JP5784538B2 - Streaming media playback device, media bit rate change determination method, and program - Google Patents

Description

  The present invention relates to streaming media distribution technology such as video streaming distribution.

  As one of conventional video distribution methods for the Internet, there is a method in which a media file is divided into a plurality of parts in advance and these are distributed by HTTP (for example, Http Live Streaming (HLS)). In addition, a video distribution method in which video content is indexed and XML type meta information is defined has been proposed as a distribution method extending the above method (eg, Dynamic Adaptive Streaming over Http (DASH)).

JP 2005-151000 A

  In video distribution, it is preferable to measure the video download speed in order to perform appropriate video playback control on the user terminal side. However, in the prior art, for example, the download speed can be measured only in units of files that store video data, and the download speed in fine time units cannot be calculated. For this reason, there has been a problem in that detection of the speed drop is delayed, and it is difficult to appropriately deal with the change in the bit rate, and the video is likely to stop.

  The present invention has been made in view of the above points, and provides a technique for measuring a communication state such as a download speed in an appropriate data unit and automatically changing a bit rate based on the measurement result. Is the main purpose.

In order to solve the above problems, the present invention is a streaming media playback device that downloads and plays media content from a streaming media distribution device connected to a network.
Communication status measuring means for determining that a predetermined unit of data in the media content has been received by referring to the index information corresponding to the media content, and measuring the communication status related to the download of the media content in the predetermined unit When,
It is configured as a streaming media playback device comprising: a bit rate change determination unit that determines whether or not to change the bit rate of the media content based on a measurement result by the communication status measurement unit.

  The communication status measurement unit measures the download speed of the media content as the communication status, for example, in units of GOP as the predetermined unit.

  The communication status measuring means may calculate the download speed based on the amount of data received between a certain time ago and the present time each time reception of one GOP is completed.

  The bit rate change determining means receives the predetermined unit of data, downloads the subsequent predetermined unit of data without changing the current bit rate, and determines the subsequent predetermined unit of data. It may be determined whether or not the buffer is in a predetermined state before reception is completed, and when the buffer is in a predetermined state, it may be determined that the bit rate is to be reduced. The predetermined state is, for example, a state that hinders reproduction of the media content.

  The bit rate change determination means may select the maximum bit rate that does not exceed a predetermined multiple of the download speed measured as the communication status when it is determined to lower the bit rate.

  The bit rate change determining means determines whether or not a download speed that is a predetermined multiple of the bit rate above the current bit rate has been maintained for a certain period of time, and if the download rate is maintained, You may comprise so that it may determine with raising.

  In the measurement of the communication status, the communication status measurement unit may start from the data acquisition request for the media content and not perform measurement across the data acquisition request.

  The present invention can also be configured as a media bit rate change determination method executed by the streaming media playback device and a program for causing a computer to function as each means of the streaming media playback device.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the technique for measuring communication conditions, such as a download speed, in an appropriate data unit, and changing a bit rate automatically based on a measurement result.

It is a figure for demonstrating the media delivery system used by embodiment of this invention. It is a figure for demonstrating the media delivery system used by embodiment of this invention. It is a system configuration figure concerning an embodiment of the invention. It is a figure for demonstrating operation | movement of download speed measurement. It is a figure for demonstrating the specific process of GOP in trick play.

  Embodiments of the present invention will be described below with reference to the drawings. The embodiment described below is only an example, and the embodiment to which the present invention is applied is not limited to the following embodiment. For example, in the present embodiment, it is assumed that DASH is used as the media distribution method, but the media distribution method to which the present invention can be applied is not limited to DASH. In addition, it is assumed that the distributed media is streaming video content encoded by MPEG, but the present invention is not limited to this.

(About the media distribution method of this embodiment)
First, the media distribution method used in this embodiment will be described. Note that the contents of the media distribution method described below mainly describe the parts related to the present invention.

  In this media distribution method, media content is divided into a plurality of segments as shown in FIG. Each segment includes a plurality of GOPs (Group of Pictures). The GOP here is a series of media data from an I frame to the next I frame.

