Quantcast DV myths vs. Canopus (hype?) - digitalFAQ Forum
  #1  
06-03-2004, 08:11 AM
GRSmith GRSmith is offline
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The DV Myth Guide has addressed my questions more directly than anything else I've discoverd. So this Forum seems like the logical place to complete my understanding.

My current understanding from the DV Myth Guide is (basically) that DV is DV is DV. It does not come in flavors. A DV "stream" generated by one vendor is indistinguishable from a DV "stream" generated by any other vendor (assuming stream is the proper word).

If this is exactly true it would answer most of my confusion. But, there is still a good deal of contradictory "information" out there on seemingly legitmate and respected sights.

So, please help me resolve the following:

1) I own an ADCV100 from Canopus. Right there on Canopus site you will see the following:

"At the heart of ADVC100 is Canopus's proprietary DV codec chip providing the industry's best picture quality preservation during analog-to-DV and DV-to-analog conversion."

What!!?? A "proprietary DV codec chip"!!?? If DV is DV is DV how can Canopus claim their DV is any better than anyone else's DV???
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  #2  
06-03-2004, 08:45 AM
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I'm sorry to pepper you with questions but I'm just full of this stuff, having looked high and low for an answer on many dozens of sites spread sparsely over many months.

Here's 2):

On the Canopus site you can download something called the "Canopus DV File Converter", which claims to convert "between all Microsoft DV file formats and all Canopus DV file formats".

"DV formats"???

Well, that isn't exactly what they say and I may have never noticed it if not for the DV Myth Guide.

Correct me if wrong, but what I now think they are saying is that this utility will re-wrap the DV, changing the Canopus wrapper to a MS wrapper and the other way around, leaving the DV itself completely untouched.

Is that correct? Am I finally getting it?
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  #3  
06-03-2004, 09:02 AM
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Like anything else, the way the file is created and implemented can vary.

Even an MPEG is an MPEG is an MPEG ... and assuming all GOP/bitrate/DC/fps/etc is the same ... where all specs match ... even then, one encoder will vary from the next. The Cyberlink way is different than the Intervideo way is different from the Matrox way is different from the Ligos way. They each have their own quirks.

I think we agree on "flavors".
Analogies: HuffYUV is strawberry AVI.
MJPEG is chocolate AVI.
DIVX is lemon.

Now, Canopus DV vs MS DV vs MainConcept DV ... that's like comparing vanilla from Blue Bell and vanilla from Ben & Jerry's. The same, maybe a slight quirk to set it apart from the rest, but not something monumental to hype up. If you went into a restaurant and order ice cream for dessert, while you can easily peg chocolate vs vanilla, there's not much chance you can pick the supplier. That's pretty much what it boils down to.

Canopus makes their chip create the files oh-so-slightly different from the next guy. Huge think worth hyping up? hardly. It's just DV (4:1:1 in NTSC, which ain't great!). Far cry from 4:4:4 uncompressed, 4:2:2 on tv and 4:2:0 from DVD.

Canopus is who I feel has saturated the market with DV baloney. DV has it's place, but it's far from perfect. I'll take a SVHS or Betacam SP camera any day compared to DV. I'll convert with any number of cards before I waste time on DV conversion. It's just another method of video, surely not the best one, and one that will likely be replaced in just a few years (by true 4:2:0 or 4:2:2 cameras, at a consumer price).

Canopus is the only video company I know that blows smoke up people's butts about "pro this" and "pro that" ... others talk about features. Canopus has this disgusting ego that you can't beat away with a stick. Actually, Sony and Panasonic are like this a bit too. No coincidence that many people readily believe the marketing hype about their items. It's a shame so many have been blinded this way.

Resolution aside, and tape problems aside, thinking just signal quality, DV was a step down from VHS as far as I'm concerned. Cramming your luma/chroma values down so low is just really not good.

Now don't get me wrong ... the cards work well ... and you'll probably have great results ... but it's not the end-all, be-all that's sold to so many. The ADVC is better than probably 90% of other cards out there (not ATI, Hauppauge, or Matrox, however).

All it has is DV ... the Canopus quirks version ... but still just plain old DV.


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  #4  
06-03-2004, 11:07 AM
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OK, I appreciate analogies. In fact, more than most guys I've met in life. But, at the same time I'm an engineer and you probably know how anal we can be.

So, even though **after** I know exactly what's going on here I may agree with your summary wholeheartedly, right now I'm strictly interested in understanding this in a very squared-away, buttoned-down, technical sense.

Technically... meaning: taking all those little things into account which you have (over time) concluded are (practically speaking) inconsequential, I still want to know the details of what's really happening.

Let me try putting it this way, in order to reduce the wiggle room.

