A static location is a natural environment for a terrestrial Set-Top box in the world of digital television (DTV). On the other hand, the automotive world implies mobility. The blending of these two worlds introduces new circumstances that result in a new engineering problem needing a solution. Motivation behind Television in the car is clear. The future of automotive is self-driving cars, so why not enable the passengers to enjoy the ride while watching their favorite TV show, news, or anything else of interest?
Problems arising from mobility
The mobility of DTV Set-Top-box brings novel issues that need to be solved. First, the cars cross county borders, and an average Set-Top-box does not know how to handle that. Different countries can have different DTV standards, which means that DTV receiver in the car must support multiple DTV standards as well as a run-time change of currently used standard. Even if we look at this issue originating from the car mobility from a narrower perspective, and consider that we are moving within one country, or even one city, potential issues still arise as in distinct parts of the country or the city different TV services can be available to the users, or broadcasting parameters of the same service can change due to various configurations of broadcasting cells. To solve these and similar issues, smart antennas are used.
Smart antenna
From a hardware perspective smart antenna is a set of several regular antennas. What makes it smart is the software that runs in DTV middleware that controls this part of the equipment. The logic implemented in DTV middleware makes sure that the signal coming from the antennas is optimally utilized all the time. It constantly runs a background scan, looking for the changes in the available services. This feature, called signal diversity, has a main goal to always keep the service list up to date. Furthermore, the signal quality levels are constantly being checked on all the available antennas to present the best one to the user and ensure the best possible user experience. Smart routing of the signal from the different antennas to the rest of the system is what makes all this possible and enables the user to consume DTV content on the go without noticing any issues when signal levels change.
Handover
If the same service is broadcasted from two different broadcasting cells, it is most likely that they will not be in perfect synchronization. This means that there will be a small delay between these two signals. To supply the best possible user experience for watching TV in the car, it is necessary to calculate this delay and make a seamless transition between the signals when their quality indicates that the switch is necessary. The delay calculation requires complex DSP processing such as a real-time cross-correlation calculation between two audio signals. To achieve the smooth transition from one signal to another, the results obtained from the cross-correlation calculation are applied to DTV time markers, such as PTS and DTS, to find the exact frame when the switch should occur.
Streaming
In-vehicle infotainment (IVI) unit does not have a direct access to the antennas; therefore a dedicated system architecture is needed to ensure that DTV content can reach IVI and be presented on its display screen. For this purpose, a server-client architecture is developed. The server controls the smart antennas and shares the received signal with the client, DTV middleware in this case. SOME/IP protocol, native to automotive world, is used for communication and control between the server and the client, and LIVE555 for the stream sharing. There is a possibility of altering the data on the server side by transcoding, if for example the IVI does not support used AV codecs. Transcoding can be performed on the IVI side as well, if there’s capacity for it, to make server’s side less demanding in terms of processing power and DTV hardware capabilities.
UI application
Finally, the content needs to be presented to the user on an IVI display, hence a touch friendly UI TV application is developed. The application can present all relevant DTV data and is highly controllable and customizable to meet all the requirements of the automotive world. Because 64bit architectures are common for the automotive IVI, while still not so common in the stationary DTV world, to reuse DTV components such as middleware or an UI application, they must be ported on the 64-bit architecture.