Possible to use PC with Firewire card as DVHS recorder? - AVS Forum
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Old 01-11-2002, 04:51 PM - Thread Starter
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I was wondering what people think about the idea of using a PC to record HDTV via the firewire out of say the current 169time mod. Do you think it is possible?
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Old 01-11-2002, 09:27 PM
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Originally posted by thorr
I was wondering what people think about the idea of using a PC to record HDTV via the firewire out of say the current 169time mod. Do you think it is possible?
Since that content doesn't involve any DTCP, an application could probably be written to do it. Windows contains drivers for the relavant protocols--the documentation is available here. Not an insignificant project. If you undertake it, have fun :).

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Old 01-11-2002, 10:22 PM
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It's certainly possible; 169Time has done this internally though there are no announced plans to turn it into a product.

Such a facility would be especially useful with the 169Time-modified Unity Motion receiver. The UM can receive (and deliver over its FireWire output) high-rate bitstreams that the PV-HD1000 VCR can't handle, such as NBC's and ABC's network HD feeds.

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Old 01-12-2002, 07:27 PM - Thread Starter
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Unfortunately, I am not a programmer (except fooling around with Delphi once in awhile), but it is cool that it seems to be possible. This would allow people to have the 169time product without the need for an expensive DVHS machine. I think if 169time released their utility for cheap purchase or for free, they would sell more of their product (assuming it can be upgraded to record HBO, etc. in the future for a free or small charge).

I am not sure what the Unity Motion is. I hear lots of talk, but I don't have a clue what it is.

EDIT: Haha rrg, welcome to the "Senior Member" club. We both *just* made the switch, but I currently have 1 more post than you. ;)

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Old 01-13-2002, 06:20 AM
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Ron

Any idea of the bit rate on the NBC and ABC HD network feeds? I have long wondered why the HS spec for HDTV recording with the Japanese DVHS recorders was 28.2 Mb/sec and maybe 28.2 Mb/sec is enough.

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Old 01-13-2002, 09:04 AM
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Quote:
Originally posted by thorr
I was wondering what people think about the idea of using a PC to record HDTV via the firewire out of say the current 169time mod. Do you think it is possible?
This subject seems to creep up every so often. The main issue is that you need to know how the devices communicate between one another. A D-VHS box uses a different protocol then what your pc knows. I think if you can figure out the protocol then you have a shot, but that means you have to litterally decipher the language that those things talk between each other.

I think there is also a voltage issue but I'm not positive.

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Old 01-13-2002, 12:17 PM
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Originally posted by chap
A D-VHS box uses a different protocol then what your pc knows. I think if you can figure out the protocol then you have a shot, but that means you have to litterally decipher the language that those things talk between each other.
I'm sorry--you're both right and wrong. That's not generally true, but it is true in the case of the 169time mod, as I recall. There's some proprietary lingo going on between the old Panasonic deck and TU-DST5x's that Sixteen Nine Time uses, making their modification incompatible with any of the new D-VHS decks. However, as I pointed out before, there are some drivers for Windows that talk the underlying AV/C, EIA-775-A and EIC 61883 protocols. DTCP on 1394 is built on top of this stack of protocols--you shouldn't have any problem talking to the JVC or Mitsubishi deck using software built on top of these Windows drivers (just so long as the tape wasn't copy-protected--you can't implement DTCP without obtaining a valid set of keys, which the DTLA must be keeping under heavily armed guard).

The online documentation for Window's support for AV/C starts here. Note the text on this page:
Quote:
Microsoft supports the Audio Video Control (AV/C) protocol, which is built upon the IEC-61883 standard.

The AV/C protocol driver Microsoft supplies is called avc.sys. It is a functional driver that supports the AV/C subunit protocol. The AV/C subunit protocol is a method for issuing commands and sending responses from subunits on devicew such as MiniDV camcorders and digital-VHS tape deck. For example, a MiniDV camcorder has two subunits, a camera subunit (the imaging device) and a tape subunit (storage of the media-signal). A digital-VHS tape deck has a tape subunit and a tuner subunit. These subunits can be controlled externally from a computer if the camcorder is connected to a PC through the IEEE 1394 serial bus and appropriate "subunit drivers" are written for the hardware. These drivers are WDM drivers that connect to the AV/C system-supplied driver (avc.sys) to provide that control.
So the necessary support is in place on Windows, with all the AV/C and IEC 61883 protocol stuff already written for you--you have to write a minidriver for D-VHS tape subunits (unless, of course, you'd also like to control any tuner that might be there, requiring an additional minidriver). A description of their AV/C command set is freely available online here. (You would also need to implement many of the common requests described in this spec). The Windows support that's in place relieves you of having to know any of the line protocol details--your driver just has to manage the procedural details of operating the tape deck. You'd also have to write an AV/C streaming protocol driver to capture the video after you'd set up the connection to your card and sent the PLAY request.

The drivers would implement functions to enable those operations--after writing them you'd need to write an application which would use them to manipulate the VCR, acquire and buffer data and write it to a file.

None of this is at all easy, but it's one hell of a lot simpler than starting from scratch, as you suggest is necessary.

But the original poster's question was whether you could record HDTV to a PC using a regular FireWire card from a 169time mod and again, you're right--that won't work, because the Panasonic D-VHS deck was not properly compliant to these protocols and 169time uses their added stuff. The Windows FireWire A/V protocol stack won't deal with that.

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