Graphic channel Business Project

The graphic channel business is a service in the set-top box software. It provides enterprise information for TV users in the form of images and sounds,

Product Information and Related Knowledge are closely related to the life of the audience.

The predecessor of the graphic channel business is the advertising business. During the playback process, images and sounds are changed every fixed period, and

Step, it adopts multi-protocol encapsulation and needs to parse Pat, PMT, DSI, DiI and DDB.

 

Preparations:

Use servict type to find the corresponding serviceid and ts_id In the SDT table, and then use ts_id to find the frequency point in the NIT table

Information, and save it as preparation for future search.

 

Post-Search:

(1) After the frequency lock, download Pat and find the pmt pid through serviceid.

(2) The PMT can be downloaded through PID addressing, and the PID of DSI, DII, and DDB of graphic channels can be parsed in PMT, and

The ID of the forward PID. When use = 0x0000 in the association_tag_descriptor () descriptor of PMT, you can obtain the DSI

And table_id_extension (moduleid ). And put the data into the cache.

Note: The moduleid obtained by this method is not reliable (as mentioned in the Protocol). The other method is: moduleid <= 1.　

 

(3) DSI can be downloaded to DSI by the PID, table_id = 0x3b, and table_id _ extension (moduleid) of DSI. DSI description

Describes the DiI tag and the moduleid in the root directory.

(4) According to the tag in DSI, the PID of the DiI is found in the PMT. The PID of the DII, table_id = 0x3b, and moduleid> 1,

To download to DiI. Dii describes the moduleid, tag, and number of file objects of all file objects.

　　In this case, you can calculate all the PID, tableid, and moduleid of the Service in the transmission stream.

(5) Find the corresponding root tag in DiI through the root moduleid in DSI, and then find the root PID in PMT through the tag,

Root can be downloaded Based on the found PID, table_id = 0x3c, and root moduleid. The moduleid of all files is described in root.

And file name (filename ).

 

Key erdiagram: