Summary of the invention
Purpose of the present invention is exactly in order to overcome that complex structure, the big shortcoming of equipment investment are broadcast in the two-way site of existing cable TV and the existing one-way CATV network network structure of a kind of utilization that provides can realize broadcasting with reconnaissance, and can enlarge with the coverage rate of cable TV network and unlimited dilatation, program request easily, conveniently is used for the user side set-top box realizes the chip that video is broadcast with reconnaissance on the net at wired TV one-way.
The technical scheme that realizes the object of the invention is: a kind ofly realize the chip that video is broadcast with reconnaissance on the net at wired TV one-way, comprising: process controller, buffer control unit and buffer, the temporary transmit control device of data; It is characterized in that, also comprise switch channel controller, arithmetic processor and input/output interface; Described switch channel controller is used to discern program video signal or other signals, and selects the vision signal that the user is required to send into process controller through passage, will not be that the required institute of user signal arrives mainboard by output interface; Described process controller receives from the bit stream data bag of switch channel controller output, and the packet segment number that relatively receives is than the packet segment number size of current broadcast, the packet that selection is bigger than the segment number of current broadcast deposits in, and, program data stream is play continuously in the defeated then segment data under the input after rolling of present segment packet; Described arithmetic processor is used for the constant speed of code stream is sent, and adopts a reference clock to come control stream to send; Described data RAM (keeping in) transmit control device, wherein data RAM is used for the packet header of data flow is removed, and delivers to the Memory Allocation table by transmit control device again, is found the data flow segment number of broadcasting earlier fast by the Memory Allocation table; Described sdram controller and SDRAM are used for the data of process controller output are read and write control, and SDRAM is as the buffering area of data code flow, and the data of taking out in buffering area are slowly play, and write fast, to reach the program request effect.
Above-mentionedly realize the chip that video is broadcast with reconnaissance on the net at wired TV one-way, wherein, described segment number is meant the number that adopts the code stream table to be preced with for each packet, and described code stream table is that the length according to program, the size of buffer memory capacity and the speed of downloading are worked out
Because the present invention has adopted above technical measures, adopt process controller and transmit control device constantly to receive and new video stream more, therefore as long as constantly receive downstream signal, the a series of cost and the operational administratives such as emission transmission of upward signal have been saved, simultaneously owing to adopt the mode of one-way video streaming, so number of users is unrestricted, and capacity is increased, program request is efficient and convenient.
Specific performance of the present invention and feature are further provided by following embodiment and accompanying drawing thereof.
Embodiment
See also accompanying drawing 1, Fig. 2.With reconnaissance broadcast chip be set-top box under the unidirectional network condition, realize the core component broadcast with reconnaissance, it is arranged on the tuner QAM decoding of common receiving digital video, information broadcast set-top box and browses between the mainboard.The present invention realizes the chip that video is broadcast with reconnaissance on the net at wired TV one-way, comprises switch channel controller, process controller, arithmetic processor, SDRAM (buffering) controller and buffer (SDRAM), data RAM (keeping in) transmit control device and input/output interface.The switch channel controller is used to discern program video signal or other signals, and useful vision signal delivered to process controller, by process controller comparing data bag segment number size, access in data cache module, and make data flow continuously smooth output by transmit control device, reach the program request effect.
Wherein:
Described switch channel controller receives through the tuner channel selection, the digital signal through the QAM demodulation after again, and to discern it be user video program request signal or out of Memory, if video-on-demand signals just allows its signal enter the VOD process controller.If not then signal is browsed plate (mainboard) from the input port through to STB.
The bit stream data bag that described process controller gets off from the switch channel controller, this bit stream data bag is according to the code stream table transmission of establishment in advance, and the code stream table to be the length according to request program, the size of buffer memory capacity and the speed of downloading, the factors such as time of wait work out.The packet that it is i that this process controller receives a segment number, if i is than the segment number of current broadcast little (expression is to export) then this section is abandoned, receive next, if i is bigger than the segment number of current broadcast, judge further then whether this section exists in the buffering, has then to abandon, otherwise judged whether the sky buffer memory, have and then store this bag, then do not compare maximum segment number MAX size in i and the buffer memory, keep little person and abandon big person.According to above-mentioned regular access, just can guarantee to have put " 0 " section (following " 0 " section all dactylus purpose opens the beginning section), necessarily " 1 " section (with next section that opens beginning section smooth connection) is deposited in, and after " 0 " section has been put, then put " 1 " section, make the continuous broadcast of program.Described segment number is meant the number that adopts the code stream table to be preced with for each packet.
