DVB-ASI for DATV

[markaren1]

Hi All,

The cost of pro-video stuff (new from China, used from eBay) is dropping, and one of the interconnects of choice appear to be ASI. This is a 270Mbs link carried over 75 ohm coax. It would be nice to bring DATV in line with professional interconnects eventually for obvious reasons.

Cost and difficulty of implementing the interface appears also to be dropping. with one possible solution as FPGA, Altera IP and LMH0070. The latter part is a 5 bit 270Mbs seriaslizer with I2C configuration control, so you only need to shovel data into the 0070 at 54Mb/s.

Before buying some 0070s, I would like to build some ASI test gear. Just spotted an IMEDIA DVB-ASI PCI card on eBay (S25-7000144) for US$35. I wonder if there is either any direct support for a hard drive spooler/recorder or something similar available at low cost based on this or similar cards.

Also spotted a DVEO LS7643, the associated desktop application eludes to ASI capability, and maybe for the price I should get one and try it out....

Hopefully someone in BATC land will have trodden this path before.

Any wisdom gratefully accepted.

-mark

[G4GUO]

I have purchased one of those used IMEDIA cards.

I don't intend trying to use it as a PCI card as the drivers are impossible to find but it does use CY7B933 DVB-ASI decoder chips.
The output of these chips are 8 bit data with a Data valid and a clock. I plan on using a CY7C68013A USB2 chip in synchronous
fifo mode. Looking at the timing it should be possible to directly connect the CY7B933 to the CY7C68013A, the USB chip is 5v
tolerant.

The PCI controller on the PCI card has 8 fifos on it but they required to be multiplexed on the local bus I am guessing but I think the
output of the 4 CY7B933 chips must go into the FPGA which does the multiplexing and then outputs to PCI via the local bus.

If that is the case it should be possible to remove the FPGA with a heat gun and Kapton tape and directly get access to the
output of the DVB-ASI chips. From there it should be fairly simple to connect up the USB chips.

As the CY7C68013A chips are identical to the ones on DATV-Express I have a lot of experience with them so writing the
firmware will be no problem.

I made the retailer on eBay and offer and got the board for considerably less than the $35 he is asking I will reuse the
BNC connectors, the baluns, 27 MHz clock and CY7B933s the rest of the parts are of little use to me.

I will let you know how I get on with this, my ultimate aim is to use it with DATV-Express and get rid of those ghastly PVRs!

If I can get it to work I will write a short article for the club magazine in case someone else wants to try doing something similar.

- Charles G4GUO

Hi All,

Before buying some 0070s, I would like to build some ASI test gear. Just spotted an IMEDIA DVB-ASI PCI card on eBay (S25-7000144) for US$35. I wonder if there is either any direct support for a hard drive spooler/recorder or something similar available at low cost based on this or similar cards.

Hopefully someone in BATC land will have trodden this path before.

Any wisdom gratefully accepted.

-mark

[G8DKC]

Hi,

I wonder if you can help getting to grips with T.S stream rate and Symbol rate, DVB-S.
Have not had reason to question...
I thought the two were independent, and as long as the T.S was fast enough to carry data?
I'm playing with a SM6610 Modulator and the T.S fixes the symbol rate?

The more you learn, the less you know, Hi.

Peter

[G4GUO]

I am afraid I can't help much as I am not familiar with the equipment you are using other than
say the modem has to transmit at a constant bitrate usually the bitrate of the elementary streams
of the TS is less than the modems bitrate and the difference is filled with SI packets and NULL packets.

The bitrate of the modem is dependent on the symbol rate, the modulation constellation and
the FEC

so for example a symbol rate of 4M, FEC of 1/2 and Modulation QPSK (2 bits per symbol)
would give a modem bitrate of

4000000 * 1/2 * 2 = 4000000 bits/s

So with those parameters the video/audio component transport stream must be less than 4 Mbits/s.
The encoder will probably add SI tables and NULL packets to make the bitrate up to the required 4Mbits/sec

I am assuming a single program with one video and one elementary stream.

- Charles

[G8DKC]

Hi Charles,

Thanks for info and expanation, sounds like the modulator is doing this for me.

Will look into this a little more, now I know where to start.

73

Peter

[ON1AVO]

Peter,

You can also download a bitratecalculator at dvbcalculator.altervista.org , to understand the relation between SR and bitrate, FEC, ...

73

Freddy

[G8DKC]

Thank you Freddy, just installing and will take a look.

73

Peter