CN101980541A - Digital television receiving device and channel-switching method thereof - Google Patents
Digital television receiving device and channel-switching method thereof Download PDFInfo
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Abstract
The invention discloses a digital television receiving device and a channel-switching method thereof. The channel-switching method comprises the following steps of: demultiplexing transport stream data; multiplexing the demultiplexed data according to each service or the combination of a plurality of services, and caching the multiplexed data; after receiving a channel-switching instruction, acquiring cache data where a target service is positioned; demultiplexing the cache data where the target service is positioned, descrambling the demultiplexed data, and unpacking and restoring into original stream data; and decoding the unpacked original stream data. Based on the channel-switching method, the invention also provides the digital television receiving device. The method can greatly reduce the delay time generated for channel switching within the same frequency point, and enhance the user experience.
Description
Technical field
The present invention relates to digital TV field, particularly a kind of digital television receiving apparatus and channel switching method thereof.
Background technology
Along with the fast development of Digital Television, Digital Television is popular to people deeply with its excellent content, abundant program and advantages such as channel, distinct image and more convenient rating, and the application in life is also more and more.Watch that Digital Television need realize by digital television receiving apparatus, digital television receiving apparatus generally comprises digital TV integrated machine, digital TV set-top box etc., especially in the popularization of Digital Television, by using digital TV set-top box just can make the traditional analog television machine sowing put digital television program, therefore, digital TV set-top box has obtained using widely.
Digital TV set-top box receives the business datum from radio network, shows professional content by the audio frequency and video mode.Its front end transmission mode includes spider lines, terrestrial broadcasting, modes such as satellite broadcasting.Domestic consumer can realize selecting to view and admire the different business content by changing the platform operation.Change platform and comprise the step and the content of following several respects technically:
Step S11, locking frequency point, comprise receive the instruction of changing platform after, by the frequency on the control tuner lock channels such as (tuner), and the signal that tuner sends is carried out demodulation by demodulator (Demodulator), obtain transport stream (TS, Transport Stream) data.
Step S12, demultiplexing comprises that (the screening packet data package obtains grouping primary flow (PES, Packetized Elementary Stream) data for DEMUX, demultiplexer) module according to the business configuration demultiplexing.
Step S13, condition receives (CA, Conditional Access) descrambling, comprises and obtains authorization control word (CW, Control Word), and grouping primary flow packet is carried out descrambling.
Step S14, the grouping primary flow is synchronous, comprises according to grouping primary flow grammer detecting grouping primary flow packet header.
Step S15, video image group (GOP, Group Of Picture) header data is synchronous, comprises according to the video coding grammer detecting video GOP header data.
Step S16, audio, video data is synchronous, comprises according to grouping primary flow timestamp information, and timer reference of programs (PCR, Program Clock Reference) information, carry out the synchronous of audio-video frequency content.
Step S17, be reduced to primary flow (ES, Elementary Stream) and the output image of decoding or/and sound, comprise grouping primary flow data are unpacked being reduced to the primary flow data, and by video or/and audio decoder with described primary flow data decode after by the display unit output image or/and sound.
In the above step, for operating with changing platform in the frequency, step S11 can omit; For scrambled data not, step S13 can omit.
Digital TV set-top box is changed platform and is divided into frequency and changes platform and stride frequency and change two kinds of patterns of platform.Usually in frequency transport stream because inner multiplexing and bandwidth condition constraint can be transmitted about 7 tunnel video frequency program, the perhaps audio program of multichannel more.With the wired digital set-top box is example, if the Cable Network network of Radio ﹠ Television Bureau comprises the video frequency program and the audio program of 150 covers, be distributed on 20 frequencies, then the user carries out taking turns the switching of whole programs, at the best of times, comprise that the same frequency that changes platform and 130 times of striding frequency for 20 times changes platform.For video frequency program, the output dependence that changes first two field picture behind the platform is in following condition:
1. in video PES, search out the GOP header data, and then obtain first width of cloth GOP data, under based on the MPEG-2 encoding condition, be called as the I frame.The I frame is because the bandwidth for transmission restriction, can in radio network, high-frequency not broadcast, under the Phase Alternation Line system pattern, each video frequency program per second only can transmit 2 I frame data, and because the I frame data are bigger, time in the transmission distributes and surpasses 0.1 second usually, so the limit consumption time is 0.1-0.58 second (is example with the Phase Alternation Line system).
2. for the radio network that adopts condition receiving system, because video PES can obtain after the acquisition condition receiving system correctly disposes descrambler.A typical flow is to receive Entitlement Control Message (ECM, Entitle Control Message), and condition receiving system needs the time of about 0.3 second (being generally in the actual conditions 0～0.5 second), obtains the control word of descrambler.
3. because the audio frequency and video of video frequency program need be done to adopt different synchronized algorithms synchronously, generally need 3～6 frame video datas can realize audio-visual synchronization output.For example, under Chinese Phase Alternation Line system pattern, one-frame video data is exported 40ms consuming time, 0.12～0.24 second consuming time of 3～6 frame video datas.
By condition 1 and condition 2 as can be known, traditional platform flow process of changing, the maximum duration that causes not adding the interference service switching with frequency can not be shorter than 0.5 second, add the maximum duration of switching between interference service and can not be shorter than 0.8 second, and on actual platform, consider the influence of condition 3, under the worst case, the time that does not add the interference service switching can not be shorter than 0.6 second, adds the time of interference service switching even may reach 1 second.And it is more serious to change the platform delay issue in China Mobile multimedia broadcasting (CMMB, China Mobile Multimedia Broadcasting) system, and scrambled program is not changed the platform time and is about 4 seconds, and scrambled program is changed the platform time and is about 7 seconds.
As seen through the above analysis, change platform when operation, can produce bigger delay issue, make thus that to change platform speed slack-off, make the user when watching that Digital Television is changed platform, produce the sensation of discomfort at digital television receiving apparatus.
Application number is that 200810300565.6 Chinese patent application discloses a kind of digital television program rapid channel switching method, thereby this method is changed platform by shortening demodulator locks time quickening digital television program, but this method only can shorten the time of changing platform between the program of different frequent points, and does not solve the delay issue when changing platform in the frequency.
Summary of the invention
The problem to be solved in the present invention is that digital television receiving apparatus carries out with changing the delay that the platform operation time is produced in the frequency in the prior art.
