Tv reception for dvb-t2 in the car

For the introduction of DVB-T2, a field trial is currently underway in Berlin and munich in Germany. The plans envisage a phased switchover from DVB-T to DVB-T2. The pilot operation will start in 2015/2016, the introduction in 2017, and the widespread operation is expected to take place by 2019. At the same time, the 700 MHz network is being cleared, which will then be available to mobile communications. systems in automobiles must therefore support not only DVB-T2, but also new video compression and encryption, so that the screen does not remain black. This will only work with new devices.

Until now, terrestrial broadcasting of TV programs via antenna was done by DVB-T – in the video format SDTV using MPEG-2 compression. No encryption is planned, which is why some private broadcasters have withdrawn from DVB-T. For mobile TV reception in cars, a number of new standards are therefore becoming the focus of future devices. In detail, these are the DVB-T2 modulation method, HEVC video compression, transmission of content with HD resolution, and encryption via DVB-CI+ (pay TV).

Figure 1: the HD62 evaluation board enables DVB-T2 reception and HEVC decoding. The presentation is done via an external display, which is directly connected via HDMI, CVBS or digital RGB. Socionext

Bavarian broadcasting and the IRT (Institut fur Rundfunktechnik) carried out a field test in munich, in which socionext participated as the only semiconductor manufacturer of HEVC-lsis (Fig. 1). One of the focal points was the interoperability of various HEVC-capable encoders on the transmitter side as well as the corresponding decoders on the receiver side.

Introduction of DVB-T2 in germany

The switchover from DVB-T to DVB-2, often referred to as digital dividend II, is primarily intended to make the 700 MHz range currently used by DVB-T available in the future to broadband services and mobile communications, which have a particularly high demand for transmission capacity. In order to continue to enable a consistent variety of programs via terrestrial broadcasting, the federal cabinet decided at the beginning of 2015 to switch from DVB-T to DVB-T2. This provides a higher bandwidth for TV broadcasting, which compensates for the loss of the 700-mhz band. By 2018, the 700-mhz range should be cleared and the switchover to DVB-T2 should have taken place.

HEVC: high efficiency video coding

If there is a willingness to change the modulation method, then the audio and video compression formats can also be modified, because if the customer is forced to buy a new device anyway, then it makes sense to bring both parts of the chain – both the channel decoding and the compression method – up to the state of the art. For comparison: DVB-T still uses MPEG-2 and broadcasts programs in SD resolution.

DVB-T2 in germany uses HEVC (high efficiency video coding) for video compression, also H.265 called. With HEVC, the latest standard for video compression is used, which in comparison to H.264 should require 40 to 50% less bandwidth with the same picture quality. DVB-T even still uses MPEG-2, so that HEVC brings a data rate gain of factor 4. Although HEVC talks about higher compression, the compression algorithm is still the old one that was used for MPEG and H.264 came into use. In contrast, tools that contribute to picture enhancement have been expanded. With these measures, it is possible to significantly reduce the data rate while maintaining the same subjective picture quality.

The combination of DVB-T2 and HEVC thus offers the possibility of an expanded variety of channels or also a high-quality broadcast of all programs in HD. With the introduction of HEVC, germany is a pioneer in the broadcast sector.

Image formats: everything in HD

Figure 2: the block diagram of the HD62 shows the most important components for in-car TV receivers. Socionext

The DVB guidelines (ETSI TS 101 154 v2.2.1) do not define a classic SD format with 720 x 575i, so that this format is not even provided for in the standard. The only format that comes close is the so-called quarter-HD format with a resolution of 940 x 540 p. At this resolution, we also say goodbye to line jumping and only broadcast full frames.

Even though there is a lot of talk about UHD, 4k is not economically viable in the terrestrial sector at present. The data rate of UHD is, purely in terms of the number of pixels, about four times as high as that of an HD picture. In addition, only high dynamic range (HDR), frame rates of 120 fps and an expanded color space trigger the desired wow effect in the viewer’s car – high resolution alone is not yet a sufficient quality criterion. With all these measures, the bandwidth requirement increases considerably, which is not available in the terrestrial area. The situation is different with satellite or cable. It therefore made sense to use HD as the picture format for DVB-T2.

DVB-CI+

An often underestimated issue in mobile reception is the decoding of copy-protected audio and video content. In the field of encryption technologies, there is a broad market of different conditional access providers. Although the systems often work according to the same principle, they have very different security requirements and are also implemented in different countries. Elaborate certifications are necessary, for which parallel support of several CA systems is not envisaged. One solution in the automotive sector is DVB-CI+. Using a suitable CI+ module and a smart card from the pay TV provider, this provides a flexible method for any CA system to decrypt audio and video content. However, the system must be very secure. In addition to the encryption method, an in-car TV receiver must therefore also offer a secure environment for the keys. Debugging port protection, secure boot and special fuse technologies are among the minimum requirements. especially the fuse technology is an easy point of attack for hackers, because the fuse traces quickly reveal bit patterns of the keys under the electron microscope. Closing the debugging port is unpopular with developers, because there are then hardly any possibilities for error analysis. Developers should therefore ensure that no functions other than TV reception are performed on the chip.

Key data

Automobile manufacturers who want to enable TV reception in vehicles must prepare for DVB-T2 in good time because, at least in Germany, the current DVB-T is to be switched off by the end of the decade. DVB-T2 enables HDTV reception. Now there is a suitable multi-format HD decoder in the form of the HD62.

In germany, the commercial broadcasters are planning to use copy protection. With the changeover from DVB-T to DVB-T2 in Austria, basic encryption of all programs has already been introduced – also for the public broadcasters. In japan, all programs except the 1-segment are encrypted with the block cipher-multi-2. The encryption capabilities are an essential part of the commercial success of a transmission system.

HD62 multi-format HD decoder

The HD62 is a multi-format HD decoder (Fig. 2) that can process up to 4 MPEG2 transport streams received from a DVB-T2 demodulator – a functionality required, for example, for multi-antenna reception or diversity. Two HEVC programs can be decoded and displayed simultaneously in HD. For graphical support, for example of hbbtv content, there is an opengl2.0-compatible 3D engine in use. A medialb-interface suitable for MOST150 is also available. If the data is to be streamed further to a smartphone or tablet, the built-in H.264 encoders are used to create a video format with the appropriate resolution and frame rate.

Socionext has developed the security elements integrated on the chip over many years and had them tested for hacker attacks by independent companies. HD62 supports audio decoding of the formats MPEG (layer 1 and 2), MP3, HE-AAC and dolby digital; other formats can be added with little effort. The chip complies with AEC-Q100 and is in mass production since mid-2015.

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