At present, 1394 Automotive for automotive multimedia networks is becoming more and more concerned, and it is expected to be versatile in the future automotive market. In recent years, countries have gradually turned to digital TV, and more and more high-definition products. In addition, the Blu-Ray player will stop analog output in 2013, making 1394Automotive suitable for the increasingly fierce digital transmission of in-vehicle networks. It is precisely because of predicting future demand for rear seat entertainment systems that Fujitsu Microelectronics led other suppliers to introduce 1394Automotive controllers in 2005.
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The following is a list of devices connected to the network to understand the bandwidth requirements of the car network (Figure 1):
Field of view camera for collision avoidance
GPS device
MP3 player
High definition multimedia player and display
Game console
PCs and other devices that can access web pages and send e-mail via cellular and Wi-Fi networks
Figure 1: Automotive Network Devices
Communication between these devices requires a large-capacity bandwidth network, and future throughput requirements will continue to increase. Traffic must be handled appropriately to provide good quality of service. The technology used in the network includes both hardware and software.
1394 car technology introduction
The first standard for 1394 high-speed transmission technology is IEEE1394-1995, which allows data to reach 400 Mbps, and the second version is 1394a-2000, which adds features such as asynchronous data streams and concatenated packets. The 1394a-2000 can support data rates of 800Mps. In recent years, support for 1600Mps and 3200Mbps has also been added to this standard. The 1394 automotive standard 1394b-2000 has been approved in 2000.
The 1394 standard includes two types of data communication: synchronous and asynchronous. Synchronous data (video and audio) is guaranteed to be time-sensitive, but delivery is not guaranteed. If you are late, the nature of this type of data makes it useless, but you can discard some data without major problems. The 1394 specification allocates a periodic time slot of 125 s to transmit synchronous data.
On the other hand, asynchronous data is guaranteed to be delivered, but timeliness is not guaranteed. This type of data must arrive at the destination, but time is not important. If it is not delivered, the node will resend the data.
The 1394 protocol stack is shown in Figure 2. It consists of a transaction processing layer, a link layer, and a physical layer. In the 1394 controller IC, the transaction processing layer is implemented in software, the link layer is implemented in software or hardware, and the physical layer is implemented in hardware.
Figure 2: IEEE1394 protocol stack
1394 automotive technology and competitive technology comparison
The easiest way to understand 1394 automotive technology is to compare it to alternative technologies. The disadvantages of MOST150 (the highest MOST version) and Gigabit Ethernet are obvious compared to the 1394 technology, as described below. These disadvantages include network standards and IC implementations on the market.
Disadvantages of MOST150
Lack of DTCP
Content protection is a must-have feature of automotive digital multimedia networks, and Digital Transmission Content Protection (DTCP) is the primary technology for achieving this capability. Due to the lack of this feature in the MOST150 product, MOST networks require other devices to implement content protection (Figure 3).
Figure 3 MOST150 does not have DTCP content protection in storage media
Lack of content protection leads to increased hardware costs and other software support costs. Also, even if an external DTCP device is used, the multimedia content in the MOST150 system can only be protected on the network instead of the storage medium (HDD, etc.).
In contrast, the 1394 car IC has built-in DTCP. This approach minimizes hardware and software costs while ensuring full protection of data.
Low bus speed
The MOST150 network is only capable of 150Mbps, which is only a fraction of the 800Mbps bus speed of today's 1394 automotive devices. In the future, the bus speed of 1394 devices is expected to double.
Need external data compression
To compensate for the low bus speed, the MOST150 network can increase data throughput to levels comparable to those of the 1394 automotive network by using data compression. This solution requires an external codec to compress and decompress the multimedia data, resulting in two problems.
First, implementing multimedia compression and decompression (such as MPEG2-TS) requires typical devices, and these devices can increase the latency dramatically – possibly up to 400ms. Therefore, the drive will notice a significant delay in the field of view camera video. The compression/decompression delay can also cause significant delays when the user fast forwards to the DVD (Figure 4).
Figure 4: External Multimedia Codec Causes Major Delays in the MOST150 Network
The second issue is the cost issue of using an external codec. Accompanying the codec is that the design requires an external frame memory to buffer the video. In fact, the MOST150 design requires as many as eight chip devices.
Since the bus speed of the 1394 car network is much higher, there is no need for compression at all. However, if the expected bandwidth requirements are extremely high, the design can take advantage of codecs built into Fujitsu 1394 automotive devices for low latency and low cost. We believe that these built-in codecs can maintain latency for 4ms and require only two chips to implement.
A comparison of the number of devices required for the 1394 car and the MOST150 is shown in Figure 5.
Figure 5: Device Comparison
software
Since a small number of companies control MOST technology, only a small number of companies have mastered the software expertise of the multimedia bus. Therefore, the software development cost of the MOST system is high, and the system integrator can only control limited software.
