JP2017084044A - Client device for content distribution system and method and program for determining reproduction start timing of content - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a client device for determining a reproduction start timing of content under the consideration of fluctuation of transmission speed.SOLUTION: A client device of a content distribution system for performing content distribution by using segments obtained by dividing content as units includes: request means for requesting the segments of the content in a reproduction time order to a server device to acquire and reproduce the content from the server device; buffer means for buffering the segments received from the server device as a response to the request by the request means; and determination means for determining a reproduction start timing of the content. Each time receiving the segment, the determination means determines, on the basis of at least the size of the segment and the reception period of the segment, transmission speed at the time of reception of the segment, and determines whether to start the reproduction of the content on the basis of the determined transmission speed.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a technique for determining reproduction start timing in a client device of a content distribution system.

  For example, in a content distribution system such as a DASH (Dynamic Adaptive Streaming over HTTP) distribution method, a client device starts reproducing content when the buffer amount reaches a predetermined value. Patent Document 1 discloses a configuration in which a timing at which a buffer amount becomes a predetermined value is obtained based on a transmission rate when content starts to be received, and thereby, a content reproduction start timing is determined.

JP 2004-229060 A

  However, the method described in Patent Document 1 does not consider fluctuations in transmission speed.

  The present invention provides a client device that determines content reproduction start timing in consideration of fluctuations in transmission speed, and a method and program for determining content reproduction start timing.

  According to an aspect of the present invention, a client device of a content distribution system that distributes content in units of segments into which content is divided, obtains the content from the server device and plays the content segment on the server device. Requesting means for requesting in order of playback time, buffer means for buffering a segment received from the server device as a response to the request by the requesting means, and determining means for determining the playback start timing of the content. Each time a means receives a segment, it determines the transmission speed using at least the size of the segment and the reception period of the segment, and determines whether to start content playback based on the determined transmission speed. It is characterized by doing.

  The content reproduction start timing can be determined in consideration of fluctuations in the transmission speed.

The lineblock diagram of the contents distribution system by one embodiment. The sequence diagram of the content delivery process by one Embodiment. The block diagram of the client apparatus by one Embodiment.

  Hereinafter, exemplary embodiments of the present invention will be described with reference to the drawings. In addition, the following embodiment is an illustration and does not limit this invention to the content of embodiment. In the following drawings, components that are not necessary for the description of the embodiments are omitted from the drawings.

  FIG. 1 is a configuration diagram of a content distribution system according to the present embodiment. For example, a server device 3 and a client device 1 are connected to a network 2 such as the Internet. The server device 3 holds the content to be distributed, and distributes the content designated by the client device 1 to the client device 1 in accordance with a request from the client device 1. In the following description, it is assumed that the server device 3 and the client device 1 perform content distribution and reception according to DASH. However, the present invention can be applied to any content distribution system that divides content into a plurality of segments and requests and distributes content in units of segments.

  FIG. 2 is a sequence diagram of content distribution according to the present embodiment. In S1, the client device 1 transmits an MPD request message for requesting the server device 3 for an MPD (Media Presentation Description) file of the content to be acquired. The MPD file describes the segments that make up the content and its URI. When the server apparatus 3 receives the MPD request message from the client apparatus 1, the server apparatus 3 transmits the requested MPD file to the client apparatus 1 in S2. Subsequently, the client device 1 transmits a time series information request message for requesting the segment size time series information of the content to the server device 3 in S3. The segment size time-series information is a description of the sizes of the segments constituting the content in the order of segment playback time. When the server device 3 receives the time series information request message from the client device 1, the server device 3 transmits the requested segment size time series information to the client device 1 in S4. The segment size time-series information may be included in the MPD file. Thereafter, the client device 1 acquires segments from the server device 3 in the order of segment playback times. For this reason, the client device 1 first transmits a segment request message for requesting the first segment to the server device 3 in S5. When the server device 3 receives the segment request message, the requested segment is selected in S6. Delivered to the client device 1.

  The client device 1 buffers the segment received as a response to the segment request message, performs a determination process described below, and determines whether to start content playback. If the content reproduction is not started, the processes of S5 to S7 are repeated. It should be noted that the segment requested by the client device 1 in the subsequent repetition is the segment next to the segment acquired immediately before. In addition, after starting the reproduction of content, the processes of S5 and S6 are repeated.