  In this media distribution method, index information corresponding to media content is prepared. This index information includes the time position in the media content of each segment and the data position in the media content. In this embodiment, the “time position” includes a time (time) when the media of the corresponding segment starts from the start of the media content and a time length of the segment. This may consist of a start time and an end time. In addition, the “data position” in the present embodiment includes the start byte position of the segment starting from the start of the media content and the byte length (size) of the segment. It may also consist of a start byte position and an end byte position.

  In this embodiment, as shown in FIG. 2, index information corresponding to each GOP in the segment is prepared for each segment, and the I frame, P frame, and first B frame in each GOP are prepared. Has index information corresponding to. In the example of FIG. 2, for example, an index S2 is prepared for GOP2 in segment 2. This index S2 has, for example, the relative start time and time length of GOP2 in segment 2, and the start data position and size.

  For example, the index L1 corresponding to the I frame in GOP2 includes, for example, the relative start time and time length in GOP2 of the I frame, and the start data position and size. The index L2 corresponding to the first P frame in GOP2 includes, for example, the relative start time and time length in GOP2 of the P frame, and the start data position and size.

  In this media delivery method, each segment is given location information (network location information) on the network as segment information, and the user terminal acquires the segment by designating this network location information. be able to. In this embodiment, this network location information is an HTTP URL, and the user terminal acquires a segment by an HTTP GET request specifying this URL. However, the signal for acquiring the media content data is not limited to the HTTP GET request, and may be acquired using another signal.

  In addition, by using the index information, it is possible to acquire data of a specific GOP by designating the data position or data range in one segment. It is also possible to acquire data of a specific frame in a specific GOP. Note that the network location information and index information can be called meta information.

  Furthermore, in this media distribution method, different media contents and meta information are prepared for each media bit rate (also called bandwidth, corresponding to image quality, the number of vertical and horizontal pixels of an image). A terminal can acquire a segment of media content having a desired bit rate by designating network location information of the media content having a desired bit rate.

  The above network location information and index information are stored on the media distribution device side as meta information associated with the media content, and the user terminal stores the network location information and the index information as necessary. The media content is acquired from the media distribution device, and the media information is downloaded and played using the acquired information.

(System configuration)
FIG. 3 shows a system configuration according to the embodiment of the present invention. As shown in FIG. 3, the system according to the present embodiment has a configuration in which a media distribution device 1 and a user terminal 2 are connected via a network 3 (for example, the Internet). The user terminal 2 may be referred to as a streaming media playback device.

  The media distribution device 1 includes a meta information storage unit 11, a media content storage unit 12, and an information distribution control unit 13.

  The meta information storage unit 11 stores the meta information described above. The media content storage unit 12 stores media content. The information distribution control unit 13 is a functional unit that transmits meta information and media data to the user terminal 2 based on a request from the user terminal 2.

  The user terminal 2 includes a user interface unit 21, a meta information acquisition unit 22, a meta information storage unit 23, a media data acquisition processing unit 24, a download speed monitoring unit 25, a bit rate change determination unit 26, and a media playback processing unit 27. Further, although not shown in the drawing, a storage means for storing the current bit rate, various parameters necessary for processing, and the like is provided.

  The user interface unit 21 is a functional unit that receives an operation instruction from the user to the user terminal 2 and notifies the function unit of the content of the instruction. The user interface unit 21 may be a functional unit integrated with a display (display unit), or the display may be another device connected to the user terminal 2.

  Examples of instructions in the present embodiment include start of reproduction and trick play. In addition, the user interface unit 21 receives and displays page information for selecting media contents from the media distribution device 1 or other Web server, and causes the user to select which media is to be viewed and the selected media. Meta information (including basic information such as the total length of the media) may be acquired and stored in the meta information storage unit 23. Further, the above functions are executed by the Web browser included in the user terminal 2 and the meta information is acquired to start the application. When the application is started, each function of the user terminal 2 shown in FIG. You may employ | adopt the form in which a part is comprised.