The disadvantage of Gigabit Ethernet
Lack of integrated DTCP
Like MOST, Ethernet controllers lack integrated DTCP functionality. Other components used to implement external DTCP functionality add cost and compromise data protection within the memory device.
Possible external codec
While Gigabit Ethernet has much higher bandwidth than the MOST150, increasing bandwidth requirements (such as for high-definition video) may eventually force Ethernet to use data compression. Since the Ethernet controller lacks an integrated codec, external components are required, thus increasing the number and cost of the required chips.
No intrinsic quality of service (QoS)
The Ethernet standard does not include QoS regulations. To achieve the same level of QoS as a 1394 automotive network, Ethernet requires additional software overhead, memory buffers, and timestamp circuitry. These are necessary to ensure reliable video and audio data communication.
The cost of discrete PHY and LINK devices
Most Ethernet media access controllers require an external PHY chip. Although these chips are not expensive, the total system cost is still higher than the 1394 automotive network.
High CPU requirements
Since Ethernet does not have inherent multimedia capabilities, the external CPU must provide a large number of auxiliary functions. In particular, the CPU must intercept and analyze packets from the network and send them to the appropriate device to convert the data into audio and video. This processing significantly increases the CPU requirements for multimedia support over Ethernet.
Software cost
Just as Ethernet requires a lot of CPU support to handle multimedia content, network standards require a lot of software to reliably implement these functions. Many Ethernet software is available, but because of the need to obtain access rights, the licensing costs are greatly increased.
MB88395: main features
Fujitsu's latest 1394 automotive serial bus controller – MB88395 – meets the requirements of the IEEE standard 1394b-2008. The chip integrates the PHY and LINK layers into a single-chip solution and has two ports for 1394 cable connections. It also integrates the DTCP protocol. Based on the IDB-1394 car multimedia network protocol, it can realize high-definition (HD) (1,280 points × 720 lines) video transmission, and can also transmit multiple streams in the car at the same time, such as HD video, digital TV, audio and video transmission from Blu-RayDVD. Car navigation picture. These functions can be realized because the chip utilizes the high-speed 800Mbps physical layer (1) and SmartCODEC (capable of high-speed compression) with Fujitsu's independent intellectual property rights for high-definition video transmission without significant lag, thus not only bringing the rear seat passengers The rich HD experience also reduces the system cost of the car multimedia network by 30%, while also reducing the number of wire harnesses (cables) by 70%, further reducing the weight of the car body and improving fuel efficiency.
As shown in Figure 6, the device has MPU/DMA or a serial interface for implementing master control. As with earlier 1394 controllers, hardware acceleration for all features of the new chip allows the use of a low MIPSMCU as the host processor to control the device. Two internal channels are provided for synchronous and asynchronous data. The sync channel is shown in the bottom half of Figure 6.
Figure 6: MB883951394 Automotive Controller
The key performance of the new controller is that its physical layer is compatible with 1394Automotive's 800Mbps specification (which is twice the speed of previous products at 400Mbps), and its SmartCODEC video compression codec version has a higher compression speed and can compress video to The original capacity is 1/4, while the previous product can only be compressed to 1/3. SmartCODEC was developed by Fujitsu Labs and used for the IEEE-1394-based BT.601 transmission (2) standard. It can compress/decompress high-resolution video in 2~3ms, and it will not cause any time lag or content out of sync when viewing the same content on the front and rear monitors.
The key features of the product enable high-definition video and high-resolution navigation images that can transmit Blu-RayDVD, digital TV without any significant time lag, making it the world's first 1394Automotive-based processing of multiple HD video streams and navigation Picture of the chip. For example, the decompressed HD video stream (1,280 dots x 720 lines) on Blu-RayDVD has a processing speed of 885 Mbps. With SmartCODEC, the capacity can be compressed to 1/4 of the original speed, and the speed becomes 249 Mbps, so the two channels can be transmitted over 800 Mbps, but not at 400 Mbps.
The SmartCODEC block diagram is shown in Figure 7. The functional module utilizes predictive coding adjacent pixel correlation techniques for video compression.
Figure 7: SmartCODEC block diagram
Figure 8MB88395 applied to car entertainment system
in conclusion
We believe that the bandwidth, flexibility, economy and technical features of the 1394 automotive standard meet the requirements of today's and tomorrow's infotainment networks. The Fujitsu MB88395 controller represents all of the benefits that 1394 brings to the automotive industry, and offers a host of new features that simplify system integration and minimize costs.
Note:
(1) Physical layer: The first layer of the 7-layer transmission function defined by the OSI basic reference model. The physical layer is an important part of the network hardware and can be used to transfer bit arrays.
(2) IEEE-1394-based BT.601 transmission: A transmission protocol issued by the 1394 Trade Association for transmitting BT.601 video streams (such as YUV, RGB, etc.) based on IDB-1394.
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