JP3907973B2 - Data transmission device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a communication apparatus that transmits a plurality of types of multimedia data such as digitized video data, audio data, and general-purpose data.
[0002]
[Prior art]
For example, a video server that distributes multimedia data such as video and audio via a fixed-band transmission line creates multimedia data to be transmitted in advance so that the output data rate does not exceed the band of the transmission line. Keep it.
[0003]
In particular, in an audio visual terminal compliant with ITU-T recommendation H.324, audio data is decoded in synchronization with the transmission path clock of the transmission path, that is, the network clock of the network, so the video server uses the transmission path clock. It is necessary to transmit audio data in synchronization.
[0004]
[Problems to be solved by the invention]
However, in communication between terminals compliant with ITU-T Recommendation H.324, a fixed-band transmission path is used to determine the multiplexing format by negotiation between terminals and to send control information during communication. However, the transmission band given to the net multimedia data may not be constant due to the difference in multiplexing format and control information.
[0005]
Therefore, when it becomes impossible to secure a transmission band required for the multimedia data to be transmitted, the multimedia data may not be transmitted from the video server at a desired timing.
[0006]
In such a case, if multimedia data is still sent, it will arrive at the receiving terminal with a slight delay from the desired timing, and the receiving terminal will receive the audio data at a clock slower than the transmission path clock. Therefore, there is a problem that when the decoding / reproducing operation is performed with the transmission path clock, there is no audio data to be reproduced.
[0007]
In addition, when only audio data is transmitted in synchronization with the transmission path clock, there is a problem that reproduction synchronization with other media data is lost.
[0008]
The present invention has been made to solve the above-described problems. Even when the transmission band of multimedia data to be transmitted is smaller than a desired band, the audio is synchronized with the transmission line clock of the transmission line. An object of the present invention is to provide a data transmission device capable of maintaining synchronization with other media data while sending specific media data such as data.
[0009]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention is characterized in that in a data transmission apparatus that packetizes and transmits a plurality of types of media data, transmission is performed while inserting dummy data only in specific types of media data.
[0010]
In particular, dummy data is inserted so that synchronization between a specific type of media data and other media data is maintained.
[0011]
Further, the dummy data is inserted when the specific type of media data cannot be transmitted at a predetermined transmission timing.
[0012]
Further, the specific media data into which the dummy data is inserted is audio data.
[0013]
The dummy data is data obtained by encoding silence data.
[0014]
The dummy data is data obtained by encoding background noise data.
[0015]
The dummy data is the same data as the previous audio frame data.
[0016]
The dummy data is control data indicating silence.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 FIG.
1 is a block diagram showing a data transmission apparatus according to Embodiment 1 of the present invention.
In the figure, 1 is a data transmission device of the present invention, 2 is a storage unit for storing distribution content, 3 is a separation unit for separating the stored content for each medium, and 4 is dummy data in the media data. Dummy data insertion unit to be inserted, 5 is a multiplexing unit that multiplexes each media data into one stream, 6 is content for distribution, 7a to 7c are content 6 separated for each media such as audio, video, and data Media data 8 is a multiplexed stream in which media data 7 is multiplexed into one stream. In the first embodiment, only one dummy data insertion unit 4 is shown. Further, the types of media data 7a to 7c to be multiplexed are not limited to three, but may be any number such as two or more than three.
[0018]
Next, the operation will be described.
The data transmission device 1 communicates with a communication terminal (not shown) via a network. At that time, the data transmission device 1 reads the content 6 stored in the storage unit 2 and separates it into media data 7 a to 7 c for each medium by the separation unit 3. At this time, the separated media data 7b and 7c are directly output to the multiplexing unit 5, while the media data 7a that needs to output data in synchronization with the transmission path clock, that is, the network clock, is the dummy data insertion unit 4 Is output to the multiplexing unit 5. The media data 7a that outputs data in synchronism with the transmission path clock is data that must be decoded and reproduced in synchronism with the network clock on the receiving side, and examples thereof include audio data.
[0019]
The multiplexing unit 5 reads the media data 7a from the dummy data insertion unit 4 at regular intervals in accordance with the clock of the transmission path, and multiplexes it with the other media data 7b and 7c read from the separation unit 4 directly. To send. At this time, the dummy data insertion unit 4 passes the media data 7a to the multiplexing unit 5 if the next media data 7a has already been sent from the separation unit 3, but if it has not been sent, That is, when the multiplexing unit 5 is still transmitting other media data 7b and 7c that need to be synchronized with the previous media data 7a, dummy data is generated instead of the next media data 7a. To the multiplexing unit 5.
