JP2010041352A - Device and method for decoding image - Google Patents

Abstract

In an image decoding apparatus that performs decoding processing by operating a plurality of processors in parallel, an image decoding apparatus capable of reducing a processor idle time and decoding a compressed image at a higher speed is provided.
An image decoding apparatus has a plurality of decoding means (108, 109) for decoding an input signal for each predetermined data unit (for example, one frame), and the input signal decoding processing has a dependency relationship of processing order. And a task control unit (105) that divides the data into a plurality of processing steps and assigns a data unit to be processed by the decoding unit for each processing step. The task control means (105) detects the processing status of the decoding means (108, 109), and determines the data unit to be processed and the processing step according to the processing status and the dependency relationship between the processing steps. 108, 109).
[Selection] Figure 1

Description

  The present invention relates to an image decoding apparatus and method for decoding an image compression stream at high speed.

  Conventionally, as a technique for decoding an image stream compressed using MPEG2 or H.264 / AVC at a high speed, when decoding using a plurality of processors, the decoding process is divided into slices for each processor. A technique for assigning and processing in parallel is generally known. However, this method cannot be applied unless one frame is divided into a plurality of slices. When one frame is not divided into a plurality of slices, the decoding process is divided for each frame and processed in parallel by each processor. Is used.

  On the other hand, there may be a dependency relationship between the compressed frames. For example, in the MPEG2 standard, an I frame can be decoded independently without depending on other frames, but a P frame is decoded with reference to the I frame, and a B frame is decoded with reference to the I frame or P frame. The That is, the compressed frames can be grouped according to the dependency relationship with other frames at the time of decoding processing.

  For example, it can be classified into three groups, group A, group B, and group C. For example, a frame that does not refer to another frame, such as an I frame, belongs to the group A. The group B belongs to a frame that refers to another frame such as a P frame and can be referred to from another frame. In group C, for example, a frame such as a B frame that refers to another frame but is not referred to by another frame belongs.

  That is, the frame belonging to group A does not depend on the decoding result of any group frame, but the frame belonging to group B depends on the decoding result of the frame belonging to group A, as long as the referenced frame is not decoded. It cannot be decrypted. In addition, frames belonging to group C also depend on the decoding results of frames belonging to group A and group B, and cannot be decoded unless the frame to be referenced is decoded.

  Therefore, there is no dependency relationship between the frames belonging to group C, and the decoding processing of each frame can be performed in parallel. However, the decoding process of a frame belonging to group A and the decoding process of a frame depending on the frame cannot be performed in parallel. For this reason, while one processor is performing such a process that cannot be performed in parallel, the other processors are in an idle state that is waiting for processing.

  In order to decode a frame having a dependency relationship, an image decoding method (see Patent Document 1) that determines the sharing of parallel processing performed by each processor according to the dependency relationship of each frame has been proposed. Also, when decoding bi-predictive encoded frames, one frame is divided into a plurality of slices and processed in parallel, and frames encoded using other methods are processed in parallel for each frame. A decoding method (see Patent Document 2) has also been proposed. In this way, the processor idle time is reduced.

JP 2000-295616 A JP 2005-175997 A

  Even when the conventional image decoding method as described above is used, the processor may be idle for a long time. Hereinafter, such an example will be described with reference to FIG.

  In the example of FIG. 8, a case is considered where decoding is performed using four processors in parallel. The frames to be decoded are a total of six frames from frame 0 to frame 5, and one frame is composed of one slice. Frame 0 belongs to group A to which a frame that does not depend on the decoding results of other frames belongs. Frame 3 refers to another frame, and belongs to group B to which a frame that can be referenced from another frame belongs, and refers to frame 0. Frames 1, 2, 4, and 5 refer to other frames, but belong to group C to which frames that are not referred to by other frames belong, and refer to frames 0 and 3. It is assumed that the time required for the decoding process of each frame is equal.

  Since frames 1 to 5 refer to frame 0, the decoding processing of these frames cannot be started until the decoding processing of frame 0 is completed. As a result, while decoding frame 0, three of the four processors are idle. After the frame 0 decoding process is completed, frame 3 can be decoded. Here, since frames 1, 2, 4, and 5 refer to frame 3, the decoding process for these frames cannot be started until the decoding process for frame 3 is completed. Therefore, while decoding frame 3, three of the four processors are idle. After the decoding process of frame 3 is completed, parallel processing of frames 1, 2, 4, and 5 becomes possible. Thus, 50% of the time required for the entire process is idle time. That is, there is a problem that only 50% of the processor capacity can be utilized.

