jwarner wrote:In my (humble) .
Why would you want to fill up your hard drive with information that says "a blue bit here, a blue bit here, a blue bit here, etc. etc." when it is far more effective to say, the next 2 million bits are blue.
This is similar to how video is compressed but that's not exacly how it works, it varies according to the compression method but basically a .jpg compresses by grouping like colors together. It in affect softens the image. With a large image a jpg compressed at 90% you would never know the difference between a bmp and a jpg unless you zoom in. Here's an example, the image in the left pane is a image from 3 megapixel camera, if notice the slider it's set at 90% compression which produces an image very near the original. If you look in the right pane you will see the image colors have changed. Where the quality loss comes in is when you keep recompressing, eventually all the detail is going to be loss and if you keep recompessing the affect is no longer a softening affect but produces blocks of color. This is the same thing as reencoding a mpeg, evertime you reencode you lose detail but it's a little more complicated than that....
Here's an example of the same image compressed at 20%, the biggest thing to note here is huge block of a single color in the upper center part of the image in the right pane.:
Where the issue comes in with MPEG is the way it's constucted, some frames take data from the previous frames which is one of the reasons it compresses so good, when cut one of these frames it needs to be reconstructed by the editor. This sometimes leads to audio sync when you cut on these frames....why I don't know. It really depends on the editor.
You can learn more about the differences between AVI and Mpeg here: http://www.digitalfaq.com/capture/avivsmpeg.htm
Encoding video needs much more processing obviously and early digital video cameras couldn't do it effectively so opted for an uncompressed format. Newer cameras don't have that problem so use compression (MPEG2 or MPEG4). Soon, I expect, all video cameras will record in MPEG4 format directly to flash media so there will be more more mechanical nonsense to deal with for storage.
I'll disagree with the mpeg4 part, mpeg4 was created to be a highly compressed format it to has the same issues as using MPEG2 as a source. The reason tape is used is because of it's storage capacity, you can only fit 20 minutes of DV-AVI on a DVD in addition to the fact of the speeds the DVD would need to be spun to record it, 16x drives might do it but I'm not sure. Remember though there is no difference between the file on tape compared to the one on DVD or any other media. If they wanted to they could record mpeg to tape as well but don't because there is no reason too. Shortly you will see another format with high capacity, blu-ray, flash whatever. They will still use a less compressed format though. And to further that you will still probably only get 1 hour since the new high definition TV's and cam's are coming on the market.
Just because Ulead seems to have a problem handling MPEG's doesn't seem sufficient reason in my mind to save a bunch of storage-hungry AVI's. Especially since, if your eventual goal is to burn a DVD, it will have to end up as an MPEG2 at some point!
Yes it aapears there is bug somewhere but VS8 isn't the only editor that has issues with mpeg. My curiosity is whether it's just prevalent when using mpeg or if AVI has the same issues too. I haven't seen anyone post that the same issue exists using AVI as source? Anyone?
Again MPEG is not for editing for more reasons that the audio sync ones. An extreme example but here's the difference http://phpbb.ulead.com.tw/EN/viewtopic.php?t=1428
3000CBR MPEG encoded from a DV-AVI, Lot's of macroblocking:
3000CBR MPEG encoded from the 8000CBR MPEG, a real lot of macroblocking:
Last edited by thecoalman on Mon Feb 14, 2005 1:43 pm, edited 9 times in total.