JP5806981B2 - Playback state estimation apparatus, method and program - Google Patents

Description

  The present invention relates to a playback state estimation apparatus, method, and program, and more particularly, to a terminal that receives a video service, detects the arrival of the upper limit of the data amount in the buffer based on packet capture data, and decodes the data at the time of data playback and the buffer upper limit. The present invention relates to a playback state estimation apparatus, method, and program for estimating a playback state.

  With the progress of broadband communication networks in recent years, progressive download type content distribution systems in which large-capacity content data are downloaded and processed in parallel at client terminals have become widespread. In such a content distribution mode, the transmission quality degradation caused by the network affects the content reproduction on the terminal side, so the content data providing business that requires an objective understanding of the user's quality of experience For network operators who provide access lines and access lines, it is important to perform remote quality monitoring, such as isolation when users report quality deterioration.

On the other hand, a mechanism that prepares a playback buffer on the terminal side and conceals the influence of the network on higher-level applications is often used as a conventional technology. In order to optimize the balance of shortening, a technique for dynamically changing the initial buffer amount based on the packet transfer delay time is also disclosed.
Furthermore, a playback stop event that occurs when the network throughput temporarily drops below the content data processing speed and the content data storage amount in the playback buffer falls below a certain amount (playback stop threshold). A service quality estimation technique for deriving an estimated value of the playback stop state by grasping the time series of the received byte amount of the terminal based on the capture data and inputting it to the modeled playout buffer is disclosed (for example, Non-patent documents 1 to 3).

  In addition, it is known that progressive download type applications are roughly classified into two types according to their reproduction methods, and the above technique can be applied to both of them. By using these techniques, the playback state of the session can be estimated based on given capture data.

Daisuke Ikegami, Yasunori Honda, Koji Yamamoto et al .: "Progressive download service stop time estimation method" IEICE Technical Report, vol. 111, no. 278, CQ2011-59, pp. 91-96, November 2011 . Daisuke Ikegami, Yasunori Honda, Koji Yamamoto: “Examination of playback state estimation method for chunked video distribution services”, IEICE General Conference, B-11-24, March 2012. Yasutoshi Honda, Daisuke Ikegami, Koji Yamamoto: “A video observation state estimation method using Ack observation”, IEICE General Conference, B-11-25, March 2012.

  In recent years, the spread of services for smartphones on 3G lines and tablet terminals in a wireless LAN environment is particularly noticeable. In general, these terminals are characterized in that the playout buffer length is shorter than that of a PC due to memory capacity constraints. As a result, the volume of downloaded unreproduced data reaches the buffer limit, and it is confirmed that the download is temporarily stopped more frequently than the PC. In particular, the sequential progressive download type service is characterized in that the download continues on the terminal that receives data even after the pause operation by the user, and as a result, the data reaches the buffer upper limit after a predetermined time has elapsed. Often reach.

  As a service provider or a line provider, it is desirable to objectively grasp the quality of experience of video services provided to users from the viewpoint of maintenance. Non-Patent Documents 1 to 3 are techniques for estimating a video playback state based on capture data. However, since the technique of this document does not consider reaching the buffer upper limit, it is necessary to use information in a viewing test or application-specific packet in order to estimate the decoding rate.

  The present invention has been made in view of the above points, and in a terminal such as a tablet terminal or a smart phone, the arrival state of the buffer upper limit can be confirmed from captured data acquired on an arbitrary network path between the server and the terminal As a premise, it is an object to provide a playback state estimation apparatus, method and program capable of estimating a playback state by estimating a decoding rate from captured data or estimating a buffer upper limit.

In order to solve the above-described problems, the present invention provides a progressive download type content distribution system that executes download and data processing in parallel at a terminal, and at the time of data reproduction that reproduces data received by the terminal via a network. A reproduction state estimation device for estimating a reproduction state,
Detecting a specific packet from capture data that is acquired on a network path between a server and a terminal and is input to the playback state estimation device and is IP packet data constituting an application session A buffer upper limit arrival time detecting means for detecting the buffer upper limit arrival time by:
The total received byte quantity in the period from the download resumption point detected from the captured data to the buffer upper limit arrival time detected by the buffer maximum arrival time detecting means calculated from the captured data, and the cumulative bytes received amount, pause Decoding rate calculation means for calculating a decoding rate estimation value based on a period from a playback resumption time, which is a time when playback is resumed after playback is stopped by an operation, to the buffer upper limit arrival time .