  The present invention has been made to solve the above-described problems, and the object of the present invention is to reduce the time during which a processor is in an idle state in a decoding process in which a plurality of processors are operated in parallel, and to increase the speed. An object of the present invention is to provide an image decoding apparatus capable of decoding a compressed image.

In a first aspect of the present invention, there is provided an image decoding apparatus that uses a compressed image stream as an input signal and decodes the input signal.
The image decoding apparatus should divide the input signal decoding process into predetermined data units and the decoding process of the input signal into a plurality of processing steps having processing order dependency and process the decoding unit by the decoding unit. Task control means for assigning a data unit for each processing step. The task control means detects the processing status of the decoding means, and assigns the data unit to be processed and the processing step to the decoding means according to the processing status and the dependency between the processing steps.

  In the second aspect of the present invention, a step of inputting a compressed image stream as an input signal, a step of dividing a decoding process of the input signal input into a plurality of processing steps having a processing order dependency, In the decoding means, the step of decoding the input signal for each predetermined data unit in the processing step unit, the processing status of the decoding means is detected, and the detected processing status and the dependency between the processing steps are determined. Thus, there is provided an image decoding method including a step of determining a data unit and a processing step to be processed in the decoding means.

  In a third aspect of the present invention, there is provided a control program for an image decoding apparatus that uses a compressed image stream as an input signal and decodes the input signal. The control program includes a procedure for inputting a compressed image stream as an input signal, a procedure for dividing a decoding process of the input signal input into a plurality of processing steps having processing order dependency, and a plurality of decoding means. A procedure for executing the decoding process on the input signal for each predetermined data unit in units of processing steps, and detecting the processing status of the decoding means, and processing in the decoding means according to the detected processing status and the dependency between the processing steps. The control unit of the image decoding apparatus executes the procedure for determining the data unit and the processing step.

  ADVANTAGE OF THE INVENTION According to this invention, the idle time at the time of performing an image decoding process in parallel using a some processor can be reduced, and the speed-up of the decoding process of a compressed image can be achieved.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

(Embodiment 1)
The image decoding apparatus according to the present embodiment receives a video byte stream compressed by an encoding method such as H.264, and decodes and outputs a digital image.

1 Configuration of Image Decoding Device FIG. 1 shows the configuration of an image decoding device according to this embodiment. The image decoding apparatus 101 inputs a byte stream via the input terminal 102 and outputs a digital image obtained by decoding via the output terminal 103.

  In the image decoding apparatus 101, the stream buffer 104 buffers the input byte stream. First and second decoding units (hereinafter simply referred to as “decoding units”) 108 and 109 perform image decoding processing in units of slices. The first decoding unit 108 and the second decoding unit 109 can perform parallel processing. The task control unit 105 is executed by the decoding units 108 and 109 to control the decoding process based on the decoding process step (described later) and the slice type. The intermediate buffer 106 holds coefficient data, prediction data, and difference images generated during the decoding process. The frame buffer 107 holds a finally obtained decoded image. Details of the task control unit 105 and the decoding units 108 and 109 will be described later.

1.1 Image Decoding Process Steps and Slice Types In the image decoding apparatus according to the present embodiment, the decoding process for one frame is divided into three steps (stages): an arithmetic decoding process, a difference image generating process, and a decoded image generating process. .

  The arithmetic decoding process is a process for decoding coefficient data necessary for creating a difference image from an input byte stream and prediction data such as a prediction mode and a motion vector necessary for creating a prediction image. This process has no dependency between frames or steps.

  The difference image creation process is a process for creating a difference image by performing inverse quantization, inverse discrete cosine transform, or the like on coefficient data. Although there is no dependency between frames in this process, there is a dependency between steps because necessary coefficient data needs to be decoded by the arithmetic decoding process.

