JP2008236103A - System, method, server, and program for distributing video - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To allow a delay time, from a reception start to a reproduction start, to be within a practical range by shortening, when an on-vehicle apparatus receives and reproduces distribution video data. <P>SOLUTION: When the video data 100 encoded by a prescribed video bit rate Bb are distributed successively from the top to the on-vehicle apparatus 7 mounted on a vehicle 6 from a video distribution server 3 via a WAN 4, the video data 100 is sequentially divided into a plurality of data blocks 101 from the top; and the video bit rate of each data block 101 is converted, thereby allowing at least the top data block 101 to be lower in video bit rate than that of the other data blocks 101, and the converted data blocks 101 are transmitted sequentially to the on-vehicle apparatus 7 from the top data block 101A. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a technique for distributing video data to an in-vehicle device via a network.

Conventionally, it communicates with a wireless base station (also called an access point) connected to a network such as the Internet using wireless communication, and can communicate with various terminals connected to the network via the wireless base station. Wireless LANs are widely used.
Wireless LAN communication standards have been established by IEEE (Institut of Electrical and Electronic Engineers), and at present, 802.11b is capable of communication up to 11 Mbps using radio waves in the 2.4 GHz band. There are three standards: 802.11g, which can communicate up to 54 Mbps using 2.4 GHz band radio waves, and 802.11a, which can communicate up to 54 Mbps using 5.2 GHz band radio waves. ing.
In recent years, a standard called 802.16a that can communicate at a maximum of 70 Mbps using radio waves of 2 to 11 GHz band has been put into practical use. In 802.16a, one wireless communication apparatus has a maximum communication distance of 30 miles (about 50 km), and is assumed to be used outdoors.

With the advancement of wireless LAN technology, in recent years, various technologies have been proposed in which a wireless LAN system is mounted on a vehicle and various information is downloaded from a terminal connected to a network while moving by vehicle. According to this technology, for example, it is possible to wirelessly connect from a vehicle to an access point and download information with entertainment properties such as traffic information and music (for example, see Patent Document 1).
In recent years, various services for streaming distribution of video data from a video distribution server via a network such as the Internet have been provided.
JP 2003-302232 A

However, in streaming distribution of video data, video data that has been encoded and compressed (so-called encoded) by a predetermined encoding (so-called codec) is distributed as video data, but the data size of the original video data is large. For this reason, even if it is encoded and compressed, the data size becomes relatively large.
Therefore, even if streaming reception of video data is started by the in-vehicle device in order to view the video in the vehicle, it takes a relatively long time to receive the video data for a certain period of time, and it is difficult to reproduce.

In addition, it takes a long time to receive the video data, and it is possible that the situation where the reception of the radio waves changes due to the movement of the vehicle and the reception of the video data fails may occur. Because of this situation, video data distribution services for in-vehicle devices are not practical and are not often performed.
In addition, it is possible to reduce the data size of the video data by increasing the encoding compression rate of the video data. However, if the encoding compression rate is increased, the image quality of the video deteriorates, and this is satisfied by the user. In many cases, image quality cannot be obtained.

  The present invention has been made in view of the above-described circumstances, and reduces the delay time from the start of reception to the start of reproduction when the in-vehicle device receives and reproduces the distributed video data. It is an object of the present invention to provide a video distribution system, a video distribution method, a video distribution server, and a video distribution program that can be accommodated within a certain range.

  In order to achieve the above object, the present invention provides an in-vehicle device including a wireless unit that communicates with a wireless base station connected to a network, and a predetermined video bit rate with respect to the in-vehicle device via the network. A video distribution system including a video distribution server that distributes encoded video data in order from the top, wherein the video data is divided into a plurality of data blocks in order from the top, and at least the top data block is other data. A distribution data generation device that converts the video bit rate of each data block so that the video bit rate is lower than the block, and the video distribution server starts each data block generated by the distribution data generation device To the in-vehicle device in order.

