CN104349163B - End-to-end video transmission delay measurements display device and the system of measurement - Google Patents
End-to-end video transmission delay measurements display device and the system of measurement Download PDFInfo
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Abstract
The invention discloses a kind of end-to-end video transmission delay measurements display device and measurement system, device includes timestamp high-speed generator, sufficient amount of display controller, described sufficient amount of display controller each connects a display unit respectively, and the arrangement of described array of display cells constitutes array of display; Described timestamp high-speed generator obtains from GPS time service clock every the scheduled time and produces a timestamp lock in time, sends described timestamp that different time produces successively to described sufficient amount of display controller; Described sufficient amount of display controller obtain from described timestamp high-speed generator send timestamp thus driving described array of display; Shown array of display shows, at each display unit, the described timestamp that different time produces successively respectively. The present invention improves latency measurement precision, and to meet the latency measurement required precision to the extremely sensitive processing system for video of time delay, the measurement system equipment of the present invention is simple simultaneously, and cost is substantially reduced.
Description
Technical field
The present invention relates to Video transmission system time delay measurement field, particularly to a kind of end-to-end video transmission delay measurements display device and the system of measurement.
Background technology
Time delay is the time order and function order between processing system for video input and output. Each component units of processing system for video, such as video acquisition, coding, transmission, decoding, display, and interface and buffer memory all can produce to postpone. Time delay is also called CDL (Capture-to-DisplayLatency) end to end, refers to that gathering video pictures from transmitting terminal shows, to receiving terminal, the time difference that video pictures experiences. CDL is one of important indicator weighing Video transmission system service quality, the real-time of the quantitative system that characterizes. The related method thereof measuring end-to-end video is more, and research worker both domestic and external, professional equipment provide commercial city to give relevant solution. These schemes are broadly divided into two big classes, specific as follows:
The first kind is called intrusive mood measuring method, cardinal principle is, the special video-audio signal that transmitting terminal customization produces, and sends into coding and transmission system, received these signals by special measurement device at receiving terminal or the measurement point specified, calculate time difference as the time delay between 2 o'clock. Adopt the usually professional equipment manufacturer of this kind of scheme, the module related measurement devices that such as Rohde & Schwarz Representative Office, Imtech etc. provide. Its advantage is that certainty of measurement is high, supports more tested point. Shortcoming is the need for equipment specialty, expensive, because relating to collection and the display of image, these professional equipments cannot substitute collection and the display device that user uses, therefore intrusive mood method is difficult to accurately measure time delay CDL end to end, particularly transmitting terminal and receiving terminal are not in the same localities, and belong to the situation in long-range strange land.
Equations of The Second Kind is called non-intrusion measurement method, its cardinal principle is, transmitting terminal embed on video pictures can express time stamp symbol, namely timestamp is sent, when receiving terminal demonstrates the video pictures with transmission timestamp, extract transmission timestamp and the local time stamp with receiving terminal compares, thus obtaining time delay CDL. Existing common methods is Presentation Time Stamp on the computer screen, gathers video pictures with video camera facing to computer screen, thus incorporating in video image by timestamp, the Video coding with timestamp is compressed by transmitting terminal, and is transferred to receiving terminal. Receiving terminal decodes and demonstrates the video pictures with timestamp. The measuring method of existing non-intrusive, timestamp generally has the special symbol of digital form, bar code, Quick Response Code and design. Main purpose is desirable to utilize codeword generator existing, more stable, that reliability is high and code reader. Though the professional test equipment that this kind of method need not be expensive, the precision of the time delay measured be limited by the refresh rate of computer display, display development delay, the frame per second of video camera, time of exposure, transmitting-receiving two-end clock synchronization accuracy impact so that its certainty of measurement is relatively low. This kind of method is usually used in the low measure of precision of video time delay of IP network, its certainty of measurement cannot meet the measurement requirement to the extremely sensitive processing system for video of time delay, such as terrestrial DTV, unmanned plane real time reconnaissance, infrared imaging guidance weapon, telesurgery systems etc.
Summary of the invention
It is an object of the invention to overcome above-mentioned deficiency existing in prior art, it is provided that a kind of end-to-end video transmission delay measurements display device and the system of measurement, to meet the latency measurement required precision to the extremely sensitive processing system for video of time delay, reduce cost.