  In the decoded image creation process, a predicted image is created from the predicted data and a decoded image necessary for reference, and a decoded image is created by combining the predicted image and the difference image. In this process, necessary prediction data is decoded by arithmetic decoding processing, necessary difference images are created by difference image creation processing, and necessary decoded images are created when reference is required. It is necessary to be. Therefore, there is a dependency between frames and between steps.

  Furthermore, the slice is classified into three types based on the dependency between frames. As described above, the type of slice constituting a frame belonging to group A to which a frame that does not refer to another frame belongs is referred to as “slice A”. A type of a slice constituting a frame belonging to group B to which another frame is referenced and a frame that can be referenced from another frame belongs is referred to as “slice B”. The type of slice that constitutes a frame belonging to group C that refers to another frame but is not referred to by another frame is referred to as “slice C”.

1.2 Task Control Unit The task control unit 105 is connected to decryption units 108 and 109. Each of the decoding units 108 and 109 can take two states, a standby state and a processing state. In addition, the task control unit 105 stores therein a task list 15 for managing tasks to be decrypted and executed by the decrypting units 108 and 109. The task list 15 manages the decoding parameter set as one element. The decoding parameter set is a set of parameters necessary for the decoding process, and specifically includes the following information.
-Slice type (information indicating the type of slice)
-Task (information indicating the type of decryption process executed by the decryption unit)
Slice data pointer (information indicating the storage position of slice data on the stream buffer 104)
Coefficient data pointer (information indicating the storage position of coefficient data on the intermediate buffer 106)
Prediction data pointer (information indicating the storage position of prediction data in the intermediate buffer 106)
Difference image pointer (information indicating the storage position of the difference image on the intermediate buffer 106)

  FIG. 2A shows an example of the task list 15. In addition to the parameter set, the task list 15 manages the element number that identifies the parameter set and the priority for processing the parameter set in association with each other.

  The task control unit 105 has a priority table 16. An example of the priority table 16 is shown in FIG. The priority table 16 defines the priority of each step in the decoding process according to the slice type. As described above, depending on the dependency between steps, the arithmetic decoding process, the difference image creation process, and the decoded image creation process need to be preferentially processed. In addition, it is necessary to preferentially process slice type A, slice type B, and slice type C in order of dependency between frames. The priority table 16 defines the priority of each step according to the slice type in consideration of the dependency between steps and between frames.

  The task control unit 105 can take a plurality of states. FIG. 3 shows the state transition of the task control unit 105. As shown in the figure, the task control unit 105 has five states: an initial state, a stream analysis state, a task allocation state, a task completion waiting state, and a task addition state. Hereinafter, each state of the task control unit 105 will be described.

  In the initial state, the number of elements in the task list 15 is set to zero. When a necessary byte stream can be read from the stream buffer 104, the initial state shifts to the stream analysis state.

  In the stream analysis state, the task control unit 105 searches for the byte stream read from the stream buffer 104 from the top, and detects all slices included in the byte stream. Each time a slice is detected, a new decoding parameter set is added to the task list 15. In the new decoding parameter set, the slice type is set to the detected slice type, the task is set to the arithmetic decoding process, and the slice data pointer is set to the data start position of the detected slice. When all the read byte streams are searched and all decoding parameter sets are added to the task list 15, the task assignment state is entered.

  In the task assignment state, when the number of elements in the task list 15 is 0, the state transitions to the initial state. Otherwise, first, the priority of each decoding parameter set included in the task list 15 is determined with reference to the priority table 16 shown in FIG. Then, when both of the decoding units 108 and 109 are in the standby state, the task control unit 105 outputs the decoding parameter set having the highest priority to the first decoding unit 108 and the decoding parameter having the second highest priority. The set is output to the second decoding unit 109, and then transitions to a task completion waiting state. If either one of the decoding units 108 and 109 is in the standby state, the task control unit 105 outputs the decoding parameter set having the highest priority to the decoding unit in the standby state, and transitions to the task completion waiting state. To do.

  However, when there are a plurality of decryption parameter sets having the same priority in the task list 15, the one with the earlier order added to the task list is prioritized. In addition, a decoding parameter set whose slice type is slice B and whose task is decoded image creation processing is not output to the decoding units 108 and 109 when the decoded image creation processing of slice A is not completed. In addition, a decoding parameter set whose slice type is slice C and whose task is decoded image creation processing is not output to the decoding units 108 and 109 when the decoded image creation processing of slice B is not completed. In these cases, the decoding parameter set having the next highest priority is output to the decoding units 108 and 109.

