JP2005175787A - Device, system, and method for distributing data - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a data distributing device, a data distribution system, and a data distribution method that reduce turbulence in a moving picture corresponding to moving image data to be distributed without requiring burdensome communication processing. <P>SOLUTION: A distribution section 404 transmits the moving image data stored in a reception buffer 403 to a reception terminal 206. The reception terminal 206 requests the retransmission of the moving image data that cannot be received. When the distribution section 404 receives the retransmission request, the distribution section 404 acquires the moving image data according to the retransmission request from a buffer 407 for retransmission and transmits the acquired moving image data to a reception terminal 206. The moving image data stored into the buffer 407 for retransmission is moving image data where the moving image data stored into the reception buffer 403 are compressed, thus transmitting the compressed data as the moving image data in retransmission, shortening retransmission time, and preventing the turbulence of the moving image following the retransmission. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a data distribution apparatus, a data distribution system, and a data distribution method, and more particularly to a data distribution apparatus, a data distribution system, and a data distribution method that retransmit data in response to a retransmission request.

  In recent years, wireless LANs represented by IEEE802.11b have been rapidly spreading. In addition, high-speed data communication in mobile phone services such as HSDPA (High Speed Downlink Packet Access) that realizes a maximum of 14 Mbps and CDMA2000 EV-DO that realizes a maximum of 2.4 Mbps in 3G networks is also being realized.

  In mobile communication, the communication network is changing from a mobile communication network specialized for voice to a more general-purpose data communication network, and at the same time, the speed of throughput is steadily increasing.

  In the future, as mobile IP communications with higher speeds expand, services that take advantage of the higher speed, such as streaming services such as video distribution, will start.

  The moving picture streaming service includes a form in which content stored in a content server or the like is distributed for each user and a form in which real-time video is distributed to the user.

  FIG. 9 is a block diagram for explaining a method for distributing real-time video. Hereinafter, a method for delivering real-time video will be described with reference to FIG.

  The moving image video signal sent from the camera 101 that is photographing the subject is compressed and encoded in the MPEG2 format by the MPEG2 real-time encoder 102, and the compressed and encoded moving image data is temporarily stored in the storage server 103.

  In response to a request from the receiving terminal 107, the distribution server 104 converts the moving image data temporarily stored in the storage server 103 into a multicast routing protocol such as PIM-SM (Protocol Independent Multicast-Sparse Mode) and a multicast route. Distribution is performed using the router 105 corresponding to the control protocol.

  If the receiving terminal 107 is connected to the wired network via the wireless LAN, the distribution server 104 passes through the router 105 and the Access Point 106 connected to the wired network to which the receiving terminal 107 is connected. Then, the moving image data temporarily stored in the storage server 103 is distributed to the receiving terminal 107.

  When a transmission error occurs in a section (for example, a wireless section) where a transmission error is likely to occur when distributing real-time video, the receiving terminal 107 generally does not attempt to recover the video data in which the transmission error has occurred. Display of the moving image is continued by continuing the reception of the moving image data or by retransmitting the same moving image data as the moving image data in which the transmission error has occurred from the multicast router 105 closest to the receiving terminal 107.

  For example, in Patent Document 1 (Japanese Patent Laid-Open No. 2002-84239), a receiving terminal that receives real-time video distribution requests the distribution side to retransmit data lost due to a transmission error, and the distribution side retransmits the data. A media information distribution system that retransmits data in response to a request to a receiving terminal is described.

In Patent Document 2 (Japanese Patent Laid-Open No. 2003-125374), before the distribution side distributes real-time video to the receiving terminal, the distribution side distributes the test data to the receiving terminal, and the receiving terminal transmits the test data. A video distribution system is described in which reception device information indicating frame dropping or the like that occurs during reproduction is transmitted to the distribution side, and the distribution side creates a video distribution condition according to the reception device information.
JP 2002-84239 A JP 2003-125374 A

  Even if a transmission error occurs when distributing a real-time video, if the error is not corrected, moving image data necessary for displaying a moving image cannot be obtained, so that the display quality of moving images is degraded. In particular, in the case of moving image distribution in the MPEG2 format, since moving image data is distributed in a compressed form, the loss of some data in the moving image data affects a wide range of moving images.

  Further, in the case of a method of retransmitting the same moving image data as the moving image data in which a transmission error has occurred as in the media information distribution system described in Patent Document 1, a delay caused by retransmission becomes a problem. When delays overlap, the delays are accumulated accordingly. As a result, finally, a situation occurs in which the moving image data before the past moving image data buffered by the multicast router 105 located closest to the receiving terminal is required. In that case, there is a disadvantage that the moving image displayed on the receiving terminal must be skipped for a certain period of time.