In order to realize foregoing invention purpose, the technical solution used in the present invention is: a kind of end-to-end video transmission delay measurements display device, including timestamp high-speed generator, described timestamp high-speed generator connects sufficient amount of display controller, described display controller each connects a display unit respectively, and the arrangement of described array of display cells constitutes array of display; Wherein, described sufficient amount refers to ensure the overlap that the timestamp image that display unit shows does not result on surrounding time;
Described timestamp high-speed generator, produces a timestamp for obtaining from GPS time service clock every the scheduled time lock in time, sends described timestamp that different time produces successively to described sufficient amount of display controller; The wherein said scheduled time is Millisecond;
Described sufficient amount of display controller, for obtain from described timestamp high-speed generator send timestamp thus driving described array of display;
Shown array of display, for showing, at each display unit, the described timestamp that different time produces respectively successively.
Preferably, described timestamp high-speed generator connects described sufficient amount of display controller by bus, and described sufficient amount of display controller each has unique bus address;
Described timestamp high-speed generator is specifically for producing a timestamp lock in time every the scheduled time from the acquisition of GPS time service clock, each described timestamp is generated with the bus data frame of described bus address, sends described bus data frame successively to described bus;
Described sufficient amount of display controller, specifically for obtaining the described bus data frame that from described timestamp high-speed generator send uniquely corresponding with respective described bus address according to respective described bus address described bus respectively, resolves described bus data frame and extracts timestamp therein thus driving described array of display;
Shown array of display, for showing, at each display unit, the described timestamp that different time produces respectively successively.
Preferably, if any one the display controller second time in described sufficient amount of display controller receives described timestamp high-speed generator and sends the described bus data frame corresponding with its unique described bus address of coming, the display unit then connected with any one display controller described in described array of display shows the timestamp corresponding with current described bus data frame, otherwise the described timestamp before display all the time.
Preferably, in described array of display, each display unit shows, according to described display unit priority distributing order from left to right, from top to bottom, the described timestamp that different time produces respectively.
Preferably, each display unit in described array of display is LCD display unit, and multiple LCD display unit constitute LCD array of display according to ranks alignment.
The present invention also provides for a kind of end-to-end video transmission delay measurements system, including:
First measures display device, and namely above-mentioned end-to-end video transmission delay measurements display device, for generating at transmitting terminal and showing, according to array way, the timestamp that different time produces on described array of display;
First video acquisition unit, for gathering the timestamp image frame that on the described first array of display measuring display device, the different time of display produces, by described image frame compression coding generation video stream to video delivery network;
Described video delivery network, is connected with described first video acquisition unit, is used for transmitting described video flowing;
Video display unit, is connected with described video delivery network, is used for receiving described video flowing, described video flowing is decoded and shows decoded image frame;
Second measures display device, measures display device with described first identical, and starts with described first measurement apparatus simultaneously, for generating at receiving terminal and showing, according to array way, the timestamp that different time produces on described array of display;
Second video acquisition unit, the video information of the decoded image frame that the timestamp image frame and described video display unit for gathering the different time generation recording display on the described second array of display measuring display device simultaneously shows;
Analytic unit, the described second described video information measuring display device and described video display unit for described second video acquisition unit is collected is decoded, each frame is saved as piece image, then described second in the picture measures the very first time stamp that display device extracted region is maximum, the second timestamp that described video display unit extracted region is maximum in the picture, the difference calculating stamp of the described very first time and the second timestamp is time delay measurement value.
Preferably, the time of the image frame video that described second measurement display device and described video display unit are recorded in described second video acquisition unit collection is 3-5 minute.
Preferably, described analytic unit is additionally operable to every two field picture is calculated respectively described time delay measurement value, takes the meansigma methods of multiple described time delay measurement value as transmission system time delay measurement value end to end.
Preferably, the frequency acquisition of described first video acquisition unit is fs, the refresh rate of described video display unit is fd, the frequency acquisition of described second video acquisition unit is fr, wherein, fd��fr��fs��
Preferably, described first video acquisition unit and the second video acquisition unit are video camera, and described video display unit is LCD display.
Compared with prior art, beneficial effects of the present invention: the present invention measures and devises the array of display that can show that the display unit of multiple timestamp is constituted in display device, at the timestamp that different position display is different, avoid at the quick Presentation Time Stamp in same position, surrounding time stamp overlap, thus defining timestamp image clearly, improve the accuracy of time-stamp Recognition. Utilize it when measuring end-to-end video transmission system time delay, more accurate, apparent timestamp image can be generated, and then improve latency measurement precision, to meet the latency measurement required precision to the extremely sensitive processing system for video of time delay, the measurement system equipment of the present invention is simple simultaneously, and cost is substantially reduced.
