Codecs (enCOde/DECode) are confusing to virtually all newcomers to digital video. All of them come in two parts, the usually free decoder and the some free, some not, encoder. With Windows Media for example, the player (decoder) is free and so is the encoding software. With DVD (MPEG-2) you must usually buy both the player and the encoder, due to licensing costs. But all encoders deal with the same issue, namely the size of NTSC/PAL digital video files.
Digital video from a camcorder is created in the RGB colour space. red, green, blue. If you're familiar with image editors like PhotoShop you have probably seen colour pickers, a little eye dropper icon that displays colours in three sets of numbers, like 235-114-190. Each of these number strings describes a combination of red, green and blue and each can be anything from 0 to 255. Zero is black, 255 is white. So, when you read that your display is set for 16 millions of colours, what you are seeing is the possibility of displaying 255 times 255 times 255 individual shades, which if you do the math is about 16.5 million. Writing that much information, and decoding it on the fly is what makes working with digital video so demanding for a computer system. And that's before you double it up with transitions and stacked clips. So, to make that much data small enough to travel through various pipelines, from dial up Internet to cable or satellite high definition television, encoders are developed. For the web as an example, turning something that requires 3.6 MBps (megabytes per second) into 500 kbps (kilobits per second) requires reading the data, replacing say 1000 shades of blue with 50, writing that new data stream and moving on, frame by frame. The reality is more complex but that's what's happening in general terms. The more bandwidth available for transmission, the less you have to squeeze the original in the encoding. That's why a video made for high speed Internet on cable can be 500-750 kbps while a DVD disk-based video stream can be as much as 9,600 kbps, although in practise more like 4-7,000 is typical. The other issue is standards. Like the old VHS versus BETA tape war of many years ago, Internet video was born with a variety of encoders available, each requiring the decoder part to be installed on the PC trying to play it. When I first saw video on PC it was from an encyclopedia on CD, and I couldn't see half the selections because I didn't have the right decoder - although at the time that message might as well have been in Greek for all I understood about it. So today we have formats like, WMV, MOV, MPEG-1, MPEG-2, MPEG-4 in various flavours including standard and several non-standard, like Microsoft's version, and I believe DIVX as well. There are some free players available that try to read everything out there but deciding on what format to use remains a problem as long as there are significant numbers of potential viewers who don't have the required software installed. In office environments it often isn't possible to load whatever software you want, due to IT department restrictions, so you pick a format you're reasonably sure your audience can work with. I'm sorry if I buried you in detail. Some of this stuff isn't easy to boil down, or to learn in a hurry. David Hurdon www.contentshop.tv At 12:32 PM 10/24/2004 +0000, you wrote: Hi Martin; I downloaded DivX, but what I dont understand is your "I used the DivX-5 codec". Thanks anyway, shall be exploring it further. Maarten ------------------------ Yahoo! Groups Sponsor --------------------~--> $9.95 domain names from Yahoo!. Register anything. http://us.click.yahoo.com/J8kdrA/y20IAA/yQLSAA/ADr1lB/TM --------------------------------------------------------------------~-> Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Adobe-Premiere/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
