JP2000138898A - Decoding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decode an audio coded signal and a still image coded signal within a limited arithmetic capability by dividing decode processing of a still image into 1st to n-th processing sets in advance so as to satisfy a specific condition. SOLUTION: Decoding processing of a still image coded signal is divided, e.g. into 1st to 3rd processing sets, variable length decoding processing for a video bit steam is employed for the 1st processing, inverse quantization processing is employed for the 2nd processing, and iDCT processing is employed for the 3rd processing. Let an arithmetic quantity per unit time Tf required for decoding an audio coded signal be A, and let an arithmetic quantity required for the i-th processing (1<=i<=3) be Vi, then an arithmetic quantity P per unit time Tf permitted for an arithmetic means in common to decode the audio coded signal and the still image coded signal is to satisfy the relation P>=A+Vi with respect to all the variable (i). When the value P does not satisfy this relation, the decoding processing for the still image is divided further.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a decoding method for decoding an audio coded signal and a still picture coded signal while using common arithmetic means in a time division manner.

[0002]

2. Description of the Related Art In recent years, a so-called "AV one-chip decoder LSI" in which audio signal processing and video signal processing are integrated into one chip has been developed. This LSI realizes a decoding method that allows real-time processing of audio signal processing and video signal processing to be performed substantially in parallel with limited computing power.

For example, in a DVD video which has already been commercialized, moving images and audio are recorded on a disk-shaped medium. In the compression mode, the audio signal is sampled at 48 kHz, and in the non-compression mode, the audio signal is sampled at 96 kHz. Many of them are
The decoding of the audio and the decoding of the moving image are performed using a common arithmetic unit in a time-division manner. In other words, these LSIs have an arithmetic capability capable of reproducing audio and moving images without interruption in real time. When the amount of operation per unit time required to reproduce audio is A, and the amount of operation per unit time required to reproduce a moving image is V, the operation capacity Pav per unit time of the operation means is , At least Pav ≧ A + V
It is necessary to satisfy the relationship. For example, if the time corresponding to one frame of an image is defined as one unit time, the moving image is decoded by one frame and the audio is decoded by the time length in one unit time.

FIG. 3 shows this state. The horizontal axis in FIG. 3 is time, and one scale is one unit time Tf, that is, time corresponding to one frame of an image. The vertical axis indicates the amount of calculation per unit time. The broken line in the figure indicates the amount of calculation (A) per unit time Tf for decoding the audio encoded signal. The thin solid line in the figure indicates the value (A + V) obtained by adding the amount of operation per unit time for decoding the encoded video signal to the amount of operation per unit time for decoding the audio encoded signal. ing. The thick solid line in the figure indicates the computing capacity per unit time of the computing means (Pav).
Is shown. As described above, the calculation means needs to have a calculation capability such that the solid line indicating Pav always comes above the solid line indicating (A + V).

However, in recent years, the DVD audio standard has been standardized so that only audio and still images are handled. If the number of audio channels is 2, A
When the V1 chip decoder LSI decodes an audio encoded signal and a still image encoded signal, the arithmetic means has sufficient arithmetic capability. When a still image encoded signal exists in the input encoded signal, one unit time Tf
In this case, a still image encoded signal for one frame and an audio encoded signal for the time length are decoded. This is shown in FIG. In this figure, it is assumed that still image data is output at times T1 and T2, and the decoding process of the still image data can be completed within one unit time Tf.

[0006]

However, for example, when outputting multi-channel audio data having a sampling frequency of 96 kHz, a huge amount of computation is required for processing the audio encoded signal itself. Therefore, as shown in FIG. 5, there is a case where a still picture code signal (one frame) cannot be decoded within one unit time. Time T1 or T2
In (2), the sum of the amount of operation per unit time Tf for decoding an encoded audio signal and the amount of operation for decoding a still image encoded signal exceeds the arithmetic capability Pav of the arithmetic means. .

SUMMARY OF THE INVENTION The present invention has been made in view of such a conventional problem, and uses an audio coded signal and a still picture coded signal while using a time-divisional operation means of a limited operation amount. It is an object of the present invention to realize a decoding method that can decode.