For addressing the above problem, the invention provides a kind of channel switching method of digital television receiving apparatus, comprising:
Transmit flow data is carried out demultiplexing;
With the data behind the demultiplexing by each professional or a plurality of business unite and carry out multiplexingly, and the data after multiplexing are carried out buffer memory;
Receive change platform instruction after, the data cached of target service place obtained in control;
To the data cached demultiplexing that carries out at described target service place, and the data behind the described demultiplexing are carried out descrambling, unpack and be reduced to the primary flow data;
To decode through the described primary flow data after unpacking.
Optionally, described transmit flow data derives from same frequency.
Optionally, described transmit flow data is the scrambled code flow data.
Optionally, describedly data behind the described demultiplexing are carried out descrambling comprise: the Entitlement Control Message data and the Entitlement Management Message data that receive the target service that comprises in the data behind the described demultiplexing, and described Entitlement Control Message data and Entitlement Management Message data decryption obtained the control word of target service, carry out descrambling by the data of described control word after to demultiplexing.
Optionally, described data behind the transmit flow data demultiplexing are comprised video data, voice data, synchrodata.
Optionally, described form with the data after the transmit flow data demultiplexing is transport stream format or grouping primary flow form.
It is optionally, described that data after multiplexing are carried out the data in buffer amount is 0.5 second to 1 second data quantity transmitted.
Optionally, the described data cached demultiplexing that carries out to described target service place comprises that the data cached demultiplexing that carries out to described target service place obtains the GOP header data, obtains the first frame GOP data by described GOP header data.
For addressing the above problem, the present invention also provides a kind of digital television receiving apparatus, comprising: first demodulation multiplexer, multiplexer, data buffer storage unit, control unit, second demodulation multiplexer, decoder,
Described first demodulation multiplexer is used for transmit flow data is carried out demultiplexing, and the data behind the demultiplexing are sent to described multiplexer;
Described multiplexer be used for to the data after the described first demodulation multiplexer demultiplexing of process that receives by each professional or a plurality of business unite carry out multiplexing, and with the metadata cache after multiplexing in described data buffer storage unit; Also be used to accept the control of described control unit, obtain the data cached of target service place and send described second demodulation multiplexer to from described data buffer storage unit;
Described data buffer storage unit be used to store described multiplexer by each professional or a plurality of business unite and carry out data cached after multiplexing;
Described control unit is used to receive and changes the described multiplexer of platform instruction back control and obtain the data cached of target service place and send described second demodulation multiplexer to from described data buffer storage unit;
Described second demodulation multiplexer is used for the data cached demultiplexing that carries out to the target service place, and the data behind the described demultiplexing are carried out descrambling, unpack and be reduced to the primary flow data, and the described primary flow data allocations after will unpacking is to described decoder;
Described decoder is used to receive the described primary flow data that described second demodulation multiplexer distributes, and described primary flow data are decoded.
Optionally, described transmit flow data derives from same frequency.
Optionally, described transmit flow data is the scrambled code flow data.
Optionally, also comprise condition receiving system, described second demodulation multiplexer comprises descrambling module, the data of described second demodulation multiplexer after to described demultiplexing are carried out descrambling and are comprised: the Entitlement Control Message data and the Entitlement Management Message data that are received the target service that comprises in the data behind the described second demodulation multiplexer demultiplexing by described condition receiving system, and described Entitlement Control Message data and Entitlement Management Message data decryption obtained the control word of target service, the descrambling module of described second demodulation multiplexer carries out descrambling by the data of described control word after to demultiplexing.
Optionally, described first demodulation multiplexer and second demodulation multiplexer include PID (Packet Identification) passage more than 2 road or 2 tunnel.
Optionally, the data behind the described first demodulation multiplexer demultiplexing of described multiplexer reception process comprise video data, voice data, synchrodata.
Optionally, the form of the data behind the described first demodulation multiplexer demultiplexing of described multiplexer reception process is transport stream format or grouping primary flow form or primary flow form.
Optionally, the quantity of described multiplexer is more than 1 group or 1 group, described multiplexer to the data after the described first demodulation multiplexer demultiplexing of process that receives by each professional or a plurality of business unite and carry out multiplexing comprising: every group of multiplexer receive the various data of a business behind the described first demodulation multiplexer demultiplexing or a plurality of business and by each professional or a plurality of business unite and carry out multiplexing it.
Optionally, described control unit receives and changes the described multiplexer of platform instruction back control to obtain the place of target service from described data buffer storage unit data cached and send described second demodulation multiplexer to and comprise: described control unit receives and changes platform instruction back control and target service is carried out that multiplexing group multiplexer obtain the data cached of target service place and send described second demodulation multiplexer to from described data buffer storage unit.
Optionally, every group of multiplexer shared described data buffer storage unit, carries out data cached after multiplexing and all is stored in described data buffer storage unit separately a business or a plurality of business being united.
Optionally, described data buffer storage unit is integrated among the described multiplexer, comprise a plurality of metadata cache subelements, every group of multiplexer comprises a described metadata cache subelement, a business or a plurality of business united data cached being stored in the described separately metadata cache subelement of carrying out after multiplexing.
Optionally, described data buffer storage unit to described multiplexer the data after multiplexing to carry out the data in buffer amount be 0.5 second to 1 second data quantity transmitted.
Optionally, described second demodulation multiplexer comprises that to the data cached demultiplexing that carries out at target service place the data cached demultiplexing that carries out to described target service place obtains the GOP header data, obtains the first frame GOP data by described GOP header data.
Optionally, described decoder comprises Video Decoder and audio decoder, described primary flow data comprise video primary flow data and audio frequency primary flow data, described decoder receives the described primary flow data that described second demodulation multiplexer distributes, and described primary flow data are decoded comprises respectively and by described Video Decoder and audio decoder video primary flow data and audio frequency primary flow data that described second demodulation multiplexer distributes being decoded.
Compared with prior art, the present invention has the following advantages:
For through the transmit flow data of scrambling by the described first demodulation multiplexer demultiplexing after, carry out the data multiplexing and transmission of buffer memory a period of time by adding the data of many group multiplexers after to demultiplexing, make to receive and to carry out demultiplexing and to finish descrambling the data cached of target service place by described second demodulation multiplexer that has descrambling module after changing platform instruction at once, rapid output image and sound, shortened greatly with changing in the frequency time of delay that platform produces, obviously strengthened user experience.
