CN103747283B - Video fragment download method - Google Patents

Abstract

The invention relates to a video fragment download method which comprises the following steps: after a video server receives a video fragment download request sent by a client, a current video fragment is downloaded for the client; if the current video fragment is downloaded within a first threshold time, a second threshold time for downloading the next video fragment is calculated; if the current video fragment hasn't been downloaded when the first threshold time arrives, first code rate of the current video fragment is lowered to second code rate; if the current video fragment which has been adjusted to the second code rate is downloaded within the first threshold time, a third threshold time for downloading the next video fragment is calculated; and if the current video fragment which has been adjusted to the second code rate hasn't been downloaded within the first threshold time, the second code rate is adjusted as the lowest code rate. By a predict interrupt mechanism and a step-by-step lowering method, fluency of the video that the client watches is guaranteed. Meanwhile, network caching resources are fully utilized, and video quality is improved.

Description

The method for down loading of video slicing

Technical field

The present invention relates to video technique, particularly to a kind of method for down loading of video slicing.

Background technology

Current the Internet experiencings people and turns to the communication pattern centered on content towards the point to point link pattern of main frame Become, compared with the position of content, user more concerned be content itself.In order to adapt to the Internet this change it is proposed that with Centered on content, network (content centric network, ccn) is the next generation network of representative, content oriented main body, and Non-content position, the router in this network architecture all has caching function, to provide for the follow-up request to identical content Service, inherently changes the transmission mode of traditional ip network end-to-end.And media file accounts for absolutely in current internet traffic Major part, in order to preferably provide multimedia service, the dynamic self-adapting Streaming Media (dynamic based on http in a network Adaptive streaming over http, dash) there is deployment simply, the advantages of impact by fire wall.In dash Adaptive strategy has simple ratebased mode, also has the adaptive algorithm (has) of sublevel segmentation, they are to a certain degree On can improve the viewing experience of user, but be simply implanted in ccn network and some problems occurred.Ccn's is slow Depositing function can make user obtain content from intermediate node or server, simply easily caused to network speed according to speed of download Erroneous judgement, leads to client buffer area underflow even to be interrupted, needs to judge as early as possible and process in time；May be cached with ccn simultaneously Abundant video resource, needs to improve the video quality of user's viewing using effective method.

Content of the invention

The purpose of the present invention is based on http, for realize to the network bandwidth erroneous judgement after handle it in time it is ensured that That plays is smoothed out, and makes full use of the resource of cache node caching simultaneously, proposes the method that code check substep is lowered, lifts video Quality.

For achieving the above object, the invention provides a kind of method for down loading of video slicing.The method comprises the following steps:

Video server receives the download request of the video slicing that client sends；

Described video server to described client downloads current video burst, if under completing within the first threshold time Carry described current video burst, calculate the Second Threshold time of next video slicing download；

If reaching the first threshold time, not completing to download described current video burst, then described current video being divided It is adjusted to second code rate under first code check of piece；If complete to download to be adjusted to described in the second code check within the first threshold time worked as Front video slicing, calculates the 3rd threshold time that next video slicing described is downloaded；If not complete within the first threshold time Become to download the described current video burst being adjusted to the second code check, then the second code check is adjusted to lowest bit rate.

Further, described video server also includes to before described client downloads current video burst, according to upper The size of the actual download time of one video slicing and a described upper video slicing calculates the lower contained network of a described upper video slicing Speed, is calculated described first code check according to the download speed of a described upper video slicing using adaptive algorithm.

Further, methods described also includes, the download speed according to a described upper video slicing and described current video The size of burst calculates and estimates download time, and estimates download time and be calculated the first threshold time according to described.

Further, the download request of the video slicing that described video server reception client sends specifically includes: regards Frequency server receives the download request of the video slicing that client sends according to mpd file, and described mpd file includes http service The media slicing of device storage, uri, demultiplexing, decoded information.

Further, it is adjusted to second code rate under described the first code check by described current video burst to specifically include: by institute The first code check stating current video burst is lowered according to cache resources substep.