  The meta information acquisition unit 22 is a functional unit that acquires meta information necessary for processing from the media distribution device 1 and stores it in the meta information storage unit 23. For example, when the user terminal 2 does not have necessary index information when receiving a trick play instruction, index information corresponding to the media is acquired. The meta information storage unit 23 stores meta information and is appropriately referred to by each functional unit that performs processing using the meta information.

  The media data acquisition processing unit 24 has a buffer 241 (memory), acquires necessary media data from the media distribution device 1 using the meta information stored in the meta information storage unit 23, and stores it in the buffer 241. To do. The media data stored in the buffer 241 is passed to the media playback processing unit 27 together with a time stamp. The media playback processing unit 27 performs media playback processing.

  For example, in the case of normal playback of media, the media data acquisition processing unit 24 sequentially acquires segments using the network position information of the segments and stores them in the buffer 241, and the media playback processing unit 27 stores in the buffer 241. The stored media data is sequentially acquired and reproduced, and displayed on the display.

  The download speed monitoring unit 25 measures the download speed of the media data acquired by the media data acquisition processing unit 24. Further, the bit rate change determination unit 26 determines whether or not to change the bit rate according to the download speed or the like. If the change is necessary, the bit rate is changed and the changed bit rate is changed. Is notified to the media data acquisition processing unit 24 and the media reproduction processing unit 27. The measurement of the download speed and the bit rate change determination will be described in detail later.

  The media data acquisition processing unit 24 includes a trick play control function, and performs control for executing trick play when receiving a trick play instruction from the user interface unit 21. Details of trick play will be described later.

  In this embodiment, both the download speed measurement / bit rate change determination function and the trick play function are provided, but only one of them may be provided.

  The user terminal 2 may be a general PC in which a computer main body and a display are separated, or may be a terminal including a touch panel in which an operation unit and a display unit are integrated, such as a smartphone. Moreover, terminals other than these may be used.

  Both the user terminal 2 and the media distribution device 1 can be realized by causing a computer having a communication function to execute a program corresponding to the processing described in the present embodiment. The program may be stored in a storage medium such as a portable memory and distributed, installed on the computer, or downloaded from a server on a network and installed on the computer.

(Download speed measurement)
Next, the download speed measurement executed by the user terminal 2 described above will be described.

  The download speed monitoring unit 25 in the present embodiment measures the download speed every time a GOP is received, starting from the start of segment data acquisition (HTTP GET request issuance).

  More specifically, the download speed is calculated from the amount of data received in the past certain time from the GOP reception time and the time required for reception (that is, the certain time). However, starting from an HTTP GET request, the download speed is not measured across the HTTP GET request. The “certain time” is a predetermined time. Considering the delay time from the HTTP GET request issuance to the arrival of the first segment data, this delay time is not subject to download speed measurement.

  FIG. 4 shows an operation image of download speed measurement. As a premise of this operation, the meta information storage unit 23 of the user terminal 2 stores the index information of each segment related to the corresponding media and the index information about each GOP, and the index information about the segment related to the HTTP GET request is stored. It can be referred to. That is, it is possible to grasp which GOP has the beginning (end) of which GOP from the beginning of the segment related to the HTTP GET request.

  When an HTTP GET request is transmitted from the media data acquisition processing unit 24 of the user terminal 2, the media distribution device 1 starts transmitting the segment data requested by the request toward the user terminal 2.

  The media data acquisition processing unit 24 of the user terminal 2 continuously receives the media data, stores it in the buffer 241, and the media data is transferred from the buffer 241 to the media playback processing unit 27.

  On the other hand, the download speed monitoring unit 25 measures the amount of received data (that is, the amount of data stored in the buffer) every predetermined short time. The download speed monitoring unit 25 refers to the index information to recognize that each GOP has been received based on the received data amount from when the data was first received. That is, for example, the download speed monitoring unit 25 recognizes that the data amount of GOP1 is Y bytes based on the index information, and has received the GOP1 data when receiving the Y byte from the beginning. Can be judged. Next, the download speed monitoring unit 25 grasps that the data amount of GOP2 is X bytes based on the index information, and receives GOP2 when the Xth byte is received after receiving GOP1 data. I can understand that. In this way, the reception point (reception time) can be determined for each GOP included in the segment. Hereinafter, this reception point is also referred to as a measurement point.

