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CN108271048B - Code rate self-adaptive adjusting device and method considering both throughput and video buffering - Google Patents

Code rate self-adaptive adjusting device and method considering both throughput and video buffering Download PDF

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CN108271048B
CN108271048B CN201810133231.8A CN201810133231A CN108271048B CN 108271048 B CN108271048 B CN 108271048B CN 201810133231 A CN201810133231 A CN 201810133231A CN 108271048 B CN108271048 B CN 108271048B
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code rate
media segment
module
throughput
media
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CN108271048A (en
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金跃辉
杨谈
邵熠
崔毅东
陈莉萍
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Beijing University of Posts and Telecommunications
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/20—Servers specifically adapted for the distribution of content, e.g. VOD servers; Operations thereof
    • H04N21/23—Processing of content or additional data; Elementary server operations; Server middleware
    • H04N21/239—Interfacing the upstream path of the transmission network, e.g. prioritizing client content requests
    • H04N21/2393—Interfacing the upstream path of the transmission network, e.g. prioritizing client content requests involving handling client requests
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/20—Servers specifically adapted for the distribution of content, e.g. VOD servers; Operations thereof
    • H04N21/25—Management operations performed by the server for facilitating the content distribution or administrating data related to end-users or client devices, e.g. end-user or client device authentication, learning user preferences for recommending movies
    • H04N21/266—Channel or content management, e.g. generation and management of keys and entitlement messages in a conditional access system, merging a VOD unicast channel into a multicast channel
    • H04N21/2662—Controlling the complexity of the video stream, e.g. by scaling the resolution or bitrate of the video stream based on the client capabilities
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/40—Client devices specifically adapted for the reception of or interaction with content, e.g. set-top-box [STB]; Operations thereof
    • H04N21/43—Processing of content or additional data, e.g. demultiplexing additional data from a digital video stream; Elementary client operations, e.g. monitoring of home network or synchronising decoder's clock; Client middleware
    • H04N21/433—Content storage operation, e.g. storage operation in response to a pause request, caching operations
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/60—Network structure or processes for video distribution between server and client or between remote clients; Control signalling between clients, server and network components; Transmission of management data between server and client, e.g. sending from server to client commands for recording incoming content stream; Communication details between server and client 
    • H04N21/63—Control signaling related to video distribution between client, server and network components; Network processes for video distribution between server and clients or between remote clients, e.g. transmitting basic layer and enhancement layers over different transmission paths, setting up a peer-to-peer communication via Internet between remote STB's; Communication protocols; Addressing
    • H04N21/643—Communication protocols
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/60—Network structure or processes for video distribution between server and client or between remote clients; Control signalling between clients, server and network components; Transmission of management data between server and client, e.g. sending from server to client commands for recording incoming content stream; Communication details between server and client 
    • H04N21/63—Control signaling related to video distribution between client, server and network components; Network processes for video distribution between server and clients or between remote clients, e.g. transmitting basic layer and enhancement layers over different transmission paths, setting up a peer-to-peer communication via Internet between remote STB's; Communication protocols; Addressing
    • H04N21/647—Control signaling between network components and server or clients; Network processes for video distribution between server and clients, e.g. controlling the quality of the video stream, by dropping packets, protecting content from unauthorised alteration within the network, monitoring of network load, bridging between two different networks, e.g. between IP and wireless
    • H04N21/64723—Monitoring of network processes or resources, e.g. monitoring of network load
    • H04N21/64738—Monitoring network characteristics, e.g. bandwidth, congestion level
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/80—Generation or processing of content or additional data by content creator independently of the distribution process; Content per se
    • H04N21/83—Generation or processing of protective or descriptive data associated with content; Content structuring
    • H04N21/845—Structuring of content, e.g. decomposing content into time segments
    • H04N21/8456—Structuring of content, e.g. decomposing content into time segments by decomposing the content in the time domain, e.g. in time segments

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Computer Security & Cryptography (AREA)
  • Databases & Information Systems (AREA)
  • Two-Way Televisions, Distribution Of Moving Picture Or The Like (AREA)

Abstract

A code rate self-adaptive adjusting device and method giving consideration to both throughput and video buffering are disclosed, when a code rate self-adaptive module of the device outputs transmission code rate information of a media segment to be requested, the throughput and video buffering information in other modules are given consideration to: firstly, smoothing historical throughput by using a Holt-Winters method, and estimating the throughput of a media segment to be requested; calculating a buffer weight parameter according to the current video buffer length in the buffer management module, and carrying out weighting adjustment on the estimated throughput to obtain the optimal transmission code rate; and finally, the code rate self-adaptive module selects and outputs the transmission code rate of the media segment to be requested from the selectable code rate list according to the optimal transmission code rate. The present invention addresses the deficiencies of the prior art while maintaining a relatively excellent playing experience in all respects. The device has the advantages of simple structure, ingenious design, simple and convenient operation steps, easy realization of operation and good popularization and application prospect.

Description

Code rate self-adaptive adjusting device and method considering both throughput and video buffering
Technical Field
The invention relates to a new technology in HTTP adaptive transmission, in particular to a code rate adaptive adjusting device and method considering both throughput and video buffering, belonging to the technical field of code rate adaptive adjusting devices and adjusting methods in streaming media adaptive transmission.