Only the data cached of target service place carried out demultiplexing and finish descrambling owing to have described second demodulation multiplexer of descrambling module, described condition receiving system only needs to decrypt the control word of target service transport stream, therefore has applicability widely.
Description of drawings
Fig. 1 is the channel switching method schematic flow sheet of digital television receiving apparatus provided by the invention;
Fig. 2 is by PSI demultiplexing schematic diagram;
Fig. 3 is a GOP frame structure schematic diagram in the video packets of data;
Fig. 4 is a kind of example structure schematic diagram of digital television receiving apparatus provided by the invention;
Fig. 5 is the another kind of example structure schematic diagram of digital television receiving apparatus provided by the invention.
Embodiment
For above-mentioned purpose of the present invention, feature and advantage can more be become apparent, the specific embodiment of the present invention is described in detail below in conjunction with accompanying drawing.
Set forth detail in the following description so that fully understand the present invention.But the present invention can be different from alternate manner described here and implements with multiple, and those skilled in the art can do similar popularization under the situation of intension of the present invention.Therefore the present invention is not subjected to the restriction of following public embodiment.
As analyzing in the background technology, traditional Digital Television channel switching method can produce bigger delay issue in changing the platform process, make thus that to change platform speed slack-off, it is big uncomfortable that the user is brought when watching that Digital Television is changed platform, so the present invention proposes a kind of channel switching method of digital television receiving apparatus, as shown in Figure 1, Fig. 1 is the channel switching method schematic flow sheet of digital television receiving apparatus provided by the invention.The channel switching method of digital television receiving apparatus provided by the invention comprises:
Step S101 carries out demultiplexing with transmit flow data;
Step S102, with the data behind the demultiplexing by each professional or a plurality of business unite and carry out multiplexingly, and the data after multiplexing are carried out buffer memory;
Step S103, receive change platform instruction after, obtain the data cached of target service place;
Step S104 to the data cached demultiplexing that carries out at described target service place, and carries out descrambling to the data behind the described demultiplexing, unpacks and is reduced to the primary flow data;
Step S105 will decode through the described primary flow data after unpacking.
Wherein, transmit flow data described in the step S101 can transmit by multiple Channel Transmission mode, for example ground digital television broadcast, digital video broadcast-satellite and Cable Network network, and derive from same frequency in certain channel, and be the scrambled code flow data.Described transmit flow data specifically is by the frequency on the locking digital television transmission channel such as tuner in the digital television receiving apparatus (for example Cable Network, terrestrial broadcasting digital tv network etc.), and carries out rectification by the signal that demodulator sends tuner and obtain.Because comprised a plurality of business data of (comprising audio/video program, data service etc.) in the transmit flow data, include video data, voice data, synchrodata and some other data message in each professional data again, these data (ES bag) are to carry out multiplexing back again and form transport stream (TS) and transmit by breaking into one by one packet (PES bag) according to certain encoding and decoding standard (for example the most frequently used Moving Picture Experts Group-2), so need carry out demultiplexing to distinguish the data of these different business to transmit flow data at receiving terminal.The structure length of transport stream is 188 bytes, is divided into packet header and bag load two parts.Packet header mainly comprises sync byte and Packet Identifier (PID, PacketIdentification) and other information, sync byte is used to refer to a TS and unwraps the beginning, and PID represents the type of TS bag, TS can be gone up the TS bag that comes from different ES according to PID and distinguish, to rebuild original ES.For example the bag of the audio frequency PES in program can possess same PID after being converted into the TS bag, and like this, receiving terminal only need receive the TS bag with this PID, just the audio frequency of this program can have been separated out.The bag load is the actual content of bag, as the case may be, can place PES bag or program specific information (PSI, Program Specific Information) bag.PSI is used for explanation: 1 program how many PES is made of; 1 program which PES is made of; Under which PID situation, can find each packet (PES) among the TS.PSI wraps in and occupies critical role in the transmission flow demultiplexing, it defines the structure of code stream by four forms, be respectively Program Association Table (PAT, Program Association Table), Program Map Table (PMT, Program Map Table), CAT Conditional Access Table (CAT, Conditional Access Table) and network information table (NIT, Network Information Table), wherein the most key part is pat table and pmt table.Pat table is a PSI information index table, and its pid value is fixed as 0.In pat table, listed the pid value of the pmt table of all programs in this transmission code stream.If the recipient wishes to receive one of them program, can solve pmt table according to this pid value corresponding to this program, therefrom can inquire the PID of all audio streams relevant, video flowing, synchrodata information, private information, when receiving, just can receive only bag with these pid values with this program.Fig. 2 is by PSI demultiplexing schematic diagram, and as shown in Figure 2, the pid value of pat table is 0, can obtain the pid value of each program correspondence according to pat table, as program 0, and PID=10, corresponding NIT network information table; Program 1, PID=60; Program 20, PID=250 etc.If wish to watch program 20, just obtain the pmt table of program 20 correspondences according to 250 these pid values, further find video packets, audio pack, the synchronization packets of program 20, the pid value of private information bag correspondence again, for example PID is that 500 video packets 1, PID are that 501 video packets 2, PID are 550 audio pack 1, PID is 551 audio pack 2, and PID is that 510 synchronization packets, PID are private information bag of 600 etc.The PES that just can solve Voice ﹠ Video by the TS bag of separating these pid values wraps, and finally solves audio stream and video flowing.The pid value of CAT table is fixed as 1, is used for transmitting enciphered message.Therefore, the process of the demultiplexing described in the step S101 can be handled the PSI table according to above-mentioned principle by a demodulation multiplexer, simultaneously packets such as each audio frequency, video, synchrodata is separated from TS.The described data packet format of separating from TS is generally PES bag, can also further unpack the bag into ES at TS under not by the situation of scrambling, and the described transmit flow data of step S101 is the scrambled code flow data, therefore wouldn't unpack the bag into ES.Certainly, also can from TS, isolate after the packet of Voice ﹠ Video, still export with the form of TS.Therefore, the form of the data after the described demultiplexing can be transport stream format or grouping primary flow form.