  In commercial services where quality is strictly questioned, it is desirable to eliminate as much as possible the problems of disturbing moving images.

  Further, in the video distribution system described in Patent Document 2, the distribution side distributes test data to the receiving terminal, and transmits to the distribution side receiving device information indicating frame dropping or the like that occurs when the receiving terminal reproduces the test data. Such a cumbersome communication process is required.

  An object of the present invention is to provide a data distribution apparatus, a data distribution system, and a data distribution method that reduce disturbance of moving images according to moving image data to be distributed without requiring troublesome communication processing.

  In order to achieve the above object, the data distribution apparatus according to the present invention transmits moving image data to a receiving apparatus, and transmits the moving image data to the receiving apparatus that has requested retransmission of the moving image data. A data distribution device that transmits moving image data, the receiving unit that receives the moving image data retransmission request, and the receiving device that has made the moving image data retransmission request, compressed data obtained by compressing the moving image data, And a transmission unit that transmits the video data for retransmission.

  Also, the data distribution method of the present invention is a data distribution for transmitting moving image data to a receiving device and transmitting moving image data for retransmission according to the retransmission request to a receiving device that has requested retransmission of the moving image data. A data distribution method performed by an apparatus, wherein a reception step of accepting a retransmission request for the moving picture data, and compressed data obtained by compressing the moving picture data for the receiving apparatus that has requested the retransmission of the moving picture data are used for the retransmission A transmission step of transmitting as moving image data.

  According to the above invention, the compressed data obtained by compressing the moving image data is transmitted as the moving image data for retransmission to the receiving device that has requested the retransmission of the moving image data. For this reason, the size of the moving image data for retransmission becomes smaller than the size of the moving image data, and the transmission time of the moving image data for retransmission can be shortened. Therefore, it is possible to reduce the image disturbance due to the long transmission time of the moving image data for retransmission. Further, troublesome communication processing using test data can be eliminated.

  In the data distribution apparatus, it is preferable that the moving image data includes at least luminance information and color difference information, and the transmission unit uses moving image data obtained by removing the color difference information from the moving image data as the compressed data.

  In the data distribution method, it is preferable that the moving image data includes at least luminance information and color difference information, and the transmission step uses moving image data obtained by removing the color difference information from the moving image data as the compressed data.

  According to the above invention, moving image data obtained by removing color difference information from moving image data is used as compressed data. In general, the human eye is less sensitive to changes in color difference than changes in luminance, so even if the color difference information is omitted, the image does not appear to be greatly degraded in the human eye. In the above invention, it is possible to reduce the size of the video data for retransmission without significantly reducing the quality of the video in the receiving device by using the video data for retransmission excluding color difference information from the video data, The transmission time of the moving image data for retransmission can be shortened.

  Further, in the data distribution device, the moving image data is moving image data obtained by compressing predetermined video data using a predetermined quantization scale code value, and the transmission unit uses the predetermined video data as the compressed data. It is preferable to use moving image data that is compressed using a quantization scale code value larger than the predetermined quantization scale code value.

  In the data distribution method, the moving image data is moving image data obtained by compressing predetermined video data using a predetermined quantization scale code value, and the transmission step includes the predetermined video data as the compressed data. It is preferable to use moving image data that is compressed using a quantization scale code value larger than the predetermined quantization scale code value.

  According to the above invention, moving image data obtained by compressing predetermined image data using a quantization scale code value larger than a predetermined quantization scale code value is used as the compressed data. For this reason, by roughening the image indicated by the compressed data, the size of the moving image data for retransmission can be reduced, and the transmission time of the moving image data for retransmission can be shortened. Further, for example, even when moving image data compressed by the MPEG2 method is used as moving image data to be transmitted to the receiving device, data obtained by compressing moving image data can always be used as moving image data for retransmission.

  In the data distribution apparatus, it is preferable that the transmission unit transmits the compressed moving image data obtained by compressing the moving image data as the moving image data after transmitting the compressed data.

  Preferably, the data distribution method further includes a moving image compressed data transmitting step of transmitting the compressed moving image data obtained by compressing the moving image data as the moving image data after transmitting the compressed data.

  According to said invention, the moving image compression data which compressed moving image data are transmitted as moving image data transmitted to a receiver after transmitting compressed data. Since the moving image compressed data is smaller in size than the moving image data, the transmission time of the moving image data can be shortened. For this reason, it is possible to recover the delay generated by transmitting the moving image data for retransmission by transmitting the compressed moving image data obtained by compressing the moving image data. Therefore, it is possible to reduce image disturbance due to a delay caused by transmitting the moving image data for retransmission.