Background
The streaming media is a media format (such as audio, video or multimedia files) which is continuously played in real time on the network by adopting a streaming transmission technology, and the streaming transmission technology is the biggest difference from the traditional transmission technology in that the streaming media does not require that the whole media file is completely downloaded before playing, but only needs to download initial part of content to analyze and output; meanwhile, the data packets are buffered in the computer so that the media data is correctly and smoothly output. For the user, the user can enjoy the effect of downloading and playing while waiting for the delay of several seconds to tens of seconds. The streaming transmission technology is widely applied to audio and video data transmission of the internet at present.
The hypertext Transfer protocol http (hyper Text Transfer protocol) is a standard for client and server side requests and responses. The client initiates an HTTP request to a designated port (default 80 port) on the server using a browser, web crawler, or other tool, and the server responds with a corresponding process.
The HTTP Adaptive transmission (HTTP Adaptive Streaming) technology is a technology for adjusting a video transmission rate according to hardware factors such as a network bandwidth and a client CPU computing power in order to provide a user with an optimal video playing experience most suitable for a real-time environment. As a mainstream streaming technology at present, HTTP adaptive transmission is widely applied to live and on-demand scenes, and an HTTP protocol is used to complete downloading and distribution of media content. However, these media contents are all cut into a series of media segments for transmission. The time length of each media segment is the same, and is usually 2-10 s. At the video coding layer, this transmission means that each segment is composed of a number of complete video pictures, i.e. each segment has a key I-frame, thereby ensuring that each segment is not associated with past and future media segments. The media segments are stored at the HTTP server, and the client requests the media segments from the server in a linear fashion and downloads the media segments in a conventional HTTP fashion. When the media segments are downloaded to the client, the client plays the series of media segments in sequence, because the media segments are encoded according to the agreed rules, there is no overlap or discontinuity of content between the media segments, and for the user, a seamless smooth playing effect is seen.
The biggest characteristic of HTTP adaptive transmission is to support rate adaptation. In the video on demand process, the client periodically evaluates the current available bandwidth of the network and the performance of the client according to a code rate self-adaptive algorithm, and selects the most suitable transmission code rate to download the media segments. For example, a movie video file with a code rate of 10Mbps can be transcoded to generate 4 copies with different code rates, namely 3Mbps, 5Mbps, 7Mbps and 10 Mbps. The video content of these 4 video files is completely identical and all are cut into media segments of duration 3 s. Supposing that before a certain moment, the client always requests the server for the media segmentation with the code rate of 5Mbps, if the downlink bandwidth of the client at the moment is suddenly reduced, the client can make code rate self-adaptive adjustment to request the media segmentation with the code rate of 3Mbps, so that the video can be smoothly played, abnormal situations such as video blockage or long-time buffering are reduced, and better video watching experience is provided.
Currently, there are three major enterprise-level implementations of the HTTP Adaptive transport protocol, i.e., the HTTP Dynamic Streaming protocol H L S (HTTP Dynamic Streaming) proposed by Adobe, the microsoft Smooth Streaming protocol mss (microsoft Smooth Streaming) proposed by microsoft, and the HTTP live Streaming protocol H L S (HTTP L live Streaming) proposed by apple, but these three implementations respectively use different media indexes and segment formats and are not compatible with each other, so the MPEG (moving picture Experts group) which is a Dynamic image expert group that is specially responsible for setting up international standards for moving images and voice compression, in combination with the international standard MPEG-DASH HTTP (Dynamic Adaptive Streaming) protocol which was released by other standardization organizations in 2011, the MPEG-DASH protocol is adopted.
Referring to fig. 1, a typical system architecture composition given in the standard document ISO/IEC 23009-1 of the MPEG-DASH protocol is introduced. The basic principle of the MPEG-DASH protocol is to encode a complete media file, generate copies with multiple code rates, slice the copies according to a time axis, generate multiple media segments, and generate a media index mpd (media Presentation description) file capable of uniformly describing the media segments. The client downloads the MPD file at first, analyzes the MPD file to obtain the storage position of the media segment, requests the server, and decodes and plays the media segment locally. In the video playing process, the client can dynamically adjust the transmission code rate of the request segment according to the network environment. The MPEG-DASH protocol is that the client is actively responsible for the playing and controlling logic of the media content, and the server is only responsible for responding to various requests of the client. For the system architecture shown in fig. 1, no explicit specifications are given for all modules within the ISO/IEC 23009-1 file, but only the interface format and media resource organization format accessible by DASH clients are mainly defined. Other relevant technical details, including video codecs, media segmentation methods, rate adaptation algorithms, etc., are not explicitly required.
Referring to fig. 2, the interaction process of the client and the server in the MPEG-DASH system is described: the client requests the MPD file through HTTP GET and then requests independent media segments sequentially through HTTP GET or requests partial data of the complete media file through Range header of HTTP 1.1. And other control protocols are not required to be relied on in the whole transmission process. Like the process of downloading other files such as pictures, texts and the like through the HTTP server, in the interactive process, after the corresponding media segment is downloaded each time, the corresponding link is disconnected.