After by step S101 transmit flow data being carried out demultiplexing, execution in step S102, with the data behind the demultiplexing by each professional or a plurality of business unite and carry out multiplexingly, and the data after multiplexing are carried out buffer memory.Described by a plurality of business unite carry out multiplexing can be with a plurality of business unite arbitrarily carry out multiplexing, for example, 7 business are arranged on certain frequency, be respectively professional 1 to professional 7, carry out when multiplexing uniting by a plurality of business, can with professional 1, professional 2, professional 4 unite carry out multiplexing, also can with professional 1, professional 2, professional 6, professional 7 unite carry out multiplexing.Particularly, step S102 can realize by a multiplexer, be the data behind the demultiplexing to be united by each business or a plurality of business through the screening back all related datas are repacked (can be to form the TS packet), and the metadata cache after will packing is among a data buffer storage unit, for with changing in the frequency after platform operation takes place, directly can read the data cached of target service place from described data buffer storage unit, be execution in step S103, receive change platform instruction after, obtain the data cached of target service place.Described target service refers to change needs the business that receives after the platform, such as, the user is current, and what watch is program 19, but wished to watch program 20 (supposing that program 20 and program 19 transmit at same frequency), so just, change platform by remote controller, the instruction that remote controller will change platform sends to digital television receiving apparatus (for example digital TV set-top box), receive described change platform instruction after, just can go to obtain the data cached of the program 20 that is cached in described data buffer storage unit.Above-mentioned program 20 just is called target service at this moment.Owing to can be undertaken multiplexing data behind the demultiplexing by each business, also can by a plurality of business unite carry out multiplexing, when being undertaken by each business when multiplexing, the place of target service described in the step S103 data cached is the data cached of target service, and carry out when multiplexing when uniting by a plurality of business, described target service place data cached not only comprises the data cached of target service, comprising also that a plurality of business are united carries out the data cached of other business when multiplexing, can only select the data cached of target service for use by in execution in step S104, filtering as for the data cached of described other business.
Need to prove that the process from step S101 to step S103, the transmit flow data that relates to is the bit stream data through scrambling, comprise target service place data cached of storage, also still is the bit stream data after the scrambling.
Get access to described target service place data cached by execution in step S103 after, execution in step S104 then, to the data cached demultiplexing that carries out at described target service place, and the data behind the described demultiplexing are carried out descrambling, unpack and be reduced to the primary flow data.Particularly, step S104 can finish by a demodulation multiplexer, described target service place data cached carried out in the process of demultiplexing, when not only having comprised the data cached of target service in described target service place data cached but also comprise other business data cached, then need the data cached of described other business filtered, only select the data cached of target service for use.Concrete filtration can be discerned by the PID to packet, when the packet PID that identifies to target service, then chooses this packet demultiplexing, when identifying to other professional packet PID, then abandons this packet.Comprise that at the data cached demultiplexing that carries out to described target service place described in the step S104 the data cached demultiplexing that carries out to described target service place obtains the GOP header data, obtain the first frame GOP data by described GOP header data, the described first frame GOP data are used to export first two field picture (certainly, also should guarantee the output to isochronous audio simultaneously).Under based on the MPEG-2 encoding condition, the first frame GOP data are called as the I frame.For under the condition of efficient compressed encoding, obtaining can random-access high compression ratio, high quality graphic, I, P, three kinds of picture formats of B have been defined among the MPEG-2, be called figure (Intra Picture), prognostic chart (Predicted Picture) and two-dimensional plot (Bidirectional Picture) in the frame, be I figure (I frame), P figure (P frame) and B figure (B frame), be used to represent the frame sequence picture in the 1/30s time interval.Because satisfy random-access requirement, it is just passable only to utilize I frame self-information to carry out intraframe coding, and to satisfy the requirement of high compression ratio and high quality graphic, the intraframe coding of depending merely on the I frame is also not all right, also to add the interframe encode that participates in by P frame and B frame, and the block matching motion compensation prediction, promptly with the causal forecasting of former frame image prediction present image with predict the interpolation prediction of present image with back one two field picture.This just requires intraframe coding and interframe encode balance, and the balance between causal forecasting and interpolation prediction, the result of balance are the unifications of random-access high compression ratio, high quality graphic.Fig. 3 shows GOP frame structure schematic diagram in the video packets of data, as shown in Figure 3, comprise data head and n GOP packet in certain video packets of data, be respectively GOP-1, GOP-2, GOP-3 ... GOP-n, with wherein GOP-1 is that example: GOP-1 comprises header data and n two field picture again, provided information such as image encoding type, code table selection, GOP head opening code, video tape recording time and control code, the processing of B frame in the header data of described GOP-1, can obtain the I frame by described header data; The n two field picture of GOP-1 be expressed as respectively first two field picture, second two field picture, the 3rd two field picture ... the n two field picture, this n two field picture is made up of I frame, P frame, B frame, for example frame sequential is I during coding output
1P
4B
2B
3P
7B
5B
6I
10B
8B
9..., then be I in receiving terminal decoding output frame order
1B
2B
3P
4B
5B
6P
7B
8B
9I
10....Because when needs output first two field picture, just must obtain the I frame, and I frame data capacity is bigger, because of the bandwidth for transmission restriction, can in radio network, high-frequency not broadcast, usually each video frequency program per second I frame data of 2 width of cloth of only having an appointment cause using traditional channel switching method to make delay near 0.5 second (obtaining the time of I frame) when changing platform with frequency just because of this restriction.Therefore, in the specific implementation, data after multiplexing are carried out the data in buffer amount be preferably 0.5 second to 1 second data quantity transmitted, rate bit stream in transmission is under the situation about 40Mb/s, 0.5 second to 1 second data quantity transmitted is 20Mb to 40Mb (being 2.5MB to 5MB), the capacity of the described data buffer storage unit of then selecting for use only need get final product greater than 5MB.Wherein, thereby get up and directly obtain the time saved when changing platform 0.5 a second data quantity transmitted can guarantee can obtain at least an I frame and buffer memory, 1 second data volume of buffer memory then can guarantee to obtain two I frames at least, thereby guarantees can realize with another I frame when mistake appears in one of them I frame.Because it is very low to obtain the probability that continuous two I frames all make mistakes, thus if buffer memory more than 1 second data volume could cause the waste of memory space, and then cause cost to rise.Certainly,, also might obtain the I frame, but can not guarantee that the probability with 100% obtains the I frame, therefore not as alternative scheme if take 0.5 second following data quantity transmitted of buffer memory.To sum up, owing in data in buffer, must obtain the I frame, under the situation of not considering audio-visual synchronization, thereby make video can early export the time of a GOP, promptly about 0.5 second left and right sides time.Certainly, general because the I frame data are bigger, the time in transmission distributes and surpasses 0.1 second usually, if on this factor also considered, then can save 0.6 second left and right sides time altogether.
