JPH09205407A - Digital data multiplex device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely select data and to suppress a buffer size to an irreducible minimum in a device for multiplexing the plural kinds of digital data. SOLUTION: The digital data A1-An are respectively written in buffer memories B1-Bn and butter occupancy amount calculation devices O1-On respectively calculate occupancy amounts in the butter memories A1-An. Threshold values are respectively set in the respective buffer occupancy amount calculation devices O1-On, and when the calculated butter occupancy amount exceeds the threshold value, multiplex control signals 5-1 to 5-n for indicating the state are sent to a data selection device 6. The data selection device 6 reads the data in an order from the buffer memory which exceeds the threshold value and outputs the multiplex data 7 of a fixed rate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital data multiplexing device having a function of multiplexing various types of digital data, and more specifically, it is provided in the preceding stage of the multiplexing device when time-division multiplexing various data generated at the same time. The present invention relates to a technique that enables reliable data selection and minimizes the buffer size by using the buffer occupancy in the buffer memory.

[0002]

2. Description of the Related Art In recent years, due to the development of digital transmission technology, the era of multimedia is approaching. For example, in the field of broadcasting, direct television (North America)
Digitalization is progressing as represented by ct TV).

As digitalization progresses with the development of multimedia, it becomes necessary to multiplex various types of digital data. For example, in the case of digital broadcasting, it is necessary to multiplex system data such as system control data and conditional access data in addition to video data and audio data.

In order to time-division-multiplex these digital data, it is necessary to store each digital data temporarily. For that purpose, a buffer memory such as a FIFO or a RAM is required for each data.

[0005]

For example, when video data and audio data are multiplexed, the audio data is kept in the buffer memory while the video data is being selected. If the multiplex selection is wrong, the audio data will overflow from the buffer memory and the data will be lost. In order to prevent the audio data from overflowing the buffer memory, for example, it is conceivable to allow the buffer memory to have a size, but such a configuration increases the cost of the product.

The present invention has been made in view of such circumstances, and an object thereof is to minimize the size of a buffer memory in a device for multiplexing a plurality of types of digital data. Another object of the present invention is to suppress increase or decrease in buffer occupancy in a device that multiplexes multiple types of digital data.

[0007]

In order to solve the above-mentioned problems, a digital data multiplexing apparatus according to the present invention is a digital data multiplexing apparatus for multiplexing a plurality of types of digital data, and the digital data is temporarily stored individually. The temporary storage means for storing and the data selection means for selecting and multiplexing the output of the temporary storage means are provided. In the data selection means, the occupancy amount of at least one temporary storage means set in advance exceeds a threshold value. In this case, the digital data temporarily stored in the temporary storage means is selected.

According to the present invention, the occupancy in at least one predetermined temporary storage means among the temporary storage means for temporarily storing a plurality of types of digital data individually is calculated, and the calculated occupancy amount is used as the threshold value. When the data is exceeded, the data selection means selects the digital data stored in the temporary storage means, so that reliable data selection can be performed.

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows an example of the configuration of a digital data multiplexing apparatus to which the present invention is applied.
This digital data multiplexing device includes a buffer memory B for temporarily storing n different digital data A1 to An.
1 to Bn and buffer occupancy calculation devices O1 to On for calculating data occupancy in the buffer memories B1 to Bn
And the buffer memory B1 based on the multiplex control signals 5-1 to 5-n output from the buffer occupancy calculation devices O1 to On.
To Bn, and a data selection device 6 for selecting the data stored in Bn.

Digital data A1 to An are written in the buffer memories B1 to Bn, respectively. The buffer occupancy calculation devices O1 to On each have a buffer memory A.
The occupancy in each buffer memory is calculated by looking at the write address and read address of the data in 1 to An. Each buffer occupancy calculation device O1 to O
A threshold value is set for each n, and when the calculated buffer occupancy exceeds the threshold value, the multiplex control signals 5-1 to 5-n indicating that state are sent to the data selecting device 6
Send to The data selection device 6 sequentially reads the data from the buffer memory exceeding the threshold value and outputs the fixed rate multiplexed data 7. Therefore, each buffer memory B
The size of 1 to Bn can be about the unit data amount of multiplex.

When multiple control signals are output simultaneously from two or more buffer occupancy calculation devices, priorities are determined in advance according to the importance of data, etc.
If the selection is performed according to the rank, the data with high importance can be surely selected. Data A1 to An are
When the respective quantities have the property that the total quantity is constant with time even if they change with time, multiple control signals are simultaneously output from two or more buffer occupancy calculation devices. Since the possibility is small, this device is particularly effective for multiplexing such data.

FIG. 2 shows an example of the configuration of a device for multiplexing video data and audio data. Here, parts corresponding to those in FIG. 1 are given the same numbers. This digital data multiplexing device includes a video buffer memory 1 for temporarily storing video data, an audio buffer memory 2 for temporarily storing audio data, and a video buffer occupation for calculating a data occupation amount in the video buffer memory 1. Quantity calculation device 3,
Audio buffer occupancy calculation device 4 for calculating the data occupancy in the audio buffer memory 2, and storage in the video buffer memory 1 or the audio buffer memory 2 based on the multiplex control signal 5 output from the audio buffer occupancy calculation device 4. And a data selection device 6 for selecting the stored data.