At present, the main research content of the code rate adaptive algorithm is how to select the most appropriate code rate from the selectable code rates according to the information of the current network bandwidth, the equipment performance and the like, so as to provide the best viewing experience. Most of the existing algorithms are based on throughput or video buffering, and can be roughly divided into two types: a rate adaptation algorithm based on throughput and a rate adaptation algorithm based on video buffering.
Throughput is the amount of data (measured in units of data, bits, bytes, packets, etc.) successfully transmitted per unit of time for a network, device, port, virtual circuit, or other facility. The throughput of each media segment in the present invention is the ratio of the size of the media segment to the download time. The download time is the time it takes from sending the HTTP request until all bytes of data for the media segment have been received.
Buffering refers to that when a network media file (such as an audio, video or multimedia file) is played, a player downloads a part of the network media file in advance of the current playing progress, and stores the part of the network media file in a temporary folder of a local hard disk. The method aims to avoid waiting time of a user and enable playing to be smoother.
It should be noted that the above classification method itself is coarser, because the size of the video buffer itself is affected by throughput, which is also used in some video buffer-based algorithms. Adaptive algorithms based on video buffering can also be considered as hybrid algorithms. Which are briefly described below:
1. code rate self-adaptive algorithm based on throughput: the code rate is adjusted mainly based on the estimated value of the future throughput, and a higher code rate is selected as far as possible on the premise of not exceeding the estimated throughput value. The key problems to be solved by such methods are how to estimate the throughput and how to adjust the code rate by using the estimation result. The algorithm is represented by a code rate Adaptive model based on a logistic equation, which is proposed by Thang TC et al in the article "Adaptive streaming of audio content using MPEG DASH".
The throughput-based code rate adaptive algorithm is characterized in that code rate jitter is inhibited through smoothing treatment, but when the network bandwidth is suddenly changed, smooth adjustment is easy to fail, and the condition of code rate jitter still occurs. In addition, the algorithm does not consider the condition of a buffer area, and buffer underflow is easy to occur, so that video pause is caused.
2. The core idea of the algorithm is to divide the buffer length into a plurality of buffer levels and adopt different code rate adjustment schemes at different buffer levels, Thang T C et al analyze and compare a plurality of algorithms in an paper of AnEval of double Adaptation Methods for HTTP L live Streaming, and the main difference of the different algorithms lies in different modes of dividing the buffer threshold.
The common disadvantage of the algorithms is that the optimal solution of code rate grade division is difficult to find, and the code rate is easy to frequently jitter if the division grade is too many. If the classification level is too low, the network change cannot be sensed in time. A similar problem exists how to determine the threshold value for each stage. In addition, part of the algorithm adopts a more aggressive processing mode, so that the limitation of the current throughput is allowed to be exceeded, and a video segment with a higher level is downloaded, which easily causes buffer underflow and video pause.
In a word, the two existing algorithms still have a room for improvement at present, and how to improve the two existing algorithms so that a user can achieve better playing experience becomes the focus of attention of technical and scientific personnel in the industry.
Disclosure of Invention
In view of this, the present invention provides a code rate adaptive adjustment apparatus and method that considers both throughput and video buffering, and the apparatus and method of the present invention can comprehensively consider throughput and buffering length, overcome the problems and defects of the two existing algorithms to a certain extent, and maintain relatively excellent playing experience in all aspects.
In order to achieve the above object, the present invention provides a code rate adaptive adjustment device that considers both throughput and video buffering, comprising: when the code rate self-adapting module of the device outputs the transmission code rate information of the media segment to be requested, the throughput and the video buffer information in the HTTP transmission module, the buffer management module and the index analysis module are considered: firstly, smoothing historical throughput by using a Holt-Winters method, and estimating the throughput of a media segment to be requested in advance; then, according to the current video buffering length in the buffering management module, calculating a buffering weight parameter, and carrying out weighting adjustment on the estimated throughput to obtain the optimal transmission code rate; finally, the code rate self-adaptive module selects and outputs the transmission code rate of the media segment to be requested from the selectable code rate list according to the optimal transmission code rate; the system is provided with six modules including code rate self-adaption, index analysis, decoding rendering, buffer management, time axis control and HTTP transmission; wherein:
the code rate self-adaptive module is responsible for deciding and selecting the transmission code rate of the media segment to be requested from the selectable code rate list after carrying out compromise processing on the throughput and the video buffering length according to the downloading rate of the media segment from the media server and the HTTP transmission module and through calculating the throughput information of the media segment, the current video buffering length directly obtained from the buffering management module and the selectable code rate list obtained from the index analysis module, and then outputting the transmission code rate of the media segment to be requested to the buffering management module;
the index analysis module is responsible for receiving the index file from the HTTP transmission module, analyzing the data of the index file, generating a data structure which can be identified by the device, acquiring the information of the played media stream, including the optional code rate and the media segmentation address, from the data stream, respectively outputting the information of the optional code rate and the media segmentation address, and providing the information for the corresponding code rate self-adaptive module and the buffer management module to select and use;
the buffer management module is used as an operation control center of the device and is responsible for managing and controlling the downloading and playing of the media segments: the method comprises the steps of providing audio and video data for a decoding and rendering module, processing and determining a media segment required by the next time period by combining time information provided by a time axis control module and a transmission code rate of a media segment to be requested provided by a code rate self-adaptive module, transmitting a download address of the media segment, which is acquired from an index analysis module, to an HTTP transmission module, buffering the media segment from the HTTP transmission module, and outputting length information of detected current buffered video data to the code rate self-adaptive module so as to enable the code rate self-adaptive module to perform self-adaptive adjustment and calculate the transmission code rate decision reference of the media segment to be requested;
the time axis control module is responsible for sensing the change of the media playing progress and positioning the time at the same time: when a user event comprising playing, pausing and dragging progress bars occurs, namely the original time axis information is changed, the sequence number of the media segment and the position of the key frame are recalculated in real time according to the new time positioning, and meanwhile, the new time positioning information is transmitted to the buffer management module;
the HTTP transmission module is responsible for carrying out data transmission with the media server by interaction of a network so as to obtain a required media index file and data of a media segment and simultaneously record related information of the downloading rate of the media segment; the index file and the data of the media segment are correspondingly transmitted to an index analysis module and a buffer management module for processing and buffering respectively, and the related information of the downloading rate of the media segment is transmitted to a code rate self-adaptive module to be used as a reference factor for calculating the transmission code rate of the media segment to be requested in real time;
and the decoding rendering module is responsible for reading the media data of the media buffer area from the buffer management module and then decoding and rendering the media data so as to present the video and the audio to a user.