  As described above, according to the present invention, it is possible to estimate the decoding rate from only limited information such as capture data. Specifically, for example, it is possible to estimate a decoding rate based only on packet capture data in a video service such as a sequential progressive download type video service, and without using information from a user viewing test. Thus, the reproduction state estimation can be realized by a more efficient means. If the pause operation time by the user is known, the buffer upper limit can be estimated from the capture data.

It is a block diagram of the reproduction | regeneration state estimation apparatus in the 1st Embodiment of this invention. It is a playout buffer image in the first embodiment of the present invention. It is a buffer length transition image in the 1st Embodiment of this invention. It is a block diagram of the reproduction | regeneration state estimation apparatus in the 2nd Embodiment of this invention.

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

  The reproduction state estimation apparatus of the present invention is provided in a terminal that reproduces data received via a network, and decodes based on a parameter estimation value calculated by an external parameter estimation value calculation apparatus, an estimated buffer model, and capture data A rate estimation value is obtained (first embodiment). Here, the capture data is data of IP packets that constitute a session of the application. Further, in the verification for investigating the buffer length, when a user pause operation time is given in a partial time interval, a buffer upper limit estimated value is calculated (second embodiment).

[First Embodiment]
FIG. 1 is a configuration diagram of a reproduction state estimation apparatus according to the first embodiment of the present invention.

  The reproduction state estimation device 10 shown in FIG. 1 includes a buffer upper limit arrival time detection unit 2 and a decode rate estimation unit 3, and the decode rate estimation unit 2 is connected to the parameter estimation value calculation device 1.

  The parameter estimation value calculation device 1 is connected to the reproduction state estimation device 10, models a player, calculates a parameter estimation value based on the model, and outputs the parameter estimation value to the decode rate estimation unit 2.

  The parameter estimated value calculation device 1 is a device that outputs a parameter estimated value to the pause operation time estimation unit 2. The parameter estimated value calculation device 1 models the player, calculates a parameter estimated value based on the model, and outputs the parameter estimated value to the pause operation time estimation unit 2. The processing can be realized by various conventional techniques that can be modeled (for example, Non-Patent Documents 1 to 3).

  The parameter estimated value output by the parameter estimated value calculation apparatus 1 is shown in FIG.

  1) Reproduction start threshold: This is the remaining amount of data in the buffer required for the first reproduction after the application is started.

  2) Playback restart threshold: This is the remaining amount of data in the buffer required for the second and subsequent playback after playback is stopped.

  3) Playback stop threshold: This is a threshold for the amount of data in the buffer that transitions from the playback state to the playback stop state.

  4) Buffer length: Playout buffer capacity. The present invention allows a finite length.

  5) The amount of data in the buffer.

  The parameter estimated value calculation apparatus 1 outputs a reproduction start threshold value, a reproduction restart threshold value, a buffer length, a decode rate, and a reproduction stop threshold value among the parameter estimated values described above. However, if the playback stop has not occurred before reaching the buffer upper limit, the playback stop threshold is not necessary.

  The process of the reproduction state estimation device 10 will be described below.

  The buffer upper limit arrival time detection unit 3 calculates the buffer upper limit arrival time from the input capture data, and outputs it to the decode rate estimation unit 2.

  Specifically, the buffer upper limit arrival time (s) is detected by detecting specific packets such as a TCP RST packet, FIN packet, and Dup Ack packet in the capture data, and output to the decode rate estimation unit 2. For example, when the buffer limit is reached due to continuous data storage in the playout buffer, the terminal closes the session by sending a TCP RST packet or FIN packet, or sets the receive window size to 0 (TCP Zero Window). Prevents buffer overflow. When the TCP session is closed, it is distinguished from session close due to timeout because there are no packets indicating transfer quality degradation such as Dup Ack and retransmission in N packets before and after the capture data.

  The decode rate estimation unit 2 calculates the decode rate d using the input capture data, the parameters acquired from the parameter estimated value calculation device 1, and the buffer upper limit arrival time acquired from the buffer upper limit arrival time detection unit 3.

  The buffer length transition image shown in FIG. 3 is obtained by converting the capture data in time series. The operation of the decode rate estimation unit 2 will be described with reference to FIG. In FIG. 3, it is assumed that after the start of playback in [a1], the user performs a pause operation during playback [a2]. Thereafter, the data amount in the buffer reaches the buffer upper limit [a3], and the data amount remains at the upper limit in the buffer. Immediately after the user resumes playback [a4], the data amount in the buffer decreases monotonously because the download is stopped. After download restart [a5], the amount of data in the buffer again increases and reaches the buffer upper limit [a6]. Here, the reproduction restart time t4 by the user is estimated from the transmission time of the packet that arrived immediately before the time when the amount of data in the buffer became smaller than the upper limit value.