Accompanying drawing illustrates:
Fig. 1 is the end-to-end video transmission delay measurements display device schematic diagram in the embodiment of the present invention;
Fig. 2 is LCD array schematic diagram in the embodiment of the present invention;
Fig. 3 is the end-to-end video transmission delay measurements system schematic in the embodiment of the present invention;
Fig. 4 is video sampling process and deviation schematic diagram;
Fig. 5 is the end-to-end video transmission delay measurements system transmitting terminal video acquisition process schematic in the embodiment of the present invention;
Fig. 6 is the end-to-end video transmission delay measurements system receiving terminal video acquisition process schematic in the embodiment of the present invention.
Detailed description of the invention
Below in conjunction with detailed description of the invention, the present invention is described in further detail. But this should not being interpreted as, the scope of the above-mentioned theme of the present invention is only limitted to below example, and all technology realized based on present invention belong to the scope of the present invention.
The present invention measures and devises the array of display that can show that the display unit of multiple timestamp is constituted in display device, at the timestamp that different position display is different, avoid at the quick Presentation Time Stamp in same position, surrounding time stamp overlap, thus forming timestamp image clearly, improve the accuracy of time-stamp Recognition.
Utilize it when measuring end-to-end video transmission system time delay, more accurate, apparent timestamp image can be generated, and then improve latency measurement precision, to meet the latency measurement required precision to the extremely sensitive processing system for video of time delay, the test system equipment of the present invention is simple simultaneously, and cost is substantially reduced. Illustrate below in conjunction with accompanying drawing.
The end-to-end video transmission delay measurements display device of the present invention, including timestamp high-speed generator, described timestamp high-speed generator connects sufficient amount of display controller, and described display controller each connects a display unit respectively, and the arrangement of described array of display cells constitutes array of display; Wherein, described sufficient amount refers to ensure the overlap that the timestamp image that display unit shows does not result on surrounding time;
Described timestamp high-speed generator, produces a timestamp for obtaining from GPS time service clock every the scheduled time lock in time, sends described timestamp that different time produces successively to described sufficient amount of display controller; The wherein said scheduled time is Millisecond, and those skilled in the art can be arranged as the case may be.
Described sufficient amount of display controller, for obtain from described timestamp high-speed generator send timestamp thus driving described array of display.
Shown array of display, for showing, at each display unit, the described timestamp that different time produces respectively successively.
Concrete, referring to Fig. 1, described timestamp high-speed generator connects described sufficient amount of display controller by bus, and described sufficient amount of display controller each has unique bus address. Described timestamp high-speed generator is specifically for producing a timestamp lock in time every the scheduled time from the acquisition of GPS time service clock, each described timestamp is generated with the bus data frame of described bus address, sends described bus data frame successively to described bus;Described sufficient amount of display controller, specifically for obtaining the described bus data frame that from described timestamp high-speed generator send uniquely corresponding with respective described bus address according to respective described bus address described bus respectively, resolves described bus data frame and extracts timestamp therein thus driving described array of display; Shown array of display, for showing, at each display unit, the described timestamp that different time produces respectively successively.
Preferably, if any one the display controller second time in described sufficient amount of display controller receives described timestamp high-speed generator and sends the described bus data frame corresponding with its unique described bus address of coming, the display unit then connected with any one display controller described in described array of display shows the timestamp corresponding with current described bus data frame, otherwise the described timestamp before display all the time. That is each display unit shows the timestamp each received successively all the time, until the timestamp again receiving a up-to-date generation then starts to show up-to-date timestamp.
Preferably, in described array of display, each display unit shows, according to described display unit priority distributing order from left to right, from top to bottom, the described timestamp that different time produces respectively. Owing to described timestamp is that described timestamp high-speed generator continuously generated every the scheduled time, the time value of timestamp is constantly to increase, according to array way, priority distributing order from left to right, from top to bottom shows respectively, so can be easy to when gathering graphical analysis quickly determine effective time stamp (timestamp of maximum), it is normally at the lower right corner of image, improves the efficiency of analyzing and processing.
Preferably, each display unit in described array of display is LCD display unit, and multiple LCD display unit constitute LCD array of display according to ranks alignment.