In order to achieve the above object, the present invention further provides a working method of a bitrate adaptive adjusting device that uses the present invention and takes throughput and video buffering into account, which is characterized in that: firstly, smoothing historical throughput by using a Holt-Winters method, and estimating the throughput of a media segment to be requested in advance; calculating a buffer weight parameter according to the real-time dynamic change of the video buffer length so as to carry out weighting adjustment on the estimated throughput and obtain the optimal transmission code rate; and finally, selecting and outputting the transmission code rate of the media segment to be requested from the selectable code rate list according to the optimal transmission code rate.
The method comprises the following operation steps:
step 1, rate adaptation module obtains from buffer management module according to it, comes from media server and via HTTP transmission module most recently downloaded media segmentation L that finishesiThe time when the client starts to request the media segment and the time when the media segment is downloaded, the actual throughput X of the media segment of the device is calculated according to the following formulai：
Figure GDA0002459609280000061
Wherein L is the size of the media segment, the natural number subscript or superscript i is the corresponding media segment serial number, the natural number subscript t is the timing time, and the subscripts req and res are the client-side respectivelyStarting to request the timing time of the media segment and the timing time of finishing downloading;
step 2, the code rate self-adaptive module adopts a Holt-Winters method and the following formula combination
Figure GDA0002459609280000062
Respectively calculating and recording the first, second and third smooth throughput values of the received media segment throughput with the sequence number i; in the formula, S(1)、S(2)And S(3)Respectively the calculated media segment LiThe coefficient α is a weighting factor with a value in the range of 0<α<1, and setting an initial smooth throughput
Figure GDA0002459609280000063
And
Figure GDA0002459609280000064
all equal to its actual throughput X1；
Step 3, the code rate self-adapting module calculates the estimated throughput value of the media segment to be requested with the sequence number i +1 according to the first, second and third smooth throughput values of the media segment with the sequence number i obtained in the step 2: according to the Holt-Winters method, if T is the estimated throughput of the media segment, the estimated throughput of the (i + 1) th media segment is:
Figure GDA0002459609280000065
wherein, ai,bi,ciAll are prediction parameters, and the respective calculation formulas are as follows:
Figure GDA0002459609280000066
Figure GDA0002459609280000067
step 4, the code rate self-adaptive module calculates the buffer weight parameter in real time according to the buffer length of the current video:
obtaining the current video buffering length Buff from the buffering management modulei+1Then, according to the Buffi+1Is divided into the following three different situations, and the buffer weight parameter value is correspondingly dynamically adjusted in real time:
1, raising the threshold BUFFhigh＜Buffi+1When the buffered video data is considered to be excessive, the transmission code rate of the media segment to be requested is allowed to exceed the estimated throughput, the value of the buffer weight parameter at the moment is more than 1, and the buffer length Buff of the current videoi+1BUFF exceeding a boost thresholdhighThe more, the larger the value should be;
2, attenuation threshold BUFFlow＞Buffi+1When the buffer weight parameter value is less than 1, Buff and the buffer weight parameter value is less than 1i+1The smaller the value of (A), the smaller the value of (B);
3，BUFFlow＜Buffi+1＜BUFFhighwhen the size of the buffered video data is considered to be proper, the blocking is not easy to occur, and the buffer area is not easy to overflow, the buffer weight parameter is kept to be 1, and the buffer weight parameter is not changed; .
According to the three different conditions, three calculation formulas of the code rate parameter are obtained:
Figure GDA0002459609280000071
in the formula (I), the compound is shown in the specification,1and2an amplitude factor describing the speed of change;
step 5, the code rate self-adapting module calculates the optimum transmission code rate Best of the media segment with the requested serial number of i +1 according to the following formulai+1：Besti+1＝Ti+1In the formula, Ti+1To estimate throughput, a buffer weight parameter;
step 6, the code rate self-adapting module transmits the code rate Best according to the Besti+1From the selectable code rate list Birates [ 2 ]]The medium decision choice is not greater than Besti+1Maximum ofCode rate as final transmission code rate B of media segment to be requestedi+1And if Besti+1Less than Bitranss [ 2 ]]When the lowest code rate is in the middle, the decision is made to select Bi+1Is a bistates [ 2 ]]The lowest code rate of; then, the selection result is transmitted to the buffer management module, so that the buffer management module can control and download the corresponding media segment to be requested.