It is an advantage of the invention that carrying out timer interrupt in advance for the erroneous judgement of the network bandwidth, it is to avoid blindly download it is ensured that That plays is smoothed out；Make full use of the resource of cache node caching, lower the code check of video slicing, lifting user's viewing in advance The total quality of video.

Brief description

Fig. 1 is a kind of method for down loading schematic flow sheet of video slicing of the embodiment of the present invention；

Fig. 2 is a kind of method for down loading application process schematic diagram of video slicing of the embodiment of the present invention.

Specific embodiment

Below by drawings and Examples, technical scheme is described in further detail.

Fig. 1 is a kind of method for down loading schematic flow sheet of video slicing of the embodiment of the present invention, as shown in figure 1, the method Comprise the steps:

Step 101, video server receives the download request of the video slicing that client sends；

Step 102, video server to client downloads current video burst, if under completing within the first threshold time Carry current video burst, calculate the Second Threshold time of next video slicing download；

Step 103, if reaching the first threshold time, not completing to download current video burst, then dividing current video It is adjusted to second code rate under first code check of piece；If complete to download within the first threshold time be adjusted to the second code check work as forward sight Frequency division piece, calculates the 3rd threshold time of next video slicing download；If do not complete to download within the first threshold time adjusted Whole be the second code check current video burst, then the second code check is adjusted to lowest bit rate.

If the code check of a upper video slicing is r₁, the actual download time is t₁, a length of τ during burst, a length of 2 during acquiescence burst Second, then the download speed going up a video slicing is:

$v_1(k,n)=\frac{r_1\mathrm{\τ}}{t_1}---\left(1\right)$

Wherein r₁τ is the size of a upper video slicing, utilizes adaptive algorithm according to the download speed of a upper video slicing () obtains the first code check r of current video burst taking ratedbased as a example₂.

$t_{{\mathrm{pk}}_2}=\frac{r_2\mathrm{\τ}}{v_1(k,n)}---\left(2\right)$

$v_2(k,n)=\frac{r_2\mathrm{\τ}}{t_2}---\left(3\right)$

Wherein r₂τ is the size of current video burst, t₂For the actual download time of current video burst, according to formula (2) Obtain the threshold time t of current video burst_Pk2,, and download speed v obtaining current video burst according to formula (3)₂(k, N), obtain the code check r of next video slicing using adaptive algorithm according to formula (3)₃.

$t_{{\mathrm{pk}}_3}=\frac{r_3\mathrm{\τ}}{v_2(k,n)}---\left(4\right)$

r₂It is the first code check for current video burst, and current video burst completed to download within the first threshold time When, draw the threshold time of next video slicing according to the download speed of current video burst, i.e. Second Threshold time t_pk3.

The first code check r when current video burst₂Under be adjusted to second code rate r₂₁When, the download speed meeting of current video burst It is changed into:

$v_{21}(k,n)=\frac{r_{21}\mathrm{\τ}}{t_{21}}---\left(5\right)$

Wherein t₂₁It is adjusted to second code rate r under current video burst₂₁When download time.

Draw the code check r of next video slicing according to formula (5) using adaptive algorithm₃₁, thus showing that next video divides The threshold time of piece, i.e. the 3rd threshold time t_pk31.

$t_{{\mathrm{pk}}_{31}}=\frac{r_{31}\mathrm{\τ}}{v_{21}(k,n)}---\left(6\right)$

In order to make full use of channel width and ensure that user watches smoothness and the high-quality of video, the present invention follows following four Individual principle: (1) avoids playing interrupting as far as possible；(2) provide high-quality video segment in the case of bandwidth permission as far as possible；(3) Video switching times are few, because from the angle of user, the video ratio being always held at low bit- rate is always between high low bit- rate The viewing experience that the video being continually changing brings will be got well；(4) start-up study is little, selects to play certain video to this from user The time that first section of video commences play out is as far as possible short.