Concrete, described array of display is alignd according to ranks by the LCD display unit of multiple very small dimensions, is spliced into a compact LCD array regularly, and Fig. 2 is the schematic diagram of LCD array. Referring to Fig. 1, timestamp panel (i.e. end-to-end video transmission delay measurements display device) is made up of five parts such as LCD array, GPS time service clock, display controller, timestamp high-speed generator, buses. Each LCD display unit has each independent display controller, and is linked together by bus and timestamp high-speed generator. Each display controller has unique bus address, obtains the timestamp being sent to this address from timestamp high-speed generator, and drive LCD display unit to demonstrate timestamp bus. GPS time service clock obtains external GPS signal, generates lock in time. Timestamp high-speed generator obtains lock in time from GPS time service clock, and according to the bus address of the display controller of LCD display unit, the timestamp sequentially sending generation displays to corresponding LCD display unit. Timestamp high-speed generator is every 1/fcSecond produces a timestamp, gives, through bus, the LCD display unit specified and shows. Each LCD display unit can show the timestamp value of correspondence all the time, until display controller receives new timestamp or removes display command. Timestamp on LCD array shows by sequencing from left to right, from top to bottom. The minimum time granularity that timestamp array of display is provided that is 1/fc. Showing multiple timestamp on timestamp array of display, the timestamp of maximum therein is called that effective time is stabbed.
Owing to the time-delay measuring method of conventional non-intrusive is usually facing to clock or stopwatch acquisition time stamp. Because being continually changing timestamp to be shown in the same position of a display device or the position of next-door neighbour, the different timestamp in front and back overlaps, and forms fuzzy timestamp image. The present invention devises timestamp array of display panel, at the timestamp that different position display is different, it is to avoid in the quick Presentation Time Stamp in same position, surrounding time stamp overlap, thus forming timestamp image clearly, improve the accuracy of time-stamp Recognition. Utilize it that more accurate, apparent timestamp image when measuring end-to-end video transmission system time delay, can be generated, and then improve latency measurement precision, to meet the latency measurement required precision to the extremely sensitive processing system for video of time delay.
The present invention also provides for a kind of end-to-end video transmission delay measurements system, including:
First measures display device, namely the end-to-end video transmission delay measurements display device of above-described embodiment is (also referred to as timestamp panel, lower same), for generating at transmitting terminal and showing, according to array way, the timestamp that different time produces on described array of display;
First video acquisition unit (such as video camera), for gathering the timestamp image frame that on the described first array of display measuring display device, the different time of display produces, by described image frame compression coding generation video stream to video delivery network;
Described video delivery network, is connected with described first video acquisition unit, is used for transmitting described video flowing;
Video display unit (such as LCD display), is connected with described video delivery network, is used for receiving described video flowing, described video flowing is decoded and shows decoded image frame;
Second measures display device, measures display device with described first identical, and starts with described first measurement apparatus simultaneously, for generating at receiving terminal and showing, according to array way, the timestamp that different time produces on described array of display;
Second video acquisition unit (such as video camera), the video information of the decoded image frame that the timestamp image frame and described video display unit for gathering the different time generation recording display on the described second array of display measuring display device simultaneously shows.
Preferably, in one example, the time of the image frame video that described second measurement display device and described video display unit are recorded in described second video acquisition unit collection is 3-5 minute, so can gather enough pictures for subsequent treatment. Second video acquisition unit can also preserve the video information of collection.
Analytic unit, the described second described video information measuring display device and described video display unit for described second video acquisition unit is collected is decoded, each frame is saved as piece image, then described second in the picture measures the very first time stamp that display device extracted region is maximum, the second timestamp that described video display unit extracted region is maximum in the picture, the difference calculating stamp of the described very first time and the second timestamp is time delay measurement value. Described analytic unit can be any calculation element with video, image procossing.
The present invention utilizes described measurement display device to measure end-to-end video transmission system time delay, more accurate, apparent timestamp image can be generated, and then improve latency measurement precision, to meet the latency measurement required precision to the extremely sensitive processing system for video of time delay, the measurement system equipment of the present invention is simple simultaneously, and cost is substantially reduced.
In order to improve certainty of measurement further, in one example, described analytic unit is additionally operable to every two field picture is calculated respectively described time delay measurement value, takes the meansigma methods of multiple described time delay measurement value as transmission system time delay measurement value end to end.
