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Discussion Starter · #1 ·
Some of the DVD recorders offer a DV (IEEE-1394 a.k.a., FireWire or iLink) input. Does anyone know whether the internal conversion to MPEG is all digital? Or, does the box accept and convert the DV to analog and then encode that to MPEG?
 

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Not sure, but not sure that it matters either. The re-encoding step going from DV to MPEG2 would render irrelevant any minor PQ hit associated with converting the incoming digital DV signal to an analog signal and re-encoding from there. Bottom line for the Panasonic HS2 (and I assume the E60 and E100 are similar) is that a DV signal recorded via the firewire input vs. the analog inputs to DVD RAM in highest quality XP mode are virtually indistinguishable to me and are quite good. In any event, I use the firewire input with a DV source primarily because of the convenience of device control of the DV playback source and single wire hookup.


Vic
 

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Discussion Starter · #3 ·
Thanks, Vic.


Simplified source device control is a good reason for using a FireWire interface. Anything that simplifies even one small part of the process makes it a better solution for me, and hopefully it will help others in my family do some DVD recording for themselves. Of course I need to make up my mind and select and buy a recorder to get started.
 

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Yes, the process from DV->MPEG2 is all digital. Inputing from s-video or composit is an analog-> digital conversion.


Troy
 

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Discussion Starter · #5 ·
I realize that the process from DV > MPEG-2 could and should be all digital. I am just looking for confirmation that it has been implemented that way. I am wondering about this because of the lengthy time it takes to transcode from DV to MPEG on a PC or Mac.


Is there a hardware device that acomplishes this (digital DV to MPEG-2)?


I am still suspicious that the consumer DVD recorders that offer DV inputs are likely converting to analog and then using their same encoder as they would with an analog input.
 

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Budget_HT,


I asked your question previously:

http://www.avsforum.com/avs-vb/showt...12#post2419612


I never got a definitive answer. Read down a few postings from mine and you will see a few comments in reply to me.


My suspicions are exactly like yours. Wouldn't it be much cheaper to do D/A -> A/D to do conversion? A D/A converter is relatively cheap, plus the recorder already has an A/D converter feeding the MPEG chip.


The recorder might even have a way to recycle the D/A that already exists to display MPEG output to do double duty converting firewire into analog input. Resulting in virtually "free" conversion. Much cheaper than trying to do real-time conversion in digital domain.


In fact, considering that consumer electronics is very carefully engineered for low build cost, I'd be surprised if there was digital circuitry to do firewire -> mpeg transcode.
 

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I can't vouch for the Panasonics, but the Pioneer DVR-7000

is all digital. In fact, I sit next to the guy that wrote

the DV transcoder for the C-Cube encoder chip used in the

DVR-7000.


Since DV is all intra blocks, it's very easy to decode.

An intermediate analog step as suggested on this thread

would actually be a more difficult design.


Ron
 

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I've only seen one comment on this forum concerning the PQ of FireWire input on the Panny recorders: They felt the analog input recording looked better than the FireWire input.
 

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Discussion Starter · #9 ·
Quote:
Originally posted by dr1394
I can't vouch for the Panasonics, but the Pioneer DVR-7000

is all digital. In fact, I sit next to the guy that wrote

the DV transcoder for the C-Cube encoder chip used in the

DVR-7000.


Since DV is all intra blocks, it's very easy to decode.

An intermediate analog step as suggested on this thread

would actually be a more difficult design.


Ron
Thanks Ron.


It seems to me that an all digital path would give better (more accurate) results than a DV->A and A->MPEG combo.
 

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I would assume that it's all digital, but I would suggest writing an email to Panasonic Tech Support to find the definitive answer.


Troy
 

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Quote:
Originally posted by Budget_HT
...It seems to me that an all digital path would give better (more accurate) results than a DV->A and A->MPEG combo.
Maybe, maybe not. The advantages of never going analog are two: avoiding conversion and avoiding being in a format (such as analog) that is susceptible to artifacting from degrading factors in the transportation environment. It's not that clear that either advantage might apply in such a case.


Avoiding such artifacting makes sense when your transportation enviroment is hostile, such as the one terrestrial DTV and SD broadcasts must endure, but the "environment" that such an analog signal would find within a DVD recorder is not hostile, and on the contrary is completely controlled, protected, and brief, making such degradation from artifacting negligible.


That leaves conversion loss. A/D or D/A conversion resultant quality depends upon the quality of the converters and the expertise used in creating their algorithms. DV to MPEG is also a conversion, and while it doesn't pass through an analog stage, still depends upon similar factors. So whether one is better than the other is probably also negligible and could differ as to which wins out depending upon the particular manufacturer.


Attempting to split such hairs probably robs all of us of time we could instead be using to enjoy the benefits of our DVD recorders.
 

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Discussion Starter · #12 ·
TomCat, your view on artifacting makes sense to me for picture resolution, but I wonder about color accuracy. Any thoughts? Does analog have a limited range of colors when compared to M-JPEG (DV/IEEE-1394) or MPEG-2 (DVD, etc.)?
 
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