  The data distribution system of the present invention is a data distribution system including a receiving device and a data distribution device that transmits moving image data to the receiving device, wherein the receiving device makes a retransmission request for the moving image data, The data distribution apparatus is the data distribution apparatus.

  The data distribution method of the present invention is a data distribution method performed by a data distribution system including a receiving device and a data distribution device that transmits moving image data to the receiving device, wherein the receiving device A retransmission request is made, and each step of the data distribution method is included.

  According to the above invention, the same effect as described above can be achieved in the data distribution system.

  According to the present invention, compressed data obtained by compressing moving image data is transmitted as retransmission moving image data to a receiving apparatus that has requested retransmission of moving image data. For this reason, the size of the moving image data for retransmission becomes smaller than the size of the moving image data, and the transmission time of the moving image data for retransmission can be shortened.

  Therefore, it is possible to reduce the image disturbance due to the long transmission time of the moving image data for retransmission. Further, troublesome communication processing using test data can be eliminated.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing a data distribution system according to an embodiment of the present invention.

  In FIG. 1, this data distribution system includes a distribution server 201, a content storage 202, a router 203, a wireless distribution station 204 as a data distribution device, a wireless base station 205, and a reception terminal 206 as a reception device. Including.

  The distribution server 201 has a function of distributing streaming video data stored in the content storage 202. The protocol used by the distribution server 201 for multicast route control is not particularly limited. As a protocol used by the distribution server 201 for multicast path control, for example, PIM-SM is conceivable.

  The content storage 202 stores moving image data that the distribution server 201 distributes to the receiving terminal 206. Note that the method of storing content (moving image data) in the content storage 202 is not limited. In this embodiment, the content server 202 stores data (MPEG2 TS) obtained by compressing and encoding a moving image signal in the MPEG2 format as moving image data.

  The routers 203a, 203b, and 203c have a function of processing a protocol (such as PIM-SM) used in multicast in addition to a function of routing an IP protocol. Each of the routers 203a, 203b, and 203c transmits the moving image data (MPEG2 TS) distributed from the distribution server 201 to the radio base station 204.

  The wireless distribution station 204 as a data distribution apparatus according to an embodiment of the present invention is a router capable of processing a multicast protocol.

  The wireless distribution station 204 receives moving image data (MPEG2 TS) from the router 203. In addition, the wireless distribution station 204 transmits moving image data to the receiving terminal 206 and transmits moving image data for retransmission according to the retransmission request to the receiving terminal 206 that has requested retransmission of the moving image data. Furthermore, the wireless distribution station 204 transmits compressed data obtained by compressing the moving image data designated by the retransmission request to the receiving terminal 206 that has requested the moving image data retransmission as retransmission moving image data.

  The radio base station 205 has a function of bearer-converting a signal from wired to wireless or from wireless to wired. For example, a wireless LAN access point or a Node B of a 3G network corresponds to the wireless base station 205.

  The receiving terminals 206a, 206b, and 206c receive moving image streaming data (moving image data) from the wireless distribution station 204. If the receiving terminals 206a, 206b, and 206c cannot receive moving image data, the receiving terminals 206a, 206b, and 206c request retransmission of the moving image data that could not be received.

  FIG. 2 is an explanatory diagram showing an example of a protocol stack of the wireless distribution station 204.

  The wireless distribution station 204 uses Ethernets 301a and 301b for the first and second layers of the OSI (Open Systems Interconnection) seven-layer model. The wireless distribution station 204 uses IPs 302a and 302b as protocols located in the network layer of the OSI 7 layer model. In addition, the wireless distribution station 204, as a protocol positioned above the IP, includes IGMP (Internet Group Management Protocol) 303 and PIM-SM 304, which are protocols used for multicast flow control, and UDP (User Datagram) used in the multicast flow itself. Protocol) 305 and distribution control unit 306 are used.

  FIG. 3 is a block diagram showing a first embodiment of the distribution control unit 306 as a transmission unit and a reception unit.

  The distribution control unit 306 includes a sequence number assigning unit 401, a reception buffer management unit 402, a reception buffer 403, a distribution unit 404, a compression unit 405, a retransmission buffer management unit 406, and a retransmission buffer 407.

  The sequence number assigning unit 401 divides MPEG2-TS (transport stream), which is moving image data received from the router 203, into headers and macroblock units of each layer, and divides each (hereinafter referred to as “divided moving image data”). Assign a sequence number to it. The divided moving image data is also moving image data. The sequence number assigning unit 401 receives the pair of the assigned sequence number and the header (divided moving image data) or the pair of the assigned sequence number and the macro block (divided moving image data) as the reception buffer managing unit 402 and the compressing unit 405. Send to.