Preferably, the frequency acquisition of described first video acquisition unit is fs, the refresh rate of described video display unit is fd, the frequency acquisition of described second video acquisition unit is fr, wherein, fd��fr��fs��
The end-to-end video transmission delay measurements system of the present invention is illustrated below by an embodiment.
Referring to Fig. 3, the present invention measures system and is made up of system under test (SUT) equipment and test equipment two parts, test equipment includes transmitting terminal timestamp panel SSTPanel and (namely first measures display device, lower with), destination time stamp panel RSTPanel (namely second measuring display device, lower same), three parts of receiving terminal video camera RCamera (i.e. the second video acquisition unit). System under test (SUT) equipment is mainly terminal unit liquid crystal display DispLCD (i.e. video display unit) of sending ending equipment video camera SCamera (i.e. the first video acquisition unit), transmission network TransmissionNetworks, receiving terminal.
Transmitting terminal SSTPanel quickly generates continuous print Millisecond timestamp, and is sequentially shown in the array of display cells of panel and gathers for sending ending equipment SCamera. SCamera gathers video image picture, and compression coding generates video flowing, and by video stream to transmission network TransmissionNetworks. In measurement process, SCamera shoots video facing to SSTPanel, has recorded the timestamp being continually changing on SSTPanel, has defined the input video picture with timestamp. TransmissionNetworks provides transmission channel for video flowing, and from transmitting terminal, video is transferred to receiving terminal, completes the transmission of video data stream. DispLCD is reception terminal, it is achieved video reception decoding display, and the video pictures of decoding is presented to user, and in the process measured, DispLCD shows the video pictures with transmission timestamp that transmitting terminal is brought. RSTPanel and SSTPanel function is similar, mainly quickly generates continuous print Millisecond timestamp, and is sequentially shown on panel and gathers for receiving terminal RCamera. RCamera is video camera, at receiving terminal simultaneously facing to DispLCD and RSTPanel fast recording from the timestamp of transmitting terminal and receiving terminal local time stamp.
The collection of making a start of tested transmission system is with sending time stamp TsVideo pictures, receiving terminal decoding display is with the video pictures sending timestamp, then the reception time stamp T of the local time stamp Display panel with receiving terminalrThe high frame rate camera RCamera of receiving end gathers display simultaneously, by analysis video image, extracts TsAnd TrAnd calculate time difference, thus acquire the measured value of end-to-end transmission delay. The present invention calculates simply, precision high, and measurement device is simple, and cost is substantially reduced.
Concrete, in the present embodiment, SSTPanel and RSTPanel forms by the liquid crystal display of 500 very small dimensions, is arranged in 20 row, 25 display units of each row. Liquid crystal display is of a size of wide 25.4 millimeters, high 14 millimeters. Time showing form is M.SS.XXX, wherein M minute, and SS is second, and XXX is millisecond, totally 8 characters, and the delay scope therefore measured, up to 10 minutes, meets existing all of network.Described bus uses CAN, and Bus Speed is 1Mbps. High speed time stamp generator is mainly realized by DSP, precise time timestamp value is obtained by serial port from GPS time service clock every 2 milliseconds, and generate the CAN Frame with purpose bus address, the display controller of the display unit specified it is sent to by CAN. The difference of adjacent two timestamps is 2 milliseconds, therefore has clock frequency fc=500Hz.
In the present embodiment, the resolution of the video camera SCamera of transmitting terminal is 1920 �� 1080, frame per second fs=60Hz, video delivery network TransmissionNetworks are DVB-T wireless transmitting system, including the manipulator made a start and power amplifier, antenna of making a start, receiving terminal antenna, receiving terminal demodulator, receiving terminal decoder (not shown). The resolution of the DispLCD display screen of receiving terminal is 1920 �� 1080, refresh rate fd=60Hz. The resolution of the video camera RCamera of receiving terminal is 1920 �� 1080, frame per second fr=60Hz.
Specific works process is as follows:
(1) system under test (SUT) is opened
It is respectively started SCamera, transmission network TransmissionNetworks, receiving device DispLCD.
(2) test equipment is started
Being respectively started SSTPanel and RSTPanel, until all demonstrating timestamp, and DispLCD and RSTPanel tightly being put together side by side.
(3) transmitting terminal acquisition time stamp video
SCamera is placed on SSTPanel just before, observe SCamer view-finder, suitably adjust distance so that SSTPanel forms picture comparatively clearly. SCamera starts to record the video with timestamp.