  The download speed monitoring unit 25 calculates the download speed by dividing the amount of data received from a certain time before the present to the present (at the time of the reception point) by the certain time for each measurement point of the GOP.

  In FIG. 4, the “certain time” is about two GOPs, but this is merely an example for convenience of illustration. In addition, when the time point before the “certain time” includes the time before receiving the first data (in the example of FIG. 4, in the case of the measurement points of GOP1 and GOP2), that is, after receiving the data for the first time. When the time to the measurement point is shorter than the “fixed time”, the time from the first reception of data to the measurement point may be used instead of the “fixed time”.

  As described above, every time a GOP is received, the download speed based on the amount of data received during a certain period of time is calculated, so that fluctuations in the download speed for each GOP can be leveled. An appropriate download speed can be obtained by avoiding fluctuations in the download speed. However, the “certain time” in this case is longer than the time taken to receive one GOP.

  Instead of measuring the download speed based on the amount of data received during a “certain time” every time a GOP is received as in the above measurement method, each time a GOP is received, The download speed may be calculated by dividing the amount of data received from the completion of GOP reception to the completion of the GOP reception by the time between them. This method is suitable, for example, in a network environment where the speed fluctuation for each GOP is expected to be small.

  The download speed measured as described above may be displayed on the display unit of the user terminal 2, for example. In the present embodiment, the bit rate change determination is performed based on the download speed as follows.

(Bit rate change judgment)
The download speed monitoring unit 25 notifies the bit rate change determination unit 26 of the measured download speed every time the download speed is measured.

<Judgment processing to lower the bit rate>
The bit rate change determination unit 26 determines whether or not the buffer 241 is depleted until the GOP download is completed when the next GOP is downloaded at the current download speed notified from the download speed monitoring unit 25. Is determined every time the download speed is measured, and if it is exhausted, it is determined that the bit rate of the media will be lowered. Note that, here, as an example, when the next GOP is downloaded, it is determined whether or not the buffer 241 is exhausted before the GOP download is completed, but this is not the next one GOP. Then, it may be determined that a plurality of subsequent GOPs have been downloaded.

  Further, determining whether or not the buffer 241 is exhausted is just an example. “Depletion” is an example of a state that hinders reproduction of media content, and other states that hinder reproduction of media content may be used for determination. For example, it is determined whether or not the accumulated amount of the buffer 241 is equal to or less than a predetermined amount, or whether the accumulated amount of the buffer 241 is equal to or less than a predetermined percentage of the entire media data, and the bit rate change is determined. Also good.

  For example, in the example of FIG. 4, it is assumed that the download speed calculated when GOP3 is received is X kbit / s, and the size of GOP4 to be received next is 3X kbit from the index information. In this case, it is calculated that it takes 3X ÷ X = 3 seconds to receive 3X kbit data. Further, it is assumed that the bit rate change determination unit 26 grasps that the data accumulation amount of the buffer 241 at the time of receiving GOP3 is 10 × kbit. If the bit rate of the medium at this time is 5Xkbit / s, data is acquired from the buffer 241 at a speed of approximately 5Xkbit / s, and the data in the buffer correspondingly decreases. Then, in 3 seconds required to receive GOP4, 15 Xkbit data should be obtained from the buffer. However, since the amount of data stored in the buffer 241 at the time of receiving GOP3 is 10Xkbit and the size of GOP4 is 3Xkbit, the total of these is 13kbit, which is less than 15Xkbit. Therefore, the data in the buffer 241 is exhausted (becomes 0) within 3 seconds. When the data in the buffer 241 is depleted, the video is stopped during media playback, and the playback quality deteriorates.

