JP2000253380A - Data transmission equipment - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To prevent transmission efficiency degradation caused by retransmission delay. SOLUTION: A counter 201 is a timer which starts counting up from the time when an image signal is received at the beginning of transmission and stops counting up when a predetermined count is reached. The retransmission permitting unit 202 has a counter 2
Retransmission is permitted when 01 continues counting up, and retransmission is prohibited when the count of the counter 201 reaches a predetermined value. Also, the retransmission instruction unit 203
When receiving a signal to permit retransmission from retransmission permitting section 202, it instructs the transmitting side to perform retransmission. The retransmission buffer 204 stores another image until an image to be retransmitted is received by a retransmission request.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data transmission apparatus used for data communication, multimedia communication, moving image communication, etc., and more particularly to MPEG (Moving Picture Experts).
(Group-4).

[0002]

2. Description of the Related Art Conventionally, in digital transmission,
A moving image signal, an audio signal, and the like are compressed by a compression method of a predetermined standard, an image stream, an audio stream, and a data stream obtained by compression are multiplexed, and the multiplexed stream data is transmitted.

[0003] In conventional data transmission, a transmitting device attaches an error detection code to data in a transmission unit and transmits the data, and a receiving device performs error detection using the error detection code, and there is an error. Sometimes all retransmission requests are issued to the transmitting device.

[0004] That is, as shown in FIG. 8, when an error is detected in the data transmission 3 transmitted from the transmission side device in the reception side device, a retransmission request is issued from the reception side device to the transmission side device. When receiving the retransmission request, the transmitting apparatus retransmits the data to be retransmitted (data transmission 3). The receiving device sends the received data to the decoding device in the order of the sequence number, and performs the decoding process.

[0005]

However, in the receiving apparatus, data is transmitted to the decoding apparatus in the order of the sequence number of the transmission data. Therefore, if the number of retransmission control targets increases, the time required for retransmission increases, There is a problem that transmission efficiency deteriorates due to retransmission delay.

[0006] The present invention has been made in view of such a point, and it is an object of the present invention to provide a data transmission apparatus capable of preventing a reduction in transmission efficiency due to a retransmission delay.

[0007]

As a data compression method in data transmission, there is an MPEG coding method. MPE
In the G encoding system, MPEG-2 has been shifted from MPEG-2 mainly for broadcasting to MPEG-4 mainly for multimedia.

When an image coding system such as MPEG-4 is adopted, a certain unit of error is allowed because the transmission unit is reduced. Therefore, even in the MPEG-4 system, although there is data such as an I (Intra) frame whose image quality is deteriorated due to lack of an image, P (Predictiv)
e) Like a frame or a B (Bidirectionally) frame,
There is data that does not necessarily need to be retransmitted.

The present inventor has paid attention to the above points, and has found that by performing retransmission control only on data affecting image reproduction, it is possible to prevent a reduction in transmission efficiency due to retransmission delay. Reached.

That is, the present invention includes a received signal,
First measuring means for measuring a predetermined time from the beginning of transmission of an image stream to which an error detection code has been added; and a retransmission request to a transmission side only when an error is detected in the image stream within the predetermined time. And retransmission means for performing

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A data transmission apparatus according to a first aspect of the present invention comprises a first measuring means for measuring a predetermined time from the beginning of transmission of an image stream to which an error detection code is added and which is included in a received signal. And a retransmitting means for making a retransmission request to the transmitting side only when an error is detected in the image stream within the predetermined time.

According to this configuration, retransmission control is performed only for important data of the image stream transmitted within a few seconds from the beginning of transmission, so that retransmission delay can be suppressed while suppressing image quality deterioration. Further, since the number of retransmissions is reduced, transmission efficiency can be improved.

[0013] In the data transmission apparatus according to a second aspect of the present invention, in the first aspect, the second transmission means measures the time from when the reception of the image stream is interrupted to when the image stream is received. And the first measuring means operates again when the time exceeds a predetermined time.

According to this configuration, retransmission control can be performed for an important image stream transmitted when transmission is restarted. Therefore, in image communication, retransmission delay can be more accurately suppressed while suppressing image quality deterioration. Can be suppressed.

