JP2007312051A - Set top box - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem, wherein the deterioration of quality and frame dropping occur, when a good reception cannot be obtained on a set top box continuously in a streaming distribution system. <P>SOLUTION: The set top box is connected to a network, and receives and reproduces content data from a streaming distribution device. The set top box comprises a buffer for temporarily accumulating the content data; a buffer-accumulated volume of data monitor for monitoring an amount of content data accumulated in the buffer; and a reproduction rate regulator for regulating the reproduction rate of the content data, based on the accumulated amount of content data reported by the buffer accumulated volume of data monitor. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a set-top box that receives content data distributed from a streaming distribution device and reproduces the streaming, and a streaming reproduction method.

  2. Description of the Related Art In recent years, IP streaming broadcasting that distributes video (moving images), music, and the like via an IP (Internet protocol) network via the Internet or a CATV network has been performed. However, there is a problem that bandwidth cannot be guaranteed in IP streaming broadcasting via an IP network.

  As an example of a conventional solution to this problem, a client that receives streaming sends a feedback packet including information about a reception state (reception bit rate, packet loss rate) to the streaming distribution device, and the streaming distribution device sends a transmission bit rate, and A technique for dynamically adjusting the content bit rate has been devised (see Patent Document 1). Hereinafter, this conventional example is referred to as a conventional configuration 1. FIG. 10 is a configuration diagram of a conventional streaming distribution system described in Patent Document 1. In FIG.

  In FIG. 10, a streaming delivery system 1010 includes a packet transmitting / receiving unit 1011 that transmits and receives IP packets, an information holding unit 1012 that analyzes a reception state from a feedback packet from a client, a transmission bit rate and content bits based on information from the information holding unit. A rate information determination unit 1013 that determines a rate, a file selection unit 1014, a file storage unit 1015, and a content bit rate adjustment unit 1016 that adjusts the content bit rate based on values from the rate information determination unit.

  The operation of the conventional streaming distribution system configured as described above will be described below.

  First, the packet transmission / reception unit 1011 receives a feedback packet transmitted from the client, and the information holding unit 1012 analyzes the reception state of the client. When it is determined that the reception state is good, the rate information determination unit 1013 first increases only the transmission bit rate. If it is determined that the content is good thereafter, the content bit rate adjustment unit 1016 increases the content bit rate. When the reception state deteriorates, the transmission bit rate is reduced to eliminate data retention in the IP network. As a result, even when the reception state changes slightly, a rapid change in image quality can be suppressed, and streaming can be delivered by effectively using the actual bandwidth of the network.

  The “transmission bit rate” is a bit rate at which the streaming distribution apparatus transmits streaming data, and depends on the line thickness of the physical IP network. The “content bit rate” is a bit rate for encoding video and audio data into digital data, and affects the image quality and sound quality of streaming data.

  In addition, the streaming delivery apparatus has a problem that the reproduction video on the receiving side becomes discontinuous due to accumulation of errors in the processing speed of the video encoding process and the content transmission process, and some frames are dropped.

  As an example of a conventional solution to this problem, a data distribution measurement unit is provided in a streaming distribution apparatus, data accumulation amount information is fed back, and data is temporarily controlled by controlling the video encoding process to have a constant average bit rate. A technique has been devised to prevent underflow and overflow of the buffer to be stored (see Patent Document 2). Hereinafter, this conventional example is referred to as a conventional configuration 2.

Note that “buffer underflow” means that data in the buffer disappears, and playback data is interrupted, causing frame dropping. In addition, “buffer overflow” causes block noise and dropped frames because the data exceeds the buffer capacity and the excess data is discarded.
JP 2004-015429 A JP 2000-350199 A

  However, in the conventional configuration 1, since the streaming distribution apparatus takes the lead in adjusting the transmission bit rate and the content bit rate, there is a possibility that the transmission bit rate is lower than the reproduction rate of the client when the reception state deteriorates. is there. When such a state continues for a long time, a buffer underflow occurs in the client, and frames are dropped. In particular, a client that does not have a large-capacity buffer such as an HDD is easily affected by such a change in the transmission bit rate because it is difficult to increase the initial data storage amount when starting streaming playback.