(4) receiving terminal acquisition time stamp video
When the picture of transmitting terminal timestamp panel SSTPanel is after DispLCD demonstrates, RCamera is placed on before RSTPanel and DispLCD, observe RCamera view-finder, adjust suitable distance so that the picture of RSTPanel and the picture of DsipLCD form picture clearly at RCamera simultaneously. RCamera records 3-5 minute video, and preserves video file.
(5) image calculating time delay CDL is analyzed
The video that RCamera records is decoded, every frame is saved as piece image. According to the sequencing recorded, observe the transmission timestamp picture of every two field picture and receive timestamp picture. Gather the picture of RSTPanel and DispLCD due to RCamera simultaneously, in the described image that the every frame preserved is corresponding, therefore there is two regions, i.e. DispLCD imaging region and RSTPanel imaging region. In the image of the RCamera video conversion gathered, from the region of DispLCD, find maximum time stamp Ts, from RSTPanel region, find maximum time stamp Tr, the measured value Delay=T of computing relayr-Ts��
In order to improve certainty of measurement further, from every two field picture, calculate a measured value Delay, take the Delay of 100 two field pictures, calculate their arithmetic averageAs transmission system time delay CDL end to end.
Below calculating time delay CDL being made and illustrating: due to the restriction by display control state switching delay, display picture is not complete moment on the one hand, there is deferring procedure; On the other hand by the restriction of refresh rate, the picture that video shows is visually continuous print, but is actually discrete, has certain time interval between adjacent two width pictures. Before display next frame picture, previous frame picture can rest on screen always. Therefore, can being regarded as pulse signal between at this moment in interval, its amplitude remains unchanged.
Video acquisition process neither the completing of transient state sudden change. By the restriction of imaging photosensitive mechanism, needing an exposure period when gathering picture, within the time of whole exposure, the picture of shooting is carried out photosensitive accumulation by the CCD of video camera, and the namely process of charge accumulation is similar to one-dimensional curve integration. If the picture being taken does not have acute variation, the picture of accumulation will constantly be strengthened, visually color burn. If the picture being taken has acute variation, there is overlap in the picture of accumulation, presents fuzzy picture.
The process of video acquisition and display is all the sampling process to the 2D signal being continually changing. If process is all discrete periodic process, because frequency can not be completely the same, and it is unable to reach precise synchronization, then can there is sampling error. If there is t continuous time definitely accurately, frequency is fiSampled signal Si, the cycle is 1/fhHigh frequency period departure process PhIt is 1/f with the cyclelLow-frequency cycle departure process Pl. Sampled signal fiTo the sampling of high and low frequency process as schematically shown in Figure 4. At TmMoment, SiSimultaneously to PhAnd PlSampling. At TnMoment observes SiThe signal adopted, remains PhAt TqThe value in moment, PlAt TkThe value in moment, due to 1/fl��1/fh, it is apparent that there is �� th�ܦ�tl. During sampling keeps, even if being there occurs change by the number of accepting and believing, but sampled value still will not change therewith, therefore can produce error. From the time, to PhThe signal of process collection is more nearly TnThe value in moment, therefore time error is smaller. Work as fhMore big, then the scope of biased error is then more little.
At the timestamp panel SSTPanel of the transmitting terminal measuring Video transmission system time delay, the frequency of clock is fc, namely every 1/fcSecond generate on new timestamp position that to be shown on array of display up-to-date. The frame per second of video camera SCamera is fs, every 1/fsSecond timestamp panel (namely first measure display device) is gathered a two field picture, the up-to-date time of display on logging timestamp panel. The schematic diagram of gatherer process is as shown in Figure 5. When camera video camera SCamera is at TmTimestamp panel is gathered image by the moment, then the up-to-date timestamp obtained is T on panelsThe time value of moment display, the error of generation is �� ts, it ranges for 0�ܦ� ts<1/fc. After the encoded compression of timestamp video that SCamera gathers, form video flowing and be admitted to transmission network.