Described in the step S104 data behind the described demultiplexing being carried out descrambling comprises: the Entitlement Control Message data and the Entitlement Management Message data that receive the target service that comprises in the data behind the described demultiplexing, and described Entitlement Control Message data and Entitlement Management Message data decryption obtained the control word of target service, carry out descrambling by the data of described control word after to demultiplexing.Because the data cached of described target service is the scrambled code flow data, and for the transport stream through scrambling, needing that also it is carried out descrambling just can export by normal decoder, carry out descrambling and then need to obtain two important data in the transport stream: Entitlement Control Message (ECM, Entitle Control Message) and Entitlement Management Message (EMM, Entitle Manage Message), and these two data be stored in described target service data cached with the audio, video data transmission package of target service.Particularly, transport stream is being carried out in the process of demultiplexing, at first in transport stream, seeking PSI, in PSI, finding CAT Conditional Access Table CAT,, finding the EMM data of corresponding encryption according to the PID of the EMM that provides in the CAT table; On the other hand, the condition of carrying in the pmt table by professional correspondence is accepted descriptor (CA descriptor) grammer, can obtain corresponding ECM data.And, also comprise information such as program source, time, classifying content and program price in the ECM data, also comprise address, authorized user message in the EMM data.
In specific embodiment, receive the Entitlement Control Message data and the Entitlement Management Message data of the target service that comprises in the data behind the described demultiplexing, and be by condition receiving system (CAS to the control word that described Entitlement Control Message data and Entitlement Management Message data decryption obtain target service, Conditional Access System) finishes, in many covers condition receiving system of actual operation, operator has a variety of to terminal use's encryption authorization mode, as artificial mandate, the magnetic card mandate, the IC-card mandate, smart card mandate (constituting the card of analysis and judgement ability with IC), center focused addressing mandate is (by control centre's direct addressin mandate, without the plug-in card mandate), the authorization that smart card and central authority are shared etc., wherein, the smart card authorization then is the main flow in present set-top box market.Concrete descrambling process is: when smart card inserts, there is individual distributing key (PDK in the smart card, Personal Distribute Key), smart card at first uses the EMM data decryption of PDK to encrypting, obtain the business cipher key (SK in the EMM data, Service Key) and authorized user message, determine according to the EMM information that solves whether this smart card is authorized to watch this program, if do not authorize and to carry out follow-up deciphering, also just can not watch this program,, obtain and enable SK behind the ECM ECM is deciphered if this card is authorized to, controlled word carries out descrambling by described control word to the transport stream of encrypting at last.Describedly by described control word the transport stream of encrypting is carried out descrambling and can finish, set into described descrambler (descrambling module) back descrambling to through the data behind the transmission flow demultiplexing of scrambling by the control word that will decrypt by a descrambler (descrambling module).
At data cached carry out demultiplexing and the descrambling of execution in step S104 to described target service place, with these data unpack be reduced to the primary flow data after, execution in step S105 will decode through the described primary flow data after unpacking.Particularly, described decoder comprises Video Decoder and audio decoder, described primary flow data comprise video primary flow data and audio frequency primary flow data, described will the decoding through the described primary flow data after unpacking comprise through the video primary flow data after unpacking with audio frequency primary flow data are respectively allocated to described Video Decoder and described audio decoder is decoded, and after decoding by a display unit output image and a sound.Described decoding back output image and sound had both comprised decoding back output image and sound, also comprised image and sound that output is follow-up.During concrete enforcement, after execution in step S104 obtains the first frame GOP data, these data are unpacked be reduced to primary flow data (video primary flow data), together be respectively allocated to described Video Decoder and described audio decoder decode back output first two field picture and sound through the audio frequency primary flow data after unpacking.Just finished the operation of changing platform after changing platform instruction and exporting first two field picture and sound receiving, follow-up step equally can be with reference to above-mentioned steps S101 to S105, difference is to some extent, after changing platform, export in the process of follow-up image and sound, no longer need " receive and change platform instruction back " this condition among the step S104, but (by selected multiplexer) directly obtains the data cached of target service place.In actual implementation process, receive the front and back of changing the platform instruction, the process of among the step S102 data after multiplexing being carried out buffer memory is a continuous firing, guarantee the continuity of data on the one hand, promptly do not have the data can be by the people for losing, what data in buffer also can be used for responding the user at any time on the other hand changes the platform operation next time.
Based on the channel switching method of digital television receiving apparatus of the present invention, also provide a kind of digital television receiving apparatus.Fig. 4 shows a kind of example structure schematic diagram of digital television receiving apparatus provided by the invention, as shown in Figure 4, described digital television receiving apparatus comprises: first demodulation multiplexer 201, multiplexer 202, data buffer storage unit 203, control unit 204, second demodulation multiplexer 205, decoder 206, described first demodulation multiplexer 201 is used for transmit flow data is carried out demultiplexing, and the data behind the demultiplexing are sent to described multiplexer 202; Described multiplexer 202 be used for to the data after described first demodulation multiplexer of process 201 demultiplexings that receive by each professional or a plurality of business unite carry out multiplexing, and with the metadata cache after multiplexing in described data buffer storage unit 203; Described multiplexer 202 also is used to accept the control of described control unit 204, obtains the data cached of target service place and sends described second demodulation multiplexer 205 to from described data buffer storage unit 203; Described data buffer storage unit 203 be used to store described multiplexer 202 by each professional or a plurality of business unite and carry out data cached after multiplexing; Described control unit 204 is used to receive and changes the described multiplexer 202 of platform instruction back control and obtain the data cached of target service place and send described second demodulation multiplexer 205 to from described data buffer storage unit 203; Described second demodulation multiplexer 205 is used for the data cached demultiplexing that carries out to the target service place, and the data behind the described demultiplexing are carried out descrambling, unpack and be reduced to the primary flow data, and the described primary flow data allocations after will unpacking is to described decoder 206; Described decoder 206 is used to receive the described primary flow data that described second demodulation multiplexer 205 distributes, and described primary flow data are decoded.