  In the conventional configuration 2, the streaming distribution apparatus monitors the data capacity stored in its own buffer to prevent underflow and overflow. However, when packet loss or delay occurs in the IP network, it is not possible to prevent frame dropping due to block noise or underflow in the client.

  The present invention solves the above-described conventional problems. Even when the reception state continuously deteriorates, it is possible to continue viewing while maintaining the image quality, and without having a large-capacity buffer such as an HDD. However, it is an object of the present invention to provide a set-top box and a streaming playback method that are resistant to fluctuations in reception conditions.

  In order to solve the conventional problems, a set top box of the present invention includes a buffer for temporarily storing content data, a buffer storage data capacity monitoring unit for monitoring the amount of content data stored in the buffer, and buffer storage data. A reproduction rate adjustment unit that adjusts the reproduction rate of the content data based on the content data accumulation amount reported by the capacity monitoring unit.

  As described above, according to the present invention, even when the reception state deteriorates and the streaming delivery apparatus lowers the transmission bit rate, the set top box lowers the playback rate by reducing the playback rate in the set top box. Flow can be prevented. Even when the reception state is improved and the streaming delivery apparatus increases the transmission bit rate, the set top box buffer overflow can be prevented by increasing the playback rate in the set top box.

  The set-top box of the present invention has the above-described configuration, and can continue viewing while maintaining image quality even when the reception state continuously deteriorates, and does not have a large-capacity buffer such as an HDD. However, it is possible to realize a set-top box that is resistant to fluctuations in reception conditions.

  A first invention of the present invention is a set-top box connected to a network and receiving and playing back content data from a streaming distribution apparatus, a buffer for temporarily storing content data, and content stored in the buffer A buffer storage data capacity monitoring unit that monitors the data amount and a playback rate adjustment unit that adjusts the playback rate of the content data based on the content data storage amount reported by the buffer storage data capacity monitoring unit.

  As described above, according to the first aspect of the present invention, even when the reception state deteriorates and the streaming delivery apparatus lowers the transmission bit rate, the playback rate is reduced by the set top box. The underflow of the top box buffer can be prevented. Even when the reception state is improved and the streaming delivery apparatus increases the transmission bit rate, the set top box buffer overflow can be prevented by increasing the playback rate in the set top box.

  A second invention of the present invention is an invention dependent on the first invention of the present invention, comprising a scene analysis unit that analyzes a playback scene and reports to the playback rate adjustment unit that a specific scene has been detected, The reproduction rate adjustment unit adjusts the reproduction rate only for a specific scene based on the content data accumulation amount and information from the scene analysis unit.

  As described above, according to the second aspect of the present invention, it is possible to reduce or increase the playback rate only in a scene where it is difficult to understand the change in the playback rate, and to prevent buffer underflow or overflow.

  A third aspect of the present invention is an invention dependent on the first aspect of the present invention, wherein a reproduction rate monitoring unit that monitors a current reproduction rate determined by a reproduction rate adjustment unit, and content in a streaming distribution device Provided with a feedback packet generation unit that makes a request to change the bit rate, the playback rate monitoring unit monitors the current playback rate, reports to the feedback packet generation unit when the playback rate is outside a specific range, and performs streaming delivery It is characterized by requesting the device to change the content bit rate.

  As described above, according to the third aspect of the present invention, when the playback rate falls below the allowable range of the viewer, the content bit rate is lowered and the playback rate is returned to the allowable range to continue the playback. it can. Even when the playback rate exceeds the allowable range of the viewer, the playback can be continued by increasing the content bit rate and returning the playback rate to the allowable range while improving the image quality.

  A fourth invention of the present invention is an invention subordinate to the third invention of the present invention, wherein a feedback packet generator for making a request to change the transmission bit rate to the streaming distribution device, and transmitted from the streaming distribution device A reception state monitoring unit that monitors the reception state of the content data is provided, and the reception state monitoring unit reports to the feedback packet generation unit when it is determined that the reception state has changed, and changes the transmission bit rate to the streaming distribution device It is requested to do.