Next, the determination process in S7 will be described. In the following, the size of the segments _{S 1,} S 2 to the chronological order, it is assumed that · · · _{S N.} N is the total number of segments constituting the content. That is, the size of the k-th segment (k is an integer from 1 to N) is S _k . It should be noted that the period of content reproduced by each segment is equal, and this is Δt. The timing (time) at which the _kth segment is received is tk.

The client apparatus 1 determines, upon receiving the k-th segment, the k-th segment及k-th reception period of the segment, the estimated transmission rate R _k at the timing that has received the k-th segment. Note that the size of the segment received in the past predetermined period and the reception period thereof can be further used for the determination of the estimated transmission rate _Rk . In this case, the number of segments used for determining the estimated transmission rate _Rk can be made variable. For example, when the first segment is received, the estimated transmission rate R ₁ is calculated from the size and reception period of the segment, and when the second segment is received, it is calculated from the size of the first segment and the reception period. The estimated transmission rate R ₂ is an average value of the calculated rate, the size of the second segment, and the rate calculated from the reception period. In the third and subsequent segments, three rates can be obtained from the size of the received segment, the past two segments, and their reception periods, and the average value of these can be used as the estimated transmission rate. In addition, the said specific number is an illustration for description, The client apparatus 1 can calculate estimated transmission rate _Rk by arbitrary methods.

Then, the client device 1 compares the total size of the segments from the kth segment to the k + qth segment, that is, the total value of S _{k to} S _{k + q} with R _k × q × Δt. The total value of S _{k to} S _{k + q} is the amount of data extracted from the buffer when q + 1 segments are reproduced from the kth segment, and R _k × q × Δt is the current estimated transmission rate continued Assuming that, q + 1 is the amount of data that can be received before reproducing q + 1 segments. The total value of S _{k to} S _{k + q} is an evaluation value of the data consumption amount in the case of reproduction. If R _k × q × Δt is larger than the total value of S _{k to} S _{k + q} , the amount of data stored in the buffer is Does not decrease. Thus, the client device 1, from the time of receiving the first _segment, S k _{to S k +} sum and comparing the _{R k} × q × _Δt of _{q, S k ~S} k _{+ q} sum from _{R k} × q of When × Δt is large, it is determined that the reproduction of the content is started. Note that the object to be compared with R _k × q × Δt may be the total value of S _{1 to} S _{1 + q} instead of the total value of S _{k to} S _{k + q} . In this case, the total value of S _{1 to} S _{1 + q} is the amount of data extracted from the buffer before receiving q segments when playback is started at the present time (when the k-th segment is received). If this value is smaller than R _k × q × Δt, the amount of data in the buffer will increase.

  As described above, each time a segment is received, the transmission rate at the time of reception is estimated, and the amount of data that can be received after a predetermined time from the time of reception is compared with the evaluation value of the amount of data consumed. Then, when the amount of data that can be received is greater than the consumption, the reproduction of the content is started. Thereby, buffer underflow can be suppressed.

  FIG. 3 is a configuration diagram of the client device 1 according to the present embodiment. The transmission / reception unit 10 performs transmission / reception processing with the network 2. The control unit 11 requests the MPD file and the segment size time series information from the server device 3 via the transmission / reception unit 10 and acquires them. Furthermore, the control unit 11 requests a segment from the server device 3 via the transmission / reception unit 10. On the other hand, the transmission / reception unit 10 stores the segment transmitted by the server device 3 in the buffer unit 12. When the control unit 11 performs the above-described determination process and determines that the content reproduction is started, the control unit 11 instructs the reproduction unit 13 to reproduce the content. When receiving the content playback instruction from the control unit 11, the playback unit 13 takes out the segments stored in the buffer unit 12 in the order of time and starts playback of the content.

  In the above-described embodiment, the content reproduction start timing is determined based on the size of a segment composed of a plurality of frames. However, the size of each frame can be estimated based on the size of the segment, and the content reproduction start timing can be determined based on the size of the frame. Specifically, as described above, the period of content reproduced by one segment is a known value Δt, and the frame rate is also known. That is, the number of frames included in one segment is known. For example, the control unit 11 obtains a variance value of the segment size, and estimates the size of each frame in one segment from the variance value.

  For example, when the size of a certain segment is 100 and the number of frames is 10, in this case, if the variance value of the segment size is 0, the control unit 11 determines that the size of each frame is the average value. Estimated to be equal to 10. On the other hand, if the variance value is A greater than 0, the control unit 11 obtains an initial value greater than the average value. For example, the initial value is 15. In this case, the control unit 11 estimates the size of the first to sixth frames of the segment as 15 and determines the size of the seventh frame as 10 which is the remaining size, and the 8th to 10th frames. Is estimated to be 0. Further, if the variance value is B greater than A, the control unit 11 determines that the initial value is greater than 15, for example, 20. In this case, the control unit 11 estimates the size of the first to fifth frames of the segment as 20 and estimates the size of the 6th to 10th frames as 0. The relationship between the variance value and the initial value is determined in advance, but the initial value increases as the variance value increases.