Internal to the ADVC, the output of the Canopus digitizer is fed through a Canopus-proprietary chip-based codec. That much we know without dispute.

Now, in order to reverse that process in a way that precisely reproduces the original digital stream (digital, not analog) -- without even a single-bit error -- is it true that you would have to use a Canopus decoder?

Then, regardless of the answer, I guess that leaves me with one or two more questions. - GRSmith
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06-03-2004, 09:12 PM
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Yes ... but that assumes the Canopus decoder is perfect, which has been debated, and is why many opt for other decoders like MainConcept and even Microsoft.

I'm actually a journalist, not too big on the tech talk. I understand a great deal of tech, video, etc, but I have my limits.


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  #6  
06-03-2004, 11:54 PM
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Understood. And feel free to refer me elsewhere. But, what I'm getting at here is this.

Basically we've just concluded that only a Canopus codec can "faithfully" decompress DV which had originally been compressed by that same Canopus codec. Where, "faithfully" means: in a precise mathmatical reversal of the original process.

That makes sense to me. And, you hear this said about other codecs all the time. So the same should be true here.

But, what that would inescapably seem to imply is this.

If you suck Canopus DV off the firewire and save it blissfully, as a "virgin" MS AVI, you must (properly) first decode it with a Canopus codec and then recode it with an MS codec.

If that's the case, then by the time your DV becomes a file it must already be a generation once removed from the original.

No one ever seems to talk about that. This is one of the big things I don't get. Do you think folks don't realize what's going on? Or that they do but have concluded it's not worth any concern?

And the other thing. If this is a proprietary Canopus codec, then how can all these third-party software tools be compatible with it, even according to Canopus' own site?

Something just isn't right here. Or, it is right but the rightness of it is never discussed or explained.

Anyway, you can tell how much this bugs us anal types.
- GRSmith
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  #7  
06-04-2004, 01:31 AM
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Well, DV is a format as such, and though the algorithms to achieve said final file are proprietary (as Canopus states about its ADVC), the final output will be a DV in spec. DV has specification to some degree (the variance is mainly on how well the 4:1:1 compression takes shape).

The only thing that these variances affect are the visual quality, normally issues like how well reds are maintained, etc.

Most people, as you have guessed, will not notice, or if they do, it's too complex for them to care. I care for most details, but I have my own cut-off points too (example: open vs closed GOP on MPEG2, something I don't care about, as the differences are not worth bothering with, as it applies to quality differences).

The AVI file is just a wrapper, a "container" if you will. When you transfer the file to the PC, it is just transferred. Now, the catch is when you READ the DV-AVI on the PC (playback, editing, whatever), the Canopus DV software CODEC will supposedly be the most faithful rendition of what the hardware codec has made. Now, is that true? Some say yes, some no. Even if it really is a perfect replica of the hardware codec, some insist that MainConcept, DataVideo, Microsoft, etc codecs will give better image quality. This is done because assumedly the info is not read back as precise with these non-Canopus codecs. Others can read it, because again, it is still DV format (meaning certain aspects of the file are still constants, even though some aspects in it creation were proprietary variables).

In situations like these, practive outweighs the need to know the theory. Even if Canopus software DV codecs are supposed to be superior, let you eyes guide you to what looks best.

And if the Canopus software DV codec falls flat, blame the Canopus marketing machine for (yet again) hyping something that needed no hype.



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  #8  
06-04-2004, 03:48 AM
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Ah yes. How quickly I forget my lessons. An AVI is just a wrapper! I even said that in my second posting!

OK, so I would have to save that DV stream as something obviously different, like an MPEG. Then my question would apply. But, it would also be moot since it's obvious that an MPEG would be one generation removed from the original anyway.

So, the bottom line on DV is that there may be technical difference but most "normal" people ignore them. Or, when they do pay attention to them the result will vary depending on taste.

Thus, while it may be true that only a Canopus codec will decode a Canopus-encoded DV in the exact way that Canopus intended --- that way may not be the way preferred by the end user.

The end user may actually perfer the results obtained by decoding a Canopus DV using an MS codec.

I just need to losen my sphincter a little and accept that. The DV realm is more an artist's quarter than a scientific community.

Is that about right?
- GRSmith
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  #9  
06-04-2004, 07:35 AM
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Now you're getting it.

The techs or video guys at Canopus thought their was was the best around. But other don't agree. Personally, I hate the red shift of Canopus (both the hardware AND the software codecs ... a direct result of bad usage of the already inferior 4:1:1 for NTSC DV).

I sometime find my 2 inches from the tv screen looking at something like this ... then I stop myself .. look up and think to myself "what the hell am I doing?" .. and then go back to the couch.


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