Described digital television receiving apparatus also comprises condition receiving system 207, described second demodulation multiplexer 205 comprises the descrambling module (not shown), data behind 205 pairs of described demultiplexings of described second demodulation multiplexer are carried out descrambling and are comprised: by the Entitlement Control Message data and the Entitlement Management Message data of the target service that comprises in the data behind described second demodulation multiplexer, 205 demultiplexings of described condition receiving system 207 receptions, and described Entitlement Control Message data and Entitlement Management Message data decryption obtained the control word of target service, the descrambling module of described second demodulation multiplexer 207 carries out descrambling by the data of described control word after to demultiplexing.
In the specific embodiment, described digital television receiving apparatus can be digital TV integrated machine or digital TV set-top box, described transmit flow data can transmit by multiple Channel Transmission mode, for example ground digital television broadcast, digital video broadcast-satellite and Cable Network network, and derive from the same frequency in certain channel, and be the scrambled code flow data.Described condition receiving system 207 depends on its included condition reception descrambling storehouse and comes described Entitlement Control Message data and Entitlement Management Message data decryption are obtained control word.In many covers condition receiving system of actual operation, operator has a variety of to terminal use's encryption authorization mode, and the smart card authorization then is the main flow in present set-top box market.When described second demodulation multiplexer 205 has the descrambling ability because of having descrambling module, a plurality of professional corresponding ECM place transmission package together can be received by described first demodulation multiplexer 201 together with the audio, video data transmission package of business and leave in the described data buffer storage unit 203 after described multiplexer 202 is multiplexing, the data de-scrambling process will realize in second demodulation multiplexer 205.Because this way is only carried out demultiplexing and finished descrambling the data cached of target service, its advantage is the ability that not dependence condition receives the descrambling storehouse, has than extensive applicability.Adopt this kind mode, postpone to depend on condition and accept the delay that the descrambling storehouse obtains control word according to the ECM data decryption with changing platform in the frequency, and this delay was generally 0.2～0.3 second when reality is implemented, this is just with having changed whole time of delays of platform in the frequency.
In the specific embodiment, described first demodulation multiplexer 201 and second demodulation multiplexer 205 include the PID passage more than 2 road or 2 tunnel, wherein, described first demodulation multiplexer 201 comprises multichannel PID passage, improve parallel processing capability, for example comprise 32 road PID passages, certainly, also can comprise a plurality of described first demodulation multiplexers in other embodiments; Described second demodulation multiplexer 205 generally comprises 2 road PID passages and gets final product, and 1 the tunnel is used for transmitting video-frequency flow, and 1 the tunnel is used for transmission of audio stream.The quantity of described multiplexer 202 is more than 1 group or 1 group, as shown in Figure 4, be respectively multiplexer 202a, multiplexer 202b, ... multiplexer 202n, the data after described first demodulation multiplexer of process 201 demultiplexings of 202 pairs of receptions of described multiplexer by each professional or a plurality of business unite and carry out multiplexing comprising: a business or a plurality of business that every group of multiplexer receives after described first demodulation multiplexer, 201 demultiplexings (comprise audio/video program, data service etc.) various data (comprise video data, voice data, synchrodatas etc.) professional or a plurality of business are united and are carried out multiplexing to it and by each.Described control unit 204 receives and changes the described multiplexer 202 of platform instruction back control and obtain the data cached of target service place and send described second demodulation multiplexer 205 to from described data buffer storage unit 203 and comprise: described control unit 204 receives and changes platform instruction back control and target service is carried out that multiplexing group multiplexer obtain the data cached of target service place and send described second demodulation multiplexer 205 to from described data buffer storage unit 203.Certainly, owing to can be undertaken multiplexing by each business through the data behind first demodulation multiplexer, 201 demultiplexings, also can by a plurality of business unite carry out multiplexing, when being undertaken by each business when multiplexing, described target service place data cached is the data cached of target service, and carry out when multiplexing when uniting by a plurality of business, described target service place data cached not only comprises the data cached of target service, comprising also that a plurality of business are united carries out the data cached of other business when multiplexing, filter during as for the data cached data cached demultiplexing that can be by 205 pairs of described target service of second demodulation multiplexer place of described other business, only select the data cached of target service for use.For example, undertaken under the multiplexing situation by each business, the user is current to watch audio/video program 19, that suppose this moment business datum to be carried out multiplexing process is multiplexer 202a, want to watch audio/video program 20 (supposing that program 20 and program 19 transmit at same frequency) and work as the user, when changing the platform operation, that suppose this moment target service to be that the data of audio/video program 20 carry out multiplexing process is multiplexer 202b, then choose multiplexer 202b, control it and obtain the data cached of audio/video program 20 and send described second demodulation multiplexer 205 to by described control unit 204.And carry out under the multiplexing situation uniting by a plurality of business, the user is current to watch audio/video program 19, suppose that be still multiplexer 202a to what business datum was carried out multiplexing process this moment, want to watch audio/video program 20 (supposing that program 20 and program 19 transmit at same frequency) and work as the user, the business datum of supposing audio/video program 20 and audio/video program 21 is by multiplexer 202b associating multiplexing process, when changing the platform operation, then choose multiplexer 202b by described control unit 204, controlling it obtains the data cached of audio/video program 20 places and sends described second demodulation multiplexer 205 to, described second demodulation multiplexer 205 is in follow-up demultiplexing process, data cached filtration the to audio/video program 20 places, only select the business datum of audio/video program 20 for use, and abandon the business datum of audio/video program 21.The quantity of described multiplexer can be chosen for 7 groups, because consider existing bandwidth condition, can be multiplexed on the same frequency video frequency program about 7 covers transmit, 7 groups of multiplexers are set can carry out multiplexing process to each the road business on the frequency by one group of multiplexer, and also convenient simultaneously described control unit 204 manages control.Certainly, choosing of the quantity of described multiplexer is arbitrarily, can only choose 1 group of multiplexer in other embodiments, do not influence enforcement of the present invention.In the present embodiment, every group of multiplexer is to adopt the mode of sharing described data buffer storage unit 203, and every group of multiplexer will be separately united a business or a plurality of business and carried out data cached after multiplexing and all be stored in described data buffer storage unit 203.203 pairs of described multiplexer 202 multiplexing data afterwards of described data buffer storage unit are carried out the data in buffer amount and are preferably 0.5 second to 1 second data quantity transmitted, with front end information source modulation system is that QAM64 is an example, rate bit stream in transmission is under the situation about 40Mb/s, 0.5 second to 1 second data quantity transmitted is 20Mb to 40Mb (being 2.5MB to 5MB), the capacity of the described data buffer storage unit of then selecting for use in the specific embodiment 203 only need get final product greater than 5MB, for example take to share the memory device of 6MB, in other embodiments, described data buffer storage unit 203 also can select for use non-power-failure easily to lose equipment, as the SD card, mmc card, NAND FLASH, USB flash disk, hard disk or remote storage device.Take the form of first in first out (FIFO, First In First Out) storage in the time of buffer memory, guarantee 0.5 second to 1 second be current up-to-date data forever in the data quantity transmitted, also can improve the utilance of described data buffer storage unit 203.