  In the task completion waiting state, the system waits until a decoding parameter set is input from the first decoding unit 108 or the second decoding unit 109. When a decoding parameter set is input from the first decoding unit 108 or the second decoding unit 109, the state transits to a task addition state. In a state other than the task completion waiting state, the input decryption parameter set of the task list enters the queue and is processed when the task control unit 105 transitions to the task completion waiting state next.

  In the task addition state, when the “task” included in the input decoding parameter set is a decoded image creation process, the task control unit 105 does nothing and transitions to the task assignment state. In other cases, the task control unit 105 adds a new decoding parameter set as an element to the task list, and transitions to the task assignment state. When the “task” included in the input decoding parameter set is an arithmetic decoding process, “task” is set to the differential image creation process in the new decoding parameter set. “Task” is set in the decoded image creation processing. Information other than the “task” included in the new decoding parameter set is the same as that of the input decoding parameter set.

1.3 Decoding Unit The decoding units 108 and 109 have two states: a standby state and a processing state. The initial state is a standby state. The standby state is a state in which a decoding parameter set is waiting to be input. When the decoding parameter set is input, the decoding units 108 and 109 transition from the standby state to the processing state. In the processing state, the operations of the decoding units 10 and 109 vary depending on the tasks included in the input decoding parameter set. Hereinafter, the operation in the processing state, which differs depending on the task, will be described.

  When the task is an arithmetic decoding process, the decoding units 108 and 109 read the byte stream from the address on the stream buffer 104 indicated by the slice data pointer included in the input decoding parameter set, and decode the coefficient data and the prediction data. Write to the intermediate buffer 106. Subsequently, the decoding units 108 and 109 output a new decoding parameter set, and transition to a standby state. In the new decoding parameter set, the coefficient data pointer and the prediction data pointer are set to the pointers to the coefficient data and the prediction data written in the intermediate buffer 106, respectively, and information other than the coefficient data pointer and the prediction data pointer is inputted decoding Set to the same as in the parameter set.

  When the task is a difference image creation process, the decoding units 108 and 109 read the coefficient data from the address on the intermediate buffer 106 indicated by the coefficient data pointer included in the input decoding parameter set, create a difference image, Write to buffer 106. Subsequently, the decoding units 108 and 109 output a new decoding parameter set, and transition to a standby state. In the new decoding parameter set, the difference image pointer is set to a pointer to the difference image written in the intermediate buffer 106, and information other than the difference image pointer is set to be the same as that in the inputted decoding parameter set.

  When the task is a decoded image creation process, the decoding units 108 and 109 read prediction data from the address on the intermediate buffer 106 indicated by the prediction data pointer included in the input decoding parameter set. Next, the decoding units 108 and 109 read out a decoded image that has already been decoded and is necessary for creating a prediction image from the frame buffer 107 based on the read prediction data, and the difference image read out from the intermediate buffer 106 is read as this decoded image. To create a decoded image. The created decoded image is written into the frame buffer 107. Subsequently, the decoding units 108 and 109 output the input decoding parameter set as it is, and transition to a standby state.

2 Parallel Decoding Operation The decoding operation of the image decoding apparatus 101 of the present embodiment configured as described above will be described. In the following description, the following points are assumed. The image decoding apparatus 101 has a byte stream composed of one GOP (Group of Pictures) including six frames in the order of I frame, B frame, B frame, P frame, B frame, and B frame as shown in FIG. To decode all frames. Each frame is composed of one slice. The GOP in FIG. 4 includes one slice A, one slice B, and four slices C. All the referenced images are included in the same GOP.

  In the image decoding apparatus 101, the byte stream input via the input terminal 102 is written into the stream buffer 104. As a result, the byte stream to be decoded can be read from the stream buffer 104, and the task control unit 105 transitions from the initial state to the stream analysis state.

