For interconnecting Home entertainment A/V appliances the IEEE1394 standard bus, also referred to as firewire, is becoming popular. PC and its peripheral devices like printers, hard-drives for storage and home entertainment devices like TV, VCR, MP3 players, Camcorders and digital cameras are coming with 1394 ports to support multimedia data transfer. This simple, low cost and high bandwidth 1394 bus with its ability to mix real-time and asynchronous data on a single connection, and the ability to mix low speed and high speed devices on the same network, provides a universal connection for almost any consumer, computer or peripheral application. As more commercial electronic gadgets are coming up with 1394 connectivity, they all can be easily hooked into the in house 1394 cabling. The greatest advantage with 1394 enabled devices is that they can be added or removed from the system without having to power-down or reset the system. With the interconnecting of the home multimedia devices, several new imaginative applications are arising in the area of home surveillance and entertainment. The intent of this article is to present the 1394 based solutions in the home environment.
Apple Computer has used serial digital link technology in 1986 to transfer high bandwidth data between multimedia devices and trade marked it as firewire. Later, in 1995, it was adopted by IEEE body as industry standard with some changes and referred to as IEEE1394 serial bus. The firewire serial bus supports asynchronous and isochronous data transfers on a single bus. For instance, a VCR can be commanded to switch on and start/stop recording and play. The video and audio data from the remote system can be passed on the same bus for recording. This is true mix of isochronous and asynchronous transaction on the same wire. The asynchronous mode of transactions is used where the data reliability is more important. These types of transfers are used mostly for command/control functions of the devices. The data transfers are assured by an acknowledgement from the receiving device. The isochronous transfers are used where constant data rate needs to be ensured for real time video applications. Here, there is no acknowledgement is expected from the receiving device. It is also possible to broadcast control or AV data from one node to several nodes. That is the video source sends data packets over 1394 bus by only identifying its channel number. Any number of nodes on the bus can be programmed to receive this channel.
The 1394a bus standard can support multiple speeds 100, 200 and 400 mbps to meet the audio/video band width requirements. With 1394a bus standard 4.5 m length cabling can be used. The 1394b standard which came later can go up to 400 mbps and support longer distances like 100m and it also defines plastic optical cabling. Due to the high bandwidth of this serial bus, cheap and low resolution devices that do not have any complex compression algorithms to reduce the data rate can also be connected on the bus. There are standards like HAVi defined to enable seamless interconnectivity between the home entertainment appliances. like TV, Music systems, PC and camcorders and surveillance cameras. Firewire ports are already appearing on PCs and other audio/video consumer electronics equipments. As the i1394 bus supports peer-to-peer, the devices can communicate directly to each other. For example, a 1394 enabled camera device can directly send the data to a 1394 enabled printer without requiring a PC to transfer data. Firewire has many other virtues that make it successful in the home market. The firewire devices are easy to install in the existing firwire network. The firewire devices are hot pluggable, that is the device can be connected while the power is on. And there is no software drivers to be loaded to at the time of installation. The device configures itself into the firewire network, i.e., self configurable. When the device is disconnected, the firewire system again automatically configures and hence resources are not locked up for the disconnected device. In the firewire network, the devices get connected in a daisy chain fashion resulting in single cable connectivity. The power to the 1394 device can also be derived from the 1394 cable itself.
This firewire technology opens up several imaginative new applications. A surveillance camera can directly connect to VCR, TV and can send a command to wake up the VCR for recording and switch on the TV to show video capture on arrival of a visitor in front of the camera. The surveillance cameras can also be connected to residential gateways that connect your home to the external world through telephone line or LAN network. The appliances in the home can be remotely controlled using internet in the office. A fire-wire camera connected to residential gateway can stream the video data over LAN to be viewed on a web page. As IEEE1394 bus allows the asynchronous data transfers while the isochronous video data is being sent on the bus, without any interruptions, command and control information can be sent without interrupting the video services. This helps in Interactive TV applications.
Figure 1: Illustrates a typical surveillance system in the Home using 1394 cabling
Another popular Computer peripheral that uses IEEE1394 technology is Hard-disk drive. A 1394 hard-disk can be easily hot plugged to the fire-wire port on the PC or notebook Computer and increase the storage space. It is an instant upgrading of Hard-disk space of a PC without any hassles are reconfiguring the PC without opening it and without running any software modifications.