A data transmission apparatus according to a third aspect of the present invention includes a sequence number recognizing means for recognizing the sequence number of an image stream included in a received signal and to which a sequence number and an error detection code are added; Retransmission means for requesting the transmission side to perform retransmission only when an error is detected in the image stream while recognizing a sequence number.

According to this configuration, since retransmission control is performed only on important data of the image stream transmitted within a few seconds from the beginning of transmission, retransmission delay can be suppressed while suppressing image quality deterioration. Further, since the number of retransmissions is reduced, transmission efficiency can be improved.

According to a fourth aspect of the present invention, there is provided a data transmission apparatus, comprising: an image type recognizing means for recognizing the image type information of an image stream included in a received signal and having image type information and an error detection code added thereto; Retransmission means for requesting a retransmission request to a transmission side based on a recognition result of an image type when an error is detected in the image stream.

According to this configuration, since retransmission control is performed only on important data of the image stream, retransmission delay can be suppressed while suppressing image quality deterioration. Further, since the number of retransmissions is reduced, transmission efficiency can be improved.

A data transmission apparatus according to a fifth aspect of the present invention is the data transmission apparatus according to the fourth aspect, wherein the image type is an I frame,
The retransmission unit is one selected from the group consisting of a P frame and a B frame, and the retransmission unit preferentially requests a retransmission when the image type is an I frame.

According to this configuration, since retransmission control is performed on I-frame data, which is important data in the image stream, it is possible to prevent the image from deteriorating.

[0021] The base station apparatus according to the sixth aspect of the present invention comprises:
The data transmission device according to any one of the first to fifth aspects is provided. A communication terminal device according to a seventh aspect of the present invention includes the data transmission device according to any one of the first to fifth aspects. According to these configurations, communication can be performed without retransmission delay in the communication system.

[0022] The data transmission method according to an eighth aspect of the present invention includes a first measurement step of measuring a predetermined time from an initial transmission of an image stream to which an error detection code is added and which is included in a received signal; Retransmission requesting a retransmission request to the transmission side only when an error is detected in the image stream within the time period.

According to this method, retransmission control is performed only on important data of an image stream transmitted within a few seconds from the beginning of transmission, so that retransmission delay can be suppressed while suppressing image quality deterioration. Further, since the number of retransmissions is reduced, transmission efficiency can be improved.

A data transmission method according to a ninth aspect of the present invention includes a sequence number recognizing step of recognizing the sequence number of an image stream included in a received signal and to which a sequence number and an error detection code have been added; Retransmitting a retransmission request to the transmitting side only when an error is detected in the image stream while recognizing a sequence number.

According to this method, retransmission control is performed only on important data of an image stream transmitted within a few seconds from the beginning of transmission, so that retransmission delay can be suppressed while suppressing image quality deterioration. Further, since the number of retransmissions is reduced, transmission efficiency can be improved.

[0026] A data transmission method according to a tenth aspect of the present invention includes an image type recognizing step of recognizing the image type information of an image stream included in a received signal and to which image type information and an error detection code have been added; A retransmission step of, when an error is detected in the image stream, making a retransmission request to the transmission side based on the recognition result of the image type.

According to this method, retransmission control is performed only for important data of an image stream, so that retransmission delay can be suppressed while suppressing image quality deterioration. Further, since the number of retransmissions is reduced, transmission efficiency can be improved.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. (Embodiment 1) FIG. 1 is a block diagram showing a communication system including a data transmission apparatus according to an embodiment of the present invention. The communication system illustrated in FIG. 1 includes a transmitting device and a receiving device, and communication is performed wirelessly. The transmission path is not limited to wireless, but may be wired.
Also, in FIG. 1, only the transmitting unit is described in the transmitting device, and only the receiving unit is described in the receiving device. However, since both the transmitting device and the receiving device can transmit and receive, the transmitting device has a receiving unit, and the receiving device has a transmitting unit.

In the transmitting apparatus, an image signal from a video material is input from an image signal input terminal and sent to the image encoding unit 101. The image encoding unit 101 performs an arithmetic process for blocking the image signal and efficiently compressing the amount of information on the blocked image signal. Specifically, for example, MPT such as DCT (discrete cosine transform), quantization,
The arithmetic processing of the EG-4 system is performed. By such an image encoding process, an image stream is obtained. Note that the block-formed image signal is added with management data indicating the position of the block on one screen and stored in the memory.

