A car rear-seat entertainment system that combines a professional entertainment system in the living room with a mobile media source

A car rear-seat entertainment system that combines a professional entertainment system in the living room with a mobile media source

For many years, people thought that the rear seat entertainment system of the car was a DVD player where passengers could watch movies and listen to music. Most car audio and video systems include a DVD drive and a monitor, which may be installed together with the drive or separately installed in the rear seat area. With the continuous development of audio and video systems, infrared or Bluetooth wireless headphones have become increasingly popular, and the codec standards supported by the optical drive are also increasing, such as MP3 or DviX decoding standards. However, the data source of these devices has basically not changed, and is still limited to two media: DVD and CD.

　　The next generation of rear-seat entertainment systems must cover a wider range of data sources, provide stronger interactive support, and integrate more functions within the vehicle infrastructure, which will not only increase the value of OEM original equipment, but also increase the value of dealer-installed equipment or retail equipment.

　　But it is clear that price is one of the key factors for the market to accept the next generation of rear seat entertainment systems now and in the future. Factors affecting price include the overall cost of materials and hardware and software, among which the main one is the cost of software development. This article mainly discusses how to reduce the overall cost of materials and the workload of software development.

　　A good first impression is key to a product gaining widespread market acceptance, and that first impression has a lot to do with how easy the user interface is to operate. Obviously, even a very professional entertainment system will not be accepted by the market if the user interface is slow or interrupted in responding to user commands. Market leaders have proven that a responsive, fast user interface is key to product success. Adding 3D multi-window support can improve the overall ease of use of the system, but this requires additional image processing capabilities.

　　Next-generation rear-seat entertainment system with more features

　　What features will rear-seat entertainment systems have to support in the future? Of course, DVD-Video will be a must for a long time to ensure that the children are happy on the road and your existing disc library can be used for a long time. In addition to DVD-Video, Blu-ray will be the second disc standard supported by the system, because it is very likely that some movie discs will only use the Blu-ray standard in the future. Blu-ray not only has better audio and video performance, but also improved security. Using a blacklist stored on the disc, Blu-ray can prohibit the playback of discs on "cracked" players. The increasing opportunities to experience interactive content (such as games) on Blu-ray players is strong evidence to support the growing market acceptance and also a sales promotion tool.

　　In addition to CDs that carry entertainment content, the new generation of entertainment systems must also consider the function of playing videos from other storage media through USB or e-SATA interfaces, such as SD cards, U disks and mobile hard disks. This will inevitably introduce a large number of audio and video packaging formats into the rear seat entertainment system. Therefore, the system must support a large number of file formats, including DivX, XviD, AVI, RealMedia, 3GP, ASV, MOV, OGM, etc.

　　The rear-seat entertainment system must also consider live content such as TV broadcasts, the most important of which are terrestrial TV broadcast formats such as DVB-T in Europe, ATSC in the United States, ISDB-T in Japan or DTMB in China. In addition, mobile TV formats must be considered, such as DVB-H in Europe, ATSC-M/H in the United States, T-DMB in South Korea and CMMB in China. New TV standards will soon appear, such as DVB-SH, a mobile satellite TV broadcast standard, which is similar to satellite radio broadcasting and is very popular in the United States. New live TV channels will also appear in the market, that is, TV programs transmitted through existing mobile phone infrastructure.

　　Our young generation also needs interactive entertainment content. Data lines connected to the Internet allow them to use various services, such as YouTube, Twitter, Facebook and many other social networking sites. In this regard, it is obvious that the entertainment system architecture also needs to accept web browsers and support common plug-ins. Only in this way can more entertainment services be provided to users, such as web radio and web TV, and as many types of entertainment content as possible. In addition, why not add home media streaming engine access function so that users can remotely access the content recorded at home? This can save the process of transmitting or synchronizing media content between home and car. Of course, these services require data transmission services at least similar to EDGE or HSDPA, and the access service provider should provide a monthly or annual subscription fee strategy. Once popularized, the existing infrastructure will need to be improved or replaced by the fourth generation of mobile communications LTE.

　　In short, the rear seat entertainment system is a combination of a professional entertainment system for the living room and a mobile media source - a mobile living room. The rear seat entertainment system needs to support the commonly used robust functional features, with the flexibility to upgrade to the latest features and enhanced features.