At the timestamp panel RSTPanel of the receiving terminal measuring Video transmission system time delay, the frequency of clock is also fc, namely every 1/fcSecond generate a new timestamp, be shown in up-to-date position. The refresh rate of receiving terminal decoding display DispLCD is fd, namely every 1/fdSecond display one two field picture. The frame per second of video camera RCamera is fr, namely every 1/frSecond timestamp panel is gathered a two field picture, the time of display on logging timestamp panel. There is f under normal circumstancesd��fr ��fs, therefore the time renewal frequency on decoding display screen is equivalent to fs. It is to say, the effective time stamp frequency shown at receiving terminal is the frequency acquisition f according to transmitting terminal video camera SCameras. The process of RCamera collection dual-time stamp is as shown in Figure 6. RCamera is at TwMoment gathers RSTPanel timestamp and is really at TrThe timestamp that moment generates, error is �� tr=Tw-Tr, it is clear that there is 0�ܦ� tr��1/fc. RCamera is at TwAlthough the timestamp of the display screen DispLCD that the moment gathers is TuThe timestamp that moment refreshes, but it is actually TpThe timestamp of moment decoding display.Namely TuThe timestamp of moment display and TpThe timestamp in moment is consistent, because fd��fs, so being belonging to repeat display. Therefore error is �� tp=Tw-Tp, it is clear that 0�ܦ� tp��1/fs��
Receiving terminal RCamera gathers the locally significant timestamp of receiving terminal from RSTPanel and DispLCD simultaneously and decoding shows the video pictures imitating timestamp. Because fd��fr��fs, so TwMoment should be T from the DispLCD timestamp obtaineduThe picture that moment refreshes, actually TpTimestamp shown by the picture in moment. The actual transmission timestamp being equivalent to transmitting terminal of this timestamp, therefore complex chart 5 and Fig. 6 are it can be seen that end to end time delay CDL can be calculated by following formula:
CDL=Tw-Tm=(Tr+��tr)-(Tp+��tp)=(Tr+��tr)-(Ts+��ts+��tp)
=(Tr-Ts)-(��tp+��ts-��tr)
It practice, RCamera collection picture is only capable of obtaining transmission time stamp T from gatheringsWith reception time stamp Tr. By TsAnd TrCalculate the measured value Delay of end-to-end delay:
Delay=Tr-Ts=CDL+ ��
Contrast both the above formula is it can be seen that error is ��=(�� tp+��ts-��tr), this error produces to come from SCamera, RCamera, DispLCD does not have precise synchronization, the change of transmission network, the change in location of sampled point and pulse starting point. In theory, this error range for [-(1/fc+fs),1/fc+1/fs). Error delta is dynamically change, causes that the CDL calculated is continually changing. In order to reduce error, calculate the arithmetic average of multiple DelayValue as time delay CDL.
The present invention utilizes recurrent pulses sampling theory, and the error of timestamp has been analyzed, and establishes the precision 1/f of measurement error scope and the Presentation Time Stamp of timestamp panelc(1/fcMore little precision is more high), the frame per second f of the video camera of transmitting terminals, receiving terminal display screen refresh rate fd, receiving terminal the frame per second f of video camerarRelation. The present invention, by improving the precision of timestamp, adopts transmitting terminal video camera and the receiving terminal video camera of high frame per second, and receiving terminal adopts the display that refresh rate is high.
The present invention measures and devises the array of display that can show that the display unit of multiple timestamp is constituted in display device, at the timestamp that different position display is different, avoid at the quick Presentation Time Stamp in same position, surrounding time stamp overlap, thus forming timestamp image clearly, improve the accuracy of time-stamp Recognition.
Utilize it when measuring end-to-end video transmission system time delay, more accurate, apparent timestamp image can be generated, and then improve latency measurement precision, to meet the latency measurement required precision to the extremely sensitive processing system for video of time delay, the measurement system equipment of the present invention is simple simultaneously, and cost is substantially reduced.
Above in conjunction with accompanying drawing, the specific embodiment of the present invention is described in detail, but the present invention is not restricted to above-mentioned embodiment, without departing from the spirit and scope situation of claims hereof, various modifications may be made or remodeling for those skilled in the art.
Claims (10)
1. an end-to-end video transmission delay measurements display device, it is characterized in that, including timestamp high-speed generator, described timestamp high-speed generator connects sufficient amount of display controller, described display controller each connects a display unit respectively, and the arrangement of described array of display cells constitutes array of display; Wherein, described sufficient amount refers to ensure the overlap that the timestamp image that display unit shows does not result on surrounding time;
Described timestamp high-speed generator, produces a timestamp for obtaining from GPS time service clock every the scheduled time lock in time, sends described timestamp that different time produces successively to described sufficient amount of display controller;The wherein said scheduled time is Millisecond;
Described sufficient amount of display controller, for obtain from described timestamp high-speed generator send timestamp thus driving described array of display;
Shown array of display, for showing, at each display unit, the described timestamp that different time produces respectively successively.