Described arithmetic processor sends for the code stream constant speed, comes control stream to send with a reference clock.Get two value PCR (i) fields and PCR (i+1) field earlier, obtain M (facing two PCR interfield frame sums mutually) by counter simultaneously,
According to formula: T=PCR (i+1)-PCR (i) (1)
TF=T/M
Utilize formula P (i, n)=PCR (i)+n * TF (2)
In above-mentioned two formula, wherein:
PCR: program clock reference;
I: expression is to the count value of PCR field, and initial value is 0;
M: two PCR interfield sums are faced in expression mutually;
N: the N frame data of two PCR interfields are faced in expression mutually, and initial value is 0, and maximum is M-1;
PCR (i): i the PCR field value that expression is read from TS stream;
TS stream: video transmission stream;
T: it is poor that two PCR interfield reproduction times are faced in expression mutually;
TF: be illustrated in and send the needed time span of every frame data among PCR (i) and the PCR (i+1);
P (i, n): expression sends the time point of the n frame data after PCR (i) field;
T
Sys: expression is from sending the count value that first frame data begin to count, and initial value is PCR (0).
Relatively: T
Sys(i in the time of n), waits data to be sent to<P, when timing begins to send the n frame data when equal;
Work as T
Sys(i in the time of n), begins to send the n frame data to=P;
Work as T
Sys(i, in the time of n), (i n) writes T to>P with P
Sys, T
SysThe time data still continue, and begin to send the n frame data.
The effect of described data RAM (keeping in) VOD transmit control device is; TS stream is the data flow in packet header, through data RAM packet header is removed, and is found that section of broadcasting earlier fast with the Memory Allocation table.
Described sdram controller and SDRAM, it reads and writes control according to the VOD process controller to SDRAM, and SDRAM is as the buffering area of data code flow, and the data of taking out in buffering area are slowly play, and write fast, to reach the program request effect.
The present invention use when set-top box the operation principle flow process as shown in Figure 3:
After the start, according to the channel selection state, the data that decision is sent into are by the switch selector channel, flow to process controller, still directly deliver to the STB mainboard and handle; If video-on-demand signals just allows its signal enter the VOD process controller.If not then signal is browsed plate (mainboard) from the input port through to STB.
When being in first in first out (FIFO) state, there are two concurrent workflows, one is the data that send in progress CS section to output port, another is that receiving port receives the data segment that transmits;
The receiving data stream journey: at first in first out (FIFO) state, whole memory block empties, and is that " 0 " section data begin to receive from video flowing PID (package informatin sign).Receive " 0 " section and just begin to play " 0 " section, receive other section, the Frame that to receive a segment number be CI, if CI then abandoned this section than the segment number CS of current broadcast little (expression was exported), receive next, if CI is bigger than the segment number CS of current broadcast, judge then whether this section exists in the buffering, has then to abandon, otherwise judge whether also free buffer memory, have and then store this bag, then do not compare maximum segment number CM size in CI and the buffer memory, keep little person, abandon big person.
Send data flow: change video flowing PID number promptly reverts to original state to PID.Judge whether the CS section is sent completely, do not finish and then continue to play, finish the data that then continue to send the CS+1 section, and empty the shared buffer memory of CS segment data.
Whether the segment number CS+1 that judges current broadcast is greater than the maximum segment number MAX of whole transmission, if not then continuing router.Otherwise end back program request to be played finishes to send end signal.
In existing set-top box that possesses unidirectional reception, load onto chip of the present invention, can finish the function of two-way program request, need not to transform existing network configuration, save great amount of manpower and the material resources of transforming network, number of users is not subjected to any restriction simultaneously, can enlarge with the expansion of wired network coverage rate.