Described decoder 206 can comprise one or more Video Decoders and audio decoder, specifically can be MPEG2@ML decoder and MPEG Audio decoder; Described primary flow data comprise video primary flow data and audio frequency primary flow data; Described decoder 206 receives the described primary flow data that described second demodulation multiplexer 205 distributes, and described primary flow data are decoded comprise respectively by described Video Decoder and audio decoder video primary flow data and audio frequency primary flow data that described second demodulation multiplexer 205 distributes decoded, and after decoding by a display unit output image and a sound.Described decoder 206 decoding back output images and sound had both comprised decoding back output first two field picture and sound, also comprised image and sound that output is follow-up.Described control unit 204 receives and changes platform instruction and by just having finished the operation of changing platform behind described decoder 206 decoding output first two field pictures and the sound, in the decoding output procedure as for follow-up image and sound, described data buffer storage unit 203 is working on, promptly store described multiplexer 202 by each professional or a plurality of business (described business for the business in the frequency) unite and carry out data cached after multiplexing, obtain the data cached of target service place and send described second demodulation multiplexer 205 to from described data buffer storage unit 203 by described multiplexer 202, guarantee the continuity of data so on the one hand, what data in buffer can be used for responding the user at any time on the other hand changes the platform operation next time.
Fig. 5 is the another kind of example structure schematic diagram of digital television receiving apparatus provided by the invention.As shown in Figure 5, different with the example structure schematic diagram shown in Fig. 4 is that in the present embodiment, described data buffer storage unit is integrated among the described multiplexer 302, comprise a plurality of metadata cache subelements, every group of multiplexer comprises a described metadata cache subelement.Consult Fig. 5, described multiplexer 302 comprises many group multiplexers, be respectively multiplexer 302a, multiplexer 302b ... multiplexer 302n, every group of multiplexer includes a data buffer memory subelement, is respectively: multiplexer 302a comprise metadata cache subelement 303a, multiplexer 302b comprise metadata cache subelement 303b ... multiplexer 302n comprises metadata cache subelement 303n.That describes among the function of other parts and realization thereof and the embodiment shown in Fig. 4 in the present embodiment is identical, does not repeat them here.
More than describe for the embodiment of digital television receiving apparatus provided by the invention, described multiplexer can be merged into a combiner with first demodulation multiplexer, also can merge into a combiner with second demodulation multiplexer, and described multiplexer, described second demodulation multiplexer and the included audio decoder of described decoder all can only be realized by software algorithm, also can contain but be not limited to the mode of hardware direct memory access (DMA, Direct Memory Access).And in specific embodiment, all constituents that described digital television receiving apparatus comprises all can be integrated on the same chip.
But the channel switching method of the process reference number radiovisor of platform is changed in the concrete enforcement of described digital television receiving apparatus, does not repeat them here.
In addition, it will be appreciated by those skilled in the art that and realize that all or part of of the foregoing description is to instruct relevant hardware to finish by program, described program can be stored in the computer-readable recording medium, and described storage medium can be ROM, RAM, magnetic disc, CD etc.
To sum up, digital television receiving apparatus provided by the invention and channel switching method thereof have following beneficial effect at least:
For through the transmit flow data of scrambling by the described first demodulation multiplexer demultiplexing after, carry out the data multiplexing and transmission of buffer memory a period of time by adding the data of many group multiplexers after to demultiplexing, make to receive and to carry out demultiplexing and to finish descrambling the data cached of target service by described second demodulation multiplexer that has descrambling module after changing platform instruction at once, rapid output image and sound, under the situation of multiple Channel Transmission mode, ground digital television broadcast for example, digital video broadcast-satellite, and Cable Network network, all can shorten greatly with changing the time of delay that platform produces in the frequency, obviously strengthened user experience, and then can not only promote the performance of digital television receiving apparatus product, also help radio and television departments to promote the conversion process of simulated television to Digital Television.
Only the data cached of target service place carried out demultiplexing and finish descrambling owing to have described second demodulation multiplexer of descrambling module, described condition receiving system only needs to decrypt the control word of target service transport stream, therefore has than extensive applicability.
In addition, finish and change the platform operation to export first two field picture, be unlikely to waste memory space again, under the prerequisite that effectively reduces cost, realize the present invention thereby can guarantee to obtain efficiently the I frame by 0.5 second to 1 second data quantity transmitted of buffer memory.
Though the present invention with preferred embodiment openly as above; but it is not to be used for limiting the present invention; any those skilled in the art without departing from the spirit and scope of the present invention; can utilize the method and the technology contents of above-mentioned announcement that technical solution of the present invention is made possible change and modification; therefore; every content that does not break away from technical solution of the present invention; to any simple modification, equivalent variations and modification that above embodiment did, all belong to the protection range of technical solution of the present invention according to technical spirit of the present invention.
Claims (22)
1. the channel switching method of a digital television receiving apparatus is characterized in that, comprising:
Transmit flow data is carried out demultiplexing;
With the data behind the demultiplexing by each professional or a plurality of business unite and carry out multiplexingly, and the data after multiplexing are carried out buffer memory;
Receive change platform instruction after, obtain the data cached of target service place;
To the data cached demultiplexing that carries out at described target service place, and the data behind the described demultiplexing are carried out descrambling, unpack and be reduced to the primary flow data;
To decode through the described primary flow data after unpacking.
2. the channel switching method of digital television receiving apparatus according to claim 1 is characterized in that, described transmit flow data derives from same frequency.
