Thursday, August 1, 2013

Ancient DVR teardown - Dallmeier DLS 6

I just bought a cheap broken DVR from eBay and thought to share pictures from inside the unit since there aren't any on the Internet.
It was a state of the art unit at the beginning of 2000, probably costing several thousands of dollars. Some documents and review from that time praise the wavelet-type encoding quality and savings, custom-made ATX power supply and build quality. I beg to differ on a few fronts.

Front panel is uninspiring, has a few status LEDs (Power, Rec/Play, Alarm, Error) and a drop-down cover hiding the floppy(!) drive.

The back panel has quite a lot of connections:
- Contact In: these pins go to the cameras to perform some specific function, have not figured out what
- Service button/switch - disables the above connector
- Service and mouse sockets - for connecting a PS/2 keyboard and mouse
- covered SCSI extension socket
- two DB9 serial ports
- one parallel port
- one 10/100 Ethernet network port
- 6 video inputs, 6 associated loop-through outputs and two monitor outputs
- Contact Out - alarm output, recording output, error output, event output, overflow output. All these contacts are normally open except error output, which is normally closed

The BNC sockets are specified at 1Vpp / 75 ohm, so they should work with any device providing AV-IN or AV-OUT. These are pretty standard for professional DVR devices, I have a converter cable (BNC to RCA) that allows me to connect to consumer stuff and test these recorders.

*The sticker specifies 100W of power, the AT power supply is rated at 267W, the German manual specifies 110W and the English manual specifies a maximum power of 70W. I wish they would decide on one figure.

The insides of the unit look like a standard PC from around 1999, it's like a trip back in time. There's the HDD holder at top-left, unit fan top-right, a Pentium MMX CPU, two FPGA boards populating ISA slots, an Ethernet board inside a PCI slot, 64 MBytes of SDRAM and contacts-in board at bottom-left.

The first ISA board from the left is branded with Dallmeier and has a few interesting chips on the load side:

SAA7185 - Philips Digital Video Encoder for S-Video out
4x EliteMT LP61256GS-12 - probably SRAM at 12 ns
2x ADSP-2181 - Analog Devices 40MIPS DSP processor
2x ispLSI 1032E - Lattice PLD, 6000 gates
SAA7111A - Philips Enhanced Video Input Processor
ADV601LCJST - Analog Devices Video Codec with DCT compression

Obviously, this board is concerned with video processing doing stuff like input decoding, output encoding, color/brightness adjustments, digital compression and perhaps overlay. The name "frame grabber" might be suited for it.

Back in 1999, H.264 compression was not available (it was standardized in 2003-2004), MPEG-4 was pretty new and MPEG-2 was not suited for low bit rates. So all these perceptual compression techniques were generically called Wavelet Encoding.

From Wikipedia:
Using a wavelet transform, the wavelet compression methods are adequate for representing transients, such as percussion sounds in audio, or high-frequency components in two-dimensional images, for example an image of stars on a night sky. This means that the transient elements of a data signal can be represented by a smaller amount of information than would be the case if some other transform, such as the more widespread discrete cosine transform, had been used.
Today all of the above could probably be done by a few ARM M4F (100 MIPS) processors on a board using 20x less power. Still, I suspect a lot of the work was offloaded to the CPU (Pentium MMX, ~250 MIPS) but I remember magazines at that time telling that one minute of MPEG-2 video took 15 minutes to compress and 30 seconds to decompress.

The second ISA board connects to the first one and provides some breakout capabilities for the computer as well, like front-panel leds.

This board connects to the camera inputs and outputs through a standard ribbon cable, nothing fancy. The chips might reveal some more info:

4x SED3064F0A - Seiko-Epson. LCD controller(?)
4x ispLSI 1032E - Lattice PLD, 6000 gates
4x IS61C1024-15J - 128k SRAM
AT28C256 - Atmel 256k EEPROM
4x 74[LS/HC]245 - octal bus transceiver
HI1179JCQ - Intersil 35MSps Video ADC
2x 74HC646 - octal 3-state transceiver and D flip
14x AD826 - Analog Devices dual 50MHz opamp
2x 4421CS - Elantec two-input video amplifier
2x 4581CS - Elantec sync separator

I cannot figure out exactly what the board does but some functions can be figured out: the video inputs come from the bottom and go through some protection diodes and some op-amps for buffering.
The Epson chips cannot be found, I assume though they might be some analog MUX or switches.

There are also 5 relays on the top (right) side of the board so this could be a generic interface board that is able to takes care of the communication between the computer, frame grabber and the outside world.

The bottom side has some dip-switches that probably physically disconnect the outside pins from the board.

Ethernet card is a standard RTL8139C PCI one, missing the network boot ROM. Probably the cheapest card available and certainly not as reliable as Intel-based ones.

The back panel comes off with the BNC connectors still attached.

Unfortunately there is nothing  on this board, I expected some analog circuitry. Just a heavily shielded PCB with the BNCs soldered on.

*All the analog processing is done on the generic ISA board and the signals are transferred there through a generic, unshielded, hard-drive ribbon cable.

The Contact In board has "a few" relays, 32 to be exact and a Motorola ZC86956P, which I assume to be a keyboard controller.

And the back side:

Another view from the inside shows the single unit fan (there's also one inside the supply) and the LED front panel, with a beeper.

The indicator board has nothing special about it, just a single-side PCB breaking out the single-color LEDs and piezo.

Taking the plastic front panel off reveals the harddrive and floppy rack, that would also take an optional ZIP drive.

*The plastic panel has some pretty crappy plastic torx screws.
I don't get it, they get eaten by metal tools and broken by little bumps. Why would anyone use them, if isolation was not needed and they have to take significant mechanical stress?

Oh, our friend, aptly named "DeathStar" back in the days. I think only the 75GB ones were prone to failure, this drive is still functioning.

It looks like a normal consumer drive, not enterprise one, so I wonder how well these held in continuous recording.

Most of the free space is available for recordings, save 1GB for the "Hardened" Linux system.
I'll make an image and analysis of the drive when I'm able to get my hands on a USB-PATA converter.

The software is licensed per unit with additional [paid] activation codes for: Ethernet, extra cameras, ISDN, network remote control, ...

Some random images with the motherboard for anyone not familiar with the jumper ways of times gone. CPU and RAM clock and voltages were set via jumpers and the nice boards had the legend on them. The crappy boards had this information only in the (possibly outdated) manual and no Internet was available.

Notice the board can take both SIMM (older) and DIMM (newer) memory, though probably not at the same time.

Some article I found claimed that Dallmeier have developed their own power supply unit able to withstand small brownouts, with improved cooling and 8yr warranty. Either my unit does not have one of those or they just specified and outsourced the supply to Enermax.

I'll try to get it running just to analyze what it did and how is the performance compared to my other (consumer) DVRs. It's currently just displaying some static (non-moving) noise on the AV-out port, but at least the boot error code beep is correct: 1 long beep and 3 short beeps = no video card.

Unfortunately I have to hunt the garbage cans now for a PS/2 mouse and keyboard and a PCI or ISA graphics card. The board might also be able to take an AGP one, but I'm not sure if the included Linux will boot with it.

No comments:

Post a Comment