An audio (sound) signal from an audio material is input from an audio signal input terminal,
Sent to 2. The audio encoding unit 102 converts the audio signal based on a predetermined audio encoding method into, for example, MPEG
-4 coding process is performed. By such an audio encoding process, an audio stream is obtained.

For other data and control data, for example, an MPE (not shown)
G-4 encoding is performed. A data stream is obtained by such an encoding process.

The image stream subjected to the image encoding process and the audio stream subjected to the audio encoding process are supplied to a selector 10.
3 is input. The selector 103 selects whether to perform retransmission management or to add an error detection code without performing retransmission management.

The selector 10 performs retransmission management.
3, the retransmission management unit 104 assigns a sequence number to each block of the image stream,
The image stream is stored in the retransmission buffer.

On the other hand, when the selector 103 selects the error detection code addition without performing the retransmission management, the error detection code addition section 105 detects the error in the audio stream or the image block. Assign a sign.

The image stream, the audio stream, and the data stream are sent to the multiplexing unit 106 and multiplexed. After the multiplexed stream is subjected to a predetermined radio transmission process, the multiplexed stream is processed by the antenna. 1
08. At the time of transmission, the stream is transmitted in single or multiple packets.

In the receiving device, the multiplexed stream received from the antenna 109 is separated by the separating unit 110 from single or plural packets into respective streams, that is, an image stream, an audio stream, and a data stream.

Each of the separated streams is sent to an error detection / code deletion unit 111, where error detection is performed in units of reception (for image streams, in units of reception blocks), and error detection codes are further deleted.

When an error is detected by the error detection / code deletion unit 111, for example, when a sequence number is missing or a bit error is detected, the retransmission management unit 112 sets A retransmission request is issued to the transmitting device for each block, and when the retransmitted data arrives at the receiving device, the stream is transmitted to the image decoding unit 11.
3. Send to the audio decoding unit 114 or the data decoding unit (not shown).

The image decoding unit 113 performs an arithmetic process for expanding the image stream. Specifically, arithmetic processing such as inverse DCT (inverse discrete cosine transform), inverse quantization, and motion compensation is performed on the image stream. An image signal is obtained by such an image decoding process. This image signal is sent to the video material via the image signal output terminal.

The audio decoding unit 114 performs a decoding process on the audio stream using a decoding method corresponding to the encoding method. By such audio decoding processing,
An audio signal is obtained. This audio signal is sent to the audio material via the audio signal output terminal.

The communication control units 107 and 115 of the transmitting device and the receiving device, when performing communication from the transmitting device to the receiving device in the communication system, call control, the capability of the receiving device, and the resource status. Negotiate information about device settings such as

FIG. 2 is a block diagram showing a configuration of retransmission management section 112 of the data transmission apparatus according to Embodiment 1 of the present invention. As shown in FIG. 2, the counter 201 is a timer that starts counting up from the time when an image signal is received at the beginning of transmission and stops counting up when a predetermined count is reached.

The retransmission permitting section 202 permits retransmission when the counter 201 continues counting up, and rejects retransmission when the count of the counter 201 reaches a predetermined value. Further, retransmission instructing section 203 instructs the transmitting side to perform retransmission when receiving a signal indicating retransmission permission from retransmission permission section 202. The retransmission buffer 204
Stores another image until an image to be retransmitted is received by a retransmission request.

The operation of the data transmission device in the communication system having the above configuration will be described with reference to FIG. In the present embodiment, a case will be described in which important data of an image stream is transmitted within a few seconds from the beginning of transmission, and retransmission control is performed only during that period.

When transmitting image signals, audio signals, and the like,
First, an image signal input via an image signal input terminal is input to the image encoding unit 101. Image encoding unit 101
In the above, the signal is subjected to DCT processing and quantization processing, and the image signal is compressed to form an image stream. In the image encoding unit 101, the image stream is divided into a plurality of blocks. Further, in the image encoding unit 101,
Operation processing such as motion compensation is performed on the image signal.

In the block formation in the image encoding unit 101, first, information about how many images are to be sent per second and information on a transmission rate are negotiated between the communication control units 107 and 115 via the communication control unit 107. To the image encoding unit 101. Next, the image encoding unit 101
Performs block division based on information on the number of images and the transmission rate so that the data length of each block is uniform.