[0020]
That is, in the multiplexing unit 5 of the first embodiment, the media data 7b and 7c are transmitted at a time when the media data 7a or dummy data is not transmitted. That is, the multiplexing unit 5 multiplexes the media data 7b and 7c in a band where the media data 7a or the dummy data is not multiplexed.
[0021]
Here, a specific example of dummy data will be described. When the media data 7a that must be decoded and reproduced in synchronization with the network clock is voice data, for example, the silent time is generally longer than the voice time during a call. As the dummy data, silence data or background noise data encoded can be used. In this way, the possibility of noticing that dummy data has been inserted is reduced, and a smooth call can be made.
[0022]
Further, speech encoded data immediately before inserting the dummy data may be used as dummy data. In this way, the receiving side communication device repeats the same voice as the previous voice, so even when background noise is heard, the voice is smooth enough not to notice that dummy data has been inserted. Can be played.
[0023]
Furthermore, control data indicating that there is no valid voice data, that is, silence, may be sent as dummy data. In this way, it is possible to reduce the amount of transmission data compared to transmitting normal speech encoded data.
[0024]
In this way, the media data 7a such as audio data that must be decoded and reproduced in synchronization with the network clock can be output while including dummy data in synchronization with the transmission path clock. 7b and 7c are transmitted according to the free state of the transmission path.
[0025]
Note that reading from the storage unit 2 by the separation unit 3 is performed in the order in which the media data 7a to 7c are stored in the order to be transmitted, so that only specific media data is not read out. It is. For this reason, the transmission order between the media data separated by the separation unit 3 and read from the multiplexing unit 5 is almost the same as the order of transmission.
[0026]
FIG. 2 is a diagram showing the transmission timing of each media data 7 in the multiplexed stream 8.
The desired transmission timings T1, T2, T3,... Of the content 4 to be transmitted are shown in (a), and the transmission timing T1, T2, when the transmission band, that is, the information rate is reduced in the same transmission order as (a). The difference in transmission timing between T3,... And media data 7a to 7c is shown in FIG. Further, (c) shows the transmission timing of the media data 7a to 7c realized in the first embodiment when the transmission band is reduced.
[0027]
That is, in FIG. 2A, the media data 7a to 7c are in a state where they are periodically transmitted. FIG. 2B shows that the contents are transmitted in the same order when the transmission band, that is, the information rate is reduced.
[0028]
In FIG. 2B, the media data 7a to 7c are periodically transmitted. However, the media data 7a is originally transmitted at desired transmission timings T1, T2, T3,... Shown in FIG. Otherwise, the communication terminal that receives the multiplexed stream 8 falls into a situation where the media data 7a to be reproduced and decoded is lost.
[0029]
Therefore, I would like to transmit the media data 7a at the same timing as the desired timing T1, T2, T3,... For transmitting the media data 7a shown in FIG. If the information rate, that is, the transmission rate cannot be sufficiently secured as shown in FIG. 2B due to the change in the situation, and the transmission rate becomes lower than that shown in FIG. 2A, for example, the media data 7a2 Even when the desired timing T2 for transmitting the data arrives, the media data 7c continues to be read, and the next media data 7a2 may not be read from the separation unit 3 yet.
[0030]
If good UNA This situation arises, dummy data inserting section 4 of the first embodiment generates dummy data, and transmits as shown in Figure 2 (c).
[0031]
That is, as shown in FIG. 2 (c), when the desired timing T2 for transmitting the media data 7a shown in FIG. 2 (a) has come, the reading of the media data 7c1 from the separation unit 3 continues, If the media data 7a2 cannot be read from the separation unit 3, the next media data 7a2 has not arrived. Therefore, the dummy data insertion unit 4 generates dummy data instead of the media data 7a2, and sends it to the multiplexing unit 5. Output.
[0032]
Then, the multiplexing unit 5 receives the dummy data of the media data 7a2 from the dummy data insertion unit 4 when the desired timing T2 for transmitting the media data 7a shown in FIG. Multiplex data preferentially. Therefore, at the desired timing T2 for transmitting the media data 7a shown in FIG. 2A, the dummy data of the media data 7a is multiplexed from the dummy data insertion unit 4.
[0033]
Therefore, as shown in FIG. 2C, dummy data of the media data 7a is preferentially inserted into the multiplexed stream 8 at a desired timing T2 for transmitting the media data 7a shown in FIG. The media data 7c1 is divided and transmitted.