The invention relates to a code rate self-adaptive adjusting device and method for giving consideration to both throughput and video buffering, which is characterized in that a key component for realizing code rate self-adaptive adjusting calculation, namely a code rate self-adaptive module, is arranged in the device, when a media segment is requested to be downloaded, the code rate self-adaptive module is responsible for firstly carrying out a plurality of times of smoothing processing on the throughput by using a Holt-Winters method, namely when the throughput of a future media segment to be requested of the device is estimated by considering historical media downloading conditions, the throughput of a plurality of media segments which are earlier is considered at the same time instead of the throughput of the previous media segment, the calculation weight of throughput data which is more adjacent to the time is high, the calculation weight of the throughput which is more remote from the time is small, and the three times of smoothing processing are carried out on the historical throughput, so that the device gives consideration to development trend and cycle factors. Meanwhile, after the estimated throughput is obtained, the estimated throughput is weighted and adjusted by combining the current video buffering length, and the adjustment amplitude can be dynamically changed along with the change of the video buffering length: i.e. setting two thresholds for the buffer length of the video media: the threshold value and the attenuation threshold value are increased, and then the video buffer is divided into three different intervals according to the two threshold values, so that the size of the buffer weight parameter is dynamically adjusted in real time in different intervals according to different calculation formulas, the throughput and the video buffer can be correspondingly considered, the code rate self-adaptive adjustment calculation is realized, the device can adopt the transmission code rate in the optimal state to output the media segmentation content requested by a user, and the proper code rate is selected from the selectable code rate list to transmit media data.
In summary, the present invention provides a bitrate adaptive adjusting device and an adjusting method with a novel structure and a significant function, which are provided by comprehensively considering throughput and video buffering, and can overcome and solve the defects of the prior art to a certain extent, while maintaining relatively excellent playing experience in all aspects. The device has the advantages of simple structure, ingenious and novel design concept, simple and convenient operation steps and easy realization of operation, and therefore, the device has good popularization and application prospects.
Drawings
Fig. 1 is a diagram illustrating a typical architecture of an MPEG-DASH system.
Fig. 2 is a timing diagram illustrating client-server interaction in the MPEG-DASH system shown in fig. 1.
Fig. 3 is a schematic structural composition diagram of the code rate adaptive adjustment device that considers both throughput and video buffering according to the present invention.
Fig. 4 is a flow chart of the operation steps of the adaptive bitrate adjustment device for considering both throughput and video buffering according to the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail with reference to the accompanying drawings and examples.
Generally, when designing an adaptive adjustment device and an operating method thereof that provide a user with an optimal video playing experience best suited to a real-time environment, the following four factors are mainly considered:
1. and smooth playing of the video is ensured.
2. The network bandwidth is fully utilized, and high-quality video is provided for users as far as possible.
3. The code rate jitter is reduced, and the condition that the code rates of adjacent segments are too different is avoided.
4. The time delay from the user sending the segment request to the start of the play-out is reduced as much as possible.
Of the above four factors, the factor 1 is considered to be the most important factor, and the factor that most affects the user experience in the video playing process is video pause. The two factors 2 and 3 are mutually restricted to a certain extent, especially in the case of frequent network bandwidth jitter, according to the factor 2, no matter in the environment of high bandwidth and low bandwidth, the media segment should be requested by using the current network bandwidth as much as possible, but this process will increase the code rate jitter, which violates the requirement of the factor 3. Similarly, there is a contradiction between the two factors 2 and 4.
The code rate self-adaptive adjusting device and the code rate self-adaptive adjusting method have the advantages that the throughput and the video buffering can be comprehensively considered, the structure is innovative, the defects and the problems in the prior art are overcome to a certain extent, the code rate self-adaptive effect is improved, the experience feeling of a user when the user watches the streaming media video is optimized, and meanwhile, the relatively excellent playing experience can be kept in the four aspects.
Referring to fig. 3, the structural composition of the adaptive code rate adjusting device of the present invention is described: the system is provided with six modules including code rate self-adaption, index analysis, decoding rendering, buffer management, time axis control and HTTP transmission; when the code rate self-adapting module outputs the transmission code rate information of the media segment to be requested, the throughput and video buffering information in the HTTP transmission module, the buffering management module and the index analysis module are considered: firstly, smoothing historical throughput by using a Holt-Winters method, and estimating the throughput of a media segment to be requested in advance; then, according to the current video buffering length in the buffering management module, calculating a buffering weight parameter, and carrying out weighting adjustment on the estimated throughput to obtain the optimal transmission code rate; and finally, the code rate self-adaptive module selects and outputs the transmission code rate of the media segment to be requested from the selectable code rate list according to the optimal transmission code rate. The functions of the six modules are described in detail below:
the code rate self-adaptive module is used as a key module for realizing code rate self-adaptive adjustment calculation of the device, namely when the media segmentation is requested, the code rate self-adaptive module is responsible for carrying out code rate self-adaptive adjustment calculation which gives consideration to throughput and video buffering, so that the device can output the media segmentation content requested by a user by adopting the transmission code rate in the optimal state, namely, the device selects the proper code rate from the selectable code rate list to transmit media data. The concrete functions are as follows: the system is responsible for deciding and selecting the transmission code rate of the media segment to be requested from the selectable code rate list after processing the throughput and the video buffering length in consideration according to the downloading rate of the media segment from the media server and the HTTP transmission module and through calculating the throughput information of the obtained media segment, the current video buffering length directly obtained from the buffering management module and the selectable code rate list obtained from the index analysis module, and then outputting the transmission code rate of the media segment to be requested to the buffering management module.