  According to the present invention, the video bit rate of at least the first data block to be transmitted is lowered and transmitted to the in-vehicle device. Therefore, since the data size of the data block to be transmitted at least first is reduced, the time required to receive all the data of the data block is shortened, whereby the in-vehicle apparatus starts receiving the data block. It is possible to shorten the delay time until the video data reproduction starts. Furthermore, this delay time can be adjusted by appropriately determining the data size of the leading data block.

In addition, according to the present invention, even when a communication error or the like occurs during reception of a data block and the reception time is extended due to temporary interruption, the reception time is reduced in a data block with a reduced video bit rate. Since the time is shortened, the influence of extending the reception time can be reduced.
Furthermore, the data block for lowering the video bit rate is limited to a few data blocks from the beginning, and the video bit rate of the subsequent data blocks is maintained at a predetermined video bit rate, resulting in a reduction in the video bit rate. Image quality degradation can be suppressed.

  Further, the present invention is the above invention, wherein the distribution data generation device includes a communication speed detection unit that detects a communication speed between the video distribution server and the in-vehicle device, and each video bit of the data block The rate is set to be equal to or lower than the communication speed detected by the communication speed detection unit.

  According to the present invention, the video bit rate of each data block of video data is limited to the communication speed or less between the video distribution server and the in-vehicle device. As a result, the time required for the in-vehicle device to receive each data block can be suppressed within the reproduction time when each data block is reproduced, so that reception of each data block is completed earlier than the reproduction time. Therefore, even if the reception is temporarily interrupted due to a communication error or the like, it is possible to suppress the frequency of interruption of video reproduction.

  In the present invention, the video data has a frame configuration that can be divided into a plurality of divisions.

  According to the present invention, processing for dividing video data into a plurality of data blocks is facilitated.

  In order to achieve the above object, the present invention provides a video that sequentially distributes video data encoded at a predetermined video bit rate from a video distribution server to an in-vehicle device mounted on a vehicle via a network. In the distribution method, the video data distributed by the video distribution server is divided into a plurality of data blocks in order from the top, and each data is set so that at least the top data block has a lower video bit rate than the other data blocks. The video bit rate of the block is converted and transmitted to the in-vehicle device in order from the head data block.

  In order to achieve the above object, the present invention encodes an in-vehicle device having a wireless unit that communicates with a wireless base station connected to a network at a predetermined video bit rate via the network. A video distribution server for distributing video data in order from the top, dividing the video data into a plurality of data blocks in order from the top, so that at least the top data block has a lower video bit rate than other data blocks. A distribution data generation device that converts the video bit rate of each data block is provided, and each data block generated by the distribution data generation device is transmitted to the in-vehicle device in order from the top.

  In order to achieve the above object, the present invention encodes an in-vehicle device having a wireless unit that communicates with a wireless base station connected to a network at a predetermined video bit rate via the network. A video distribution server that distributes video data in order from the top, divides the video data into a plurality of data blocks in order from the top, and sets each data so that at least the top data block has a lower video bit rate than other data blocks. There is provided a video distribution program characterized by converting a video bit rate of a block and functioning as a means for transmitting each data block to the in-vehicle device in order from the top.

According to the video distribution method, the video distribution server, and the video distribution program according to the present invention, the same effects as the video distribution system of the present invention can be obtained.
The video distribution program according to the present invention can be recorded on a computer-readable recording medium and executed.