The image stream thus obtained is subjected to error detection, error correction,
In the adaptation layer that performs retransmission, etc.,
After the selector 103 makes a selection as to whether or not to perform retransmission management, the data is sent to the error detection code adding section 105 where an error detection code is added.

The image stream to which the error detection code has been added as described above is sent to the multiplexing unit 106. On the other hand, the audio signal input via the audio signal input terminal is input to the audio encoding unit 102, and is encoded by the audio encoding unit 102 according to a predetermined audio encoding method to become an audio stream. In the adaptation layer, The error detecting code adding section 105 adds the error detecting code to the multiplexing section 1.
06. The other data is also subjected to predetermined encoding by an encoder to form a data stream, and in the adaptation layer, an error detection code is assigned by an error detection code assigning unit 105 to the multiplexing unit 1.
06.

These image streams, audio streams, and data streams are composed of multiple layers (MUs).
(X layer). In the MUX layer, each stream is converted into a packet (image packet, audio packet, data packet) to form, for example, a MUX packet as shown in FIG. That is, in the MUX packet, a voice packet 402,
A data packet 403 and an image packet 404 are included. The multiplexed signal is transmitted to the receiving device via the antenna 108.

The signal received via antenna 109 is
The data is sent to the separation unit 110 and separated into each stream. The separated image stream and audio stream are input to the error detection / code deletion unit 111, and error detection is performed using the error detection code. In addition, as a method of error detection, a commonly used method is adopted. For example, a cyclic code (CRC) widely used in practice is adopted.

Next, the image stream on which the error detection is performed is sent to the retransmission buffer 204 of the retransmission management unit 112 after the error code is deleted. When this image stream is received, that is, when the image stream is input to the retransmission management unit 112, the counter 201 operates and starts counting up. Then, after a predetermined time, for example, several seconds, the operation of the counter 201 is stopped. In this way, time measurement is performed. The operation of the counter 201 is performed, for example, by determining a threshold value of the count number and stopping when the threshold value is exceeded.

During the time measurement, a signal indicating that the time is being measured (retransmission control is being performed) is sent from the counter 201 to the retransmission permitting unit 202. Then, in the retransmission permitting unit 202,
Only during the time measurement, retransmission of the image stream in which an error is detected is permitted. When retransmission is permitted by retransmission permitting section 202, a request for transmission is made from retransmission instructing section 203 to the transmitting apparatus via communication control section 115.
Note that the retransmission buffer 204 stores an image stream as needed. That is, in the receiving device, the received image stream is sent to the decoding device in the order of the sequence number, and the decoding process is performed.
The image stream is stored in the retransmission buffer 204 until the retransmission target arrives.

When retransmission control is performed using such retransmission management section 112, the result is as shown in FIG. That is, as can be seen from FIG. 3, during the measurement by the counter 201, that is, during the retransmission control execution period, important data in the image is transmitted, so that the retransmission permission unit 202 permits the retransmission and the retransmission instruction unit 203 A retransmission request is made for the image stream (I-frame transmission 2) in which an error has been detected, based on the instruction. Then, the transmitting device retransmits the image stream in response to the retransmission request.

On the other hand, after the measurement by the counter 201 is completed, that is, during the retransmission control suspension period, no retransmission request is made for the image stream (P frame transmission 2) in which an error has been detected by error detection. Therefore, there is no subsequent retransmission delay.

As described above, since retransmission control is performed only for important data of an image stream transmitted within a few seconds from the beginning of transmission, retransmission delay can be suppressed while suppressing image quality deterioration. Further, since the number of retransmissions is reduced, transmission efficiency can be improved.

(Embodiment 2) In this embodiment, a case will be described in which a method for recognizing a sequence number given to transmission data is used for retransmission control performed only on data that affects image reproduction. In data transmission of an image stream, important data such as an I frame is transmitted at an early stage of transmission. Therefore, by recognizing the sequence number assigned to the transmission data, it is possible to determine whether the transmission data requires retransmission or not. Therefore, in the data transmission apparatus of the present embodiment, retransmission control is performed based on the sequence number of transmission data.