And the index analysis module is responsible for receiving the media index file from the HTTP transmission module, analyzing the data of the media index file, generating a data structure which can be identified by the device, acquiring information including the optional code rate and the media segmentation address of the played media stream from the data stream, respectively outputting the information of the optional code rate and the media segmentation address, and providing the information for the corresponding code rate self-adaption module and the buffer management module to select and use.
The buffer management module is used as an operation control center of the self-adaptive adjusting device and is responsible for managing and controlling the downloading and playing of the media segments: the method comprises the steps of providing audio and video data for a decoding and rendering module, processing and determining a media segment required by the next time period by combining time information provided by a time axis control module and a transmission code rate of a media segment to be requested provided by a code rate self-adaptive module, transmitting a download address of the media segment, which is acquired from an index analysis module, to an HTTP transmission module, buffering the media segment from the HTTP transmission module, and outputting length information of detected current buffered video data to the code rate self-adaptive module so as to enable the code rate self-adaptive module to perform self-adaptive adjustment calculation to make a decision reference for the transmission code rate of the media segment to be requested.
The time axis control module is responsible for sensing the change of the media playing progress and positioning the time at the same time: when a user event including playing, pausing and dragging the progress bar occurs, namely the original time axis information is changed, the sequence number of the media segment and the position of the key frame are recalculated in real time according to the new time positioning, and meanwhile, the new time positioning information is transmitted to the buffer management module.
The HTTP transmission module is responsible for carrying out data transmission with the media server by interaction of a network so as to obtain a required media index file and data of a media segment and simultaneously record related information of the downloading rate of the media segment; and respectively correspondingly transmitting the index file and the data of the media segment to an index analysis module and a buffer management module for processing and buffering, and transmitting the related information of the downloading rate of the media segment to a code rate self-adapting module to be used as a reference factor for calculating the transmission code rate of the media segment to be requested in real time.
And the decoding rendering module is responsible for reading the media data of the media buffer area from the buffer management module and then decoding and rendering the media data so as to present the video and the audio to a user.
The innovative characteristics of the working method of the code rate self-adaptive adjusting device which gives consideration to both throughput and video buffering are as follows: the traditional code rate self-adaptive algorithm based on throughput or buffering is improved, and the decision of the throughput and the video buffering information is taken into consideration to select the transmission code rate. The specific method comprises the following steps: firstly, smoothing historical throughput by using a Holt-Winters method, and estimating the throughput of a media segment to be requested in advance; calculating a buffer weight parameter according to the real-time dynamic change of the video buffer length so as to carry out weighted increase, decrease or unchanged adjustment on the estimated throughput and obtain the optimal transmission code rate; and finally, selecting and outputting the transmission code rate of the media segment to be requested from the selectable code rate list according to the optimal transmission code rate.
The following specific operation steps of the working method of the device of the present invention are described with reference to fig. 4:
step 1, rate adaptation module obtains from buffer management module according to it, comes from media server and via HTTP transmission module most recently downloaded media segmentation L that finishesiThe time when the client starts to request the media segment and the time when the media segment is downloaded, the actual throughput X of the media segment of the device is calculated according to the following formulai：
Figure GDA0002459609280000111
L is the size of the media segment, where the natural number subscript or superscript i is the corresponding media segment serial number, and the natural number subscript t is the corresponding media segment serial numberThe subscript req and res are the timing time when the client starts to request the media segment and the timing time when the client finishes downloading respectively;
step 2, the code rate self-adaptive module adopts a Holt-Winters method and the following formula combination
Figure GDA0002459609280000112
Respectively calculating and recording the first, second and third smooth throughput values of the received media segment throughput with the sequence number i; in the formula, S(1)、S(2)And S(3)Respectively the calculated media segment LiThe coefficient α is a weighting factor with a value in the range of 0<α<1, and setting an initial smooth throughput
Figure GDA0002459609280000113
And
Figure GDA0002459609280000114
all equal to its actual throughput X1；
Step 3, the code rate self-adapting module calculates the estimated throughput value of the media segment to be requested with the sequence number i +1 according to the first, second and third smooth throughput values of the media segment with the sequence number i obtained in the step 2: according to the Holt-Winters method, if T is the estimated throughput of the media segment, the estimated throughput of the (i + 1) th media segment is:
Figure GDA0002459609280000115
wherein, ai,bi,ciAll are prediction parameters, and the respective calculation formulas are as follows:
Figure GDA0002459609280000116
Figure GDA0002459609280000117
step 4, the code rate self-adaptive module calculates the buffer weight parameter in real time according to the buffer length of the current video:
obtaining the current video buffering length Buff from the buffering management modulei+1Then, according to the Buffi+1Is divided into the following three different situations, and the buffer weight parameter value is correspondingly dynamically adjusted in real time:
1, raising the threshold BUFFhigh＜Buffi+1When the buffered video data is considered to be excessive, the transmission code rate of the media segment to be requested is allowed to exceed the estimated throughput, the value of the buffer weight parameter at the moment is more than 1, and the buffer length Buff of the current videoi+1BUFF exceeding a boost thresholdhighThe more, the larger the value should be;