  According to the present invention, the video bit rate of at least the first data block to be transmitted is lowered and transmitted to the in-vehicle device. Accordingly, since the data size of at least the first data block to be transmitted is reduced, the reception time of the data block is shortened. As a result, the in-vehicle apparatus starts to reproduce the video data after starting to receive the data block. It becomes possible to shorten the delay time until. Further, the delay time can be adjusted by appropriately determining the data size of the leading data block.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram illustrating a configuration of an in-vehicle video distribution system 1 according to the present embodiment.
The in-vehicle video distribution system 1 includes one or a plurality of video distribution servers 3 installed in a service center 2 owned by a video distribution service provider, a WAN (Wide Area Network) 4 as an example of a network, and communication with the WAN 4. A plurality of radio base stations (access points) 5 that can be connected to each other and an in-vehicle device 7 mounted on the vehicle 6, and the in-vehicle device 7 includes a radio unit 8 that performs radio communication with the radio base station 5. And an in-vehicle AV machine main body 9 that performs video display and audio output.
Under such a configuration, in the in-vehicle video distribution system 1, the video data 100 (see FIG. 3) is stream-distributed from the video distribution server 3 to the in-vehicle device 7 via the WAN 4 and the wireless base station 5. The unit 8 sequentially receives the video data and outputs it to the in-vehicle AV machine main body 9, and the in-vehicle AV machine main body 9 performs video display based on the video data 100 and audio output based on the audio data included in the video data 100.

FIG. 2 is a block diagram showing a functional configuration of the video distribution server 3.
The video distribution server 3 includes a control unit 19, a WAN I / F unit 10, a video data selection unit 11, a video data storage unit 12, a video data division unit 13, a communication state determination unit 14, a video data bit rate. And a conversion unit 15.
The control unit 19 centrally controls each unit, and includes a program execution unit, a CPU as a calculation unit, and a ROM 17 as a storage unit. The ROM 17 is a control for distributing the video data 100 to the in-vehicle device 7. A video distribution program 18 that defines processing is stored.

  The WAN I / F unit 10 is a communication interface for bidirectional data communication with the in-vehicle device 7 via the WAN 4, and connection request data transmitted from the wireless unit 8 of the in-vehicle device 7 and a user of the in-vehicle device 7 Various data such as video selection data indicating video desired to be distributed is received and output to the video data selection unit 11, the communication state determination unit 14, the control unit 19, and the like.

The video data selection unit 11 outputs the video selection data received from the in-vehicle device 7 to the video data storage unit 12.
The video data storage unit 12 stores a large number of video data 100 to be distributed. When video selection data is input, the video data storage unit 12 reads the video data 100 indicated by the video selection data and outputs it to the video data dividing unit 13. .

The video data 100 stored in the video data storage unit 12 is encoded and compressed at a predetermined video bit rate and stored by a predetermined encoding / compression method (CODEC) such as MPEG (Moving Picture Experts Group). Yes.
In the present embodiment, as shown in FIG. 3, a case will be described in which video data having a total playback time of 30 minutes is encoded and compressed at a video bit rate of 4 Mbit / s.
The video data includes audio data encoded and compressed by a predetermined encoding / compression method together with the video data. When the video data is reproduced, the audio is output together with the video display.

The video data division unit 13, the communication state determination unit 14, and the video data bit rate conversion unit 15 divide the video data 100 into a plurality of data blocks 101 (see FIG. 3), and the video bit rate of each data block 101 is divided. The distribution data generation device 16 that converts and generates distribution video data is configured.
More specifically, the video data dividing unit 13 divides the video data 100 output from the video data storage unit 12 into a plurality of data blocks 101 (see FIG. 3) from the top, and converts each data block 101 to video data bit rate conversion. The data are output to the unit 15 in order from the top.
In the present embodiment, as shown in FIG. 3, the video data dividing unit 13 converts the video data 100 encoded and compressed at a video bit rate of 4 Mbit / s into video data 100 of 30 minutes and a playback time of 5 minutes. Each of the data blocks 101 is divided every time to generate six data blocks 101.