Since the configuration of the communication system including the data transmission apparatus according to the present embodiment is almost the same as that shown in FIG. 1, the description will focus on the configuration of retransmission management section 112 of the receiving side apparatus. FIG. 5 is a block diagram showing a configuration of retransmission management section 112 of the data transmission apparatus according to Embodiment 2 of the present invention.

As shown in FIG. 5, the sequence number recognizing unit 501 recognizes the sequence number given to the transmitted stream and determines whether the stream requires retransmission control.

[0059] Retransmission permitting section 502 permits retransmission of a stream having a sequence number requiring retransmission control, and disallows retransmission when the sequence number reaches a predetermined value. Further, retransmission instructing section 503 includes retransmission permitting section 50.
2, when receiving a signal indicating that retransmission is permitted, the transmission side instructs retransmission. Note that the retransmission buffer 504 stores another image until an image to be retransmitted is received in response to a retransmission request.

When an image signal is received by the data transmission apparatus having the above configuration, the signal received via the antenna 109 is sent to the separation unit 110 and separated into each stream. The separated image stream and audio stream are input to the error detection / code deletion unit 111, and error detection is performed using the error detection code. In addition, as a method of error detection, a commonly used method is adopted. For example, a cyclic code (CRC) widely used in practice is adopted.

Next, the image stream on which the error detection is performed is sent to the retransmission buffer 504 of the retransmission management unit 112 after the error code is deleted. When the image stream is received, that is, when the image stream is input to the retransmission management unit 112, the sequence number recognition unit 501 recognizes the sequence number assigned to the image stream. That is, it is determined whether or not the sequence number has a predetermined value. Thus, it is determined whether the data is important data in the image stream at the beginning of transmission.
The operation of the sequence number recognizing unit 501 performs, for example, a threshold determination on the sequence number, and stops the operation when the threshold is exceeded.

Until the stream having the predetermined sequence number is sent, a signal indicating that retransmission control is being performed is sent to retransmission permitting section 502. Then, the retransmission permitting unit 5
In 02, retransmission of the image stream in which an error is detected is permitted only during the retransmission control. Retransmission permission section 5
When retransmission is permitted in 02, a transmission request is made from the retransmission instruction unit 503 to the transmission side device via the communication control unit 115. Note that the retransmission buffer 504 stores an image stream as needed. That is, the receiving apparatus sends the received image stream to the decoding apparatus in the order of the sequence number and performs the decoding process. Therefore, the image stream is stored in the retransmission buffer 504 until the retransmission target arrives.

When retransmission control is performed using such a retransmission management unit 112, the result is as shown in FIG. That is, as can be seen from FIG. 3, since important data is transmitted in the image until the sequence number reaches a predetermined value, that is, during the retransmission control execution period, retransmission is permitted by the retransmission permission unit 502 and retransmission is performed. Based on the instruction from the instruction unit 503, a retransmission request is made for the image stream (I frame transmission 2) in which the error has been detected. Then, the transmitting device retransmits the image stream in response to the retransmission request.

On the other hand, if the sequence number exceeds a predetermined value, that is, during the retransmission control suspension period, no retransmission request is made for the image stream (P frame transmission 2) in which an error has been detected by error detection. Therefore, there is no subsequent retransmission delay.

As described above, since retransmission control is performed only on important data of an image stream transmitted within a few seconds from the beginning of transmission, retransmission delay can be suppressed while suppressing image quality deterioration. Further, since the number of retransmissions is reduced, transmission efficiency can be improved.

(Embodiment 3) In the present embodiment, a case will be described in which a method of recognizing image type information added to transmission data is adopted for retransmission control performed only on data affecting image reproduction. . In an image, there is important data and less important data.
For example, important data includes I-frame data and data at the center of the screen. The data that is not so important includes P frame data, B frame data, data at the upper and lower ends of the screen, and the like.

Accordingly, the image type information added to the transmission data, for example, information for identifying I frame data, P frame data, or B frame data, and the position on the screen (center, lower end, upper end) are identified. By recognizing the image header including the information to be transmitted, it is possible to determine whether the transmission data requires retransmission or not. Therefore, in the data transmission device of the present embodiment, retransmission control is performed using the image header of the transmission data.