[0034]
As a result, the media data 7a or its dummy data is always multiplexed at a desired timing T2 for transmitting the media data 7a, and synchronization with the other media data 7b and 7c is ensured. Then, although the media data 7a-7c arrives with a little delay from the desired timing, there is no absence of the media data 7a to be reproduced even if the media data 7a is decoded and reproduced by the transmission path clock. It is also possible to prevent 7a from being out of sync with other media data 7b and 7c. That is, at the desired timing T1, T2, T3,... For transmitting the media data 7a, the media data 7a or its dummy data is always multiplexed and the media data 7a, 7b, 7c to be synchronized, that is, the media data 7 a 1, 7 b 1, 7 c 1, media data 7 a 2, 7 b 2, 7 c 2, media data 7 a 3, 7 b 3, 7 c 3... May be synchronized although some multiplexing order may be changed or media data may be divided during multiplexing. Since the media data 7a, 7b, 7c to be taken is solidified, that is, multiplexed and transmitted in synchronization, the transmission of the media data 7a, 7b, 7c is delayed, but the reproduction of the media data 7a is lost or other The reproduction synchronization between the media data 7b and 7c is not lost.
[0035]
In particular, in an audiovisual communication terminal compliant with ITU-T recommendation H.324 or the like, since audio data is decoded in synchronization with a transmission path clock, that is, a network clock, the audio data corresponds to the media data 7a. However, although media data such as audio data and other video data arrives with a little delay from the desired timing, there is no audio data to reproduce even if the audio data is decoded and reproduced with the transmission path clock, In addition, it is possible to prevent the audio data from being out of synchronization with other video data.
[0036]
Then, as shown in FIG. 2 (c), after the dummy data of the media data 7a is preferentially inserted at the timing T2, the media data 7c1 is divided and transmitted, and the transmission of the media data 7c1 is completed. When transmission of the media data 7a1 to 7c1 to be completed is completed, if there is time until a desired timing T3 for transmitting the next media data 7a, the media data 7a2 is not transmitted and the media data 7b2 is transmitted. To.
[0037]
Further, as shown in FIG. 2 (c), when the desired timing T3 for transmitting the next media data 7a arrives, even if the transmission of the media data 7b2 transmitted until that time is not completed, the media data 7b2 is stopped, and media data 7a2 is preferentially multiplexed and transmitted. After transmission of media data 7a2, if there is remaining media data 7b2, transmission is performed, and transmission of remaining media data 7b2 is completed. Later, media data 7c3 synchronized with these media data is transmitted. Of course, during the transmission of media data 7c3, when the desired timing T4 for transmitting a next media data 7a came, as described above, because not yet completed the transmission of media data 7c3, dummy data inserting section 4 Then, dummy data is generated instead of the media data 7a3 and output to the multiplexing unit 5.
[0038]
Therefore, the media data 7a or the dummy data is preferentially multiplexed and transmitted at a desired timing synchronized with the transmission path clock, and is synchronized with the media data 7a in a time (band) during which the media data 7a is not transmitted. The media data 7b and 7c to be secured are transmitted at an arbitrary timing in synchronization with the corresponding media data 7a.
[0039]
Therefore, according to the first embodiment, only the media data 7a or its dummy data is transmitted preferentially over the other media data 7b and 7c at a desired timing synchronized with the transmission path clock. The receiving terminal that receives the data can always receive the data of the media data 7a without excess or deficiency.
[0040]
In the first embodiment, when the transmission band is lower than the information rate of the content to be transmitted, the content is transferred slowly as a whole. For example, 10 minutes of content may be 12 minutes. Although no data is discarded, all media data can be sent synchronously, and the use of dummy data for audio media data that requires data on a regular basis has an adverse effect. It can be said that the content can be distributed without affecting.
[0041]
Embodiment 2. FIG.
In the first embodiment described above, each media data is multiplexed in time series to be transmitted and stored as one content. However, the embodiment in which each media data is stored separately next. Will be described.
[0042]
FIG. 3 is a block diagram showing the configuration of the data transmitting apparatus according to the second embodiment. In the figure, reference numerals 2a, 2b and 2c denote storage units for storing contents for media data 7a to 7c, respectively. That is, in the first embodiment, unlike the data transmitting apparatus of the first embodiment shown in FIG. 1, a program composed of a plurality of media data 7a to 7c is stored in one storage unit 2 and separated. 3, the media data 7a to 7c are stored in the corresponding storage units 2a, 2b, and 2c in advance without being separated. Other configurations are the same as those in FIG.
[0043]
Next, the operation will be described.
