# Hardware Update through Digital TV Signals
## 3 Hardware Data Broadcast through a Digital TV Signal  
DTV TSs consist of packets with audio, video, and data and are 188 bytes in length. TS packets are the basic TS data unit. They are composed of a sync byte field whose value is 0x47, followed by 3 1-bit fields--a transport error indicator, payload unit start indicator, and transport priority--and an identification (13-bit), known as a packet identifier (PID) [42], among other aspects. The PID information provides a means of differentiating payload content regarding distinct transport units (packets) in a TS. If a PID is allocated and reported to a receiver (through a table), that means a given packet carries video, audio, or other data, according to what was informed. Thus, the broadcast content is identified by its respective PID value. Aside from that, the field transport error indicator can be used for indicating a packet that contains at least one uncorrectable bit error, which may lead an application to discard it, avoiding the use of corrupted data.  
Figure 2 represents a transport stream with different packets consisting of video, audio, program association table (PAT) sections, and hardware payload (PID 0x77). This transport stream slice shows that packets with the same PID and carrying parts of the same information are spaced over time. Demultiplexers then need to filter a transport stream, using the corresponding PIDs for accessing its payload content.  
DTV systems can broadcast binary applications [42] interleaved with other HDTV contents (e.g., audio, video, and data). To inform that an application is being broadcasted, a DTV standard employs the application information table (AIT) [43], which the receiver resident system then uses to download all content related to that same application.  
DTV telecommunication networks allow the broadcasting of several data types. Here, it is essential to consider two main features: the data format and the required synchronization, which are necessary for broadcasting some data types. The formats may be classified into delimited data, un-delimited data, and datagrams following some protocol. Delimited data can be divided into units of predefined size (e.g., files and objects). However, un-delimited data are considered continuous bitstreams. Finally, datagrams correspond to data packets related to a communication protocol (e.g., IPv4 and IPv6).  
Regarding synchronization, the transmitted data are divided into synchronous, synchronized, and asynchronous [44]. Synchronous data have synchronization requirements with other data in the same stream, known as intramedia synchronization. Synchronized data must be presented at predetermined time instances and synchronized with elements of different media (e.g., closed captions), which is called intermedia synchronization. Finally, asynchronous data, in turn, have no temporal synchronization requirements.  
Figure 2: Transport stream packet structure used to carry different data types, which include hardware reconfiguration data.  
The data format characteristics and the required data synchronization are important when choosing the best data broadcasting method.