Note that the video data dividing unit 13 is not limited to the configuration in which the video data 100 is divided every predetermined reproduction time from the top, for example, every predetermined data size from the top of the video data 100, every data size weighted by the number of divisions, etc. Alternatively, the video data 100 can be divided using various criteria such as random.
In addition, the video data 100 usually includes a plurality of divisions called chapters linked with the content of the video, or a plurality of key frames used in an encoding compression method such as MPEG. This key frame is a frame having no correlation with the immediately preceding frame in the frame data sequence generated by encoding and compressing the original video data, and the video data 100 is divided by this frame. In some cases, it is not necessary to re-encode the frame at the division point.
Therefore, the video data dividing unit 13 may be configured to perform division according to the content of the video by dividing the video data 100 at the delimiter positions indicated by the chapters. Also, the video data 100 may be divided at each key frame position. It is good also as a structure which makes the process which re-encodes the flame | frame before and behind a dividing point unnecessary by dividing | segmenting.

  Next, when the WAN I / F unit 10 receives the connection request data and video selection data, the communication state determination unit 14 shown in FIG. 2 receives the bit error rate and frame error rate that have occurred in the received data. Based on the number of mobile units connected in the service area of the radio base station 5 to which the in-vehicle device 7 is connected, the communication data rate that can be used for communication with the in-vehicle device 7 is determined. Calculate and output to the video data bit rate converter 15.

  Each time the data block 101 is input from the video data dividing unit 13, the video data bit rate conversion unit 15 calculates the communication data rate calculated by the communication state determination unit 14 and the order from the top of the data block 101. Based on this, the video bit rate of the data block 101 is determined, and the video data of the data block 101 is encoded and compressed again at the determined video bit rate and output to the WAN I / F unit 10. 7 is transmitted.

The determination of the video bit rate by the video data bit rate conversion unit 15 and re-encoding and compression will be described in further detail.
In the present embodiment, the third data from the first data block 101 is set so that at least the video bit rate of the first data block 101 among the plurality of data blocks 101 is smaller than the video bit rate of the other data block 101. For block 101, the video bit rate is defined as follows.
That is, as shown in FIG.
The video bit rate of the first data block 101 is 1/8 of the original video bit rate.
The video bit rate of the second data block 101 is 1/4 of the original video bit rate.
The video bit rate of the third data block 101 is ½ of the original video bit rate.
The video bit rate of the fourth and subsequent data blocks 101 is the same as the original video bit rate.

  According to the definition of the video bit rate based on the order of the data blocks 101, the video bit rate of the first data block 101 is 0.5 Mbit / s and the video bit rate of the second data block 101 as shown in FIG. Is 1 Mbit / s, the video bit rate of the third data block 101 is 2 Mbit / s, and the video bit rate of the fourth and subsequent data blocks 101 is 4 Mbit / s.

Here, when the communication speed (bps) between the in-vehicle device 7 and the video distribution server 3 is low, the in-vehicle device 7 receives all the data blocks 101 of the video data 100 with respect to the total reproduction time of the video data 100. The reception time until the playback becomes longer and playback is interrupted.
Therefore, in the present embodiment, the ratio between the communication speed Ba obtained by converting the communication data rate calculated by the communication state determination unit 14 into the bit rate and the video bit rate Bb determined based on the order of the data blocks 101. The video bit rate of each data block 101 is corrected so that is at least 1.

That is, if the video bit rate Bc at the time of data block transmission determined by the video data bit rate conversion unit 15 is
1) When Ba / Bb ≦ 1, Bc = Bb
2) When Ba / Bb> 1, Bc = Ba × α (where α is a constant of 1 or less)
It becomes.

  For example, when the communication speed Ba is 3 Mbps, in the example shown in FIG. 3, the video bit rate Bb of the third data block 101 from the head is smaller than the communication speed Ba. The video bit rate Bc = Bb of the data block 101 is determined. On the other hand, since the video bit rate Bb of the fourth and subsequent data blocks 101 is larger than the communication speed Ba, the video data bit rate conversion unit 15 sets the video bit rate Bc of the fourth and subsequent data blocks 101 to, for example, 3 Mbit / s is determined, and each data block 101 is encoded and compressed again to sequentially generate data blocks 101A.