  The reception buffer management unit 402 stores the sequence number and macroblock (divided moving image data) pair and the sequence number and header (divided moving image data) pair received from the sequence number assigning unit 401 in the receiving buffer 403.

  If the pair received from the sequence number assigning unit 401 includes a macro block (divided moving image data), the compressing unit 405 compresses the macro block (divided moving image data) included in the pair received from the sequence number assigning unit 401. The compression result is sent to the retransmission buffer management unit 406 together with the sequence number received from the sequence number assignment unit 401.

  The retransmission buffer management unit 406 stores the sequence number received from the compression unit 405 and the header pair of each layer and the received sequence number and compressed data pair in the retransmission buffer 407.

  The distribution unit 404 transmits the moving image data stored in the reception buffer 403 to the reception terminal 206. Specifically, the distribution unit 404 transmits the moving image data stored in the reception buffer 403 to the receiving terminal 206 in units of divided moving image data.

  Also, the distribution unit 404 receives a retransmission request for moving image data (divided moving image data) transmitted from the receiving terminal 206, and responds to the receiving terminal 206 that has made a retransmission request for moving image data (divided moving image data) with a retransmission request. The compressed data obtained by compressing the indicated moving image data (divided moving image data) is transmitted as moving image data for retransmission.

  Specifically, upon receiving a retransmission request from the receiving terminal 206, the distribution unit 404 acquires moving image data (divided moving image data) that is compressed data from the retransmission buffer 407, and acquires the acquired moving image data (divided moving image data). Is distributed to the receiving terminal 206 via the radio base station 205. In FIG. 3, the radio base station 20 is omitted.

  Next, the operation will be described.

  In FIG. 4, the sequence number assignment unit 401 divides MPEG TS, which is moving image data, into header and macroblock units, assigns a sequence number to each divided (divided moving image data), and the compression unit 405 performs moving image data. It is explanatory drawing for demonstrating the operation | movement which compresses.

  Hereinafter, referring to FIG. 4, sequence number assigning section 401 divides MPEG TS, which is moving image data, into header and macroblock units, assigns sequence numbers to each divided (divided moving image data), and compresses An operation 405 compresses moving image data.

  When the sequence number assigning unit 401 receives the MPEG2-TS 501 that is the moving image data from the router 203, the sequence number assigning unit 401 receives the received MPEG2-TS 501 from the layer higher than the macro block layer, the macro block information, and the macro block information. Is divided into each of the blocks belonging to (divided video data).

  Specifically, the sequence number assignment unit 401 belongs to the TS2-header, PES-header, sequence header, GOP header, picture header, slice information, macroblock information, and macroblock information for the MPEG2-TS501 supplied from the router 203. Divide into blocks (divided video data).

  The number of blocks belonging to the macro block information varies depending on the format of the moving image data (MPEG2-TS) sent. If the format of the moving image data (MPEG2-TS) to be sent is 4: 4: 4 format 503, the number of blocks belonging to the macroblock information is 12.

  When the format of the moving image data (MPEG2-TS) to be sent is 4: 2: 2 format 502, the number of blocks belonging to the macroblock information is 8.

  The sequence number assigning unit 401 assigns a sequence number to each of the divided moving image data. When the sequence number allocation for each of the divided moving image data ends, the sequence number assigning unit 401 passes the moving image data including a pair of the sequence number and the divided moving image data to the compression unit 405.

  When the moving image data received from the sequence number assigning unit 401 includes a macro block, the compressing unit 405 converts the moving image data received from the sequence number assigning unit 401 into a 4: 2: 0 format 504 having 6 blocks. Convert.

  Specifically, when the moving image data is sent in the 4: 4: 4 format from the sequence number assigning unit 401, the compression unit 405 reduces the data for 6 blocks from the moving image data, and the moving image data When it is sent from the sequence number assigning unit 401 in the 4: 2: 2 format, the data of two blocks of the moving image data is reduced.

  Returning to FIG. 3, the compression unit 405 passes the moving image data (compressed data) whose data amount is compressed by reducing the data to the retransmission buffer management unit 406. The retransmission buffer management unit 406 stores the compressed data passed from the compression unit 405 in the retransmission buffer 407.

  FIG. 5 is a sequence diagram for explaining an operation at the time of retransmission of moving image data (divided moving image data). Hereinafter, the operation at the time of retransmission of moving image data will be described with reference to FIG.

  The distribution unit 404 assumes that the divided moving image data DATA (k-1) up to the sequence number k-1 has been sent to the receiving terminal 206 (step 601).