2, attenuation threshold BUFFlow＞Buffi+1When the buffer weight parameter value is less than 1, Buff and the buffer weight parameter value is less than 1i+1The smaller the value of (A), the smaller the value of (B);
3，BUFFlow＜Buffi+1＜BUFFhighwhen the size of the buffered video data is considered to be proper, the blocking is not easy to occur, and the buffer area is not easy to overflow, the buffer weight parameter is kept to be 1, and the buffer weight parameter is not changed;
according to the three different situations, three calculation formulas of the buffer weight parameter are obtained:
Figure GDA0002459609280000121
in the formula (I), the compound is shown in the specification,1and2an amplitude factor describing the speed of change;
step 5, the code rate self-adapting module calculates the optimum transmission code rate Best of the media segment with the requested serial number of i +1 according to the following formulai+1：Besti+1＝Ti+1In the formula, Ti+1To estimate throughput, a buffer weight parameter;
step 6, the code rate self-adapting module transmits the code rate Best according to the Besti+1From the selectable code rate list Birates [ 2 ]]The medium decision choice is not greater than Besti+1The maximum code rate of the request is used as the final transmission code rate B of the media segment to be requestedi+1And if Besti+1Less than Bitranss [ 2 ]]When the lowest code rate is in the middle, the decision is made to select Bi+1Is a bistates [ 2 ]]The lowest code rate of; then, the selection result is transmitted to the buffer management module, so that the buffer management module can control and download the corresponding media segment to be requested.
The invention has carried out many times of simulation implementation tests, the result of the implementation test of the device and the working method thereof is successful, and the aim of the invention is achieved.

Claims (4)

1. A code rate self-adaptive adjusting device giving consideration to both throughput and video buffering is characterized in that: when the code rate self-adapting module of the device outputs the transmission code rate information of the media segment to be requested, the throughput and the video buffer information in the HTTP transmission module, the buffer management module and the index analysis module are considered: firstly, smoothing historical throughput by using a Holt-Winters method, and estimating the throughput of a media segment to be requested in advance; then, according to the current video buffering length in the buffering management module, calculating a buffering weight parameter, and carrying out weighting adjustment on the estimated throughput to obtain the optimal transmission code rate; finally, the code rate self-adaptive module selects and outputs the transmission code rate of the media segment to be requested from the selectable code rate list according to the optimal transmission code rate; the system is provided with six modules including code rate self-adaption, index analysis, decoding rendering, buffer management, time axis control and HTTP transmission; wherein:
the code rate self-adaptive module is responsible for deciding and selecting the transmission code rate of the media segment to be requested from the selectable code rate list after carrying out compromise processing on the throughput and the video buffering length according to the downloading rate of the media segment from the media server and the HTTP transmission module and through calculating the throughput information of the media segment, the current video buffering length directly obtained from the buffering management module and the selectable code rate list obtained from the index analysis module, and then outputting the transmission code rate of the media segment to be requested to the buffering management module;
the index analysis module is responsible for receiving the index file from the HTTP transmission module, analyzing the data of the index file, generating a data structure which can be identified by the device, acquiring the information of the played media stream, including the optional code rate and the media segmentation address, from the data stream, respectively outputting the information of the optional code rate and the media segmentation address, and providing the information for the corresponding code rate self-adaptive module and the buffer management module to select and use;
the buffer management module is used as an operation control center of the device and is responsible for managing and controlling the downloading and playing of the media segments: the method comprises the steps of providing audio and video data for a decoding and rendering module, processing and determining a media segment required by the next time period by combining time information provided by a time axis control module and a transmission code rate of a media segment to be requested provided by a code rate self-adaptive module, transmitting a download address of the media segment, which is acquired from an index analysis module, to an HTTP transmission module, buffering the media segment from the HTTP transmission module, and outputting length information of detected current buffered video data to the code rate self-adaptive module so as to enable the code rate self-adaptive module to perform self-adaptive adjustment and calculate the transmission code rate decision reference of the media segment to be requested;
the time axis control module is responsible for sensing the change of the media playing progress and positioning the time at the same time: when a user event comprising playing, pausing and dragging progress bars occurs, namely the original time axis information is changed, the sequence number of the media segment and the position of the key frame are recalculated in real time according to the new time positioning, and meanwhile, the new time positioning information is transmitted to the buffer management module;
the HTTP transmission module is responsible for carrying out data transmission with the media server by interaction of a network so as to obtain a required media index file and data of a media segment and simultaneously record related information of the downloading rate of the media segment; the index file and the data of the media segment are correspondingly transmitted to an index analysis module and a buffer management module for processing and buffering respectively, and the related information of the downloading rate of the media segment is transmitted to a code rate self-adaptive module to be used as a reference factor for calculating the transmission code rate of the media segment to be requested in real time;
and the decoding rendering module is responsible for reading the media data of the media buffer area from the buffer management module and then decoding and rendering the media data so as to present the video and the audio to a user.