The data transmission device 1 reads the content stored in each of the three storage units 2a to 2c. However, the packet unit of the media data their respective content, timing information to be transmitted for synchronization between the media are granted, the media data from the storage unit 2a~2c in the order of timing for the transmission Is read.
[0044]
Thus, as in the case of the first embodiment, only the specific media data is not read out, and the media as the contents from each of the three storage units 2a to 2c while maintaining synchronization for transmission between the media. Data 7a-7c can be read.
[0045]
Then, only the media data 7a that needs to output data in synchronization with the transmission path clock is input to the dummy data insertion unit 4 as in the first embodiment.
[0046]
Thereafter, as in the case of the first embodiment, the multiplexing unit 5 reads and multiplexes the media data 7a from the dummy data insertion unit 4 and transmits it at a constant period in accordance with the clock of the transmission path. In the dummy data insertion unit 4, if the media data 7a to be transmitted has already been read from the storage unit 2, the media data 7a is transferred to the multiplexing unit 5, and if it has not been sent, dummy data is generated instead. The multiplexing unit 5 transmits the data read at the time when the media data 7a is not transmitted with respect to the media data 7b and 7c. As a result, the media data 7a can output data while including dummy data in synchronization with the transmission path clock, and the media data 7b and 7c are transmitted according to the free state of the transmission path. .
[0047]
Moreover, since the media data 7a-7c read from each storage part 2a-2c are data which should be transmitted at the substantially same time, the synchronization between each media data 7a-7c can be maintained.
[0048]
Therefore, according to the second embodiment, control is performed so as to always read data having similar transmission timing information values from the storage units 2a to 2c corresponding to the media data 7a to 7c, and the media data 7a or dummy data thereof is controlled. Is transmitted preferentially over the other media data 7b and 7c at a desired timing synchronized with the transmission path clock, so that the media data 7a can always be received and reproduced without excess or deficiency as in the first embodiment. In addition, the media data 7a to 7c can be kept synchronized.
[0049]
In the description of the first and second embodiments, audio data has been described as an example of the media data 7a to be transmitted at a predetermined transmission timing. However, the present invention is not limited to this, and transmission is performed at a desired timing. Of course, data other than audio data may be used as long as it should be media data.
[0050]
【The invention's effect】
As described above, in the present invention, when a plurality of types of media data is packetized and transmitted, dummy data is inserted only into a specific type of media data, so that, for example, the specific type of media data is transmitted. If dummy data is inserted so that synchronization between data and other media data is maintained, multiple types of media data can be synchronized, and multiple types of media data can be synchronized and played back on the receiving side. It becomes possible.
[0051]
In particular, when the media data of a specific type is determined to be transmitted at a predetermined transmission timing such as audio data, the specific type of media data is determined at a predetermined transmission timing. If dummy data is inserted when data cannot be transmitted by the method, it is possible to prevent a certain type of media data from being reproduced.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration example of a data transmission apparatus according to a first embodiment of the present invention.
FIG. 2 is a diagram showing the transmission timing of each media data 7 in the multiplexed stream 8 in the first embodiment.
FIG. 3 is a block diagram illustrating a configuration example of a data transmission device according to a second embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Data transmission device, 2 Storage part, 3 Separation part, 4 Dummy data insertion part, 5 Multiplexing part, 6 Content for delivery, 7a-7c Media data, 8 Multiplexed stream.

Claims (7)

A data transmission device that transmits media data of a specific type in synchronization with a transmission path clock,
  Dummy data insertion means for inserting dummy data into the specific type of media data in order to synchronize with a transmission path clock;
  The specific type of media data or the dummy data is transmitted at a constant period synchronized with the transmission path clock, and the specific type of media data or the dummy data is not transmitted for media data other than the specific type of media data. When transmitting multimedia data having a rate equal to or higher than the transmission band by transmitting in time, multiplexing means for transmitting the multimedia data while delaying the desired timing according to the transmission band;
  A data transmission device comprising: 2. The data transmitting apparatus according to claim 1, wherein the dummy data inserting means inserts dummy data so that synchronization between the specific type of media data and other media data is maintained. The data transmission apparatus according to claim 1 or 2 , wherein the specific type of media data into which the dummy data is inserted is audio data. The data transmission apparatus according to any one of claims 1 to 3 , wherein the dummy data is data obtained by encoding silence data. The data transmission apparatus according to any one of claims 1 to 3 , wherein the dummy data is data obtained by encoding background noise data. The data transmission apparatus according to any one of claims 1 to 3 , wherein the dummy data is the same data as the previous audio frame data. The data transmission apparatus according to any one of claims 1 to 3 , wherein the dummy data is control data indicating silence.

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