  The distribution unit 404 acquires the divided moving image data DATA (k) to which the sequence number k is assigned from the receiving buffer 403 in order to transmit the moving image data to the receiving terminal 206 (step 602).

  When the distribution unit 404 acquires the divided moving image data DATA (k) to which the sequence number k is assigned, the distribution unit 404 transmits the acquired divided moving image data DATA (k) to the receiving terminal 206 (step 603). Similarly, the distribution unit 404 transmits the divided moving image data DATA (k + 1) to which the sequence number k + 1 is assigned to the receiving terminal 206 (steps 604 and 605).

  In this embodiment, it is assumed that the divided moving image data DATA (k + 1) has not reached the receiving terminal 206 (step 605).

  The distribution unit 404 acquires the divided moving image data DATA (k + 2) to which the sequence number k + 2 is assigned from the reception buffer 403, and transmits the acquired divided moving image data DATA (k + 2) to the receiving terminal 206. (Steps 606, 607).

  The receiving terminal 206 that has received the divided moving image data DATA (k + 2) knows that the divided moving image data DATA (k + 1) to which the sequence number k + 1 is assigned is missing.

  The receiving terminal 206 notifies the distribution unit 404 of NACK (k +) in order to notify the distribution unit 404 that the video data division DATA (k + 1) to which the sequence number k + 1 is assigned has not reached itself. 1) A signal is transmitted (step 608). Note that NACK (k + 1) transmitted by the receiving terminal 206 is a retransmission request signal for requesting retransmission of the divided video data DATA (k + 1) to which the sequence number k + 1 is assigned.

  The distribution unit 404 that has received the NACK (k + 1) signal starts an operation of retransmitting the divided moving image data to which the sequence number k + 1 is assigned to the receiving terminal 206.

  At this time, the distribution unit 404 acquires the divided moving image data to which the sequence number k + 1 for retransmission is assigned from the retransmission buffer 407, not from the reception buffer 403.

  The distribution unit 404 that has obtained the divided moving image data DATA (k + 1) ′ for retransmission from the retransmission buffer 407 transmits the divided moving image data DATA (k + 1) ′ for retransmission to the receiving terminal 206 (step S40). 610).

  If the sequence number indicated by the retransmission request signal is paired with a block that is divided moving image data corresponding to the color difference information, there is no divided moving image data for retransmission in the retransmission buffer 407. Then, retransmission moving image data in which the divided moving image data whose data amount is “0” is added to the sequence number indicated by the retransmission request signal is generated, and the generated retransmission moving image data is transmitted to the receiving terminal 206. Therefore, the data amount of the moving image data for retransmission can be reduced, and the transmission time of the moving image data for retransmission can be shortened.

  In the present embodiment, the NACK-based method is used as a retransmission method from the distribution unit 404 to the receiving terminal 206, but the effect of the present invention is not impaired even if other methods are used.

  Also, in this embodiment, different sequence numbers are assigned to each of the TS header, PES header, sequence header, GOP header, picture header, and slice information, which are different information from the macroblock, and these are transmitted separately. However, for example, information different from the macro block may be collected within a range that can be accommodated in the maximum length of the UDP payload.

  In this embodiment, the distribution unit 404 reads the moving image data from the reception buffer 403 and the retransmission buffer 407 in units of one sequence number, but a plurality of sequence numbers (for example, from the reception buffer 403 and the retransmission buffer 407, for example, Moving image data having a plurality of sequence numbers paired with each of the entire data of one MPEG2 TS may be read at a time.

  Further, the distribution unit 404 acquires moving image data in units of moving image data (MPEG2 TS) from the reception buffer 403 and the retransmission buffer 407, and transmits the acquired moving image data to the receiving terminal 206 in units of moving image data (MPEG2 TS). It may be.

  For example, the distribution unit 404 normally acquires moving image data in units of moving image data (MPEG2 TS) from the reception buffer 403, and transmits the acquired moving image data to the receiving terminal 206 in units of moving image data (MPEG2 TS). The receiving terminal 206 requests retransmission of moving image data. Upon receiving the retransmission request, the distribution unit 404 acquires compressed data obtained by compressing the moving image data requested for retransmission from the retransmission buffer 407 in units of moving image data (MPEG2 TS), and acquires the acquired compressed data as moving image data (MPEG2 TS). ) To the receiving terminal 206 in units.

  In this case, moving image data obtained by removing color difference information from moving image data (MPEG2 TS) can be used as moving image data for retransmission.

  In this embodiment, the following effects can be obtained.