  Therefore, the bit rate change determination unit 26 according to the present embodiment determines to decrease the bit rate in this case.

  In the present embodiment, when the bit rate change determination unit 26 determines that the bit rate is to be lowered, the bit rate change determination unit 26 is a fixed multiple of the download speed calculated immediately before (the download speed calculated by the current GOP reception) (D times this). The maximum bit rate that does not exceed is selected as the changed bit rate.

  For example, D times 3 times, current download speed is X kbit / s, current bit rate is 5X kbit / s, and lower bit rates are 2.5X kbit / s and X kbit / s. In this case, when the download speed is lowered, 2.5Xkbit / s, which is the maximum bit rate not exceeding D times (3 times) of X kbit / s, is selected as the bit rate after the change. It should be noted that an appropriate value is set in advance for this D times. For example, the relationship between the download speed, bit rate, buffer amount, and the like in this method may be measured by experiment, and an appropriate value as D times may be determined in advance, or a theoretical value or the like may be used. . Alternatively, the bit rate change determination unit 26 may grasp these relationships at regular time intervals and dynamically determine D times.

  For example, in the above example, when D times is set to 2 times, X kbit / s is selected. At this time, it is assumed that a lot of data continues to be held in the buffer 241. If this occurs, it is possible to use a higher bit rate. A high bit rate is preferable because the user can view high-quality video. In order to reduce the above situation as much as possible and provide a user with the most comfortable media playback environment as much as possible, the D-times when the maximum bit rate not exceeding D-times is selected as the changed bit rate is determined.

  The bit rate change determination unit 26 notifies the media data acquisition processing unit 24 and the media reproduction processing unit 27 of the changed bit rate changed as described above. If the meta information of the media content corresponding to the changed bit rate is stored in the meta information storage unit 23, the media data acquisition processing unit 24 uses the network location information (the changed bit rate after the change) for the media data to be acquired next. Network position information of the media data corresponding to) is created from the meta information and index information, and the corresponding media data is obtained by sending a request to the media distribution device 1, and this is repeated to change the media data after changing the bit rate In addition to performing acquisition, the media playback processing unit 27 performs media playback at the changed bit rate.

  When the meta information storage unit 23 does not have the meta information of the media content corresponding to the changed bit rate, the meta information acquisition unit 22 acquires the meta information according to the instruction of the media data acquisition processing unit 24, and the meta information storage unit After storing in 23, the above processing is performed.

<Determination process to increase bit rate>
In addition, the bit rate change determination unit 26 determines whether or not the download speed equal to or higher than a fixed rate of the bit rate that is one bit higher than the current bit rate (this is U times) can be maintained for a certain period of time. It is judged. Alternatively, it may be determined whether or not the “fixed time” or more can be maintained at a time interval longer than the “fixed time”.

  If the download speed that is U times higher than the bit rate one higher than the current bit rate can be maintained for a certain time or longer, the bit rate one higher is selected and the bit rate is changed. The processing after changing the bit rate is the same as when the bit rate is lowered. Here, as an example, the bit rate that is one bit higher is selected, but a bit rate other than the bit rate that is one bit higher (for example, two or three or higher) may be selected. .

  For example, the download speed of measurement results continues for a certain period of time in the range of 2.5Xkbit / s to 3Xkbit / s, the current media bit rate is 0.5Xkbit / s, and the bit rate above this is Xkbit Assume that there are / s and 2.5Xkbit / s, and U times is twice. In this case, twice the Xkbit / s, which is the next higher bit rate, is 2Xkbit / s. In the above example, 2Xkbit / s or more can be maintained for a certain period of time, so the bit rate is determined to be Xkbit / s. To do.

  In the above example, for example, when a situation occurs in which the bit rate is immediately reduced after the bit rate is increased, the bit rate is immediately decreased. However, frequent bit rate changes are undesirable for users. Therefore, in this case, it is sufficient that, for example, 3 times is set as U times. This is because if it is three times, the decision to increase the bit rate is not made. However, if the magnification is increased too much, there is no problem even if the bit rate is increased, but the case where the bit rate is not increased is likely to occur.

