Building a Personal Video RecorderBuilding a Personal Video Recorder

Motherboard

Probably the most important part of the PVR. It will determine many features and usually this is the most expensive part of the system. Some people likes to use the state of the art motherboard with highest class Pentium processor and many GHz clock rate. But in this case you will not be able to handle the noise problem. The only solution is to put your PVR into a separated room and use long cables or another computer as a terminal.

In my case i have no separated room for the PVR, and i don't like long cable or separated terminal idea. So my choice was a fanless SBC (Single Board Computer) motherboard. There are several on the market. Their most important properties are the small size, low power consumption, higly integrated functions, simple power supply requirements (usually simple 12V DC). Their disadvantage however the lower processor power than state of the art computers and relative high price.

These motherboars usually equiped with 1-2GHz VIA C3 processor. Even the few GHz clock frequency sounds good, but don't be so optimistics. Their computational power is similar to an old Pentium III 600-700MHz processor. But if you carefully select the other components of the recorder you can use these motherboards easily.

My choce was a motherboard from LEX system (www.lex.com.tw). The reason is simple. I had experience earlier with this boards and i as satisfied with their functionality. But i have to mention LEX motherboards are not the chapest ones...

Anyway my choice was a MV823S motherboard from the LEX system.

MV832S Motherboard
Picture from LEX Computech Co., Ltd. Web Site

The features of the motherboard:

• VIA C3 Nemiah processor with 1GHz clock frequency
• VIA CLE266 chipset
• Integradted VGA card (S3) with MPEG2 hardware decoder and video output (S-video and composite video)
• 5.1 analog and optical S/PDIF audio output
• onboard ethernet, serial port, USB
• Compact flash connector which can be configured as a boot harddisk
• PCI slot (to be precise PCI edge connector)
• Simple 12V DC power supply input
• The power supply comes with the motherboard (fanles, laptop like power supply)
• There is only a small fan on the processor, but the speed can be configured from the BIOS

Let's discuss about the features in more details.

The processor

The 1GHz VIA C3 Processor is just enough for a PVR. If you have chance, choose bigger one. I'm almost sure lower clock rate will not work. And because of the low processor power you _must_ use hardware MPEG2 encoders and decoders for recording and watching TV programs especially when you want to use time shifting function. Software encoders will not work. Of course the usual decoders DixV, XVid and most of the audio decoders will work on this processor. But this is really the lower edge of the usable processors.

Chipset

The second important feature. In my case it almost became the first important. The VIA CLE266 is a very good chipset with many functions (like MPEG2 decoder). But there is a serious problem with it. This chipset is not fully supported by the newer DirectX versions. Some PVR software uses DirectX functions (namely VMR - Video Mixer Renderer) to render output video stream on your screen. However this function is not supported by the diver...

I was surprised when i discovered this. I could play DVD using Media Player but i couldn't get continous video stream using PVR software. So if you want to use CLE266 chipset motherboard be sure your PVR software supports 'Video Overlay' mode not only DirectX VMR. I will explain this issue more details in the PVR software chapter.

Audio output

As i mentioned earlier, the audio output is a very important feature for me. I think in the case of the SV823A i have no reason to complain. It has 5.1 channel audio output (however you have to make a cable for it) and optical S/PDIF output. It has also audio some inputs but i didn't wanted to use them.

Power supply

This is one of the best feature of this motherboard. It only needs 12V DC. The motherboard generates all other voltage by itself. The motherboard comes with a 12V DC power supply. This is like a laptop power supply. Small black brick without anythig which can generate noise. The output power of this unit is 60W, it must be enough for the motherboard and one harddisk and DVD player. Of course the motherboard has connector for harddisk/DVD power supply. 

This is another practical feature. You can use a compact flash card to store your operation system and PVR software. For this nothing else needs only an empty compact flash card. I use 1GByte CF card, it should be enough for everyone :-)

PCI slot

PCI slot is very important because we have to add TV card to our system. This is the easiest, chapest way to do this. There are TV cards with another connection options, like USB, PCMCIA. I don't recommend them except if you are sure your PVR software supports them.

Actually on the LEX motherboard this is not a slot. LEX calls it 'PCI gold finger' and it looks like an edge connector of a PCI card. So you need some adapter to plug your PCI card into it. Fortunatelly LEX sells these adapters (there are some versions). I use 'RS005' type connector. It can be used to connect one PCI card to the motherboard. And it turs back the card by 180° so it turns your TV card just above the motherboard, which is very practical if you want to use slim housing.

RS005 PCI Adapter Card
Picture from LEX Computech Co., Ltd. Web Site

TV/Monitor Output

There are three ways to connect your motherboard to the display. You can use standard VGA connector, RCA composit video connector or S-Video connector. I recommend VGA connector if your TV has this type of connector (newest LCD TV usually has). I think this gives you the best picture quality. The other connectors could be usefull when you want to connect you PVR to old video tape recorder or to an old TV without VGA input.

Other features

The motherboard has 10/100MBit/s ethernet interface. This is very practical to access recorded programs or up- and download video, music or other data. Usually PVR software has WEB interface to access recording shedule information. And if you use remote desktop you can easyli maintenance your PVR.

The motherboard has PS2 type keyboard and mouse connector. However these connectors are not installed on the motherboard. There is only a ten pin header connector. So if you intend to use PS2 type keyboard or mouse you have to make cable. If you don't want to make cable, i suggest you to use USB keyboard and mouse. There are a lot (3) of USB connectors on this motherboard.

There are also two serial port connectors. They can be configured to be RS232 or other RS standard. They might be usefull if you want to make some interface by yourself.

I already mentioned the digital audio output (S/PDIF). There is a 5.1 analog output too, but it's also only available on ten pin header connector. You have to make cable by yourself. There are some audio inputs (3.5mm Jack) and stereo audio output (3.5mm Jack).

Ther are two type of harddisk connector. One is the usual 40pin ATA cable and the other one is the laptop like 44pin cable. And there is a separated standard 5V/12V connector for HDD and DVD ROM power supply.

The power switch button is installed on the motherboard, but the contacts of this are available on two pins header connector. This is very usefull if you want to use your external hardware to turn on the PVR using e.g. IR remote control.

MV823S Connectors
Picture from LEX Computech Co., Ltd. Web Site

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