  In the stream analysis state, the task control unit 105 reads and analyzes the byte stream from the stream buffer 104, adds a new decoding parameter set to the task list 15, and transitions to the task assignment state. The state of the task list 15 in this state is shown in FIG. 5A. In FIG. 5A, for convenience of explanation, only the element number indicating the order of the decoding parameter set, the slice type and task included in each decoding parameter set, and the priority of each decoding parameter set are shown (the followings). The same applies to FIGS. 5B to 5G). The slice data pointer of each decoding parameter set is set as the data start position of each slice.

  In the task assignment state, the task control unit 105 outputs the decoding parameter set (E1 in this example) having the highest priority in the task list 15 to the first decoding unit 108, and the parameter having the second highest priority. The set (E4 in this example) is output to the second decoding unit 109. Next, the task control unit 105 deletes the output two decryption parameter sets from the task list 15 and transitions to a task completion waiting state.

  A decoding parameter set is input to the first decoding unit 108 and the second decoding unit 109, and a transition is made from the standby state to the processing state.

  In the processing state, the decoding units 108 and 109 perform arithmetic decoding processing with reference to the input decoding parameter set, and then output the decoding parameter set to the task control unit 105 and shift to a standby state. In the decoding parameter set to be output, the coefficient data pointer and the prediction data pointer become pointers to the coefficient data and the prediction data obtained by the arithmetic decoding process, respectively. Here, it is assumed that the first decoding unit 108 completes the process first and outputs a decoding parameter set, and the second decoding unit 109 outputs the decoding parameter set immediately thereafter.

  First, the decoding parameter set is input from the first decoding unit 108 to the task control unit 105, and the task control unit 105 transits to a task addition state. Since the “task” of the input decoding parameter set is an arithmetic decoding process, the information other than “task” is the same as that in the input decoding parameter set. Therefore, a new decoding parameter set in which the difference image creation processing is set in “task” is added to the task list 15, and the task assignment state is entered. The task list 15 at this time is shown in FIG. 5B. As shown in FIG. 5B, since the decoding parameter set with the highest priority in the task assignment state is E7, E7 is output to the first decoding unit 108, and E7 is deleted from the task list. Thereafter, the task control unit 105 transitions to a task completion waiting state.

  Next, when a decryption parameter set is input from the second decryption unit 109, the task control unit 105 transitions to the task addition state again. In the task addition state, a new decryption parameter set is added to the task list 15 in the same manner, and the state transitions to the task assignment state again. The task list 15 at this time is shown in FIG. 5C. E8 having the highest priority is output to the second decoding unit 109, and E8 is deleted from the task list 15. Thereafter, the state transits to a task completion waiting state.

  Each of the first and second decoding units 108 and 109 enters the processing state again when the decoding parameter set is input from the task control unit 105. The input decoding parameter set is referred to, a difference image creation process is performed, and then a new decoding parameter set is output to the task control unit 105 to shift to a standby state. The difference image pointer in the new decoding parameter set is a pointer to the difference image obtained by the difference image creation process. Here, it is assumed that the first decoding unit 108 completes the process first and outputs a new decoding parameter set, and the second decoding unit 109 outputs a new decoding parameter set immediately thereafter.

  The task control unit 105 first receives a decoding parameter set from the first decoding unit 108, and transitions to a task addition state. Since the “task” of the input decoding parameter set indicates a differential image creation process, information other than the task is the same as that in the input decoding parameter set. A new decoding parameter set in which the decoded image creation processing is set in “task” is added to the task list, and the task assignment state is entered. The task list at this time is shown in FIG. 5D. As shown in FIG. 5D, since the decoding parameter set with the highest priority is E9 in the task assignment state, E9 is output to the first decoding unit 108, and E9 is deleted from the task list. After that, the task transitions to a task completion wait state.

  Next, when a decryption parameter set is input from the second decryption unit 109, the task control unit 105 transitions to the task addition state again. Similarly, a new decryption parameter set is added to the task list 15, and a transition is made to the task assignment state. The task list at this time is as shown in FIG. 5E. The decoding parameter set with the highest priority is E10. On the other hand, the decoded image creation process for slice B cannot be executed unless the decoded image creation process for slice A is completed. For this reason, E2 having the next highest priority and being added to the task list is output to the second decryption unit 109, and E2 is deleted from the task list. After that, the task transitions to a task completion wait state.

  Here, when the decoding parameter set is input, the first decoding unit 108 enters the processing state again. The first decoding unit 108 performs a decoded image creation process with reference to the input decoding parameter set, and then outputs the input decoding parameter set as it is to the task control unit 105 and transitions to a standby state. To do.

