AVR Freaks

DVR's are what I do for a living. I think the suggestion that you could do it on an 8bit micro is rather a wonderful one. Even the idea you can do it on just a 32bit (or a DSP) is quite interesting. It's true that I looked at using the dualcore ADi Blackin 591 that contains two 600MHz C55xx DSP cores and this was able to MPEG4 encode two lots of CIF (352x240) at 25 frames per second. But this is nowhere near D1 quality that you need even for SD-TV, let alone HD-TV.

The bottom line is that DVRs are based on specialised MPEG2 or MPEG4 dec/encoding silicon (and the same silicon probably contains transport stream demultiplexers too). Chips that do this are things like the STi5514, the NEC EMMA2 and a (for MPEG4) things like Conexan't and Broadcomms ranges (Angelina, Trinity, etc.)

Typically these silicon have about 200MHz+ of 32bit host core (ARM, MIPS, ST20) but then a whole bunch of autonomous processors operating their own DMAs and functions. Some of the Conexant's for example, have the equivalent of NINE ARMs on the one piece of silicon in amongst everything else.

What's more most of these chips are only MPEG2/4 *decoders*. They receive the transport stream of MPEG2 from a headend (via cable, satellite, IP) that has already been MPEG2/4 encoded and they just have to decode it at live vieweing or recording playback time. Doing the MPEG2/4 *encode* thing to record an external source like a camera is FAR more compute intensiive.

So do not underestimate the complexity of the processing power you require. If you truly want to DVR record video from an external source you will need MPEG encode/decode in silicon or a MASSIVELY powerful CPU to do it in realtime in software (anything from about a 1GHz Intel upwards can actually do D1 MPEG4 encode in software alone)

One thing's for sure: you aren't going to achieve this with an AVR (though we do use them for the front panels to do the buttons/switches and IR to take some more of the load off the main CPU)

Cliff

Yup and those TI chips are bascially 600MHz DSPs at the core with 8 40-bit ALUs, about 2MB of L1/L2 cache and come in a 548 pin Ball Grid Array.

I'll bet you are loking at about $20 of silicon there (in quantities of 100,000 to 1,000,000).

We typically take about 20-40 man years of engineering to get something like this working with something like 5 million lines of C source code

This kind of thing is NOT for the feint-hearted and is not the sort of thing a home hobbiest could ever achieve.

Cliff

PS But if you do you have a job waiting here

PPS my email is clawson@amstrad.com - our company is now a division of Rupert Murdoch's News Coproration (20th Century Fox, Wall Street Journal, Facebook, DirectTV etc.) and BSkyB (of which we're a part) is the leading supplier of domestic satellite TV systems in Europe.

Cliff!!! I was having fun with this... :lol: You wet blanket.....

Anyway, because the op did not know it could not be done, he might have come up with an algorithym to store several movies inside the EEPROM of a M168...now all of that is gone thanks to you.

He would have had all the encouragement from me. :lol:

How fast do you think the AVR needs to be clocked to sustain a 3MB/s data rate to an SD/MMC ? (don't forget it's not just dumping raw 512 byte buffers, you have to keep stopping for cluster allocation). Or were you suggesting the file is pre-created and so FAT allocation is not needed?

But I'd love to see hobbiest solder a 576 pin BGA ! :lol:

Nope, I don't think so. For reasons of stability we've looked at the possibility of using flash for stream storage in DVRs but the write bandwidth cannot sustain the data rates (and that's SD, not HD). Having said that things like Samsungs 64GB SSDs offer blistering data rates (up with PATA/SATA rates). But this isn't SD/MMC!

Now you will have all the horsepower you need. The XESS board is what I am using, and I like it a lot for video work. I also found Verilog to be much easier to work with than VHDL.

Verilog is actually easier than basic, but getting past the sequential mode of thinking when used to working with microcontrollers took a while.

Now I just pretend I have a 200MHz AVR that can execute every single line of code once every clock cycle! Oh, and don't forget ns propagation delays... those are a real bugger.

Good luck.
Brad