  As described above, according to the fourth aspect of the present invention, when the reception state is improved, the transmission bit rate is first increased, and the transmission of the content data is advanced without the congestion of the IP network. At the same time, the playback rate is increased in the set top box, and playback is continued while preventing buffer overflow. At this time, if it is determined that the playback rate exceeds the allowable range of the viewer, the content bit rate can be increased, the playback rate can be returned to the allowable range while improving the image quality, and the playback can be continued.

  When the reception state deteriorates, first, the transmission bit rate is lowered to improve the reception state. At the same time, the playback rate can be reduced in the set top box, and playback can be continued while preventing buffer underflow.

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

(Embodiment 1)
FIG. 1 is a configuration diagram of a set-top box according to Embodiment 1 of the present invention. In FIG. 1, a set top box 100a that performs streaming playback includes a CPU 101 that controls the set top box, a packet transmission / reception unit 102 that transmits and receives IP packets, a TS extraction unit 103 that extracts TS (Transport Stream) from IP packets, Buffer 104 for temporarily storing TS, buffer storage data capacity monitoring unit 105 for monitoring the amount of content data stored in the buffer, and adjusting the playback rate according to the content data storage amount reported from the buffer storage data capacity monitoring unit The playback rate adjusting unit 106 and an MPEG decoder 107 for decoding the content data stored in the buffer are configured.

  The set top box 100 a is connected to the monitor 108 and the IP network 160, and the IP network 160 is further connected to the connection streaming distribution device 150.

  The operation of the set top box 100a configured as described above will be described.

  The set top box 100a has a network interface and is connected to the IP network 160. A predetermined procedure for receiving the streaming distribution is performed, and then the TS that is the content data is received as an IP packet from the streaming distribution device 150 via the packet transmitting / receiving unit 102, and the TS extracting unit 103 extracts the TS from the IP packet. . The extracted TS is sequentially stored in the buffer 104, and the data amount of the TS stored in the buffer is monitored by the buffer storage data capacity monitoring unit 105. Further, the buffer accumulated data capacity monitoring unit 105 reports the content data accumulation amount to the reproduction rate adjusting unit 106, and the reproduction rate adjusting unit 106 determines the reproduction rate based on the reported value. The TS stored in the buffer is transferred to the MPEG decoder 107, and the MPEG decoder 107 decodes the TS at the playback rate determined by the playback rate adjusting unit 106 and outputs the content video to the monitor 108.

  As described above, according to the first embodiment, by providing the playback rate adjustment unit, even when the reception state deteriorates and the streaming delivery apparatus lowers the transmission bit rate, the playback rate is set by the set top box. It is possible to prevent the underflow of the set top box buffer. Even when the reception state is improved and the streaming delivery apparatus increases the transmission bit rate, the set top box buffer overflow can be prevented by increasing the playback rate in the set top box.

(Embodiment 2)
FIG. 2 is a configuration diagram of the set top box according to the second embodiment of the present invention. In FIG. 2, the same components as those in FIG.

  The set-top box 100b of FIG. 2 differs from the configuration of FIG. 1 in that a scene analysis unit 109 that analyzes a scene and reports that a specific scene has been detected is provided to the playback rate adjustment unit 106. Based on information from the analysis unit, a function for adjusting the playback rate only for a specific scene is provided.

  The operation of the set top box 100b configured as described above will be described.

  The set top box 100b has a network interface and is connected to the IP network 160. A predetermined procedure for receiving the streaming distribution is performed, and then the TS that is the content data is received as an IP packet from the streaming distribution device 150 via the packet transmitting / receiving unit 102, and the TS extracting unit 103 extracts the TS from the IP packet. . The extracted TS is sequentially stored in the buffer 104, and the buffer accumulated data capacity monitoring unit 105 monitors the content data amount stored in the buffer and reports the value to the reproduction rate adjusting unit 106. The scene analysis unit 109 analyzes the playback scene and reports to the playback rate adjustment unit 106 that a specific scene has been detected. The playback rate adjustment unit 106 determines the current playback rate based on the reported content data accumulation amount and scene detection information. The TS stored in the buffer is transferred to the MPEG decoder 107, and the MPEG decoder 107 decodes the TS at the playback rate determined by the playback rate adjusting unit 106 and outputs the content video to the monitor 108.

