CN108882054B - Data packet structure and encapsulation method for STL-SFN transmission process - Google Patents
Data packet structure and encapsulation method for STL-SFN transmission process Download PDFInfo
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- CN108882054B CN108882054B CN201710332187.9A CN201710332187A CN108882054B CN 108882054 B CN108882054 B CN 108882054B CN 201710332187 A CN201710332187 A CN 201710332187A CN 108882054 B CN108882054 B CN 108882054B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
- H04N21/60—Network structure or processes for video distribution between server and client or between remote clients; Control signalling between clients, server and network components; Transmission of management data between server and client, e.g. sending from server to client commands for recording incoming content stream; Communication details between server and client
- H04N21/63—Control signaling related to video distribution between client, server and network components; Network processes for video distribution between server and clients or between remote clients, e.g. transmitting basic layer and enhancement layers over different transmission paths, setting up a peer-to-peer communication via Internet between remote STB's; Communication protocols; Addressing
- H04N21/643—Communication protocols
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
- H04N21/60—Network structure or processes for video distribution between server and client or between remote clients; Control signalling between clients, server and network components; Transmission of management data between server and client, e.g. sending from server to client commands for recording incoming content stream; Communication details between server and client
- H04N21/63—Control signaling related to video distribution between client, server and network components; Network processes for video distribution between server and clients or between remote clients, e.g. transmitting basic layer and enhancement layers over different transmission paths, setting up a peer-to-peer communication via Internet between remote STB's; Communication protocols; Addressing
- H04N21/643—Communication protocols
- H04N21/64322—IP
Abstract
The invention provides a data packet structure and a packaging method for STL-SFN transmission process, the data packet structure comprises: an 8-bit PLP number field, an 8-bit content type field, a 16-bit frame sequence number field, a 16-bit packet sequence number field, a 32-bit data packet length field, a 64-bit presentation time field, and a 16-bit checksum field. The data packaging method comprises the following steps: the data packets are encapsulated at the data source to provide the broadcast gateway with the required information and encapsulated again at the broadcast gateway to provide the exciter with the required information. The same header field is adopted in the two times of encapsulation, and only the fields which are not added or need to be modified in the first time of encapsulation are modified in the second time of encapsulation. Compared with the packaging method of two layers of IP packets in the current STL protocol, the invention saves the overhead of transmitting the header, improves the network utilization rate and saves the processing time of the header.
Description
Technical Field
The invention relates to the field of digital television transmission, in particular to a data packet header structure and an encapsulation method for an STL-SFN transmission process.
Background
In the process of three-network convergence, the IP of the broadcast network plays an important role. The technical characteristics of telecommunication networks, computer networks and broadcast television networks tend to be consistent, and a new generation of broadcast television standards supports IP protocols.
The ATSC3.0 standard, which is established by the american Advanced Television Services Committee (ATSC), is a broadcast television protocol standard based on IP data stream transmission, which performs physical partitioning of ethernet segments, defines a transmission link from a video source to an exciter as an SFN-STL link, and accordingly establishes an STLTP transmission protocol.
The protocol uses a two-layer IP/UDP/RTP structure to realize the segmentation of an inner-layer long data packet into an outer-layer small data packet. The structure is flexible and can well support various conditions. But this structure is too redundant and a total of 320 bits of data header overhead is really useful of 167 bits only.
At present, no explanation or report of the similar technology of the invention is found, and similar data at home and abroad are not collected.
Disclosure of Invention
The present invention is directed to reducing data header overhead in an STL-SFN procedure while enabling full support of the functionality required by the protocol.
The invention is realized by the following technical scheme.
According to an aspect of the present invention, there is provided a datagram header structure for an STL-SFN transmission procedure, the datagram header structure having a total of 20 bytes, comprising:
-an 8-bit PLP number field for indicating the PLP number of the current packet;
-an 8-bit content type field for indicating the type number of the data packet;
-a 16bit frame sequence number field for marking the physical layer frame to which the data packet belongs;
-a 16bit packet sequence number field for recovering the order of the data packets at the receiving end;
-a 32bit packet length field defining the length of the entire STL packet;
-a 64bit presentation time field for indicating the latest time that the current packet needs to be processed;
a 16-bit checksum field for verifying whether the current packet is complete.