　　How to reduce development costs?

　　How can hardware overcome the challenges of so many features in entertainment systems while keeping development costs low? Obviously, the solution to this problem is mainly to reuse existing platform architectures outside the consumer electronics industry, provide high-end media playback support and various external interfaces. Intense price pressure forces manufacturers to provide cost-effective solutions that are consistent with commonly used features that have been proven in the market.

　ST's entertainment-specific series STi71xx supports high-definition decoding (1080i/p) and multi-channel audio decoding and post-processing. The main application runs on the ST40 processor compatible with the SH4 CPU. The main task of this CPU is to run customer-specific programs and control audio and video signal processing. All audio and video decoding tasks are transferred from the main CPU to two very long instruction word (VLIW) processors. One processor is responsible for audio processing and the other is responsible for video decoding. This method of separating audio and video from CPU applications helps to reduce system complexity and enhance the overall robustness of the entire system. If an error occurs during the processing of corrupted data, the audio and video processors can be easily reset. The use of firmware on two VLW processors increases the flexibility of firmware. Depending on the codec request, the processor can load one or more firmware to support video coding standards (such as H.264, MPEG-2, VC-1 or AVS) and audio coding standards (such as MPEG-2, MP3, WMA, AAC, Dolby, DTS, OggVorbis) and other file formats. In addition, the audio processor performs post-processing functions such as audio signal mixing, sample rate conversion, stereo multi-channel to two-channel mixing (down-mix), and surround sound. The codec can be upgraded by loading new firmware into the processor. Before loading, it is important to make sure that the processor supports new or improved codec standards. The firmware is developed and provided by the chip manufacturer, so application developers do not have to worry about firmware development and maintenance. Moreover, the driver ensures that the firmware is correctly integrated into the main application. Because the firmware is very flexible, the decoder can also be used for audio and video encoding and transcoding, changing the format and/or transmission rate of existing bitstreams. The application memory is a 32-bit DDR2 memory that can be directly accessed by the three CPUs, which ensures that the bandwidth-consuming processor has priority access to the memory.

　　In addition to multiple CPUs, the 71xx series SoCs also provide video output stages, audio output stages, and peripheral interfaces. The video output stage provides analog and digital video outputs. Depending on the system architecture, you can choose CVBS, Y/C, RGB for analog connections, or digital RGB, YCrCb, or HDMI for digital connections. The 71xx series supports two independent video signal outputs, allowing two rear-seat displays (left and right) to be driven with one decoder. The audio output supports multi-channel digital I2S outputs including parallel stereo mix signals. In parallel stereo, an on-chip DAC provides stereo analog signals compatible with headphone jacks, eliminating the need for an external DAC. Digital audio signals can be transmitted to a remote audio amplifier via a car audio network such as MOST. In addition, the series provides a multi-channel output with S/PDIF capabilities. All STi71xx series products are equipped with a digital audio and video input, allowing the rear-seat entertainment system to connect other audio and video devices, such as digital cameras.

　　The system chip concept can provide many of the most commonly used peripheral interfaces. Some products in the STi71xx series provide two USB 2.0 ports with embedded physical layer chips, which can be connected to USB flash drives, mobile hard drives, UMTS/HSDPA wireless network cards, etc. If more on-chip host ports are needed, the number of USB ports can be expanded using an on-board hub.

　　For connecting hard disk drives and optical drives such as Blu-ray or DVD within applications, the STi71xx series provides two SATA interfaces. For connecting external SATA devices, these interfaces also support the e-SATA standard. For connecting old DVD drives, the EMI port also provides a traditional ATAPI parallel port, which is a 16-bit data bus.

　　There are several ways to access the Internet in a car. You can plug in a UMTS / HSDPA dongle on the USB port or connect to the existing communication equipment in the car via Ethernet. The Ethernet cable can be either wired or optical, depending on the existing infrastructure in the car. An external UMTS / HSDPA dongle avoids the problem of certifying the entire system in each country or region. If the end user plugs in a USB dongle, he or she will need to deal with network compatibility and service provider contracts. Bluetooth and WiFi connectivity are easy to implement by adding a two-in-one device that supports one or both formats. The SDIO interface allows the entertainment system to add an SD or MMC card reader. For example, users can view photos in a digital camera and expand the memory capacity for recording TV programs. The on-chip infrared transceiver supports remote control functions. In addition, the chip is equipped with peripheral interfaces such as I2C, SPI, UART, GPIO, etc.