In the area of entertainment, camcorders and digital cameras are getting 1394 enabled so that they can be interconnected easily. So after taking nice pictures using your digital camera/camcorder, it can be plugged into the 1394 port of the PC and images can be viewed and also can be edited to make your own movies out of your video clippings with the help of applications software available on your PC. It will also be possible to connect the digital camera directly to a printer using 1394 cable and take prints without any intervention by PC. For interfacing PC to 1394 serial bus, 1394 OHCI host adaptor is required. This OHCI is a de-facto standard for interfacing to any host system and defines a very high performance interface. Microsoft provides standard driver software integrated in their windows operating system for OHCI controller. This 1394 OHCI PCI add-on is available from TI and many other vendors. Some PC’s nowadays integrate OHCI in the motherboard.
Over 1394 bus both audio and video data can be transferred. But for transmitting over 1394, that data needs to be packetized to 1394 format and there could be delays while transporting the packets depending on the topology of the firewire network. IEC-6188 standard defines how to form 1394 packets for different video and audio sources like MPEG, DV, DSS data. The standard also addresses the time stamping and buffering requirements for jitter compensation while transferring the data on 1394 bus. The audio/music system makers like Yamaha have already developed mLAN (a LAN for music) specification, using 1394 as basis. mLAN can send digital audio (such as AES3 or IEC 958 data), raw audio, MIDI, time code, word clock, and control data over a FireWire cable using isochronous channels. As with other FireWire-based protocols, mLAN inherits all the attributes of IEEE1394 such as high-speed transmission and easy cabling as well as its A/M protocol. A portion of mLAN was adopted as IEC 61883-6, the supplemental standard for the A/M protocol.
Another application in home environment is placing of speakers in different rooms in the house and controlling them by a remote. The main source of audio data can be in a separate room. Traditionally, analog transportation of the decoded audio signal from the source of the audio/music data like VCR, Set Top Box, introduces signal distortion. By transferring the digital audio data without encoded format from the source to the actual speaker system will help in avoiding signal degradation. With the high bandwidth available with 1394, it is possible to transport high quality 24 bit/sample multi channel audio data. From the Set Top Box, VCR, or MP3 player, the multi channel audio can be transported over 1394 cable to connect speakers in different rooms of your home. So the speakers can be placed in a convenient room and can be directly controlled by a remote to send 1394 commands to the central server to play the selected audio channel. This illustrates the capability of 1394 to transfer audio and command/control information on a single bus. The MPEG encoded audio data can be sent on the 1394 and audio decoding can happen in the speaker system. Several manufacturers are pushing for autonomous speaker systems where the audio data processing takes place within the speaker system.
Figure 2 : Illustrates the Speaker systems placed in different rooms using 1394 cabling
The standard MPEG transport stream coming from the cable operators and other video formats like DSS, DV have their own packet format. To transfer this standard formatted stream over 1394 cables, IEC 61883 specifies how to form common isochronous header. It also specifies how to take care of the jitter due to varying delay of packets while transferring on the 1394 bus which is inherence on a arbitrated shared bus. It defines common isochronous header specifying the type of packet MPEG, DSS, DV and also time stamping required at the source so that it can be used at the time of presenting the data to video decoder on the receiving side. This ensures flicker free video at the receiver. The commercially available Camcorders have iec-61883 AV encoder implemented in them to connect to 1394 bus. On the receiving side, AV decoding is done to get the video/audio data.
The 1394 data can be protected using Encryption algorithms as the video data normally requires to be protected for copy rights. 5C content protection is very popular for encrypting the data on the 1394 bus, so that the coping can be controlled. The 5C content protection allows copy once, copy never and copy freely modes. These mechanisms protect the information in the home from being accessed without authentication. Thus a secure and active home can be built on the backbone of 1394 bus.
A new initiative to upgrade the 1394 technology to cater to the needs of the automobile industry is in progress. This new initiative called IDB1394 is being driven by AMIC. The main objective of this initiative is to make the 1394 bus as backbone bus for automobiles and interoperate with the existing MOST and CAN. It basically addresses the command/control protocol required to control the functions in automobile and to provide multimedia entertainment in the cars. It addresses the safety and power management requirements that are very specific to the automotive industry. It defines a CCP (Consumer convenient port) so that commercial camcorders, MP3 players can be plugged into the 1394 POF cabling used inside the automobile. A video taken by a camcorder can be viewed inside the car TV system. The consumer electronics gadgets can be moved around to interconnect easily with other gadgets whether in your home or when you are on move. The future homes will have most of the consumer devices communicating multimedia data over 1394 bus.
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