Preferably, the value of the PLP number field ranges from 0 to 65; where 0 to 63 are used for data transmission, 64 represents preamble packets, and 65 represents PLP streams of time information (timing) packets required by the exciter, respectively.
Preferably, in the content type field:
bit 0x01 is a baseband frame (BBP) packet;
0x02 bit is preamble (preamble) packet;
bit 0x04 is a time information (timing) packet;
the rest bits in the content type field are reserved bits;
at the data source, the content type field distinguishes upper layer signaling and emergency broadcast information and adds a type definition to the upper layer information as needed.
Preferably, the frame sequence number field starts from 0, and each physical layer frame is sequentially incremented and filled in by the broadcast gateway;
at the data source, the frame sequence number field is also used to mark the same group of GOPs (group of pictures).
Preferably, the packet sequence number field starts from a randomly generated number, and 1 is added to each data packet in sequence to complete the sequence of recovering the data packets at the receiving end.
Preferably, the presentation time field is indicated at the data source as the latest time that the current packet needs to be processed, and when the packet arrives at the broadcast gateway, the presentation time field is rewritten by the broadcast gateway to the latest time that the current packet needs to be processed at the exciter according to the time schedule.
Preferably, the checksum field sums each part of the data packet in turn in units of 16 bits when calculating the checksum, and adds the carry value for the most significant bit to the least significant bit until the most significant bit does not generate a carry.
According to another aspect of the present invention, there is provided a data encapsulation method for an STL-SFN transmission procedure, including the steps of:
step S100, at a data source, writing presentation time into a presentation time field of a data packet header structure according to the presentation time requirement of a data packet to be transmitted currently; filling corresponding content type fields, filling the rest fields if necessary, and setting 0 if not necessary; calculating the checksum of the whole data packet and filling the checksum into corresponding checksum fields; sending the encapsulated data packet;
step S101, after receiving the data packet packaged in step S100, the broadcast gateway allocates the position of the physical layer frame for the data packet according to the presentation time field and the content type field; filling a PLP number field, a frame sequence number field and a packet sequence number field according to the actual scheduling condition of the broadcast gateway; the encapsulated data packet enters a sending queue to wait for sending;
and S102, after the exciter receives the data packet which is packaged again in the S101, confirming a PLP queue to which the current data packet belongs according to a PLP number field, distinguishing whether the current data packet is preamble information or timing information according to a content type field, confirming a physical layer frame to which the current data packet belongs according to a frame number field, determining the sequence of the current data packet according to the packet number field, and correcting if the sequence is wrong.
Compared with the existing transmission protocol, the invention has the following beneficial effects:
1. the invention is used for the STL-SFN data transmission process, reduces the data header overhead, improves the network utilization efficiency and reduces the complexity of terminal data processing.
2. The present invention reduces data header overhead while still supporting all services required by the SFN-STL procedure.
Drawings
Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:
fig. 1 is a schematic diagram of ATSC3.0STL protocol data encapsulation structure.
Fig. 2 is a schematic diagram of a data encapsulation structure after applying the present invention to an ATSC3.0STL-SFN transmission procedure.
Detailed Description
The following examples illustrate the invention in detail: the embodiment is implemented on the premise of the technical scheme of the invention, and a detailed implementation mode and a specific operation process are given. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention.
Example 1
The embodiment provides a new data header structure for data packet encapsulation in the STL-SFN procedure. The new data header format is shown in table 1 and includes: PLP number field (8bit), content type field (8bit), frame number field (16bit), packet length field (32bit), presentation time field (64bit), checksum field (16bit), totaling 160bit (20 Byte).
Wherein, the specific meaning of each field is as follows:
PLP number field: the PLP number of the current packet ranges from 0 to 65. Where, sub-tables 0 to 63 are used for data transmission, 64 represents preamble packets, and 65 represents PLP stream of timing packets required by the exciter.
A content type field: the field indicates the type number of the packet, and currently defines 0x01 bit as a BBP packet, 0x02 bit as a preamble packet, 0x04 bit as a timing packet, and the rest of the bits as reserved bits. At the data source, this field may be used to distinguish upper layer signaling and emergency broadcast information. Type definitions can be added as needed for upper layer information.
