Hi, welcome to the site!
I read this statement in the capture cards section:
Cannot do MPEG. DV colorspace is often harmful to analog color quality, especially if converting VHS to DVD. Few options, minimal control.
I'm really interested in the source for this statement. How do I learn more about DV to MPEG colourspace in such a way that I can verify this statement.
The source of this information is me -- somebody who's been working with digital video for well more than a decade now, and analog for almost a decade before that.
There are two schools of thought, when it comes to analog to digital transfer.
- the "good enough" crowd (compression and noise is acceptable)
- and the "it needs to be better" crowd (compression is not suggested under certain conditions, noise should be pre-filtered)
Honestly, that's how you separate pros from amateurs. And just to make sure there's no confusion, pros always want the best quality.
Most of the "compressors" out there (referring to the people doing the compression) are willing to jump straight to MPEG-2 or MPEG-4, and to hell with quality. It's about speed, churning out crap as quickly and cheaply as possible -- quality is secondary.
Some compressors are more careful with it, using intelligent settings to get compressed-but-good quality -- but they're the minority. These are folks who seek out the best hardware MPEG encoders, and do their best to pre-filter the analog signal.
The main benefit of compression is size, and therefore ease of use. (DVD-Video, Flash video, H.264, etc)
The "better" crowd goes one further, preferring uncompressed or lossless video conversions, because their footage is needed for later editing. They don't want compression to be re-compressed for a lower quality output.
The main benefit of uncompressed/lossless is quality, but sacrificing use.
DV falls between these two.
While some would say it's the "best of both worlds" -- it's actually just a terrible format at either one. It compresses poorly and isn't portable. But then it also isn't a clean signal for editing, as it generally has artifacts.
Also distinguish "shooting" and "converting" in your head. DV footage shot with a DV camera will be clean, as it relies purely on its sensor for acquiring the source image. Analog-sourced video is much dirtier. And as you may know, noise is what makes compression fail to work effectively. So DV converted video will be noisier.
If you look back at the earlier documentations of the DV format, you'll notice there was never any mentions made of using it as a "all-purpose" video format. It was made to shoot with. Using it for conversion is a backwards hack, if anything, made at a time when Pentium II and 5400rpm hard drives were as fast as tech really got for consumers (the target audience of the format).
Now, to aid in DV compression, they cut an unusual corner -- colorspace.
You almost need to understand how analog colorspaces work. I'd suggest reading VCR Troubleshooting & Repair by Gregory Capelo and Robert Brenner
(ISBN 0-7506-9940-X) for help with that. It's a long hard read, but ultimately worth it.
Now then, most analog video is 4:2:2 colorspace. The chrominance is -- in the interest of keeping it quick and simple -- half of the luma. DV further splits it into quarters.
Now this is where the schools of thought start to mush together a bit. Some claim that DV is "good enough" to capture all the bandwidth available on VHS. Others notice flaws in it. Both could be correct, as it's not uncommon for certain issues to vary from source to source, or even hardware to hardware.
Further compounding this issue is that fact that DV is an open format, and several companies have their own ideas of what that looks like. They each have their own codec versions: Canopus, Sony, Canon, JVC, Matrox, etc. Personally, I think Matrox has the best one, and it can be very good at times.
4:1:1 when shooting video is fine, because that's the native recording spec. But converting from one format to another, it can be obvious that something has been lost in the digital translation.
Adam Wilt has gone over some of this on his site, although his opinions are yet again a bit different. I don't think he really likes any of the colorspaces, or its use as a conversion format, but he does seem to think it is (at least in theory) "good enough" to capture everything. Don't let me put words in his mouth, though -- his writings are out there for you to read on your own.
So there's really not going to be anything for you to "verify" aside from the theory. In practice, professionals have differing opinions on whether the theory actually happens.
I will soon have a job and will be making a donation. Thank you very much for all your help!
This is a wonderful website and thanks to LordSmurf too!
Excellent! It's how we're able to do what we do for folks like yourself.
Generally such long answers would be reserved for Premium Members, but it's hard to pass up a great question.
Hope that helps.