As a result, as shown in FIG. 3, the reception time required for the in-vehicle device 7 to receive each data block 101A is the reproduction time of the video of the data block 101A (this embodiment) even for the data block 101A having the largest video bit rate. In the embodiment, the reception time is much shorter than usual in the first data block 101A having the lowest video bit rate.
Then, when the in-vehicle device 7 sequentially receives the data block 101A via the wireless base station 5, video reproduction based on each data block 101A is performed.

If the video data 100 includes audio data, the constant α is set in consideration of the audio bit rate of the audio data.
That is, the constant α is determined so that the video bit rate Bc at the time of data block transmission is equal to or less than the bit rate obtained by subtracting the audio bit rate Bd from the communication speed Ba, and it is necessary to transmit one data block 101A. The time is ensured to be within the reproduction time when the data block 101A is reproduced.

FIG. 4 is a diagram showing a functional configuration of the radio base station 5 shown in FIG.
The wireless base station 5 includes a WAN I / F unit 20 that is a communication interface for communicating with the video distribution server 3 via the WAN 4, and a wireless LAN unit 21 that performs wireless communication with the in-vehicle device 7 in accordance with the wireless LAN standard. And a base station data control unit 22 that controls the relay operation of data communication, and functions as a relay device that relays bidirectional data communication between the video distribution server 3 and the in-vehicle device 7.

FIG. 5 is a diagram showing the configuration of the in-vehicle device 7 shown in FIG.
As shown in FIG. 5, the in-vehicle device 7 includes a main control unit 30, a wireless LAN unit 31, a display unit 32, an audio unit 33, and a user I / F (interface) unit 34.
The main control unit 30 centrally controls each unit, and performs O (Input / Output) control such as a CPU as a program execution unit, a DSP as a signal processing unit, and an input from the user I / F unit 34. An I / O control unit to be executed is included. The main control unit 30 has a ROM 35 and a RAM 36 as storage means, and various programs and data such as a video data receiving program 37 are stored in the ROM 35.

  The video data receiving program 37 is a program for receiving and playing back video data from the video distribution server 3, and when the main control unit 30 executes the video data receiving program 37, data communication control and video data reception are performed. Various controls such as demodulation and reproduction control are performed, which will be described in detail later.

  The wireless LAN unit 31 is responsible for processing of the physical layer, data link layer, and media access layer in the OSI reference model, and the main control unit 30 executes processing in layers higher than the media access layer such as the transport layer and the session layer. Thus, in cooperation with the main control unit 30, wireless communication is performed with the wireless base station 5, and bidirectional communication with the video distribution server 3 is performed via the wireless base station 5 and the WAN 4. The wireless LAN unit 31 and the main control unit 30 constitute the wireless unit 8 shown in FIG.

The display unit 32 includes a liquid crystal panel as an example of a flat panel display and a drive unit that drives the liquid crystal panel, and displays video based on video data received from the video distribution server 3 under the control of the main control unit 30. And various displays such as a menu screen display.
The audio unit 33 includes an amplifier that amplifies an audio signal, and a speaker device that outputs sound into the vehicle interior based on the audio signal amplified by the amplifier. From the video distribution server 3 under the control of the main control unit 30. Play audio data contained in the received video data.

The user I / F 34 is an input device for inputting operations by a user such as various operation devices such as a touch panel and a switch and an infrared remote control receiving device. The user I / F unit 34 receives, for example, a video for the video distribution server 3. A data download request and an operation for selecting video data to be downloaded are input and output to the main control unit 30.
Note that the main control unit 30, the display unit 32, the audio unit 33, and the user I / F unit 34 constitute the in-vehicle AV machine main body 9 shown in FIG.

Next, a functional configuration of the in-vehicle device 7 realized by the main control unit 30 of the in-vehicle device 7 executing the video data reception program 37 will be described.
FIG. 6 is a block diagram showing a functional configuration of the in-vehicle device 7.
As shown in this figure, the main control unit 30 executes a video data reception program 37 to thereby perform a video distribution server connection control unit 40, a transmission unit 41, a reception unit 42, a reception data processing unit 43, and video data. It functions as a demodulation / reproduction unit 44.
The video distribution server connection control unit 40 outputs a connection request for the video distribution server 3 to the transmission unit 41 when a video distribution request is input from the user I / F unit 34 by the user.