  The size of the data transmitted for the second time is smaller than the size of the data transmitted for the first time for the macro block information and the data related to the block. The data sent for the second time is compared with the data sent for the first time, and the luminance information is maintained as it is, but the color difference information is omitted, so the data size can be compressed.

In general, the human eye is insensitive to the color difference with respect to the luminance, so even if the color difference information is omitted, the image does not appear to be greatly deteriorated in the human eye. By reducing the amount of data to be retransmitted by omitting color difference information, video degradation can be reduced, time loss due to retransmission can be minimized, frame loss caused by accumulation of time loss that occurs during retransmission, etc. Large image disturbance can be minimized.
(Second embodiment)
Next, a second embodiment of the present invention will be described. The present embodiment is an embodiment in which the information compression method is changed as compared with the first embodiment. The basic configuration of the present embodiment is the same as the configuration shown in FIGS.

  FIG. 6 is a block diagram showing a second embodiment of the present invention, and only the compression unit is changed as compared with the configuration shown in FIG. In FIG. 6, the same components as those shown in FIG. 3 are denoted by the same reference numerals.

  In FIG. 6, since the moving image data stored in the reception buffer 403 is MPEG2 TS, the moving image data stored in the reception buffer 403 is moving image data obtained by compressing predetermined video data using a predetermined quantization scale code value. .

  The compression unit 405a generates moving image data in which predetermined video data is compressed using a quantization scale code value larger than a predetermined quantization scale code value.

  Specifically, the compression unit 405a once dequantizes each block included in the macroblock received from the sequence number assignment unit 401, and requantizes the dequantized block again. When the compression unit 405a requantizes each block included in the macroblock, the compression unit 405a requantizes the block at a compression rate higher than the compression rate of each block included in the macroblock received from the sequence number assignment unit 401. Turn into.

  FIG. 7 is an explanatory diagram for explaining the operation of the compression unit 405a of the present embodiment. Hereinafter, the operation of the compression unit 405a will be described with reference to FIG.

  The compressing unit 405a performs variable length decoding on each block included in the macroblock received from the sequence number assigning unit 401 (step 702). When the compression unit 405a includes the variable length decoding unit 702, the variable length decoding unit 702 may execute the process of step 702.

  The compression unit 405a performs inverse quantization on each variable-length-decoded block using the quantization scale code S704 included in the macroblock information and the quantization matrix 705 included in the sequence header (Step S405). 703). When the compression unit 405a includes the inverse quantization unit 703, the inverse quantization unit 703 may execute the process of step 703.

  Through the processing of step 702 and step 703, a DCT (Discrete Cosine Transform) result of each block is obtained (step 706).

  Next, the compression unit 405a quantizes the DCT result of each block again using the quantization scale code S′708 and the quantization matrix 705 included in the sequence header (step 707). Note that when the compression unit 405a includes the quantization unit 707, the quantization unit 707 may execute the processing of step 707.

  Note that the quantization scale code S ′ 708 used in step 707 is larger than the quantization scale code S 704.

  The relationship between the quantization scale code and the quantization scale value used in the quantization is determined to be linear or non-linear depending on the q scale type in the picture header.

  In the case of a linear relationship, the relationship of quantization scale value = 2 × quantization scale code value is established. On the other hand, in the case of a non-linear relationship, it is omitted to describe the relationship between each quantization scale code value and the quantization scale value, but the quantization scale code value is a monotonically increasing relationship with the quantization scale value. It remains the same.

  Therefore, the larger the value of the quantization scale code, the larger the quantization scale value used for quantization. That is, as the value of the quantization scale code increases, the DCT result of each block is quantized with a large quantization scale value, and the quantization granularity becomes coarser. When the granularity of quantization becomes rough, the degree of compression of moving image data increases.

  The compression unit 405a quantizes each block in step 707, and then performs variable length coding on each quantized block (step 710). Note that when the compression unit 405 a includes the variable length coding unit 710, the variable length coding unit 710 may execute the process of step 710.

  The compression unit 405a substitutes the quantization scale code value S ′ used in the quantization as the quantization scale code value in the macroblock information for the variable-length encoded block in Step 710.

  Through the above processing, the moving image data for retransmission is completed. The compression unit 405a passes the completed video data for retransmission to the retransmission buffer management unit 406. The retransmission buffer management unit 406 stores the moving image data for retransmission passed from the compression unit 405 a in the retransmission buffer 407.

  The effect of this embodiment is that the MPEG2 TS format transmitted from the distribution server 201 can be compressed even when it is in the 4: 2: 0 format that cannot be compressed in the case of the first embodiment. Is a point. In addition, the degree of compression can be freely changed by changing the quantization scale code value.