[0008]

In order to solve the above-mentioned problems, the invention of claim 1 of the present application provides an audio encoded signal and a still picture encoded signal which are multiplexed by time division processing by common operation means. , And when the decoding process of the still image coded signal is divided into a first process,..., And an n-th process, the respective computation amounts are set to V1,. When the amount of operation per unit time required to decode the encoded signal is A and the amount of operation per unit time of the operation means is P, all i
For (1 ≦ i ≦ n), the still image decoding process is divided in advance into first processing,..., N-th processing so that P ≧ A + Vi, and the time T at which the still image is output (N-1) The first process is started before a unit time or more, and the n-th process is completed by the time T.

According to a second aspect of the present invention, in the decoding method of the first aspect, i (1 ≦ i ≦
n) The (ni) process is performed before a unit time.

[0010]

(Embodiment 1) A decoding method according to Embodiment 1 of the present invention will be described with reference to the drawings. In the present embodiment, it is assumed that the decoding process of the still image coded signal is divided from the first process to the third process, the first process is a variable length decoding process of a video bit stream, and the second process is Inverse quantization processing, and the third processing is ID
This is a CT process.

In this embodiment, the amount of operation per unit time Tf required for decoding an audio coded signal is represented by A, which is necessary for the i-th processing (1 ≦ i ≦ 3). Assuming that the computation amount is Vi, the computation amount P allowed per unit time Tf of the common computation means for decoding the audio encoded signal and the still image encoded signal is P ≧ A + Vi (1) is satisfied. Of course, when P does not satisfy the expression (1), the still image decoding process is further finely divided. For example, when n = 10, all j (1 ≦ j
<10), the following equation (2) P ≧ A + Vj (2) may be satisfied.

In the present embodiment, the input coded signal is a bit stream in which an audio coded signal and a still picture coded signal are multiplexed. It is assumed that a flag F indicating that the flag has been added.

FIG. 1 is a flowchart showing the operation of the decoding method according to the first embodiment. The operators are displayed in C language. In FIG. 1, a variable p is a variable indicating a state of a decoding process of a still image, and when p = 0, it indicates that there is no still image coded signal. Hereinafter, the operation of the decoding method according to the present embodiment will be described with reference to FIG.
Will be described based on the change of

First, in step S1 of FIG.
Is initialized to 0. Next, in step S2, the coded signal is input for one unit time Tf. Next, step S
In 3, it is determined whether the variable p is 0 or not. Since the current variable p is 0, the process proceeds to step S4, and it is determined whether or not the previously input encoded signal includes a still image encoded signal. For this determination, the flag F may be inspected. If the still image encoded signal is not included, the process proceeds to step S7 to decode the audio encoded signal for one unit time. In the next step S8, it is determined whether or not the variable p is 3. Since the current variable p is 0, the process proceeds to step S11, where the previously decoded audio data (PCM
Audio), and returns to step S2.

In step S2, the next coded signal is input for one unit time. Next, in step S3, it is determined whether or not the variable p is 0. Since the variable p is still 0, the process proceeds to step S4, and it is determined whether or not the still image encoded signal is included in the newly input encoded signal. Here, assuming that the still image encoded signal is included, the process proceeds to step S5, and the variable p is incremented. In the next step S6, the p-th (= 1) process in decoding the still image coded signal is performed. Here, the first
Is a variable-length decoding process. Next, step S7
To decode the encoded audio signal. In the next step S8, it is determined whether or not the variable p is 3. Since the current variable p is 1, the process proceeds to step S11, outputs the previously decoded audio data, and returns to step S2 again.

In step S2, the next coded signal is input for one unit time. In the next step S3, the variable p
Is determined to be 0 or not. Since the current variable p is 1,
Proceeding to step S5, the variable p is incremented. In the next step S6, the p-th (= 2) process in decoding the still image coded signal is performed. Here, the second process is a process of inverse quantization. Next, proceed to step S7,
Decode the audio encoded signal. In the next step S8, it is determined whether or not the variable p is 3. The current variable p is 2
Therefore, the process proceeds to step S11, where the previously decoded audio data is output, and the process returns to step S2.

In step S2, the next coded signal is input for one unit time. In the next step S3, the variable p
Is determined to be 0 or not. Since the current variable p is 2,
Proceeding to step S5, the variable p is incremented. In the next step S6, the p-th (= 3) th process in decoding the still image encoded signal is performed. Here, the third process is an iDCT process, and the decoding of the still image is completed. Next, proceeding to step S7, the audio encoded signal is decoded. In the next step S8, the variable p
Is 3 or not. Since the current variable p is 3, the process proceeds to step S9, and the variable p is initialized to 0. In the next step S10, the decoded still image data is output. Then, the process proceeds to step S11, where the previously decoded audio data is output, and the process returns to step S2.