  The decoding parameter set is also input to the second decoding unit 109, and the processing state is entered again. Arithmetic decoding processing is performed with reference to the input decoding parameter set, and then, a new decoding parameter set is output to the task list 15 to the task control unit 105 to shift to a standby state. The coefficient data pointer and the prediction data pointer of the new decoding parameter set are pointers to data storing the result of the arithmetic decoding process. It is assumed that the new decoding parameter set is output after the first decoding unit 108 outputs the decoding parameter set.

  When a decryption parameter set is first input from the first decryption unit 108 to the task control unit 105, the task control unit 105 transitions to a task addition state. Since the “task” in the input decoding parameter set is “decoded image creation processing”, the task assignment state is entered without doing anything. The task list 15 at this time is as shown in FIG. 5F. In the task assignment state at this time, the decoding parameter set with the highest priority is E10, and the decoded image creation processing for slice A has already been completed. Therefore, the task control unit 105 sends E10 to the first decoding unit 108. And E10 is deleted from the task list 15. Thereafter, the state transits to a task completion waiting state.

  Next, the task control unit 105 receives the decoding parameter set from the second decoding unit 109, and transitions to the task addition state again. Similarly, a new decryption parameter set is added to the task list, and the task assignment state is entered. The task list 15 at this time is as shown in FIG. 5G. There are three decoding parameter sets with the highest priority, E3, E5, and E6. In such a case, the task control unit 105 outputs E3 registered first in the task list 15 to the second decryption unit 109, and deletes E3 from the task list 15. Thereafter, the state transits to a task completion waiting state.

  Thereafter, the decoding process of slice C is repeated in the same manner, decoding of 1 GOP is completed, and output from the output terminal 103 is performed.

  By the above method, the decoding process of the frame belonging to the group B and the frame belonging to the group C can be started even before the decoding process of the frame belonging to the group A is completed, and the idle time of the decoding unit (processor) is reduced. It can be reduced.

  In the present embodiment, the number of decoding units has been described as two, but may be three or more. In the present embodiment, the number of slices included in one frame has been described as 1. However, two or more slices may be used.

  Also, in this embodiment, an example of decoding all 1 GOP is given, but the stream buffer 104 may buffer only the necessary byte stream, or the task control unit 105 may not output an unnecessary decoding parameter set. Good. As a result, any one frame can be decoded. It is also possible to decode a plurality of GOPs together.

(Embodiment 2)
The image decoding apparatus according to the present embodiment receives, for example, a video byte stream compressed by an encoding method such as H.264, and outputs a decoded digital image. FIG. 6 shows the configuration of the image decoding apparatus in the present embodiment. Also in the present embodiment, as in the first embodiment, the decoding process for one frame is divided into three steps: an arithmetic decoding process, a difference image creating process, and a decoded image creating process.

  The image decoding apparatus 201 has the same function as the image decoding apparatus 101 described in Embodiment 1, and receives a byte stream from the input terminal 202 and outputs a digital image from the output terminal 203. The stream buffer 204, task control unit 205, intermediate buffer 206, and frame buffer operate in the same manner as the stream buffer 104, task control unit 105, intermediate buffer 106, and stream buffer 104 described in the first embodiment. Also, the first decoding unit 208 to the fourth decoding unit 211 operate in the same manner as the first decoding unit 108 and the second decoding unit 109 described in the first embodiment.

  FIG. 7 shows frames and steps processed by the first to fourth decoding units 208 to 211 in the present embodiment. Regarding the numbers in parentheses in the figure, the numbers before the parentheses indicate the frame numbers of the frames to be processed, and the numbers after the numbers indicate steps in the decoding process. The steps in the decoding process are “0” for the arithmetic decoding process, “1” for the difference image creating process, and “2” for the decoded image creating process. For example, the first process performed by the first decoding unit 208 is indicated as (0, 0) in the drawing, which indicates “arithmetic decoding process” of “frame 0”. Compared with the conventional case of FIG. 8, it can be understood that the time during which the decoding unit is in the idle state is significantly reduced, and the time required for the entire process is also reduced.

