114 is similarly 2048 bytes on one side. It corresponds to one side. Although it largely depends on the bit rate, it cannot be determined how many sides of the ES buffer 114 correspond to one side of the ES buffer 114 due to the boundary condition of ES extraction.

  Accordingly, if this threshold value is set to a small value, the ES extraction task TSK2 may not be completely executed and may fall into the sleep state. On the other hand, if the threshold value is set large, the transition to the sleep state is delayed.

  In order to solve such a problem, the sleep operation detection task is counted when the task has been executed continuously before, a new threshold is calculated based on this information, and feedback is always applied. Provide a mechanism for transitioning to sleep mode in an optimal state. A mechanism for dynamically changing the threshold value will be described with reference to FIG.

  FIG. 6 is a flowchart for explaining another example of processing by the sleep operation detection task. In FIG. 6, as in the process shown in FIG. 5, the main task consecutive non-execution count sleep_cnt counts the number of times the task has not been continuously executed. A main task continuous execution count task_cnt that counts the value of continuous execution of tasks is newly provided.

  First, the current state is confirmed (step S151). If not in operation, the process proceeds to step S157. On the other hand, if it is in operation, the task operation determination flag is checked to check whether the main task has been executed (step S152). If the main task is being executed, the main task continuous non-execution count sleep_cnt is cleared to zero, the main task continuous execution count task_cnt is incremented by 1 (step S153), and the process proceeds to step S157.

  If the main task is not executed, the main task continuous non-execution count sleep_cnt is incremented by 1 (step S154), and the main task continuous execution count task_cnt is compared with the main task maximum execution count max_task_cnt indicating the maximum count so far ( Step S155). When the main task continuous execution count task_cnt is less than or equal to the main task maximum execution count max_task_cnt, the process proceeds to step S157. On the other hand, if the main task continuous execution count task_cnt is larger than the main task maximum execution count max_task_cnt, the main task continuous execution count task_cnt is substituted for the main task maximum execution count max_task_cnt, and the main task continuous execution count task_cnt is cleared to zero (step S156). . If the same processing is repeated until the sleep state is entered, as a result, the maximum number of tasks executed continuously is recorded in the main task maximum execution count max_task_cnt.

  Next, it is confirmed whether or not the current state is stopped (step S157). If the current state is stopped, the process proceeds to step S159 in order to unconditionally execute the CPU sleep instruction. If it is not stopped, it is determined whether or not the current state is in operation and the main task continuous non-execution count sleep_cnt exceeds a threshold value task_threshold (step S158). When the current state is in operation and the number of consecutive main task unexecuted sleep_cnt exceeds the threshold value task_threshold, the process similarly proceeds to step S159 to execute the CPU sleep instruction. In step S159, a CPU sleep command is executed to enter a sleep state.

  Immediately after returning from the sleep state, it is determined whether there are two or more PCM buffers 134 (step S160). If there are two or more, the main task maximum execution count max_task_cnt is substituted for the sleep transition threshold task_threshold (step S161), and the process proceeds to step S163. On the other hand, if there are no more than two faces, the value 10 is substituted into the sleep transition threshold task_threshold (step S162), and the process proceeds to step S163. In step S163, the main task maximum execution count max_task_cnt, the main task continuous non-execution count sleep_cnt, and the main task continuous execution count task_cnt are cleared to zero. Thereafter, the CPU returns from the processing by the sleep operation detection task.

  On the other hand, in step S158, if the number of consecutive main task unexecuted sleep_cnt does not exceed the threshold value task_threshold, the process returns from the processing by the sleep operation detection task.

  In the above processing, the transition condition to the sleep state is replaced with a variable of the sleep transition threshold task_threshold with respect to the fixed threshold of FIG. When the value exceeds this value, the initial value of the sleep transition threshold value task_threshold that causes the CPU to execute the sleep command and enter the sleep state starts from a fixed value 10 as in FIG.

  Further, as described above, the sleep transition threshold task_threshold is updated immediately after returning from the sleep state, and the accumulated amount of the PCM buffer 134 is determined. If there is not enough room in the PCM buffer 134, the sleep transition threshold task_threshold is set to the initial value. A value with a margin of 10 is set. This is a consideration that avoids the extreme sleep transition threshold value task_threshold when the PCM buffer 134 has little room, thereby eliminating the possibility of failure of the PCM buffer 134 as much as possible.

  Further, in the processing examples shown in FIGS. 5 and 6, it is determined that the task is continuously executed from only the result of the previous sleep state, but an average of several sleep states is taken. You can also. That is, it is possible to take care not to cause a sudden change in the sleep transition threshold.