Frame sequence number field: starting at 0, each physical layer frame is incremented in turn and filled in by the broadcast gateway. This field is used by the exciter to quickly distinguish the physical frame to which the data belongs. At a data source, this field can be used to mark the same group of GOPs.
Packet sequence number field: starting with a randomly generated number, each packet is incremented by 1. Since UDP is a transport protocol that provides unreliable services, it does not guarantee the order in which packets arrive. This field is added for restoring the order of the data packets at the receiving end.
Packet length field: this field defines the length of the entire STL packet.
Presentation time field: this field indicates the latest time that the current packet needs to be processed. At the data source, this field may represent the latest time that the current video segment needs to be processed. When the packet arrives at the broadcast gateway, the broadcast gateway rewrites this field to the latest time the current packet is to be processed at the exciter, according to the time schedule. This field is 64 bits in total and expresses a completed UTC time (universal coordinated time) in a time format consistent with the transmit reference time in bootstrap.
Checksum field: and the 16-bit checksum is used for verifying whether the current data packet is complete. When the checksum is calculated, each part in the data packet is summed in sequence by taking 16 bits as a unit, and the carry value of the highest bit is added to the lowest bit until the highest bit does not generate a carry.
The datagram header structure for STL-SFN transmission procedure provided in this embodiment defines a 20Byte data header for indicating the data type and presentation time of the current segment in the file stream that the broadcasting gateway needs to obtain from the data source, and also provides a 16-bit checksum field for verifying the correctness of the data packet. When the data packet flows through the broadcast gateway, PLP number, frame number, packet number fields are provided for the broadcast gateway to allocate resources to the data segment. At this point the presentation time field is rewritten to bootstrap reference launch time.
Example 2
The embodiment provides a data packet encapsulation method for an STL-SFN transmission procedure, which specifically includes the following sub-steps:
step S100, writing the presentation time into the presentation time field in the data packet header structure at the data source according to the presentation time requirement of the current data packet to be transmitted. Filling in the corresponding content type field, filling in the rest fields if necessary, and setting 0 if not necessary. And calculating the checksum of the whole data packet and filling the corresponding checksum field. And sending the encapsulated data packet.
And step S101, after receiving the data packet packaged in the step S100, the broadcast gateway allocates the position of the physical layer frame to the data packet according to the presentation time field and the content type field. And filling a PLP number field, a frame sequence number field and a packet sequence number field according to the actual scheduling condition of the broadcast gateway. And the encapsulated data packet enters a sending queue to wait for sending.
And step S102, after the exciter receives the data packet of the repackaging number in the step S101, the PLP queue of the current data packet is confirmed according to the PLP number field, whether the current data packet is preamble information or timing information is distinguished according to the content type field, the physical layer frame to which the current data packet belongs is confirmed according to the frame number field, the sequence of the current data packet is determined according to the packet number field, and if the sequence is wrong, the current data packet is corrected.
Table 1 data header structure fields and length description
The data encapsulation method for the STL-SFN transmission procedure provided by the present embodiment encapsulates the output data stream at the data source, provides the broadcast gateway with the required information, and re-encapsulates at the broadcast gateway to provide the exciter with the required information. The same header field is adopted in the two times of encapsulation, and only the fields which are not added or need to be modified in the first time of encapsulation are modified in the second time of encapsulation. Compared with the method for encapsulating two layers of IP packets in the current STL protocol, the method saves the overhead of transmitting the header, improves the network utilization rate and saves the processing time of the header.
The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes and modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention.
Claims (7)
1. A data header structure for use in an STL-SFN transmission procedure, wherein the data header structure has a total of 20 bytes, comprising:
-an 8-bit PLP number field for indicating the PLP number of the current packet;
-an 8-bit content type field for indicating the type number of the data packet;
-a 16bit frame sequence number field for marking the physical layer frame to which the data packet belongs;
-a 16bit packet sequence number field for recovering the order of the data packets at the receiving end;
-a 32bit packet length field defining the length of the entire STL packet;
-a 64bit presentation time field for indicating the latest time that the current packet needs to be processed;
-a 16bit checksum field for verifying whether the current data packet is complete;
the presentation time field is represented at a data source as the latest time that the current data packet needs to be processed, and when the data packet arrives at the broadcast gateway, the broadcast gateway rewrites the presentation time field into the latest time that the current data packet needs to be processed at the exciter according to time scheduling;
and receiving the encapsulated data packet transmitted by the data source at the broadcasting gateway, filling the PLP number field, the frame sequence number field and the packet sequence number field according to the actual scheduling condition of the broadcasting gateway, and transmitting the encapsulated data packet to the exciter.