The transmission unit 41 generates communication data of various data to be transmitted to the video distribution server 3 according to a predetermined communication protocol. When a connection request is input from the video distribution server connection control unit 40, Connection request data is generated, output to the wireless LAN unit 31, and transmitted from the wireless LAN unit 31 to the video distribution server 3.
The reception unit 42 generates reception data from various communication data received from the video distribution server 3 via the WAN 4 according to the predetermined communication protocol, and outputs the reception data to the reception data processing unit 43.

The reception data processing unit 43 generates various data included in the reception data output from the reception unit 42. When the data block 101A of the video data 100 is included, this data block 101A is output to the video data demodulation / reproduction unit 44.
When the data block 101A of the video data 100 is input, the video data demodulating / reproducing unit 44 demodulates the predetermined coding compression applied to the data block 101A to generate video data and audio data. The video data is output to the display unit 32, and the audio data is output to the audio unit 33. As a result, video and audio are reproduced.

  Here, the video data demodulating / reproducing unit 44 is provided with a buffer memory 45, and the data of the data block 101A being received is sequentially buffered (accumulated) in the buffer memory 45. When reproducing the distributed video, first, the first data block 101A of the video data 100 is buffered in the buffer memory 45, and then the data block 101A is reproduced. In parallel with this reproduction, the data of the next data block 101A is buffered in the buffer memory 45.

Next, the operation of the in-vehicle video distribution system 1 according to this embodiment will be described.
FIG. 7 is a sequence diagram showing both the operations of the in-vehicle device 7 and the video distribution server 3.
When the user inputs from the user I / F 34 of the in-vehicle device 7 that the video distribution server 3 receives video distribution, the in-vehicle device 7 transmits connection request data to the video distribution server 3 (step S1).
The video distribution server 3 receives the connection request data by receiving the connection request data, and transmits a list of video data 100 that can be distributed stored in the video data storage unit 12 to the in-vehicle device 7 (step S2). ). Note that when this connection request is received, user authentication processing is also performed.

When receiving the list, the in-vehicle device 7 displays the list on the display unit 32 so that the user can select a video requesting distribution, obtains the user's selection result from the user I / F unit 34, and displays the video as video selection data. It transmits to the distribution server 3 (step S3).
When receiving the video selection data, the video distribution server 3 reads the video data 100 selected by the user from the video data storage unit 12 (step S4).
In addition, in the video distribution server 3, the communication state determination unit 14 determines that the in-vehicle device 7 and the video distribution server 3 are based on the connection request data received in step S1 or the video selection data received in step S3. The communication speed Ba between the two is calculated (step S5).

Next, the video distribution server 3 divides the video data 100 read in step S4 into a plurality of data blocks 101 in order from the top based on a predetermined division criterion (step S6), and the top of these data blocks 101 is the top. The following processing is performed in order from the data block 101.
That is, the video distribution server 3 sets the video bit rate Bc of the data block 101 based on the order from the top of the data block 101 to be processed and the communication speed Ba calculated in step S5. When the video bit rate Bc is different from the current video bit rate Bb of the data block 101, the data block 101 is encoded and compressed again at the video bit rate Bc to generate the data block 101A (step S7). The data block 101A is transmitted to the in-vehicle device 7 (step S8).
Then, the video distribution server 3 performs the processing of step S7 and step S8 for all the data blocks 101A (step S9: Y), and then ends the processing.