  It should be noted that an appropriate value is set in advance for U times. For example, the relationship between the download speed, bit rate, buffer amount, etc. in this method may be measured by experiment, etc., and an appropriate value as U times may be determined in advance, or a theoretical value or the like may be used. . Alternatively, the bit rate change determination unit 26 may grasp these relationships at regular time intervals and dynamically determine U times.

  In addition, when the fixed magnification is dynamically determined for both D times and U times, the moving average of the download speed over a long period of time is always calculated. You may make it make fixed magnification small. It is also possible to review the fixed rate from the download speed after changing the bit rate.

  In addition, the example of each fixed magnification, the bit rate, the buffer amount, and the download speed in the above example is for convenience to make the explanation easy to understand, and the specific example of each fixed magnification is an actual appropriate value. Not always.

<Other examples of changing the bit rate>
In determining the bit rate, a method may be adopted in which the download rate is not used and the bit rate is lowered by one when the buffer time falls below a certain time. The buffer time is the time from when data is stored in the buffer until it is read, and is measured by the bit rate change determination unit 26.

  Further, the bit rate change determination unit 26 may change the bit rate only by looking at the change in the buffer amount without using the download speed.

  Further, the bit rate change determination unit 26 calculates RTT in packet transmission / reception (SYN → SYN, ACK) in the TCP layer without using the download speed, and lowers the bit rate when RTT is larger than a predetermined value, It is also possible to perform control to increase the bit rate when it is less than a predetermined value.

Furthermore, the long-term trend and the short-term trend of the download speed may be compared, and the bit rate change may be determined based on the trend. For example, even if the speed decreases due to the short-term trend, it is possible to determine that the bit rate is maintained if there is no downward trend due to the long-term trend. The long-term trend here is, for example, an increase / decrease amount within a certain period of the moving average value (calculated for each GOP reception) in the time window T for the download speed measured every GOP reception. Is an increase / decrease amount within a certain period of the moving average value in the time window in a time shorter than the time window T. The long-term trend and the short-term trend are not limited to this, and the long-term trend and the short-term trend can be grasped by using various analysis methods. The judgment of the long-term trend and the short-term trend is used to determine whether or not the actual change is made when it is determined that the change is made in the result of the bit rate change determination using the download speed described above. Also good.
Note that the initial bit rate at the start of reproduction may be selected as the maximum value that does not exceed the band selected in the initial setting.

(Trick play)
In conventional video distribution technology that does not have an index such as HLS, in order to enable trick play such as jump, fast forward, rewind, etc., the entire video file is analyzed or another video file for trick play is created. There is a problem that a large burden is placed on the implementation, such as the need to do so. Below, the processing content of the trick play which solved this subject is demonstrated.

<Jump>
The media data acquisition processing unit 24 receives a jump instruction from the user interface unit 21. For example, while the user is viewing the media, the operation unit displayed on the screen designates a position T for a predetermined time from the start of the media content (for example, a time point 30 minutes after the start of the media), and moves to this position. The user interface unit 21 sends a jump instruction including information of T “30 minutes” to the media data acquisition processing unit 24.

  The media data acquisition processing unit 24 accesses the meta information storage unit 23 and refers to index information corresponding to the media content currently being viewed. If there is no necessary index information, the media data acquisition processing unit 24 causes the meta information acquisition unit 22 to acquire the index information and uses the acquired index information.

  The media data acquisition processing unit 24 specifies the segment corresponding to the designated time position T and the byte position in the segment.

  For example, assuming that the segment including the time position T is identified as the segment 10 based on the time information in the segment index information, next, the index information for each GOP in the segment 10 is referred to, and the time position Specify the first byte position of the GOP corresponding to T. The GOP corresponding to the time position T can be a GOP having the head closest to the time position T, for example. For example, as shown in FIG. 5, if the top time position of the segment 10 that can be grasped from the index information is T-TΔ, the GOP4 having the top time position closest to TΔ in the segment 10 is specified as the jump destination. Will be. The byte position from the segment head of GOP4 can be acquired from the index information.