  As described above, according to the second embodiment, by providing the playback rate adjustment unit, it is possible to reduce or increase the playback rate only in a scene where the change of the playback rate is difficult to understand, and to prevent buffer underflow or overflow. Can do.

(Embodiment 3)
FIG. 3 is a configuration diagram of the set top box according to the third embodiment of the present invention. In FIG. 3, the same components as those in FIG.

  The set-top box 100c of FIG. 3 differs from the configuration of FIG. 1 in that a playback rate monitoring unit 110 that monitors the current playback rate determined by the playback rate adjustment unit and a request to change the content bit rate to the streaming distribution device. The feedback packet generation unit 111 is provided.

  The operation of the set top box configured as described above will be described.

  The set top box 100c has a network interface and is connected to the IP network 160. A predetermined procedure for receiving the streaming distribution is performed, and then the TS that is the content data is received as an IP packet from the streaming distribution device 150 via the packet transmitting / receiving unit 102, and the TS extracting unit 103 extracts the TS from the IP packet. . The extracted TS is sequentially stored in the buffer 104, and the data amount of the TS stored in the buffer is monitored by the buffer storage data capacity monitoring unit 105. Further, the buffer accumulated data capacity monitoring unit 105 reports the content data accumulation amount to the reproduction rate adjusting unit 106, and the reproduction rate adjusting unit 106 determines the reproduction rate based on the reported value. The playback rate monitoring unit 110 monitors the current playback rate, reports to the feedback packet generation unit 111 when the playback rate is out of a specific range, and performs streaming from the packet transmitting / receiving unit 102 via the IP network 160. A request for changing the content bit rate is made to the distribution apparatus 150. The TS stored in the buffer 104 is transferred to the MPEG decoder 107. The MPEG decoder 107 decodes the TS at the reproduction rate determined by the reproduction rate adjusting unit 106, and outputs the content video to the monitor 108.

  As described above, according to the third embodiment, by providing the playback rate monitoring unit and the feedback packet generation unit, when the playback rate falls below the allowable range of the viewer, the content bit rate is reduced, and the playback rate is reduced. Playback can be continued by returning to the allowable range. Even when the playback rate exceeds the allowable range of the viewer, the playback can be continued by increasing the content bit rate and returning the playback rate to the allowable range while improving the image quality. The allowable range of the viewer means a range in a state where the viewer can view without feeling uncomfortable with a change in the playback rate.

(Embodiment 4)
FIG. 4 is a configuration diagram of a set top box according to Embodiment 4 of the present invention. 4, the same components as those in FIG. 3 are denoted by the same reference numerals, and description thereof is omitted.

  The set-top box 100d in FIG. 4 differs from the configuration in FIG. 3 in that a reception state monitoring unit 112 that monitors the reception state of content data transmitted from the streaming distribution device is provided, and the feedback packet generation unit 111 performs streaming. A function for requesting the delivery apparatus to change the transmission bit rate is added.

  The operation of the set top box configured as described above will be described.

  The set top box 100d has a network interface and is connected to the IP network 160. A predetermined procedure for receiving the streaming distribution is performed, and then the TS that is the content data is received as an IP packet from the streaming distribution apparatus 150 via the packet transmitting / receiving unit 102. The reception state monitoring unit 112 monitors the reception state, and reports to the feedback packet generation unit 111 when it is determined that the reception state has changed, and the food back packet generation unit 111 changes the transmission bit rate to the streaming distribution device 150. Request to do. The TS extraction unit 103 extracts TS from the IP packet and sequentially stores the extracted TS in the buffer 104. The amount of TS data stored in the buffer is monitored by the buffer storage data capacity monitoring unit 105. The buffer accumulation data capacity monitoring unit 105 reports the content data accumulation amount to the reproduction rate adjustment unit 106, and the reproduction rate adjustment unit 106 determines the reproduction rate based on the reported value. The playback rate monitoring unit 110 monitors the current playback rate, reports to the feedback packet generation unit 111 when the playback rate is outside a specific range, and requests the streaming distribution device 150 to change the content bit rate. . The TS stored in the buffer is transferred to the MPEG decoder 107, and the MPEG decoder 107 decodes the TS at the playback rate determined by the playback rate adjusting unit 106 and outputs the content video to the monitor 108.