  Since the VSYNC of Video is periodically input at 16.6 ms intervals, an interrupt is generated once within 24 ms of one frame to release from sleep. Therefore, even if the sleep transition threshold is set to the extreme sleep transition threshold by self-learning the sleep transition threshold according to the previous processing amount and obtaining the optimum sleep transition threshold, the decoding process is delayed and the PCM buffer 134 is depleted. Such failures are avoided.

  Next, an example of the sleep state when the respective processes by the sleep operation detection task shown in FIGS. 5 and 6 are executed will be described with reference to FIGS.

  FIG. 7 is a diagram illustrating an example of a sleep state when processing by the sleep operation detection task illustrated in FIG. 5 is executed. In FIG. 7, the bit string indicates the value of the task operation determination flag until the sleep state is entered, loop (i) indicates the number of times the sleep operation detection task shown in FIG. 5 is executed until the sleep state is entered, and the sleep transition threshold value task_threshold indicates a fixed value 10, and the main task continuous non-execution count sleep_cnt indicates the number of times that the main task has not been continuously executed until the sleep state is entered. When the sleep state is released, loop (i) is cleared to zero and is counted until the sleep state is entered.

  As shown in FIG. 7, in the processing by the sleep operation detection task shown in FIG. 5, the sleep transition threshold task_threshold is fixed. Therefore, when the value of the main task continuous non-execution count sleep_cnt counts 11, I understand.

FIG. 8 is a diagram illustrating an example of a sleep state when processing by the sleep operation detection task illustrated in FIG. 6 is executed. In FIG. 8, the bit string indicates the value of the task operation determination flag until the sleep state is entered, loop (i) indicates the number of times the sleep operation detection task shown in FIG. 6 is executed until the sleep state is entered, and the sleep transition threshold value task_threshold fluctuates by self-learning from the initial value 10, main task continuous non-execution count sleep_cnt indicates the number of times the main task has not been executed continuously until it enters the sleep state, and main task maximum execution count max_task_cnt enters the sleep state The maximum number of times the main task has been continuously executed until the main task is executed, and the main task continuous execution count task_cnt indicates the number of times the main task has been continuously executed before going into the sleep state. The main task maximum execution count max_task_cnt is set to the sleep transition threshold task_threshold after the sleep state is canceled.

  As shown in FIG. 8, it can be understood that the sleep task threshold value task_threshold fluctuates, so that the main task consecutive non-execution count sleep_cnt until the sleep state is changed.

  As can be seen from the examples shown in FIGS. 7 and 8, the number of times that no main task is continuously executed is counted, and when the value exceeds the threshold, the CPU shifts to the sleep operation, thereby reducing the current consumption. An audio decoding device can be configured. Furthermore, it is possible to efficiently shift to the sleep operation by counting the case where the task has been executed continuously before and adaptively determining the sleep transition threshold based on this information.

  The present invention can be applied to, for example, a DVD player, a digital TV, and particularly a highly portable movie recorder.

Regarding the above description, the following items are further disclosed.
(Appendix 1)
Main task execution determination means for determining whether a main task related to decoding of the compressed stream has been executed;
A sleep count means for incrementing a sleep count when it is determined that the main task has not been executed;
When it is determined that the main task has been executed, sleep count initialization means for clearing the sleep count to zero,
Sleep determination means for determining whether the state is in operation and the sleep count exceeds a sleep transition threshold;
An audio decoding device comprising: sleep state transition means for transitioning to a sleep state when the sleep count exceeds a sleep transition threshold.
(Appendix 2)
The audio decoding apparatus according to claim 1, wherein the sleep determination unit uses, as a sleep transition threshold, the maximum number of times that the main task is continuously executed at the time of transition to the previous sleep state.
(Appendix 3)
When the sleep count is incremented by the sleep count means, the maximum number of times determination means for determining whether or not the number of times that the main task is continuously executed is larger than the maximum number of times that the main task is continuously executed. When,
When it is determined that the number of times that the main task has been executed continuously is greater than the maximum number of times that the main task has been executed continuously, the system has a maximum number substituting unit that assigns the number of times to the maximum number of times. The audio decoding device according to supplementary note 2, which is characterized.
(Appendix 4)
When the sleep state is canceled, a buffer capacity determination unit that determines whether or not a buffer for storing the decoded stream for outputting audio has a predetermined capacity or more;
4. The audio decoding apparatus according to claim 3, further comprising threshold value substituting means for substituting the maximum number of times the main task has been executed continuously into the sleep transition threshold value when the buffer has a predetermined capacity or more.
(Appendix 5)
The audio decoding device according to appendix 4, further comprising predetermined value substitution means for substituting a constant value into the sleep transition threshold when the buffer is not larger than a predetermined capacity.
(Appendix 6)
The audio decoding apparatus according to any one of appendices 1 to 5, wherein the main tasks include a PES transfer task, an ES extraction task, and a decoding processing task.
(Appendix 7)
A main task execution determination procedure for determining whether a main task related to decoding of a compressed stream has been executed;
A sleep count procedure for incrementing a sleep count if it is determined that the primary task has not been executed;
When it is determined that the main task has been executed, a sleep count initialization procedure for clearing the sleep count to zero;
A sleep determination procedure for determining whether the state is in operation and the sleep count exceeds a sleep transition threshold;
A sleep control method comprising: a sleep state transition procedure for transitioning to a sleep state when the sleep count exceeds a sleep transition threshold.
(Appendix 8)
An audio decoding device comprising sleep state transition means for transitioning to a sleep state when a main task related to decoding of a compressed stream is not continuously executed a predetermined number of times.