  Then, the control unit 11 determines whether or not to start reproduction every period Δt / 10 for each frame reproduction period, that is, when the reproduction period of one segment is Δt and one segment is 10 frames. Judgment is made. Note that the determination method only replaces the segment with a frame, and will not be described again. The estimated transmission rate is determined based on the size and reception period of the most recently received segment.

  The client device according to the present invention can be realized by a program that causes a computer to operate as the client. These computer programs can be stored in a computer-readable storage medium or distributed via a network.

  11: Control unit, 12: Buffer unit

Claims (10)

A client device of a content distribution system that distributes content in units of segments into which content is divided,
Requesting means for requesting the content segments from the server device in order of playback time in order to acquire and play the content from the server device;
Buffer means for buffering a segment received from the server device as a response to the request by the request means;
Determination means for determining the reproduction start timing of the content;
With
The determination means determines the transmission rate at least using the size of the segment and the reception period of the segment every time a segment is received, and determines whether to start content playback based on the determined transmission rate A client device characterized by determining The apparatus further comprises acquisition means for acquiring size information indicating the size of each segment of the content from the server device,
When the determination unit receives the segment, the determination unit determines the amount of data that can be received between the time when the segment is received and the time after the predetermined time based on the determined transmission rate, and the time until after the predetermined time based on the size information. 2. The client according to claim 1, wherein an evaluation value of a data consumption amount of the client is determined, and whether or not content reproduction is started is determined by comparing the received data amount with the evaluation value. apparatus.   The client apparatus according to claim 2, wherein the evaluation value is a total value of the sizes of segments to be reproduced during the predetermined time.   The client device according to claim 2, wherein the determination unit determines that the reproduction of content is started when the amount of data that can be received is larger than the evaluation value. A client device of a content distribution system that distributes content in units of segments into which content is divided,
The segment includes a plurality of frames;
The client device is
Requesting means for requesting the content segments from the server device in order of playback time in order to acquire and play the content from the server device;
Buffer means for buffering a segment received from the server device as a response to the request by the request means;
Determination means for determining the reproduction start timing of the content;
With
When the determination unit receives the segment, it determines the transmission rate using at least the size of the segment and the reception period of the segment, and plays back the content for each frame playback period based on the determined transmission rate. A client apparatus for determining whether or not to start the client. Obtaining means for obtaining size information indicating the size of each segment of the content from the server device;
Estimating means for estimating the size of each frame of each segment based on a variance value of the size of each segment of the content;
Further comprising
The determination means determines the amount of data that can be received from when the segment is received to a predetermined time later based on the determined transmission rate, and based on the estimated size of each frame. 6. The client apparatus according to claim 5, wherein an evaluation value of a data consumption amount is determined, and it is determined whether or not content reproduction is started by comparing the received data amount with the evaluation value. .   The client apparatus according to claim 6, wherein the evaluation value is a total value of the sizes of frames to be reproduced during the predetermined time. A method of determining a content reproduction start timing in a client device of a content distribution system that distributes content in units of segments obtained by dividing content,
A requesting step for requesting the content segments from the server device in order of playback time in order to acquire and play the content from the server device;
A buffer step for buffering a segment received from the server device as a response to the request;
A determination step of determining the playback start timing of the content;
Including
In the determination step, each time a segment is received, a transmission rate is determined using at least the size of the segment and the reception period of the segment, and whether or not to start content playback based on the determined transmission rate A method characterized by determining whether or not. A method of determining a content reproduction start timing in a client device of a content distribution system that distributes content in units of segments obtained by dividing content,
The segment includes a plurality of frames;
The method
A requesting step for requesting the content segments from the server device in order of playback time in order to acquire and play the content from the server device;
A buffer step for buffering a segment received from the server device as a response to the request;
A determination step of determining the playback start timing of the content;
Including
In the determination step, when a segment is received, a transmission rate is determined using at least the size of the segment and the reception period of the segment, and based on the determined transmission rate, the content rate is determined for each frame reproduction period. A method for determining whether or not to start reproduction.   A method of causing a computer to function as the client device according to claim 1.

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