2. A data packet header structure for an STL-SFN transmission process in accordance with claim 1, wherein the PLP number field has a value ranging from 0 to 65; where 0 to 63 are used for data transmission, 64 represents a preamble packet, and 65 represents a PLP stream of time information packets required by the exciter, respectively.
3. A datagram header structure for an STL-SFN transmission process in accordance with claim 1, wherein in the content type field:
0x01 bits are baseband frame data packets;
0x02 bit is a preamble packet;
the 0x04 bit is a time information packet;
the rest bits in the content type field are reserved bits;
at the data source, the content type field is also used to distinguish upper layer signaling and emergency broadcast information and to add type definitions as needed for the upper layer signaling.
4. A data packet header structure for an STL-SFN transmission procedure in accordance with claim 1, wherein the frame number field starts from 0 and each physical layer frame is sequentially incremented and filled in by a broadcast gateway;
at the data source, the frame sequence number field is also used to mark the same group of GOPs.
5. A data packet header structure for an STL-SFN transmission procedure in accordance with claim 1, wherein the packet sequence number field starts with a randomly generated number, and each data packet is sequentially incremented by 1 to complete the sequence of recovering data packets at the receiving end.
6. A datagram header structure for an STL-SFN transmission process in accordance with claim 1, wherein the checksum field, when calculating the checksum, sums each portion of the packet in turn in units of 16 bits, adds the carry value for the most significant bit to the least significant bit until the most significant bit does not generate a carry.
7. A method for data encapsulation for an STL-SFN transmission procedure, comprising the steps of:
step S100, at a data source, writing presentation time into a presentation time field of a data packet header structure according to the presentation time requirement of a data packet to be transmitted currently; filling corresponding content type fields, filling the rest fields if necessary, and setting 0 if not necessary; calculating the checksum of the whole data packet and filling the checksum into corresponding checksum fields; sending the encapsulated data packet;
step S101, after receiving the data packet packaged in step S100, the broadcast gateway allocates the position of the physical layer frame for the data packet according to the presentation time field and the content type field; filling a PLP number field, a frame sequence number field and a packet sequence number field according to the actual scheduling condition of the broadcast gateway; the encapsulated data packet enters a sending queue to wait for sending;
step S102, after the exciter receives the data packet which is packaged again in the step S101, the PLP queue to which the current data packet belongs is confirmed according to the PLP number field, whether the current data packet is leading symbol information or time information is distinguished according to the content type field, a physical layer frame to which the current data packet belongs is confirmed according to the frame number field, the sequence of the current data packet is determined according to the packet number field, and correction is carried out if the sequence is wrong;
the presentation time field is represented at the data source as the latest time that the current packet needs to be processed, and when the packet arrives at the broadcast gateway, the presentation time field is rewritten by the broadcast gateway to the latest time that the current packet needs to be processed at the exciter according to the time schedule.
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| CN1552159A (en) * | 2001-07-23 | 2004-12-01 | 汤姆森特许公司 | System and method for broadcast of independently encoded signals on ATSC channels |
| CN106105150A (en) * | 2015-03-01 | 2016-11-09 | Lg 电子株式会社 | For sending the equipment of broadcast singal, for receiving the equipment of broadcast singal, the method sending broadcast singal and the method receiving broadcast singal |
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| CN1552159A (en) * | 2001-07-23 | 2004-12-01 | 汤姆森特许公司 | System and method for broadcast of independently encoded signals on ATSC channels |
| CN106105150A (en) * | 2015-03-01 | 2016-11-09 | Lg 电子株式会社 | For sending the equipment of broadcast singal, for receiving the equipment of broadcast singal, the method sending broadcast singal and the method receiving broadcast singal |
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| ATSC3.0关键技术介绍;何大治等;《电视技术》;20151231;全文 * |
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