2. The apparatus of claim 1, wherein: the code rate self-adaptive module is a key module for realizing code rate self-adaptive adjustment and calculation of the device, namely when the media segmentation is requested, the code rate self-adaptive module is responsible for carrying out code rate self-adaptive adjustment and calculation considering both throughput and video buffering, so that the device can output the media segmentation content requested by a user by adopting the transmission code rate in the optimal state, namely, the device selects the proper code rate from the selectable code rate list to transmit media data.
3. A working method of the adaptive bitrate adjustment device considering both throughput and video buffering according to claim 1, wherein: firstly, smoothing historical throughput by using a Holt-Winters method, and estimating the throughput of a media segment to be requested in advance; calculating a buffer weight parameter according to the real-time dynamic change of the video buffer length so as to carry out weighting adjustment on the estimated throughput and obtain the optimal transmission code rate; and finally, selecting and outputting the transmission code rate of the media segment to be requested from the selectable code rate list according to the optimal transmission code rate.
4. The operating method of the adaptive bitrate adjusting device according to claim 3, wherein: the method comprises the following operation steps:
step 1, rate adaptation module obtains from buffer management module according to it, comes from media server and via HTTP transmission module most recently downloaded media segmentation L that finishesiThe time when the client starts to request the media segment and the time when the media segment is downloaded, the actual throughput X of the media segment of the device is calculated according to the following formulai：
Figure FDA0002459609270000021
Wherein L isThe size of the media segment, wherein the natural number subscript or the superscript i is the corresponding media segment serial number, the natural number subscript t is the timing time, and the subscripts req and res are the timing time when the client starts to request the media segment and the timing time when the client finishes downloading respectively;
step 2, the code rate self-adaptive module adopts a Holt-Winters method and the following formula combination
Figure FDA0002459609270000031
Respectively calculating and recording the first, second and third smooth throughput values of the received media segment throughput with the sequence number i; in the formula, S(1)、S(2)And S(3)Respectively the calculated media segment LiThe coefficient α is a weighting factor with a value in the range of 0<α<1, and setting an initial smooth throughput
Figure FDA0002459609270000032
And
Figure FDA0002459609270000033
all equal to its actual throughput X1；
Step 3, the code rate self-adapting module calculates the estimated throughput value of the media segment to be requested with the sequence number i +1 according to the first, second and third smooth throughput values of the media segment with the sequence number i obtained in the step 2: according to the Holt-Winters method, if T is the estimated throughput of the media segment, the estimated throughput of the (i + 1) th media segment is:
Figure FDA0002459609270000034
wherein, ai,bi,ciAll are prediction parameters, and the respective calculation formulas are as follows:
Figure FDA0002459609270000035
Figure FDA0002459609270000036
step 4, the code rate self-adaptive module calculates the buffer weight parameter in real time according to the buffer length of the current video:
obtaining the current video buffering length Buff from the buffering management modulei+1Then, according to the Buffi+1Is divided into the following three different situations, and the buffer weight parameter value is correspondingly dynamically adjusted in real time:
1, raising the threshold BUFFhigh＜Buffi+1When the buffered video data is considered to be excessive, the transmission code rate of the media segment to be requested is allowed to exceed the estimated throughput, the value of the buffer weight parameter at the moment is more than 1, and the buffer length Buff of the current videoi+1BUFF exceeding a boost thresholdhighThe more, the larger the value should be;
2, attenuation threshold BUFFlow＞Buffi+1When the buffer weight parameter value is less than 1, Buff and the buffer weight parameter value is less than 1i+1The smaller the value of (A), the smaller the value of (B);
3，BUFFlow＜Buffi+1＜BUFFhighwhen the size of the buffered video data is considered to be proper, the blocking is not easy to occur, and the buffer area is not easy to overflow, the buffer weight parameter is kept to be 1, and the buffer weight parameter is not changed;
according to the three different conditions, three calculation formulas of the code rate parameter are obtained:
Figure FDA0002459609270000041
in the formula (I), the compound is shown in the specification,1and2an amplitude factor describing the speed of change;
step 5, the code rate self-adapting module calculates the optimum transmission code rate Best of the media segment with the requested serial number of i +1 according to the following formulai+1：Besti+1＝Ti+1In the formula, Ti+1To estimate throughputIs a buffer weight parameter;
step 6, the code rate self-adapting module transmits the code rate Best according to the Besti+1From the selectable code rate list Birates [ 2 ]]The medium decision choice is not greater than Besti+1The maximum code rate of the request is used as the final transmission code rate B of the media segment to be requestedi+1And if Besti+1Less than Bitranss [ 2 ]]When the lowest code rate is in the middle, the decision is made to select Bi+1Is a bistates [ 2 ]]The lowest code rate of; then, the selection result is transmitted to the buffer management module, so that the buffer management module can control and download the corresponding media segment to be requested.
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