  The media data acquisition processing unit 24 designates the network location information (HTTP-URL) of the segment specified as described above and the byte location therein, and transmits a media data acquisition request to the media distribution device 1. Then, media data is acquired, and thereafter, media acquisition and distribution are performed in the same manner as normal distribution.

  In the above example, the jump is performed in GOP units, but the jump may be performed in segment units. Further, as long as the time position and the byte position can be grasped using the index information, the jump may be performed in units of frames.

<Fast forward / rewind>
Next, fast forward / rewind processing will be described. Assume that the media data acquisition processing unit 24 receives a fast-forward instruction from the user interface unit 21. For example, when the user selects a fast-forward button on the operation unit displayed on the screen while viewing the media, the selection information is notified to the user interface unit 21, and the user interface unit 21 obtains a fast-forward instruction to obtain media data. This is performed on the processing unit 24. This fast-forwarding instruction includes information on the time from the start of the media at the time of the instruction.

  Upon receiving the fast-forward instruction, the media data acquisition processing unit 24 uses the media time position information and the index information at the time of the instruction in the same manner as in the case of the jump, and the media content corresponding to the time point when the fast-forward instruction is received. Specify the GOP. Further, by referring to the index information of the GOP, after specifying the byte position and size of the I frame, a request for requesting only the I frame from the target segment is sent to the media distribution device 1 to download the I frame. .

  Thereafter, the next I frame is identified in accordance with the fast-forward rate determined by the setting, and the downloading and decoding of the I frame are repeated until the end of the content is reached or the reproduction state is switched by the user operation. For example, continuous I frames are selected according to the fast-forwarding double speed rate, or I frames are selected every predetermined number.

  In the case of rewinding, the I frame at the time of receiving the instruction is specified in the same way as in the case of fast forward, and the I frame is sequentially specified in the start direction of the media and reaches the beginning of the content or is played by the user operation. Repeat downloading and decoding of I-frame until switched to.

  In the present embodiment, it is assumed that the video playback function of the media playback processing unit 27 is not equipped with a fast forward / rewind function. Therefore, a time stamp to be notified to the media playback processing unit 27 is provided. By operating, the fast-forward / rewind function can be realized without making the moving-image playback function of the media playback processing unit 27 aware of fast-forward / rewind. Regarding the operation of the time stamp, the media data acquisition processing unit 24 artificially attaches a time stamp of actual time stamp × 1 / N (in the case of N double speed) and passes the data to the media reproduction processing unit 27.

  In the prior art, the bit rate cannot be changed at the time of trick play, but in this embodiment, the bit rate can be changed. That is, in jumping, fast-forwarding / rewinding, it is possible to review the bit rate by continuously performing the bit rate change determination using the above-described method using the download speed even after executing these. As for fast-forwarding / rewinding, the bit rate change determination may not be performed during fast-forwarding / rewinding, and the bit rate may be reviewed after shifting to normal reproduction. When jumping, the bit rate may be reviewed and the jump may be performed. In this case, after the bit rate is determined, the jump position is determined using the index information of the media corresponding to the bit rate.

  As described above, in the fast forward / rewind, the download speed when performing the bit rate change determination using the download speed is the same every time an I frame is received (each time the data corresponding to the I frame corresponding to the request is received). It can be calculated using the amount of data received during the past fixed time from the time when the I frame was received.

  Further, the bit rate may be reduced during fast forward / rewind. That is, in this case, when a fast-forward / rewind instruction is received, the meta information relating to the media content having a different bit rate is used, and an I frame of the media content having the different bit rate is acquired.

  In this case, for example, during playback at a high bit rate, fast forward / rewind is performed at a medium bit rate, and during playback at a medium bit rate, fast forward / rewind is performed at a low bit rate, and playback is performed at a low bit rate. During this period, the bit rate is not reduced. Which of the plurality of defined bit rates is set to the high bit rate, which is set to the medium bit rate, and which is set to the low bit rate is determined in advance and set in the user terminal 2.