The in-vehicle device 7 receives the data block 101A transmitted from the video distribution server 3 in step S8 (step S10), sequentially buffers it in the buffer memory 45, and completes reception of the first data block 101A. Then, the reproduction of the video data of the data block 101A is started (step S11).
Thus, as shown in FIG. 3, the data block 101A is reproduced after the delay time Ta from the start of reception of the first data block 101A of the video data 100 until the reception of the data block 101A is completed. Is started.
As described above, the delay time Ta depends on the video bit rate Bc of the leading data block 101A. Since this video bit rate Bc is smaller than the normal video bit rate Bb of the other data block 101A, the reception time is shortened, whereby the delay time Ta is shortened and the waiting time until the start of reproduction is reduced. Shortened.

Next, as shown in FIG. 7, the in-vehicle device 7 continues to execute steps S10 and S11 until reception of all data blocks 101A is completed, and when reception of all data blocks 101A is completed (step S12: Y), the process ends.
If unreproduced data blocks 101A are stored in the buffer memory 45 at the end of this process, the video reproduction process is continued until the reproduction of these data blocks 101A is completed.

As described above, according to the present embodiment, when video data is transmitted from the video distribution server 3 to the in-vehicle device 7, the video data 100 is divided into a plurality of data blocks 101 in order from the top, and at least the top Each data block 101A in which the video bit rate of the data block 101 is lower than the predetermined video bit rate Bb of the other data block 101 is sequentially transmitted to the in-vehicle device 7.
With this configuration, since the data size of the data block 101A transmitted to the in-vehicle device 7 at first is smaller than usual, the reception time required to receive all data of the data block 101A is shortened. It is possible to shorten the delay time Ta from the start of reception of the data block 101A until the in-vehicle device 7 starts to reproduce the video data. Further, the delay time Ta can be adjusted by appropriately determining the data size of the leading data block 101A.

Furthermore, even when a communication error or the like occurs during reception of the data block 101A, and the reception time of the data block 101A is extended due to temporary interruption, the reception time is shortened by the data block 101A having a reduced video bit rate. Therefore, the effect of extending the reception time can be reduced.
Furthermore, by limiting the data block 101A for lowering the video bit rate to a few data blocks 101A from the top, it is possible to suppress image quality degradation accompanying a reduction in the video bit rate.
Especially in the case of video such as movies and dramas, since the beginning of the playback often includes videos that are not closely related to the main part, such as the opening video, image quality degradation at the beginning of the playback has a major impact on the main part. Never give.

According to the present embodiment, the video bit rate Bc of each of the data blocks 101A transmitted from the video distribution server 3 is configured to be lower than the communication speed Ba between the video distribution server 3 and the in-vehicle device 7. did.
With this configuration, since the reception time required for the in-vehicle device 7 to receive each data block 101A is suppressed within the reproduction time when reproducing each data block 101A, the reception of each data block 101A is earlier than the reproduction time. Therefore, even if reception is temporarily interrupted due to a communication error or the like, it is possible to suppress the frequency of interruption of video reproduction.

  Also, by encoding and compressing the video data 100 so as to have a frame structure that can be divided into a plurality of frames, the process of dividing the video data into a plurality of data blocks 101 is facilitated.

  The above-described embodiment is merely an aspect of the present invention, and can be arbitrarily modified and applied within the scope of the present invention.

For example, in the above-described embodiment, the video distribution server 3 includes the distribution data generation device 16 including the video data division unit 13, the communication state determination unit 14, and the video data bit rate conversion unit 15. However, the distribution data generation device 16 may be provided separately from the video distribution server 3.
That is, the distribution data generation device 16 is interposed between the video distribution server 3 and the WAN 4, and the video data 100 output from the video distribution server 3 is transferred to a plurality of data blocks 101 by the distribution data generation device 16. The video bit rate of each data block 101 may be converted by dividing.

  Further, in the above-described embodiment, the case where the video distribution server 3 distributes the video data 100 only to the in-vehicle device 7 is illustrated. However, in addition to the in-vehicle device 7, for example, a mobile terminal such as a mobile phone, a notebook personal computer, or a PDA Of course, the video data 100 may be distributed. In this case, the video data 100 may be divided into a plurality of data blocks 101 and delivered in the same manner as in the case of delivering the video data 100 to the in-vehicle device 7, or delivered in the same manner as normal streaming delivery. You may do it.