  As described above, according to the fourth embodiment, when the reception state is improved, the transmission bit rate is first increased, and the transmission of the content data is advanced without the congestion of the IP network. At the same time, the playback rate can be increased in the set top box, and playback can be continued while preventing buffer overflow. When it is determined that the playback rate exceeds the allowable range of the viewer, the content bit rate is increased, and the playback rate is returned to the allowable range while improving the image quality, and the playback can be continued.

  When the reception state deteriorates, first, the transmission bit rate is lowered to improve the reception state. At the same time, the playback rate can be reduced in the set top box, and playback can be continued while preventing buffer underflow. If it is determined that the playback rate exceeds the allowable range of the viewer, the content bit rate can be lowered, and the playback rate can be returned to the allowable range to continue playback.

  Next, the control procedure of the set top box in the fourth embodiment will be described. FIG. 5 is a flowchart of the set top box according to the fourth embodiment of the present invention.

  As shown in FIG. 5, in the streaming playback method of the set top box 100d in the fourth embodiment, first, content data transmitted from the streaming distribution device is received as an IP packet, and the reception state monitoring unit 112 determines the reception state. To detect. At this time, it is determined whether or not the reception state falls below a certain standard (step S501). If it is determined that the reception state falls below, a request is made to lower the transmission bit rate to the streaming delivery device 150 (step S502). If it is not determined in step S501 that the reception state has been exceeded, it is determined whether or not the reception state exceeds a certain reference (step S503). If it is determined that the reception state has been exceeded, a request is made to increase the transmission bit rate (step S504).

  Next, TS data is extracted from the IP packet by the TS extraction unit 103 and sequentially stored in the buffer 104. The buffer accumulated data capacity monitoring unit 105 reports the content data amount stored in the buffer 104 to the reproduction rate adjusting unit 106. The playback rate adjustment unit 106 determines whether or not the content data amount stored in the buffer 104 has fallen below the threshold value Ba (step S505). If it is determined that the content data has fallen below the threshold value Ba, it requests the MPEG decoder 107 to lower the playback rate (step S505). S506). If it is not determined in step S505 that the content rate has been reduced, the playback rate adjustment unit 106 determines whether the content data amount stored in the buffer 104 exceeds the threshold Bb (step S507). If it is determined that the content data amount has exceeded, the playback rate is set. A request is made to raise (step S508).

  Note that the “threshold value Ba” is a lower limit data amount set in order to prevent buffer underflow. The “threshold value Bb” is an upper limit data amount set in order to prevent buffer overflow.

  Further, the playback rate monitoring unit 110 monitors the current playback rate. It is determined whether the playback rate has fallen below the threshold Pa (step S509). If it is determined that the playback rate has fallen below, the streaming delivery device 150 is requested to lower the content bit rate (step S510). If it is not determined in step S505 that the playback rate has fallen below, it is determined whether the playback rate has exceeded the threshold value Pb (step S511). S512).

  The “threshold Pa” is the minimum playback rate at which the viewer can view without feeling uncomfortable. The “threshold value Pb” is the maximum playback rate at which the viewer can view without feeling uncomfortable.

  6, 7, 8 and 9 are conceptual diagrams showing changes in the bit rate on the network when the content bit rate and the transmission bit rate are changed. For simplicity, the data amount of one frame is set to 5 data.