2. end-to-end video transmission delay measurements display device according to claim 1, it is characterized in that, described timestamp high-speed generator connects described sufficient amount of display controller by bus, and described sufficient amount of display controller each has unique bus address;
Described timestamp high-speed generator is specifically for producing a timestamp lock in time every the scheduled time from the acquisition of GPS time service clock, each described timestamp is generated with the bus data frame of described bus address, sends described bus data frame successively to described bus;
Described sufficient amount of display controller, specifically for obtaining the described bus data frame that from described timestamp high-speed generator send uniquely corresponding with respective described bus address according to respective described bus address described bus respectively, resolves described bus data frame and extracts timestamp therein thus driving described array of display;
Shown array of display, for showing, at each display unit, the described timestamp that different time produces respectively successively.
3. end-to-end video transmission delay measurements display device according to claim 2, it is characterized in that, if any one the display controller second time in described sufficient amount of display controller receives described timestamp high-speed generator and sends the described bus data frame corresponding with its unique described bus address of coming, the display unit then connected with any one display controller described in described array of display shows the timestamp corresponding with current described bus data frame, otherwise the described timestamp before display all the time.
4. the end-to-end video transmission delay measurements display device according to any one of claim 1-3, it is characterized in that, in described array of display, each display unit shows, according to described display unit priority distributing order from left to right, from top to bottom, the described timestamp that different time produces respectively.
5. end-to-end video transmission delay measurements display device according to claim 4, it is characterised in that each display unit in described array of display is LCD display unit, multiple LCD display unit constitute LCD array of display according to ranks alignment.
6. an end-to-end video transmission delay measurements system, it is characterised in that including:
First measures display device, i.e. the end-to-end video transmission delay measurements display device of any one of the claims 1-5, for generating at transmitting terminal and showing, according to array way, the timestamp that different time produces on described array of display;
First video acquisition unit, for gathering the timestamp image frame that on the described first array of display measuring display device, the different time of display produces, by described image frame compression coding generation video stream to video delivery network;
Described video delivery network, is connected with described first video acquisition unit, is used for transmitting described video flowing;
Video display unit, is connected with described video delivery network, is used for receiving described video flowing, described video flowing is decoded and shows decoded image frame;
Second measures display device, measures display device with described first identical, and starts with described first measurement apparatus simultaneously, for generating at receiving terminal and showing, according to array way, the timestamp that different time produces on described array of display;
Second video acquisition unit, the video information of the decoded image frame that the timestamp image frame and described video display unit for gathering the different time generation recording display on the described second array of display measuring display device simultaneously shows;
Analytic unit, the described second described video information measuring display device and described video display unit for described second video acquisition unit is collected is decoded, each frame is saved as piece image, then described second in the picture measures the very first time stamp that display device extracted region is maximum, the second timestamp that described video display unit extracted region is maximum in the picture, the difference calculating stamp of the described very first time and the second timestamp is time delay measurement value.
7. end-to-end video transmission delay measurements system according to claim 6, it is characterised in that the time of the image frame video that described second measurement display device and described video display unit are recorded in described second video acquisition unit collection is 3-5 minute.
8. end-to-end video transmission delay measurements system according to claim 6, it is characterized in that, described analytic unit is additionally operable to every two field picture is calculated respectively described time delay measurement value, takes the meansigma methods of multiple described time delay measurement value as transmission system time delay measurement value end to end.
9. end-to-end video transmission delay measurements system according to claim 6, it is characterised in that the frequency acquisition of described first video acquisition unit is fs, the refresh rate of described video display unit is fd, the frequency acquisition of described second video acquisition unit is fr, wherein, fd��fr��fs��
10. the end-to-end video transmission delay measurements system according to any one of claim 6-9, it is characterised in that described first video acquisition unit and the second video acquisition unit are video camera, and described video display unit is LCD display.
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| CN110740227B (en) * | 2019-10-25 | 2021-08-10 | 武汉大学 | Camera time synchronization device and method based on GNSS time service and image display information coding mode |
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| CN111372105A (en) * | 2020-03-26 | 2020-07-03 | 深圳市微测检测有限公司 | Video information transmission delay test method, device, terminal and storage medium |
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