OT: Some basic HD questions

will-3 wrote on 8/7/2009, 2:33 PM
Certainly the video quality/resolution of the inexpensive "HD" cams... like the "flip cam" or others... can not be the same as HD cams costing a few thousand dollars or more...

1 - As I understand it the HD file format output by these cam's may be the same... is that true?

2 - What is the most common HD file format called? (like AVI is very common for standard def)

3 - Given that many HD cams output a popular HD file format... what ever it is... what are key parameters to look at when evaluating which cam to buy and trying to compare picture quality and/or resolution?

(Other than simple optics, stabilization, accessible controls, etc)

a - 3 CCD vs 1-CCD cams??
b - CCD size? (physical)
c - Pixel density (distance between pixels horz and vert)
d - data processing within the cam's electronics...
e - is there a "raw" out put where real pixel values are transferred and stored... or do some or all HD cam's do some sort of conversion and/or compression before outputting to tape, memory, or whatever?

Thanks for any help as I'm playing catch-up on HD... as you can clearly see :)

Comments

gogiants wrote on 8/7/2009, 4:24 PM
A few quick thoughts from someone who is far from expert on such matters...

1 - As I understand it the HD file format output by these cam's may be the same... is that true?

Not necessarily. Many flash-based camcorders now use AVCHD, which promises better picture quality for comparable file size versus other formats. The big issue here is that AVCHD can be tough to edit on less-than-powerful PCs. You'll see lots of discussion of that issue here.

2 - What is the most common HD file format called? (like AVI is very common for standard def)

For flash-based camcorders, AVCHD is more and more prevalent. For tape-based camcorders (mostly going away at the consumer end of the price scale) you'll find HDV. Much easier to edit than AVCHD once you get the files onto your computer. You'll also find cameras with other file variants. In general, file format does not necessarily dictate level of quality as much as other factors with the camera.

3 - key parameters

Physical image sensor size (CCD or otherwise) will make a big difference. That plus optics and the overall system all combine. You pretty much get what you pay for. One indicator of image quality that can help is bit rate, as opposed to frame rate or resolution, but that is not the end all of quality either.

I don't know of a "raw" format on camcorders that would compare to "raw" on digital cameras.

busterkeaton wrote on 8/7/2009, 9:51 PM
You need to research HDV and AVCHD. AVCHD is a newer codec with even greater compression (think more pixels in less file size), however your computer really needs to be very fast to have a good experience editing it. HDV also requires a robust computer, but AVCHD truly pushes systems to their limits.

Also, these are both capture formats. Once Vegas has it on the timeline, you can render to various HD formats. For a lot of people the workflow might be

Capture in AVCHD
Transcode to another format for editing purposes
Render to whatever format you are delivering in.
Render to an format to archive.

You can write a whole book on working in HD. Hey, someone did.

Budget is the biggest factor in narrowing down which camcorders to recommend.
will-3 wrote on 8/8/2009, 7:42 AM
Thanks for the info. Very helpful.

Bit rate was mentioned as one of the important paramaters...

"One indicator of image quality that can help is bit rate, as opposed to frame rate or resolution"

Is the rate the data are collected from the CCD... or what?

I'm guessing the "transfer rate" from cam to compuer is fixed by either firewire or usb standards...

So what bit rate is being referenced?

Thanks again for the help.
gogiants wrote on 8/8/2009, 10:12 AM
Someone here please correct me if I don't convey this correctly!

Bit rate is a measure of the amount of data captured within the video. For example, every 720p high-def camera captures, by definition, 1280x720 pixels per frame. But some cameras have a higher bit rate, which means they are able to capture more nuanced information about things like color within the frame.

That's my understanding, in any case!