<Effect of trick play according to this embodiment>
In conventional RTP IPTV, the server extracts the I frame only and prepares the video in advance or sequentially so that it can be delivered in the fast forward / rewind mode. Also, in HLS, it is not possible to extract only the I frame, so prepare a video with only the I frame extracted in advance, or download all at N times the speed and extract the I frame at the terminal It will be.

  On the other hand, in the technique according to the present embodiment, only the I frame is extracted from the segment based on the index information, so that the fast forward / rewind function can be realized with the minimum network transfer amount.

(Effect of embodiment)
By implementing a media playback function using a media distribution method having index information, download speed calculation in GOP units can be realized, and bit rate switching can be performed in GOP units. In addition, trick play, which has been a high load until now, can be performed with a low load by using index information. Therefore, convenience for the user is improved and efficiency in using the network is improved.

  The present invention is not limited to the above-described embodiments, and various modifications and applications are possible within the scope of the claims.

DESCRIPTION OF SYMBOLS 1 Media delivery apparatus 2 User terminal 3 Network 11 Meta information storage part 12 Media content storage part 13 Information delivery control part 21 User interface part 22 Meta information acquisition part 23 Meta information storage part 24 Media data acquisition process part 241 Buffer 25 Download speed monitoring 26 Bit rate change determination unit 27 Media playback processing unit

Claims (9)

A streaming media playback device that downloads and plays media content from a networked streaming media distribution device,
By referring to the index information corresponding to the media content, it is understood that a predetermined unit of data in the media content has been received, and a communication status measuring unit that measures the download speed of the media content in the predetermined unit;
Bit rate change determination means for determining whether to change the bit rate of the media content based on the measurement result by the communication status measurement means ,
The bit rate change determination means selects the maximum bit rate that does not exceed a predetermined number of times greater than 1 of the download speed when it is determined to lower the bit rate of the media content. Playback device. The streaming media playback device according to claim 1, wherein the communication status measuring unit measures the download speed of the media content in GOP units as the predetermined unit. The said communication condition measurement means calculates the said download speed based on the data amount received during the present time from the fixed time every time reception of one GOP is completed. Streaming media playback device. The bit rate change determining means receives the predetermined unit of data, downloads the subsequent predetermined unit of data without changing the current bit rate, and determines the subsequent predetermined unit of data. 4. It is determined whether or not the buffer is in a predetermined state before reception is completed, and when the buffer is in a predetermined state, it is determined to reduce the bit rate. A streaming media playback device according to claim 1.   5. The streaming media playback apparatus according to claim 4, wherein the predetermined state is a state that interferes with playback of the media content. The bit rate change determining means determines whether or not a download speed that is a predetermined multiple of the bit rate above the current bit rate has been maintained for a certain period of time, and if the download rate can be maintained, the bit rate is changed to the upper bit rate. The streaming media playback device according to any one of claims 1 to 5 , wherein the streaming media playback device is determined to increase. The communication status measuring means, in the measurement of the download speed, and starting from the data acquisition request of the media content, any one of claims 1, characterized in that not measured straddling the data acquisition request 6 2. The streaming media playback device according to item 1. A media bit rate change determination method executed by a streaming media playback device that downloads and plays media content from a networked streaming media distribution device,
A communication status measurement step of grasping that a predetermined unit of data in the media content has been received by referring to the index information corresponding to the media content, and measuring the download speed of the media content in the predetermined unit;
A bit rate change determination step for determining whether to change the bit rate of the media content based on the measurement result of the communication status measurement step;
In the bit rate change determination step, when it is determined that the bit rate of the media content is to be lowered, the streaming media playback device selects a maximum bit rate that does not exceed a predetermined number of times greater than 1 of the download speed. A media bit rate change determination method characterized by the above. The program for functioning a computer as each means of the streaming media reproducing apparatus of any one of Claims 1 thru | or 7 .

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