(Third embodiment)
Next, a third embodiment of the present invention will be described.

  In the first and second embodiments, only the moving image data to be retransmitted is compressed, but in this embodiment, the time loss required for retransmission is recovered by compressing the moving image data to be transmitted after the retransmission is completed. To do. The basic configuration of the present embodiment is the same as the configuration shown in FIGS.

  FIG. 8 is a block diagram showing the distribution control unit 306 of the present embodiment. In FIG. 8, the same components as those shown in FIG. 3 are denoted by the same reference numerals.

  In this embodiment, a retransmission management buffer 804 is added to the configuration shown in FIG.

  The retransmission management buffer 804 is received in the reception buffer 403 when the distribution unit 404a receives the reception terminal information indicating the reception terminal that has requested retransmission among the plurality of reception terminals 206a, 206b, and 206c, and the retransmission request. This is a buffer for recording the amount of moving image data to be transmitted that remains in an untransmitted state.

  Next, the operation of this embodiment will be described.

  Note that the overall operation of this embodiment is almost the same as that of the first embodiment, so only the operation of the parts different from the operation of the first embodiment will be described.

  For example, it is assumed that a retransmission request is generated from the receiving terminal 206 when the distributing unit 404a distributes moving image data (divided moving image data) to the receiving terminal 206a.

  The distribution unit 404a performs retransmission management on the amount of moving image data (divided moving image data) to be transmitted remaining in the reception buffer 403 when a retransmission request is generated and the receiving terminal information indicating the receiving terminal 206a that has generated the retransmission request. Records in the buffer 804.

  Next, the distribution unit 404a acquires the moving image data for retransmission (divided moving image data) in response to the retransmission request from the retransmission buffer 407, and transmits the moving image data for retransmission to the receiving terminal 206a.

  When the transmission of the moving image data for retransmission ends, the distribution unit 404a receives the amount of moving image data (divided moving image data) to be transmitted remaining in the reception buffer 403 and the retransmission request reception recorded in the retransmission management buffer 804. The amount of moving image data (divided moving image data) to be transmitted at the time is compared.

  The amount of moving image data (divided moving image data) to be transmitted remaining in the reception buffer 403 is larger than the amount of moving image data (divided moving image data) to be transmitted at the time of retransmission request reception recorded in the retransmission management buffer 804. In this case, the difference in the data amount is caused by a time loss caused by retransmission of the moving image data (divided moving image data). Therefore, in order to recover the time loss, the distribution unit 404a sends the next to the receiving terminal 206a. The moving image data is not acquired from the reception buffer 403 but is acquired from the retransmission buffer 407, and the compressed data acquired from the retransmission buffer 407 is transmitted to the reception terminal 206a.

  Subsequently, the distribution unit 404a receives the transmission of the moving image data (divided moving image data) acquired from the retransmission buffer 407 and the data amount of the moving image data (divided moving image data) to be transmitted that existed when the retransmission request was received, and the data transmission. Continue until there is no difference from the data amount of the moving image data (divided moving image data) to be transmitted existing in the buffer 403, and when there is no difference, obtain moving image data (divided moving image data) to be transmitted from the receiving buffer 403, The acquired moving image data is transmitted to the receiving terminal 206a.

  Also in this embodiment, the distribution unit 404a receives a plurality of sequence numbers (for example, a plurality of sequence numbers paired with each of the entire data of one MPEG2 TS) from the reception buffer 403 and the retransmission buffer 407. You may make it read the moving image data which it has collectively.

  Further, the distribution unit 404a acquires moving image data in units of moving image data (MPEG2 TS) from the reception buffer 403 and the retransmission buffer 407, and transmits the acquired moving image data to the receiving terminal 206 in units of moving image data (MPEG2 TS). It may be.

  For example, the distribution unit 404a normally acquires moving image data in units of moving image data (MPEG2 TS) from the reception buffer 403, and transmits the acquired moving image data to the receiving terminal 206 in units of moving image data (MPEG2 TS). The receiving terminal 206 requests retransmission of moving image data. Upon receiving the retransmission request, the distribution unit 404a acquires compressed data obtained by compressing the moving image data requested for retransmission from the retransmission buffer 407 in units of moving image data (MPEG2 TS), and acquires the acquired compressed data as moving image data (MPEG2 TS). ) To the receiving terminal 206 in units. The distribution unit 404a also acquires compressed moving image data to be transmitted after the retransmission is completed from the retransmission buffer 407 in units of moving image data (MPEG2 TS), and transmits the acquired moving image data to the receiving terminal 206.

  In this case, moving image data obtained by removing color difference information from moving image data (MPEG2 TS) can be used as moving image data for retransmission.