In step S2, the next coded signal is input for one unit time. Next, in step S3, it is determined whether or not the variable p is 0. Since the current variable p has returned to 0, the process proceeds to step S4, and thereafter, the same processing is repeated.

As described above, according to the present embodiment, when the decoding process of the still picture coded signal is divided into the first process,..., And the n-th process, the respective calculation amounts are V1,. , Vn. Also, let A be the amount of operation per unit time required to decode the audio encoded signal, and let P be the amount of operation per unit time allowed by the operation means. At this time, the decoding process of the still image is divided in advance from the first process to the n-th process so that P ≧ A + Vi for all i (1 ≦ i ≦ n), and the time when the still image is output (N-1) of T
The first process is performed before the unit time, and the decoding process of the still image coded signal divided for each unit time is performed to limit the decoding of the audio coded signal and the still image coded signal. It can be performed within the limited computing capacity.

Embodiment 2 Next, a decoding method according to Embodiment 2 of the present invention will be described with reference to the drawings. In the present embodiment, as in the first embodiment, the decoding process of the still image coded signal is divided into first to third processes. Then, the first process is a variable length decoding process of the video bit stream, the second process is an inverse quantization process, and the third process is an iDCT process.

In this embodiment, as in the first embodiment, the amount of calculation per unit time required for decoding an audio coded signal is A, and the i-th processing (1
The calculation amount required for ≦ i ≦ 3) is defined as Vi. At this time, the operation amount P allowed per unit time by the common operation means for decoding the audio encoded signal and the still image encoded signal is a value that satisfies the following expression (3) for all i. Must. P ≧ A + Vi (3) Also, in the present embodiment, the input coded signal is
It is assumed that the audio encoded signal and the still image encoded signal are separated and the time T at which still image data is to be output is known in advance.

FIG. 2 is a flowchart showing the operation of the decoding method according to the second embodiment, in which operators are displayed in C language. In FIG. 2, a variable t is a variable indicating the current processing unit time. FIG. 6 is an explanatory diagram showing an allocation time of an operation for the i-th process when a still image and audio are decoded by the decoding method of the present invention. Hereinafter, FIG.
The operation of the decoding method according to the present embodiment will be described with reference to FIG.

First, a variable t is initialized to 0 in step S20. In the next step S21, the time at which the still image data is output is set to T. For example, here T
= T1 (= 3). In FIG. 6, the time width of one frame of an image is Tf, and the first still image data is output at time T1. In this case, the variable t = 0 is T1-3
It corresponds to the time of Tf.

Next, in step S22, it is determined whether the variable t is larger than T1-3 (= 0) and equal to or smaller than T1 (= 3). Since the current variable t is 0, the process proceeds to step S26 to decode an audio encoded signal for one unit time Tf. Next, the process proceeds to step S27, in which the previously decoded audio data (PCM audio) is output.
In step S28, the variable t is incremented,
It returns to step S22.

Next, in step S22, it is determined whether or not the variable t is greater than T1-3 (= 0) and equal to or less than T1 (= 3). Since the current variable t is 1, the process proceeds to step S23, where the t-th time in the decoding of the still image encoded signal is performed.
The processing of -T1 + 3 (= 1) is performed. Here, as the first processing, variable length decoding is performed within the time Tf from the time (T1-2Tf) in FIG. Next, in step S24,
It is determined whether the variable t is T1 (= 3). Current variable t
Is 1, the process proceeds to step S26 to decode the audio encoded signal for one unit time. Next, step S2
The process proceeds to step S7, where the previously decoded audio data is output. In step S28, the variable t is incremented, and the process returns to step S22.

Next, in step S22, it is determined whether or not the variable t is greater than T1-3 (= 0) and equal to or less than T1 (= 3). Since the current variable t is 2, the process proceeds to step S23, where the t-th time in the decoding of the still image encoded signal is performed.
The processing of -T1 + 3 (= 2) is performed. Here, as the second process, the inverse quantization process is performed within the time Tf from the time (T1-Tf) in FIG. In the next step S24, it is determined whether or not the variable t is T1 (= 3). Since the current variable t is 2, the process proceeds to step S26 to decode the audio encoded signal for one unit time. Next, step S27
Then, the previously decoded audio data is output, the variable t is incremented in step S28, and the process returns to step S22.