Since the configuration of the communication system including the data transmission apparatus according to the present embodiment is almost the same as that shown in FIG. 1, the description will focus on the configuration of retransmission management section 112 of the receiving apparatus. FIG. 7 is a block diagram showing a configuration of retransmission management section 112 of the data transmission apparatus according to Embodiment 3 of the present invention.

As shown in FIG. 7, the image type recognition unit 701
Recognizes the image header added to the transmitted stream and determines whether the stream requires retransmission control.

The retransmission permitting unit 702 permits retransmission of an image header stream requiring retransmission control, for example, I-frame data or data at the center of the screen, and retransmits an image header for which image retransmission control is unnecessary. Retransmission of streams, for example, P frame data, B frame data, and data at the upper and lower ends of the screen is not permitted. Further, retransmission instructing section 703 instructs the transmitting side to perform retransmission when receiving a signal indicating retransmission permission from retransmission permitting section 702. The retransmission buffer 704 stores another image until an image to be retransmitted is received by a retransmission request.

When the image signal is received by the data transmission apparatus having the above configuration, the signal received via the antenna 109 is sent to the separation unit 110 and separated into each stream. The separated image stream and audio stream are input to the error detection / code deletion unit 111, and error detection is performed using the error detection code. In addition, as a method of error detection, a commonly used method is adopted. For example, a cyclic code (CRC) widely used in practice is adopted.

Next, the error-detected image stream is sent to the retransmission buffer 704 of the retransmission management unit 112 after the error code is deleted. When the image stream is received, that is, when the image stream is input to the retransmission management unit 112, the image type recognition unit 701
Recognizes the image header added to the image stream. That is, it is determined whether or not the image header includes information of a stream that requires retransmission. Thus, it is determined whether the data is important data in the image stream at the beginning of transmission.

A signal indicating whether retransmission control is necessary is sent to retransmission permitting section 702. Then, the retransmission permitting unit 7
In 02, retransmission is permitted for an image stream in which an error is detected only when the retransmission control is required. When retransmission is permitted by retransmission permitting section 702, a transmission request is made from retransmission instructing section 703 to transmitting apparatus via communication control section 115. Note that the retransmission buffer 704 stores an image stream as necessary. That is, in the receiving device, the received image stream is sent to the decoding device in the order of its sequence number,
Since the decoding process is performed, the image stream is stored in the retransmission buffer 704 until the retransmission target arrives.

As described above, since retransmission control is performed only for important data of the image stream, retransmission delay can be suppressed while suppressing image quality deterioration. Further, since the number of retransmissions is reduced, transmission efficiency can be improved.

(Embodiment 4) When an image stream cannot be received correctly and image reception is interrupted for several seconds,
When image transmission is resumed, important image streams such as I-frame data are transmitted. At this time, if retransmission control is not performed, there is a possibility that image degradation will occur. Therefore, in the present embodiment, when an image stream cannot be received correctly, a timer is started, and retransmission control is performed after a predetermined time has elapsed to prevent deterioration of an important image stream after image transmission is resumed. Will be described.

The retransmission control according to the present embodiment can be realized by retransmission management section 112 shown in FIG.

[0077] Retransmission management unit 1 of the apparatus in the present embodiment
In step 12, when image data cannot be received correctly, for example, when a packet is discarded, the counter 201 starts counting up (timer activation). When the image data has been correctly received, the counting up is stopped (timer stop).

Retransmission permitting section 202 permits retransmission when the count of counter 201 reaches a predetermined count. In addition, retransmission is not permitted when image data is correctly received. In addition, by setting the predetermined count number in consideration of the delay of the network, that is, by setting the time from when the image data cannot be correctly received to when the retransmission control is restarted to almost the delay time of the network. ,
When the switching time of the frame image is longer than the network delay, retransmission control can be efficiently performed.

Further, retransmission instructing section 203 includes retransmission permitting section 2
From 02, when a signal indicating that retransmission is permitted is received, the transmission side is instructed to perform retransmission. Note that the retransmission buffer 204
Another image is stored until a retransmission target image is received by a retransmission request.

As described above, retransmission control can be performed for an important image stream transmitted when transmission is resumed. Therefore, in image communication, retransmission delay can be suppressed more accurately while suppressing image quality deterioration. Can be.