  In the above-described embodiment, the configuration in which the communication state determination unit 14 that calculates the communication speed Ba between the in-vehicle device 7 and the video distribution server 3 is provided in the video distribution server 3 is described. It is good also as a structure which is provided in the vehicle-mounted apparatus 7 and transmits the calculation result of communication speed Ba to the video delivery server 3. FIG.

  In the above-described embodiment, the case where the video data 100 is encoded and compressed in advance at a constant video bit rate has been exemplified. However, the present invention is not limited thereto, and the video data amount per unit frame and the preceding and following frames are not limited. It may be encoded and compressed by varying the video bit rate according to the correlation.

It is the schematic which shows the structure of the vehicle-mounted video delivery system. It is a block diagram which shows the functional structure of a video delivery server. It is a figure which shows the aspect of delivery with the data block of video data. It is a block diagram which shows the functional structure of a wireless base station. It is a figure which shows the structure of a vehicle-mounted apparatus. It is a block diagram which shows the functional structure of a vehicle-mounted apparatus. The timing chart which shows operation | movement of the vehicle-mounted image delivery system.

Explanation of symbols

1 In-vehicle video distribution system 3 Video distribution server 4 WAN
DESCRIPTION OF SYMBOLS 5 Radio base station 6 Vehicle 7 In-vehicle apparatus 8 Radio | wireless part 12 Image | video data storage part 13 Image | video data division | segmentation part 14 Communication state determination part 15 Image | video data bit rate conversion part 16 Distribution data generation apparatus 18 Image | video distribution program 19 Control part 45 Buffer memory 100 Video data 101, 101A Data block Ba Communication speed Bb, Bc Video bit rate Ta Delay time

Claims (6)

An in-vehicle device including a wireless unit that communicates with a wireless base station connected to a network;
A video distribution system comprising a video distribution server that sequentially distributes video data encoded at a predetermined video bit rate to the in-vehicle device via the network,
The distribution data generation device that divides the video data into a plurality of data blocks in order from the top and converts the video bit rate of each data block so that at least the top data block has a lower video bit rate than other data blocks With
The video distribution server transmits each data block generated by the distribution data generation device to the in-vehicle device in order from the top. The video distribution system according to claim 1,
The delivery data generation device includes:
A communication speed detection unit that detects a communication speed between the video distribution server and the in-vehicle device;
A video distribution system, wherein a video bit rate of each of the data blocks is set to be equal to or lower than a communication speed detected by the communication speed detector. The video distribution system according to claim 1 or 2,
The video distribution system, wherein the video data has a frame configuration that can be divided into a plurality of frames. A video distribution method for sequentially distributing video data encoded at a predetermined video bit rate from a video distribution server to an in-vehicle device mounted on a vehicle via a network,
The video data distributed by the video distribution server is divided into a plurality of data blocks in order from the top, and the video bit rate of each data block is set so that at least the top data block has a lower video bit rate than other data blocks. Converting and transmitting to the in-vehicle device in order from the head data block. A video distribution server that sequentially distributes video data encoded at a predetermined video bit rate from the top to an in-vehicle device having a radio unit that communicates with a radio base station connected to a network. And
The distribution data generation device that divides the video data into a plurality of data blocks in order from the top and converts the video bit rate of each data block so that at least the top data block has a lower video bit rate than other data blocks With
A video distribution server, wherein each data block generated by the distribution data generation device is transmitted to the in-vehicle device in order from the top. A video distribution server that distributes video data encoded at a predetermined video bit rate in order from the top to an in-vehicle device including a wireless unit that communicates with a wireless base station connected to a network,
The video data is divided into a plurality of data blocks in order from the top, and the video bit rate of each data block is converted so that at least the top data block has a lower video bit rate than other data blocks. A video distribution program that functions as means for transmitting to the in-vehicle device in order from the top.

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