  It is clear that the upper limit stop time (t4−t3) of the data amount in the buffer is the pause state time. In this case, the pause operation continues from [a2] before [a3] when the buffer upper limit is reached. Here, the decoding rate estimation based on the buffer upper limit reaching event of [a4] and [a6] is described.

  First, the decode rate estimation unit 2 calculates the cumulative received byte amount B1 [byte] between the restart of download [a5] that can be detected when the received data is confirmed again in the capture data and the buffer upper limit reached [a6]. . The cumulative received byte amount B1 is the sum of the following 1) and 2).

1) Amount of bytes corresponding to the amount that was regenerated and replenished from the buffer: Amount of bytes regenerated in [a4] to [a5]:
2) Amount of bytes played back without accumulating from pause operation [a2] to reaching the buffer upper limit [a6]: Amount of bytes played back from [a5] to [a6]:
Next, the playback time (t6−t4) [seconds] is calculated from the packet capture data.

Based on the above, the average decoding rate d [Byte / sec]
d = B1 / (t6−t4) Equation (1)
Can be calculated. The reproduction restart time estimated value t4 is calculated from the last transmission time of the packet having the RST / Zero Window indicating the buffer upper limit reached in the packet capture data.

  In addition, here, it is assumed that the user pause operation is not included between the restart of viewing [a4] and reaching the buffer upper limit [a6], but the pause operation is included even when the pause operation is included. When the time p is given by some method (for example, when input from the user), the decoding rate can be calculated in the same manner.

Specifically, the accumulated received byte amount B1 from t5 to t6 is the viewing time during that period, that is,
(t6−t4−p)
The decoded code estimated value d is calculated by dividing by.

d = B1 / (t6−t4−p)
[Second Embodiment]
The apparatus of the present invention can also be realized as a reproduction state estimation device provided with a buffer length estimation unit that calculates a buffer upper limit estimated value using the final output of the reproduction state estimation techniques in Non-Patent Documents 1 to 3.

  FIG. 4 is a configuration diagram of a reproduction state estimation device according to the second embodiment of the present invention.

  The reproduction state estimation device 20 shown in the figure is provided with a buffer length estimation unit 4 in addition to the configuration of FIG. The decoding rate estimation unit 2 receives capture data, the buffer upper limit arrival time from the buffer upper limit arrival time detection unit 3, and the parameter estimation value from the parameter estimated value calculation device 1. The decode rate estimation unit 2 performs the same processing as in the first embodiment described above, and outputs the decode rate estimation value to the buffer length estimation unit 4 as well.

  Capture data and pause operation time are given to the buffer length estimation unit 4, and the buffer upper limit arrival time t 3 is input from the buffer upper limit arrival time detection unit 3, and the decode rate estimation value d is input from the decode rate estimation unit 2.

  In the present embodiment, the buffer length estimation unit 4 will be described again with reference to FIG.

The buffer length estimation unit 4 calculates a cumulative received byte amount B1 [Byte] from the reproduction start operation [a0] to the first buffer upper limit arrival [a3] corresponding to the buffer upper limit arrival time t3 in the capture data. The decoding rate estimation value acquired from the decoding rate estimation unit 2 is d [byte / sec], the buffer upper limit estimation value is B [Byte], and the user pause time between [a1] and [a3] which is a known amount is p. If [seconds]
B = B1 − d × (t3−t1−p) (2)
Holds. Thereby, the buffer upper limit estimated value B can be calculated. The calculated buffer upper limit estimated value B can be used for investigation purpose verification or the like.

[Decoding rate estimation]
First, a specific example of the processing of the decode rate estimation unit 2 will be shown.

  In this embodiment, it is assumed that the values in FIG. 3 are given as follows.

T4: 20 seconds; t6: 30 seconds;
-Accumulated received byte amount from [a5] to [a6]: 10 [Mbyte];
Based on the above information, the decoding rate estimation value d [byte / sec] is obtained from the equation (1) of the first embodiment described above.
10 / (30−20) = 1 [Mbyte / sec]
Can be calculated.

[Buffer upper limit estimation]
Next, a specific example of processing of the buffer upper limit estimated value estimation unit 4 will be shown.

Assuming that the accumulated received byte amount from [a0] to [a3] is 6 [Mbyte], t3−t1 = 10 [seconds], and the user pause operation time is 5 seconds, the above-mentioned first According to the expression (2) in the second embodiment,
B = 6 − 1M * (10−5)
From this, the buffer upper limit estimated value B = 1 [Mbyte] is calculated.