　　In terms of digital TV support, the STi71xx series provides up to three code stream input channels, one or two of which are used for real-time playback decoding, and the third is used for background TV recording, channel scanning or data services. Compared with home set-top boxes, car TVs need to be prepared to adjust the frequency because cars are in motion most of the time. In order to be able to handle encrypted content, the STi71xx series has an on-chip encryption core that can decrypt major copy protection formats, such as TV recording protection, DVD-Video, Blu-ray and streaming media copy protection. The keys required for the decryption process can be accessed through two smart interfaces. Alternatively, a conditional access module can be connected to the chip, providing the system with the flexibility to connect a local encryption module. A NAND flash memory can be used to store applications and media files or TV recordings for time-shifted viewing. Flash memory can replace the internal hard drive, without solving the problem of data access during the bumpy ride of the car.

　　To operate the STi71xx family, only one 30 MHz oscillator is needed. The family has an on-chip frequency synthesizer and voltage-controlled crystal oscillator to generate the audio and video decoding clock and the system clock independently, for example, so that it can be synchronized with the broadcaster's clock. Compared with other solutions that require multiple clock sources, one oscillator can reduce the bill of materials cost.

　　The power supply must provide four voltages: 1.2V core voltage, 1.8V DDR2 memory voltage, 2.5V and 3.3V peripheral interface voltages. The average power consumption is about 2W, which is related to the application being executed. The next generation of products will focus on reducing power consumption. Driven by the "green" concept and the mobility of media processors, the next generation of products will not only reduce working power consumption, but also reduce standby power consumption.

　This is a brief introduction to the STi71xx family of products from a technical functional level, some of which can achieve automotive-grade quality standards for OEM applications. More detailed product and system information is available upon request.

　　Software is another aspect of solving the problem of how to reduce development costs. It is not cost-effective to develop a multimedia software stack from scratch. The surge in the number of codecs and packaging formats has greatly increased the cost of software development. In this regard, chip providers provide a lot of development support to equipment manufacturers by providing software stacks for system chips. The software stack integrates the most commonly used audio and video codec software mentioned above. The driver interface provides a well-known API interface for system integrators. Unlike the driver software stack that focuses on all hardware-specific projects, the factor considered in system development is the operating system. The strong market demand for enhanced media decoding features and online access applications requires the use of an existing application library that can provide most of the application software. These software modules are called middleware, and the providers are software companies or open source communities that integrate intellectual property in the middleware.

　　Compared with a rear-seat entertainment system with only a DVD, the choice of operating system becomes increasingly difficult. Proprietary operating systems have advantages in terms of code size and efficiency, but require a lot of hardware driver and application software development work. If you use a familiar operating system such as WinCE or Linux, there are a variety of applications and driver software available. Because the driver software is hardware-specific, the chip manufacturer must provide the driver in the software development kit. The development kit contains all the components required to run the application: operating system, driver and codec software. Some open source applications such as WebKit browser or media player may be placed in the package to speed up application development. These applications rely on the existence of video APIs. For example, in Linux platforms, V4L (Linux Video) or ALSA (Advanced Linux Audio Architecture) must exist. Other middleware such as DVD-Video or Blu-ray playback engines, MHEG, MHP, BML or Java components can run and be easily implemented on the video API, which is independent of the hardware used. Finally, the top-level application that runs the user interface will be the framework of the entire system, and system developers can invest a lot of effort in the framework to make it more unique than competing systems. The on-chip graphics core enables developers to create an easy-to-use interactive user interface.

　　From playing discs and external storage content to live TV decoding and network media streaming, the next generation of rear seat entertainment systems will provide rich functions. As end-users use more standards, the video formats supported by the system will expand from QCIF/QVGA to HD standards. Effective use of existing systems, including software and hardware, is an element to speed up the development cycle and control the development workload. A large amount of audio and video code development requires long-term development experience in proven consumer electronic devices.