Video data is written in the video buffer memory 1, and audio data is written in the audio buffer memory 2. Here, both the video data and the audio data have a fixed rate. The video buffer occupancy calculation device 3 calculates the buffer occupancy in the video buffer memory 1 by looking at the write address and the read address of the video data in the video buffer memory 1. Further, the audio buffer occupancy calculation device 4 calculates the buffer occupancy in the audio buffer memory 2 by looking at the write address and the read address of the audio data in the audio buffer memory 2. A threshold is set in the voice buffer occupancy calculation device 4, and when the threshold is exceeded, the multiplex control signal 5 is sent to the data selection device 6.
The data selection device 6 reads out and selects the audio data stored in the audio buffer memory 2 when the multiplex control signal 5 is input, and otherwise selects the video data stored in the video buffer memory 1. Read and select,
The fixed rate multiplexed data 7 is output.

That is, this digital data multiplexing device preferentially reads out audio data. As described above, by preferentially reading the audio data, the size of the audio buffer memory 2 can be minimized. Since this device selects two types of digital data, the video buffer occupation amount calculation device 3 may or may not be provided.

FIG. 3 shows another configuration of a device for multiplexing video data and audio data. Here, parts corresponding to those in FIG. 2 are designated by the same reference numerals, and description thereof will be omitted. In this digital data multiplexer, the audio data has a fixed rate as in FIG. 2, but the video data has a variable rate.

In this digital data multiplexer,
The video data generated by the video data generator 9 is written in the video buffer memory 1. The video buffer occupation amount calculation device 3 calculates the occupation amount of the video buffer memory 1. Then, the control signal 8 for keeping the occupied amount constant is given to the video data generator 9. The video data generator 9 controls the amount of video data generated based on the control signal 8. As a result, the average rate of the video data generated by the video data generator 9 becomes a constant value, and as a result, the average occupation amount of the video buffer memory 1 also becomes constant.

The operations of the voice buffer memory 2, the voice buffer occupancy calculation device 4, and the data selection device 6 are the same as those of the digital data multiplexer of FIG. That is, when the threshold value set in the voice buffer occupancy calculation device 4 is exceeded, the multiplex control signal 5 is sent to the data selection device 6. Then, the data selection device 6 reads out and selects the audio data stored in the audio buffer memory 2 when the multiplex control signal 5 is input, and otherwise, selects the video data stored in the video buffer memory 1. The data is read and selected, and fixed-rate multiplexed data 7 is output.

In the case of this digital data multiplexer, FIG.
Since the variation range of the occupied amount in the video buffer memory 1 becomes larger than that in the case of 1, it is necessary to make the size of the video buffer memory 1 larger than in the case of FIG.

FIG. 4 shows an example of the configuration of an apparatus for multiplexing video data, audio data, and system data. Here, parts corresponding to those in FIG. 2 are designated by the same reference numerals, and description thereof will be omitted. In this digital data multiplexer, video data and audio data have a fixed rate as in FIG. Further, it is assumed that the output of the system data generator 10 is multiplexed at fixed time intervals.

The operations of the video buffer memory 1, the video buffer occupation amount calculation device 3, the audio buffer memory 2, and the audio buffer occupation amount calculation device 4 are the same as those in FIG. In other words, even in this digital data multiplexer, when the occupation amount of the voice buffer memory 2 exceeds the threshold value set in the voice buffer occupation amount calculating device 4, the multiplexing control signal 5 is sent to the data selecting device 6. . Then, the data selection device 6 reads out and selects the audio data stored in the audio buffer memory 2 when the multiplex control signal 5 is input, and otherwise, selects the video data stored in the video buffer memory 1. Read and select the data. However, when the system data generator 10 is outputting the system data, since it is multiplexed with priority, the video data and the audio data are kept waiting for that period. Therefore, it is necessary to increase the size of the video buffer memory 1 and the size of the audio buffer memory 2 by the amount of system data as compared with the case of FIG.

[0021]

As described in detail above, according to the present invention, the size of the temporary storage means can be minimized in a device for multiplexing a plurality of types of digital data.
Further, it is possible to suppress an increase or decrease in the data occupation amount in the temporary storage means.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a configuration of a digital data multiplexing device to which the present invention has been applied.

FIG. 2 is a diagram showing one form of a configuration of an apparatus for multiplexing video data and audio data.

FIG. 3 is a diagram showing another configuration of a device for multiplexing video data and audio data.

FIG. 4 is a diagram showing an example of a configuration of a device for multiplexing video data, audio data, and system data.

[Explanation of symbols]

A1 to An ... Digital data, B1 to Bn ... Buffer memory, O1 to On ... Buffer occupancy calculation device, 1 ... Video buffer memory, 2 ... Audio buffer memory, 3 ... Video buffer occupancy calculation device, 4 ... Audio buffer occupancy Quantity calculation device, 5-1 to 5-n, 5 ... Multiple control signal, 6 ... Data selection device, 10 ... System data generation device

Claims (5)

[Claims] 1. A digital data multiplexer for multiplexing a plurality of types of digital data, wherein the temporary storage means temporarily stores the digital data individually, and the data selection means for selecting and multiplexing the output of the temporary storage means. The data selection means selects the digital data temporarily stored in the temporary storage means when the occupancy in at least one predetermined temporary storage means exceeds a threshold value. A digital data multiplexing device characterized by: 2. The digital data multiplexing apparatus according to claim 1, wherein the digital data is video data and audio data, and the predetermined temporary storage means is temporary storage means for temporarily storing the audio data. 3. The digital data multiplexer according to claim 2, wherein the audio data rate and the video data rate are fixed. 4. The digital data multiplexer according to claim 2, wherein the audio data rate is fixed and the video data rate is variable. 5. The digital data multiplexing device according to claim 1, wherein the digital data is video data, audio data, and system data, and the system data is preferentially multiplexed every predetermined period.