  FIG. 6 is a conceptual diagram showing changes in the bit rate when the transmission bit rate is lowered. In this case, although the amount of content data per frame is not different from 5 data, the number of transmission data per unit time is reduced to 3 data, so that the transmission time per frame becomes longer. For this reason, when the playback rate on the set top box 100d side is uniform, underflow of the buffer 104 occurs and frame dropping occurs. In the fourth embodiment, the content data amount stored in the buffer 104 falls below the threshold value Ba. , Lowering the playback rate and preventing underflow.

  FIG. 7 is a conceptual diagram showing changes in the bit rate when the transmission bit rate is increased. In this case, on the contrary, since the transmission time per frame is shortened, the buffer overflow occurs when the reproduction rate on the set top box 100d side is uniform. However, in the fourth embodiment, when the amount of content data stored in the buffer 104 exceeds the threshold Bb, the playback rate is increased to prevent overflow.

  FIG. 8 is a conceptual diagram showing changes in the bit rate when the content bit rate is lowered. In this case, the content data amount of one frame is reduced to 3 data and the image quality is deteriorated. However, since the reproduction rate exceeds the allowable range of the viewer, priority is given to continuing the reproduction with the image quality lowered.

  FIG. 9 is a conceptual diagram showing changes in the bit rate when the content bit rate is increased. In this case, since it is determined that the playback rate exceeds the allowable range of the viewer and the bandwidth of the IP network is sufficiently secured, the content data amount of one frame is increased to 7 data to improve the image quality.

  The set-top box according to the present invention can continue viewing while maintaining the image quality even when the reception state continuously deteriorates, and can be in the reception state without having a large-capacity buffer such as an HDD. Since it is resistant to fluctuations, it is useful as a streaming playback method.

Configuration diagram of set-top box in Embodiment 1 of the present invention Configuration diagram of set-top box in Embodiment 2 of the present invention Configuration diagram of set-top box according to Embodiment 3 of the present invention Configuration diagram of set-top box in Embodiment 4 of the present invention Flowchart of set-top box in embodiment 4 of the present invention Conceptual diagram showing changes in bit rate when the transmission bit rate is lowered Conceptual diagram showing changes in bit rate when the transmission bit rate is increased Conceptual diagram showing changes in bit rate when content bit rate is lowered Conceptual diagram showing changes in bit rate when content bit rate is increased Configuration diagram of a conventional streaming distribution system

Explanation of symbols

100 set top box 101 CPU
DESCRIPTION OF SYMBOLS 102 Packet transmission / reception part 103 TS extraction part 104 Buffer 105 Buffer accumulation data capacity monitoring part 106 Playback rate adjustment part 107 MPEG decoder 108 Monitor 109 Scene analysis part 110 Playback rate monitoring part 111 Feedback production | generation part 112 Reception condition monitoring part 150 Streaming delivery apparatus 160 IP network

Claims (4)

A set-top box connected to a network for receiving and playing content data from a streaming distribution device,
A buffer for temporarily storing content data;
A buffer storage data capacity monitoring unit for monitoring the amount of content data stored in the buffer;
A playback rate adjustment unit that adjusts the playback rate of content data based on the content data storage amount reported by the buffer storage data capacity monitoring unit;
Set top box. A scene analysis unit that analyzes the playback scene and reports the detection of the specific scene to the playback rate adjustment unit,
2. The set top box according to claim 1, wherein the playback rate adjustment unit adjusts the playback rate only for a specific scene based on the content data storage amount and information from the scene analysis unit. A playback rate monitoring unit for monitoring a current playback rate determined by the playback rate adjusting unit;
A feedback packet generator for making a request to change the content bit rate to the streaming delivery device;
The playback rate monitoring unit monitors the current playback rate, reports to the feedback packet generation unit when the playback rate is out of a specific range, and requests the streaming delivery device to change the content bit rate. The set top box according to claim 1. A feedback packet generator for making a request to change the transmission bit rate to the streaming delivery device;
A reception state monitoring unit for monitoring a reception state of content data transmitted from the streaming distribution device;
4. The reception state monitoring unit reports to the feedback packet generation unit when it is determined that the reception state has changed, and requests the streaming delivery device to change the transmission bit rate. Set top box as described.

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