The above-described first to fourth embodiments can be implemented in an appropriate combination.

[0082]

As described above, the data transmission apparatus of the present invention performs retransmission control only on important data of an image stream transmitted within a few seconds from the beginning of transmission, so that retransmission delay is suppressed while suppressing image quality deterioration. be able to. Further, since the number of retransmissions is reduced, transmission efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a communication system including a data transmission device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a retransmission management unit of the data transmission apparatus according to Embodiment 1 of the present invention.

FIG. 3 is a timing chart showing transmission timing of the data transmission apparatus according to the first embodiment.

FIG. 4 is a diagram showing a packet configuration of a signal transmitted in the embodiment of the present invention.

FIG. 5 is a block diagram showing a configuration of a retransmission management unit of the data transmission apparatus according to Embodiment 2 of the present invention.

FIG. 6 is a diagram showing a transmission frame in a data transmission device according to Embodiment 3 of the present invention.

FIG. 7 is a block diagram showing a configuration of a retransmission management unit of the data transmission apparatus according to the third embodiment.

FIG. 8 is a timing chart showing transmission timing of a conventional data transmission device.

[Explanation of symbols]

 Reference Signs List 101 Image encoding unit 102 Audio encoding unit 103 Selector 104, 112 Retransmission management unit 105 Error detection code addition unit 106 Multiplexing unit 107, 115 Communication control unit 110 Separation unit 111 Error detection / code deletion unit 113 Image decoding unit 114 Voice decoding unit 201 Counter 202, 502, 702 Retransmission permitting unit 203, 503, 703 Retransmission instruction unit 204, 504, 704 Retransmission buffer 501 Sequence number recognition unit 701 Image type recognition unit

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5C059 KK00 PP04 RF02 RF14 RF23 SS06 TA76 TB01 TC22 UA02 UA05 5C063 AA01 AB03 AC01 AC05 CA40 DA01 DA07 DA13 5C064 BA01 BA07 BB05 BC10 BC16 BC18 BC20 BC27 BD01 BD07 BD08 BD09 5K014 A01 GA01 HA05

Claims (10)

[Claims] A first measuring means for measuring a predetermined time from the beginning of transmission of an image stream to which an error detection code is added, the error detecting code being added to the image stream, and an error being detected in the image stream within the predetermined time. And a retransmitting means for making a retransmission request to the transmitting side only when the transmission is performed. 2. The apparatus according to claim 1, further comprising: a second measuring unit that measures a time from when the reception of the image stream is interrupted to when the image stream is received, wherein the first measuring unit determines that the time exceeds a predetermined time. 2. The data transmission device according to claim 1, wherein the data transmission device operates again at a time. 3. A sequence number recognizing means for recognizing the sequence number of an image stream included in a received signal and having a sequence number and an error detection code added thereto, and an error in the image stream while recognizing a specific sequence number. Retransmission means for requesting the transmission side to perform retransmission only when the transmission is detected. 4. An image type recognizing means for recognizing the image type information of an image stream to which image type information and an error detection code are added, the image type recognizing means being included in a received signal, Retransmission means for requesting the transmission side to perform retransmission based on the type recognition result. 5. The retransmission unit according to claim 1, wherein said image type is one selected from the group consisting of an I frame, a P frame, and a B frame, and said retransmission unit gives a priority to a retransmission request when said image type is an I frame. The data transmission apparatus according to claim 4, wherein the data transmission is performed. 6. A base station apparatus comprising the data transmission apparatus according to claim 1. Description: 7. A communication terminal device comprising the data transmission device according to any one of claims 1 to 5. 8. A first measuring step of measuring a predetermined time from the beginning of transmission of an image stream included in a received signal and to which an error detection code is added, and detecting an error in the image stream within the predetermined time. And a retransmission step of making a retransmission request to the transmission side only when the transmission is performed. 9. A sequence number recognizing step of recognizing the sequence number of an image stream included in a received signal and provided with a sequence number and an error detection code, and detecting an error in the image stream while recognizing a specific sequence number. And a retransmission step of making a retransmission request to the transmission side only when is detected. 10. An image type recognizing step of recognizing the image type information of an image stream included in a received signal and to which image type information and an error detection code have been added; A retransmission step of making a retransmission request to the transmission side based on the type recognition result.