In this four principles, first principle should have highest priority, because causing worst Consumer's Experience It is stagnation or the interruption of video playback, also imply that the fluency in order to ensure client video quality, to a certain extent The quality of video can be sacrificed.Second and the 3rd principle need to be weighed, the best method making full use of bandwidth is each Select the video of the highest code check of current network support, but the switching times that this can make video in the network of change are significantly Increase.Simultaneously second and the 4th principle be also required to be compromised, because startup time delay will be reduced require client downloads the One video segment time is the shortest, so can only ask minimum code check for the first time, cause the wave of bandwidth to a certain extent Take, final judging process is above balance in four principles and selects.

The present invention follows above four principles and proposes specific embodiment, and Fig. 2 is that one kind of the embodiment of the present invention regards The method for down loading application process schematic diagram of frequency division piece, as shown in Fig. 2 this implementation process is:

Step 201, makes t=0, and k=1, t=0 are initial time, and k=1 is that to number be first point for the burst of request video Piece；

In order to ensure the minimum delay starts, by video the first burst s₁Code check r₁It is set as minimum code rate, i.e. r₁=r_min；

Wait code check is r₁Video slicing s₁Download, if code check is r₁Video slicing s₁After the completion of download, go to Step 202, otherwise goes to step 203；

Step 202, code check is r₁Video slicing s₁After the completion of download, burst k Jia 1 automatically, i.e. k=k+1, and calculates Video slicing s₁Download speed v (k, n)；

Video slicing s is drawn according to adaptive algorithm₁Next burst s_kCode check r_k,s_kEstimate download time t_pk, this In k=2, go to step 204；

Step 203, video slicing is waited, and request is downloaded again；

Step 204, is r to code check_kVideo slicing s_kSend request, concurrently set count-down device t_Ck,Work as s_kTo have downloaded Cheng Hou, and count-down device t_ckMore than 0 and less than t_pkWhen, go to step 206；

If described count-down device t_ckEqual to 0, go to step 205；

Step 205, in advance by video slicing s_kCode check r_kLower, go to step 207；

Step 206, timer interrupt, carry out video slicing s_kNext fragment request；

Step 207, first by video slicing s_kCode check r_kIt is transferred to r_k', r_k' it is less than code check r_kMaximum, in the event of the Secondary interruption, goes to step 208；

Step 208, by video slicing s_kCode check r_kIt is transferred to code check r_kLowest bit rate r_k=r_kmin.

In Fig. 2, involved symbol description is as shown in table 1:

Table 1

When the speed of download of known front n fragment, we can be given by certain adaptive algorithm and will descend slide glass Section s_kCode check r_k.This based on download mode estimate that the method for link bandwidth is not fee from the erroneous judgement to network speed, especially when When having cache node in network.Assume that the speed of download calculating is v (k, n), the burst code obtaining according to adaptive algorithm Rate is r_kIt is known that burst duration τ, fragment s_kEstimate download time.After sending the request to this code check it is contemplated that network not If intellectual completes it is believed that can download in the time, illustrate that network link is close with expection, can continue further fragments are initiated Request；Otherwise it is meant that link circuit condition is than expected bad luck, or because nodes do not cache this high code check fragment, In order to prevent the wait of longer time futile effort, also avoid relief area that the interruption play occurs because of empty grade, we terminate in advance This is asked and starts to send request to this fragment low bit- rate.

For the phenomenon of waiting-timeout appearing above, we should ask the file of this fragment low bit- rate, but with regard to relatively low The number of times of the setting of code check and downward does not do specific restriction.Because it is contemplated that user watches the seriality of video, that is, user sees Fragment s of certain video complete_kIt is more likely that also having seen fragment s_k+1, in such network, it is cached with fragment s_k+1Probability very Greatly；It is also contemplated that the impact of network-caching, same video, the average quality of the client's viewing asked afterwards ratio is above Good, also disclose fragment s for a video simultaneously_k, the people seeing how, also can cache various code rate in network.In conjunction with , lowering fragment s at upper 2 points_kCode check r_kWhen, the various code rate resource substep that may cache in network can be made full use of and lower Code check, is adjusted to r under first time_k=r_k', request is downloaded.If there is no r_k, but be likely to have and compare r_kOne or two grades low Code check, if this fragment s_kInterrupt for second, stagnate for avoiding playing, r should be adjusted to down immediately_k=r_kmin.