  The operation of each component of the decoding rate estimation device shown in FIG. 1 can be constructed as a program and installed in a computer used as a decoding rate device for execution or distributed via a network. It is.

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

DESCRIPTION OF SYMBOLS 1 Parameter estimated value calculation apparatus 2 Decoding rate estimation part 3 Buffer upper limit arrival time detection part 4 Buffer length estimation part 10 and 20 Playback condition estimation apparatus

Claims (7)

In a progressive download type content distribution system that executes download and data processing in parallel at a terminal, a playback state estimation device for estimating a playback state at the time of data playback in which the terminal plays back data received via a network, ,
Detecting a specific packet from capture data that is acquired on a network path between a server and a terminal and is input to the playback state estimation device and is IP packet data constituting an application session A buffer upper limit arrival time detecting means for detecting the buffer upper limit arrival time by:
The total received byte quantity in the period from the download resumption point detected from the captured data to the buffer upper limit arrival time detected by the buffer maximum arrival time detecting means calculated from the captured data, and the cumulative bytes received amount, pause Decoding rate calculation means for calculating a decoding rate estimation value based on a period from a playback restart time that is a time when playback is restarted after playback is stopped by an operation to the buffer upper limit arrival time ;
A reproduction state estimation device comprising: The decoding rate calculation means includes
When a pause operation time between the playback restart time and the buffer upper limit arrival time is given, a difference obtained by subtracting the pause operation time from the period from the playback restart time to the buffer upper limit arrival time is obtained. , Including, in the capture data, a decoding rate estimation value obtained by dividing a cumulative received byte amount from the download resumption time to the buffer upper limit arrival time by the difference,
The playback resume time is
2. The reproduction state estimation device according to claim 1, wherein the reproduction state estimation device detects the packet indicating the buffer upper limit reached from the last transmission time from the terminal to the server . A cumulative received byte amount from the playback start operation to the first buffer upper limit reaching time is obtained from the capture data, and a difference between the time from the playback start operation to the first buffer upper limit reaching time and a given user pause operation time is obtained. 3. The reproduction state estimation device according to claim 1, further comprising buffer length estimation means for calculating a buffer upper limit estimated value by subtracting a value obtained by multiplying the decode rate estimated value from the accumulated received byte amount. In a progressive download type content distribution system that executes download and data processing in parallel at a terminal, a playback state estimation method for estimating a playback state at the time of data playback in which the terminal plays back data received via a network, ,
In the apparatus having the buffer upper limit arrival time detection means and the decode rate calculation means,
The buffer upper limit arrival time detecting means is acquired on a network path between a server and a terminal , and is input to the device, and is captured data that is IP packet data constituting an application session. A buffer upper limit arrival time detecting step for detecting a buffer upper limit arrival time by detecting a specific packet ;
The decoding rate calculation means, a total received byte quantity in the period from the download resumption point detected from the captured data to the buffer upper limit arrival time detected by the buffer maximum arrival time detecting step is calculated from the captured data, wherein A decoding rate calculation step of calculating a decoding rate estimation value based on the cumulative received byte amount and the period from the playback restart time, which is the time when playback is restarted after playback is stopped by a pause operation, to the buffer upper limit reaching time When,
A reproduction state estimation method characterized by: In the decoding rate calculation step,
When a pause operation time between the playback restart time and the buffer upper limit arrival time is given, a difference obtained by subtracting the pause operation time from the period from the playback restart time to the buffer upper limit arrival time is obtained. In the capture data, a value obtained by dividing the cumulative received byte amount from the download resumption time to the buffer upper limit arrival time by the difference is a decode rate estimation value,
The playback resume time is
5. The reproduction state estimation method according to claim 4, wherein a packet indicating reaching the buffer upper limit is detected from a last transmission time from the terminal to the server . In an apparatus further comprising buffer length estimation means,
The buffer length estimation means obtains a cumulative received byte amount from the reproduction start operation to the first buffer upper limit arrival time from the capture data, and gives a time and a given time from the reproduction start operation to the first buffer upper limit arrival time. The reproduction state according to claim 4 or 5, further comprising a buffer length estimation step of calculating a buffer upper limit estimated value by subtracting a value obtained by multiplying a difference between user pause operation times by the decode rate estimated value from the accumulated received byte amount. Estimation method. Computer
A reproduction state estimation program for functioning as each unit of the reproduction state estimation device according to any one of claims 1 to 3.

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