3. the channel switching method of digital television receiving apparatus according to claim 1 is characterized in that, described transmit flow data is the scrambled code flow data.
4. the channel switching method of digital television receiving apparatus according to claim 1, it is characterized in that, describedly data behind the described demultiplexing are carried out descrambling comprise: the Entitlement Control Message data and the Entitlement Management Message data that receive the target service that comprises in the data behind the described demultiplexing, and described Entitlement Control Message data and Entitlement Management Message data decryption obtained the control word of target service, carry out descrambling by the data of described control word after to demultiplexing.
5. the channel switching method of digital television receiving apparatus according to claim 1 is characterized in that, described data behind the transmit flow data demultiplexing is comprised video data, voice data, synchrodata.
6. the channel switching method of digital television receiving apparatus according to claim 1 is characterized in that, described form with the data behind the transmit flow data demultiplexing is transport stream format or grouping primary flow form.
7. the channel switching method of digital television receiving apparatus according to claim 1 is characterized in that, described data after multiplexing are carried out the data in buffer amount is 0.5 second to 1 second data quantity transmitted.
8. the channel switching method of digital television receiving apparatus according to claim 1, it is characterized in that, the described data cached demultiplexing that carries out to described target service place comprises that the data cached demultiplexing that carries out to described target service place obtains the GOP header data, obtains the first frame GOP data by described GOP header data.
9. a digital television receiving apparatus is characterized in that, comprises first demodulation multiplexer, multiplexer, data buffer storage unit, control unit, second demodulation multiplexer, decoder,
Described first demodulation multiplexer is used for transmit flow data is carried out demultiplexing, and the data behind the demultiplexing are sent to described multiplexer;
Described multiplexer be used for to the data after the described first demodulation multiplexer demultiplexing of process that receives by each professional or a plurality of business unite carry out multiplexing, and with the metadata cache after multiplexing in described data buffer storage unit; Also be used to accept the control of described control unit, obtain the data cached of target service place and send described second demodulation multiplexer to from described data buffer storage unit;
Described data buffer storage unit be used to store described multiplexer by each professional or a plurality of business unite and carry out data cached after multiplexing;
Described control unit is used to receive and changes the described multiplexer of platform instruction back control and obtain the data cached of target service place and send described second demodulation multiplexer to from described data buffer storage unit;
Described second demodulation multiplexer is used for the data cached demultiplexing that carries out to the target service place, and the data behind the described demultiplexing are carried out descrambling, unpack and be reduced to the primary flow data, and the described primary flow data allocations after will unpacking is to described decoder;
Described decoder is used to receive the described primary flow data that described second demodulation multiplexer distributes, and described primary flow data are decoded.
10. digital television receiving apparatus according to claim 9 is characterized in that described transmit flow data derives from same frequency.
11. digital television receiving apparatus according to claim 9 is characterized in that, described transmit flow data is the scrambled code flow data.
12. digital television receiving apparatus according to claim 9, it is characterized in that, also comprise condition receiving system, described second demodulation multiplexer comprises descrambling module, the data of described second demodulation multiplexer after to described demultiplexing are carried out descrambling and are comprised: the Entitlement Control Message data and the Entitlement Management Message data that are received the target service that comprises in the data behind the described second demodulation multiplexer demultiplexing by described condition receiving system, and described Entitlement Control Message data and Entitlement Management Message data decryption obtained the control word of target service, the descrambling module of described second demodulation multiplexer carries out descrambling by the data of described control word after to demultiplexing.
13. digital television receiving apparatus according to claim 9 is characterized in that, described first demodulation multiplexer and second demodulation multiplexer include the PID passage more than 2 road or 2 tunnel.
14. digital television receiving apparatus according to claim 9 is characterized in that, described multiplexer receives through the data behind the described first demodulation multiplexer demultiplexing and comprises video data, voice data, synchrodata.
15. digital television receiving apparatus according to claim 9 is characterized in that, the form that described multiplexer receives through the data behind the described first demodulation multiplexer demultiplexing is transport stream format or grouping primary flow form or primary flow form.
16. digital television receiving apparatus according to claim 9, it is characterized in that, the quantity of described multiplexer is more than 1 group or 1 group, the data of described multiplexer after to the described first demodulation multiplexer demultiplexing of process that receives by each professional or a plurality of business unite and carry out multiplexing comprising: every group of multiplexer receive the various data of a business behind the described first demodulation multiplexer demultiplexing or a plurality of business and by each professional or a plurality of business unite and carry out multiplexing it.
17. digital television receiving apparatus according to claim 16, it is characterized in that described control unit receives and changes the described multiplexer of platform instruction back control and obtain the data cached of target service place and send described second demodulation multiplexer to from described data buffer storage unit and comprise: described control unit receives and changes platform instruction back control and target service is carried out that multiplexing group multiplexer obtain the data cached of target service place and send described second demodulation multiplexer to from described data buffer storage unit.
18. digital television receiving apparatus according to claim 16 is characterized in that, every group of multiplexer shared described data buffer storage unit, carries out data cached after multiplexing and all is stored in described data buffer storage unit separately a business or a plurality of business being united.
19. digital television receiving apparatus according to claim 16, it is characterized in that, described data buffer storage unit is integrated among the described multiplexer, comprise a plurality of metadata cache subelements, every group of multiplexer comprises a described metadata cache subelement, a business or a plurality of business united data cached being stored in the described separately metadata cache subelement of carrying out after multiplexing.
20. digital television receiving apparatus according to claim 9 is characterized in that, it is 0.5 second to 1 second data quantity transmitted that described data buffer storage unit carries out the data in buffer amount to the multiplexing data afterwards of described multiplexer.
21. digital television receiving apparatus according to claim 9, it is characterized in that, described second demodulation multiplexer comprises that to the data cached demultiplexing that carries out at target service place the data cached demultiplexing that carries out to described target service place obtains the GOP header data, obtains the first frame GOP data by described GOP header data.
22. digital television receiving apparatus according to claim 9, it is characterized in that, described decoder comprises Video Decoder and audio decoder, described primary flow data comprise video primary flow data and audio frequency primary flow data, described decoder receives the described primary flow data that described second demodulation multiplexer distributes, and described primary flow data are decoded comprises respectively and by described Video Decoder and audio decoder video primary flow data and audio frequency primary flow data that described second demodulation multiplexer distributes being decoded.
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