  The effect of the present embodiment is that the video data is largely disturbed by skipping video data generated by the accumulation of time loss that occurs at the time of retransmission by recovering the time loss that has occurred by retransmission by transmitting compressed video data after retransmission. Can be prevented from being generated.

  In this embodiment, the compression unit 405 a shown in FIG. 6 may be used as the compression unit 405.

  In the present embodiment, the number of receiving terminals is three, but the number of receiving terminals is not limited to three and can be changed as appropriate.

  In each of the embodiments described above, the illustrated configuration is merely an example, and the present invention is not limited to the configuration.

It is the block diagram which showed the data delivery system of one Example of this invention. FIG. 2 is a block diagram illustrating an example of a wireless distribution station illustrated in FIG. 1. It is the block diagram which showed an example of the delivery control part shown in FIG. It is explanatory drawing for demonstrating the operation | movement of a present Example. It is a sequence diagram for demonstrating operation | movement of a present Example. It is the block diagram which showed the principal part of the data delivery apparatus of the other Example of this invention. It is explanatory drawing for demonstrating operation | movement of the delivery control part shown in FIG. It is the block diagram which showed the principal part of the data delivery apparatus of the further another Example of this invention. It is the block diagram which showed the conventional data delivery system.

Explanation of symbols

201 distribution server 202 content storage 203 router 204 wireless distribution station 205 wireless base station 206 receiving terminal 301 Ethernet
302 IP
303 IGMP
304 PIM-SM
305 UDP
306 Distribution control unit 401 Sequence number allocation unit 402 Reception buffer management unit 403 Reception buffer 404 Distribution unit 404a Distribution unit 405 Compression unit 405a Compression unit 406 Retransmission buffer management unit 407 Retransmission buffer 702 Variable length decoding unit 703 Inverse quantization unit 707 Quantization unit 710 Variable length encoding unit 804 Retransmission management buffer

Claims (10)

A data distribution device that transmits moving image data to a receiving device and transmits moving image data for retransmission in response to the retransmission request to a receiving device that has requested retransmission of the moving image data,
A receiving unit that receives a retransmission request of the video data;
A data distribution apparatus, comprising: a transmission unit that transmits compressed data obtained by compressing the moving image data as the moving image data for retransmission to a receiving device that has requested retransmission of the moving image data. The data distribution apparatus according to claim 1, wherein
The moving image data includes at least luminance information and color difference information,
The transmission unit uses moving image data obtained by removing color difference information from the moving image data as the compressed data. The data distribution apparatus according to claim 1, wherein
The moving image data is moving image data obtained by compressing predetermined video data using a predetermined quantization scale code value,
The data transmission device, wherein the transmission unit uses moving image data obtained by compressing the predetermined video data using a quantization scale code value larger than the predetermined quantization scale code value as the compressed data. The data distribution device according to any one of claims 1 to 3,
The transmission unit transmits the compressed compressed data, and then transmits, as the moving image data, compressed moving image data obtained by compressing the moving image data. A data distribution system including a receiving device and a data distribution device that transmits moving image data to the receiving device,
The receiving device makes a retransmission request for the moving image data,
The data distribution system according to any one of claims 1 to 4, wherein the data distribution apparatus is the data distribution apparatus according to any one of claims 1 to 4. A data distribution method performed by a data distribution device that transmits moving image data to a receiving device and transmits moving image data for retransmission in response to the retransmission request to a receiving device that has requested retransmission of the moving image data,
A receiving step for accepting a retransmission request for the video data;
A data distribution method comprising: a transmission step of transmitting compressed data obtained by compressing the moving image data as the moving image data for retransmission to a receiving apparatus that has requested retransmission of the moving image data. The data distribution method according to claim 6, wherein
The moving image data includes at least luminance information and color difference information,
The transmission step uses moving image data obtained by removing color difference information from the moving image data as the compressed data. The data distribution method according to claim 6, wherein
The moving image data is moving image data obtained by compressing predetermined video data using a predetermined quantization scale code value,
In the data distribution method, the transmission step uses moving image data obtained by compressing the predetermined video data using a quantization scale code value larger than the predetermined quantization scale code value as the compressed data. The data distribution method according to any one of claims 6 to 8,
A data distribution method further comprising: a moving image compressed data transmission step of transmitting the compressed moving image data obtained by compressing the moving image data as the moving image data after transmitting the compressed data. A data distribution method performed by a data distribution system including a reception device and a data distribution device that transmits moving image data to the reception device,
The receiving device makes a retransmission request for the moving image data,
A data distribution method comprising the steps of the data distribution method according to claim 6.

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