Next, in step S22, it is determined whether or not the variable t is greater than T1-3 (= 0) and equal to or less than T1 (= 3). Since the current variable t is 3, the process proceeds to step S23, and the t-th time in decoding the still image encoded signal is performed.
The processing of -T1 + 3 (= 3) is performed. Here, as the third process, the iDCT process is performed within the time Tf from the time T1 in FIG. Thus, the decoding processing of the still image encoded signal is completed. Next, in step S24, it is determined whether the variable t is T1 (= 3). Since the current variable t is 3, the process proceeds to step S25, where the previously decoded still image data is output.

Then, the flow advances to a step S26 to decode the audio coded signal for one unit time. Next, step S2
The process proceeds to step S7, where the previously decoded audio data is output. In step S28, the variable t is incremented, and the process returns to step S22. Next, in step S22,
The variable t is larger than T1-3 (= 0) and T1 (=
3) Determine whether or not: Since the current variable t is 4, the process proceeds to step S26, and the same processing is repeated thereafter, for example, to output the next still image data at time T2 in FIG.

As described above, the decoding process of the still image coded signal is divided into three, the first process is performed two unit times (2Tf) before the time of outputting the still image, and one unit time (1T
f) The second process is performed before, the third process is performed at the time T at which the still image is output, the decoding process is completed, and the still image data is output at the scheduled time.

As described above, according to the present embodiment, when the decoding processing of a still image is divided into the first processing,..., And the n-th processing, the respective calculation amounts are V1,. I do. A is the amount of operation per unit time required to decode the audio encoded signal, and P is the amount of operation per unit time of the operation means. At this time, the decoding process of the still image is divided in advance from the first process to the n-th process so that P ≧ A + Vi for all i (1 ≦ i ≦ n), and the time when the still image is output The first processing is performed before (n-1) unit time before T, and the (ni) th processing is performed before i unit time before time T, and the still image coded signal divided for each unit time By decoding the audio encoded signal and the still image encoded signal,
This can be performed within a limited computing capacity.

[0031]

As described above, according to the present invention, the decoding processing of a still picture coded signal is divided from the first processing to the n-th processing, whereby the audio coded signal and the still picture coded signal are divided. Can be decoded within a limited computing capacity.

[Brief description of the drawings]

FIG. 1 is a flowchart showing an operation of a decoding method according to Embodiment 1 of the present invention.

FIG. 2 is a flowchart showing an operation of a decoding method according to Embodiment 2 of the present invention.

FIG. 3 is an explanatory diagram showing a relationship between a calculation capability of a conventional AV1 chip decoder LSI and a calculation amount.

FIG. 4 is an explanatory diagram showing a relationship between a calculation capability and a calculation amount when a still image and audio data are decoded by a conventional AV1 chip decoder LSI.

FIG. 5 is an explanatory diagram showing a relationship between a calculation capability and a calculation amount when decoding a still image and audio data in a conventional AV1 chip decoder LSI with insufficient calculation capability.

FIG. 6 is an explanatory diagram showing the relationship between the calculation capability and the calculation amount when a still image and audio data are decoded by the decoding method of the present invention.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masahiro Sueyoshi 1006 Kazuma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. 72) Inventor Masaharu Matsumoto 1006 Kadoma Kadoma, Kadoma City, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. 1006, Kadoma, Kadoma Matsushita Electric Industrial Co., Ltd. KA28 5C059 KK07 KK33 MA23 ME01 PP01 RB01 RC32 RC33 SS13 SS30 UA05 5J064 AA02 BA09 BB13 BC02 BD03

Claims (2)

[Claims] 1. A time-sharing process by common arithmetic means,
A decoding method for decoding a multiplexed audio coded signal and a still picture coded signal, wherein the decoding processing of the still picture coded signal is a first processing,.
, V1,..., V
n, the amount of operation per unit time required to decode the audio encoded signal is A, and the amount of operation per unit time of the operation means is P, and all i (1 ≦ 1) For i ≦ n), the still image decoding process is divided in advance into first processing,..., n-th processing so that P ≧ A + Vi, and (n− 1)
A decoding method, wherein the first processing is started before a unit time or more, and the n-th processing is completed by the time T. 2. i at time T when a still image is output (1 ≦ i ≦
2. The decoding method according to claim 1, wherein (n) the (ni) th processing is performed before a unit time.