Above-described specific embodiment, has been carried out to the purpose of the present invention, technical scheme and beneficial effect further Describe in detail, be should be understood that the specific embodiment that the foregoing is only the present invention, be not intended to limit the present invention Protection domain, all any modification, equivalent substitution and improvement within the spirit and principles in the present invention, done etc., all should comprise Within protection scope of the present invention.

Claims (5)

1. a kind of method for down loading of video slicing is it is characterised in that comprise the following steps:

Video server receives the download request of the video slicing that client sends；

Described video server is to described client downloads current video burst, if completing to download institute within the first threshold time State current video burst, calculate the Second Threshold time of next video slicing download；

The computing formula of described first threshold time is:

$v_1(k,n)=\frac{r_1\mathrm{\τ}}{t_1}$

$t_{{\mathrm{pk}}_2}=\frac{r_2\mathrm{\τ}}{v_1(k,n)}$

Wherein v₁(k, n) is the speed of download of a upper burst, r₁For the code check of a upper video slicing, τ is burst duration, t₁For reality Border download time, r₂For the first code check of current video burst, t_pk2For the described first threshold time, k is the volume of video slicing Number, n is front n (n < k) individual burst；

The computing formula of described Second Threshold time is:

$v_2(k,n)=\frac{r_2\mathrm{\&tau;}}{t_2}$

$t_{{\mathrm{pk}}_3}=\frac{r_3\mathrm{\&tau;}}{v_2(k,n)}$

Wherein t_pk3For described Second Threshold time, r₃For the resolution code check of next video, v₂(k, n) is the upper of current video burst Pass network speed；

If reaching the first threshold time, do not complete to download described current video burst, then by described current video burst It is adjusted to second code rate under first code check；If completing to download to be adjusted to described in the second code check within the first threshold time and working as forward sight Frequency division piece, calculates the 3rd threshold time that next video slicing described is downloaded；If under not completing within the first threshold time Carry the described current video burst being adjusted to the second code check, then the second code check is adjusted to lowest bit rate；

The computing formula of described 3rd threshold time is:

$v_{21}(k,n)=\frac{r_{21}\mathrm{\&tau;}}{t_{21}}$

$t_{{\mathrm{pk}}_{31}}=\frac{r_{31}\mathrm{\&tau;}}{v_{21}\left(k{,}^{1}n\right)}$

Wherein v₂₁Download speed for current video burst；r₂₁For the second code check；r₃₁For the code check of next video slicing, t_pk31For Described 3rd threshold time.

2. the method for down loading of video slicing according to claim 1 is it is characterised in that described video server is to described visitor Family end also includes before downloading current video burst, and the actual download time according to a upper video slicing and a described upper video divide The size of piece calculates the download speed of a described upper video slicing, and the network speed according to a described upper video slicing utilizes self adaptation to calculate Method is calculated described first code check.

3. the method for down loading of video slicing according to claim 2 is it is characterised in that methods described also includes, according to institute The size of the download speed and described current video burst of stating a video slicing calculates estimates download time, and according to described pre- Meter sends Time Calculation and obtains the first threshold time.

4. the method for down loading of video slicing according to claim 1 is it is characterised in that described video server receives client The download request of the video slicing that end sends specifically includes: video server receives the video that client sends according to mpd file The download request of burst, described mpd file include http-server storage media slicing, uri, demultiplexing, decoded information.

5. video slicing according to claim 1 method for down loading it is characterised in that described by described current video burst The first code check under be adjusted to second code rate and specifically include: by the first code check of described current video burst according to cache resources substep Lower.