Does HDV compress more than standard DV?

Question

and if yes, is this necessarily a bad thing? the more I read, my mind keeps being steered into thinking "compression is bad" and "the more compression, the worse the quality." I'm on the verge of finally buying an HDV camcorder (like the HV20) and as long as it defeats DV in all the important areas like color depth, I don't see why it's a bad move to move on from standard definition! I understand that HDV takes up much more hard drive space, etc. on a computer, but if it's worth it in the long run, then it's worth it. you wanna jump on this one, Nu'uanu? and while someone is at it, just if you're able to, could you confirm that the HV20 shoots in BOTH 24p and 30p in HD?

Answer 1

It is not a matter of more compression, but a different kind of compression. HDV uses Mpeg2, which has temporal compression. Regular DV is like motion picture film, it is made of a series of complete frames, the video in each frame is compressed by a factor of 6, which is very mild, nearly lossless.  HDV has one frame in six or so, and the between frames are generated by formula. HDV is hard to edit because you don't have a frame to work with at every place you might want one to make a cut. Second HDV temporal compression does not handle action shots very well. You only see the HiDef advantage when the picture is stationary. Sports is better shot in miniDV using the 16:9 mode. HDV will become increasingly popular as more people opt for HD televisions. But for now SD is still standard.

Answer 2

High def is much more compressed than DV - it uses a form of MPEG-2.  It's a bad thing in that it makes editing a pain, and you're going to lose more video if you have a dropped frame (you lose an entire gop).  There's also the possibility of the compression being done badly.  But then it's high def, and that's a big plus!

Answer 3

In order to fit in the same space, HDV does indeed compress more than DV.

When I take 1 hour of standard definition, DV encoded, miniDV tape and bring it into my computer, it comes in at real-time. The computer' CPU is not doing much other than moving the digital information from the digital tape over firewire to the hard drive.

When I take 1 hour of high definition, HDV encoded, miniDV tape video and bring it into my computer, it comes in at less than real-time. The the camcorder's decoder and computer's CPU are having to crunch a whole lot more data that make up the (HDV) digital images from the digital tape over firewire to the hard drive.

Keep in mind, that we went from 480 lines of standard definition (DV) video data to 1080 lines of (HDV) high definition information. This is one - of several - reasons why the high definition image is so much clearer than SD.

In order for that 60 minutes of substantially more (HDV) digital information to fit in the same space, it needs to be compressed.

There are still lots of people who continue to enjoy using standard definition video... that is why cameras like the Canon XL2, GL2, Sony DCR-VX2100 and Panasonic DVX100B cameras continue to be manufactured (and sold/purchased)... and of course, ALL the high definition camcorders - of which I am aware - have the option of shooting in (4:3 or 16:9) standard definition. And if you drop below the Canon HV20, HV30, Sony HDR-HC9 and HC7, there are a couple of dozen cansumer camcorders for many manufacturers that are SD-only.

I think the statement that "compression is bad" is a little too simplistic... If I could be so bold as to change that to, "too much compression is bad", I think it would be more accurate. Personally, I think that too much compression at the first step of the process is what starts the "garbage in" because anything in the downstream process has only that original source to work with. If the amount of compression (hence data loss) is minimized, the the downstream processes have more to work with - and as the LAST step of the process, compress to fit the requirement...

Does this make sense?

Do I think it is worth it? Yes. I made the jump to HD a couple of years ago - before I had a HDTV. Now I have a HDTV - and the view is GREAT! Do I shoot in SD? Occasionally, yes - it depends on the project (if 4:3 is needed, for example). For the most part, though, I shoot HD and compress (and change resolution), as needed, at the end of the project.