  The functions of the image decoding apparatus described in the first and second embodiments may be realized by hardware such as an electronic circuit, or may be realized by a combination of a computer such as a CPU and a control program (software). Good.

  According to the image decoding apparatus of the present invention, even when there is a dependency relationship between frames, the processor idle time can be shortened and the decoding process can be performed at a high speed. Etc. are effective.

Block diagram of an image decoding apparatus according to Embodiment 1 of the present invention (A) The figure which shows the structure of a task list, (b) The figure which shows the priority table which manages the priority of the task for every slice type State transition diagram of task controller The figure which showed an example of the byte stream input into an image decoding apparatus Diagram for explaining changes in task list (part 1) Diagram for explaining changes in task list (2) Illustration for explaining changes in task list (Part 3) Diagram for explaining changes in task list (Part 4) Diagram for explaining changes in task list (Part 5) Illustration for explaining changes in task list (Part 6) Diagram for explaining changes in task list (Part 7) Block diagram of an image decoding apparatus according to Embodiment 2 of the present invention The figure explaining the frame and step which each decoding part processes in Embodiment 2. The figure explaining the frame which each processor decodes in the conventional parallel decoding process

Explanation of symbols

15 Task list 16 Priority table 101, 201 Image decoding device 102, 202 Input terminal 103, 203 Output terminal 104, 204 Stream buffer 105, 205 Task control unit 106, 206 Intermediate buffer 107, 207 Frame buffer 108, 109, 208- 211 Decoding unit

Claims (9)

An image decoding apparatus that uses a compressed image stream as an input signal and decodes the input signal,
A plurality of decoding means for decoding the input signal for each predetermined data unit;
A task control unit that divides the decoding process of the input signal into a plurality of processing steps having processing order dependency, and assigns a data unit to be processed by the decoding unit for each processing step;
The task control means detects a processing status of the decoding means, and assigns a data unit to be processed and a processing step to the decoding means according to the processing status and a dependency relationship between processing steps.
An image decoding apparatus characterized by that. The task control unit further assigns a data unit to be processed and a processing step to the decoding unit in consideration of a dependency relationship between frames included in the image stream.
The image decoding apparatus according to claim 1.   The image decoding apparatus according to claim 1, wherein the dependency relationship between the frames is a relationship as to whether or not other frames are referred to and whether or not other frames can be referred to. Considering the dependency between frames and the dependency between processing steps, further comprising priority information defining the order of data units to be preferentially processed,
3. The image decoding apparatus according to claim 2, wherein the task control unit assigns a data unit to be processed and a processing step to the decoding unit with reference to the priority information. The plurality of processing steps include an arithmetic decoding step of decoding prediction data such as a prediction mode and a motion vector necessary for creating a coefficient image and a prediction image necessary for creating a difference image from the input byte stream When,
A processing difference image creation step for creating a difference image by applying inverse quantization or inverse discrete cosine transform to the coefficient data;
The image decoding apparatus according to claim 1, further comprising: a decoded image generating step of generating a predicted image from the predicted data and a decoded image necessary for reference, and generating a decoded image by combining the predicted image and the difference image.   The image decoding apparatus according to claim 1, wherein the predetermined data unit is a frame or a slice.   The encoding method of the image stream is H.264. The image decoding device according to claim 1, wherein the image decoding device is H.264. Inputting a compressed image stream as an input signal;
Dividing the input input signal decoding process into a plurality of processing steps having processing order dependency;
In a plurality of decoding means, a step of performing decoding processing of the input signal in units of the processing steps for each predetermined data unit;
Detecting a processing status of the decoding means, and determining a data unit and a processing step to be processed in the decoding means according to the detected processing status and a dependency between processing steps. An image decoding method. A control program for an image decoding apparatus that uses a compressed image stream as an input signal and decodes the input signal,
A procedure for inputting a compressed image stream as an input signal;
A procedure for dividing the input input signal decoding process into a plurality of processing steps having processing order dependency;
In a plurality of decoding means, a procedure for executing the decoding process in units of the processing steps for each predetermined data unit of the input signal;
Control of the image decoding apparatus detects the processing status of the decoding means, and determines the data unit and processing steps to be processed in the decoding means according to the detected processing status and the dependency between the processing steps. A program that is executed by a means.

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