  The present invention is not limited to the specifically disclosed embodiments, and various modifications and changes can be made without departing from the scope of the claims.

It is a block diagram for demonstrating the principle of the audio apparatus which concerns on this invention. It is a flowchart figure for demonstrating the process performed by CPU which concerns on this invention. It is a figure which shows the breakdown of the processing time which paid its attention to 1 frame decoding. It is a figure which shows the processing time timing of several frames. It is a flowchart figure for demonstrating an example of the process by a sleep operation | movement detection task. It is a flowchart for demonstrating the other example of the process by a sleep operation | movement detection task. It is a figure which shows the example of a sleep state at the time of performing the process by the sleep operation | movement detection task shown in FIG. It is a figure which shows the example of the sleep state at the time of performing the process by the sleep operation | movement detection task shown in FIG.

Explanation of symbols

110 CPU and main memory 112 PES buffer 114 ES buffer 116 Temporary buffer 120 DMA transfer circuit 130 SDRAM
TSK1 PES transfer task TSK2 ES extraction task TSK3 decode processing task TSK4 PCM transfer task TSK5 PCM output task

Claims (4)

A main task execution determining means for determining whether the main task of the said decoding is performed by the CPU to decode the compressed stream,
A sleep count means for incrementing a sleep count when it is determined that the main task has not been executed;
When the sleep count is incremented by the sleep count means, the maximum number of times determination means for determining whether or not the number of times that the main task is continuously executed is larger than the maximum number of times that the main task is continuously executed. When,
When it is determined that the number of times that the main task has been continuously executed is greater than the maximum number of times that the main task has been executed continuously, maximum number substituting means for substituting the number of times into the maximum number of times,
When it is determined that the main task has been executed, sleep count initialization means for clearing the sleep count to zero,
The current state is a during the operation of the CPU, and the maximum number of times the main task was run continuously at the time of transition to a previous sleep state to the sleep transition threshold, the sleep count is the sleep Sleep determination means for determining whether or not the transition threshold is exceeded;
A sleep state transition means for transitioning to a sleep state when the sleep count exceeds a sleep transition threshold ;
When the sleep state is canceled, a buffer capacity determination unit that determines whether or not a buffer for storing the decoded stream for outputting audio has a predetermined capacity or more;
An audio decoding device comprising: threshold value substitution means for substituting the maximum number of times the main task has been continuously executed into the sleep transition threshold value when the buffer has a predetermined capacity or more . The audio decoding device according to claim 1, further comprising: a predetermined value substituting unit that substitutes a constant value into the sleep transition threshold when the buffer does not have a predetermined capacity or more. 3. The audio decoding apparatus according to claim 1, wherein the main tasks include a PES transfer task, an ES extraction task, and a decoding processing task. A main task execution determination procedure for determining whether or not a main task related to the decoding has been executed by a CPU that decodes the compressed stream;
A sleep count procedure for incrementing a sleep count if it is determined that the primary task has not been executed;
When the sleep count is incremented by the sleep count procedure, the maximum number of times determination procedure for determining whether the number of times that the main task is continuously executed is larger than the maximum number of times that the main task is continuously executed When,
If it is determined that the number of times that the main task has been continuously executed is greater than the maximum number of times that the main task has been continuously executed, a maximum number of times substitution procedure for substituting the number of times into the maximum number of times,
When it is determined that the main task has been executed, a sleep count initialization procedure for clearing the sleep count to zero;
The maximum number of times the main task is continuously executed when the current state of the CPU is in operation and the previous transition to the sleep state is defined as a sleep transition threshold, and the sleep count is the sleep count. A sleep determination procedure for determining whether or not the transition threshold is exceeded;
A sleep state transition procedure for transitioning to a sleep state if the sleep count exceeds a sleep transition threshold; and
When the sleep state is released, a buffer capacity determination procedure for determining whether or not the buffer for storing the decoded stream for audio output has a predetermined capacity or more;
A sleep control method in an audio decoding device, comprising: a threshold value substituting procedure for substituting the maximum number of times the main task has been continuously executed into the sleep transition threshold value when the buffer has a predetermined capacity or more .

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