Thanks a lot, David.. I feel so much dumber now, lol. Ok, I'm going to need sometime to digest all this great infomation. May I asked where you learned all this great technical knowledge that you have? I do use the wmv encoder in premiere often, to get video on my site. The client had given me a dvd with a 6 minute clip, and just wanted an avi file back. I was not encoding it for the web, basically, I was just ripping the dvd. I was trying to see if I could get the avi file size down to something that would fit on a CD. I got it down to 1.25 GB with good quality. I spent a lot of time exploring the export settings, but had no idea about how the keyframing worked, so I never employed it. Ditto for the data rate options. I have noticed how data rate affects encoding for wmv or rm files, but was not sure if the same principles were at work in the export settings options box. I will definitely be adding this letter to my " TopForum Letters" folder, lol. Guess I'm going to need to test out various other settings, since I have a better, yet still foggy, idea of what the export settings mean.... Thanks again, -Frank www.Time-LineProductions.com
David Hurdon <[EMAIL PROTECTED]> wrote: Hi Frank. The first thing I should point out is that the Export Movie>Settings function is not where you want to be for creating web-directed output. You want whatever choices you have under something like "Windows Media Export". You can use the Export Movie choices to compress video using older codecs like Indeo, used some years ago for CD play, but these days the bigger bang for your buck is web compression algorithms, and depending on the tools available these can include Windows Media Video (wmv), DivX, Real, Quick Time, and MPEG-4 to name the major players. Whatever codec you work in the parameters are the same. All web compressions are known as lossy. Some data is thrown away to reduce the file size, as it is with still image codecs like jpg. Reducing resolution and frame rate are biggies, and frame rate reduction is common in web video, although it will, depending on the source material, sometimes create jerky video because it leaves out frames that would otherwise convey smooth, continuous motion. It has no affect on duration, it just holds longer on a single frame before changing to the next one. If there's a lot of difference from frame to frame this can create that jerky look. Keyframes: In DV25 which includes miniDV, DVCAM and DVCPRO, the file is written at a constant bit rate of 3.6 MBps (MegaBytes per second). Each frame is a complete picture. Export a few frames and you'll find they are all the same size (about 126 kp if I recall correctly) which is why you can't zoom them. There isn't much information there but it's enough to convey a moving picture. When you want to make a file smaller something has to give. Compression, in simple terms, works by taking a full frame of information (keyframe) and then creating follow frames that record only what has changed between the first and next keyframe. At 30 frames per second a keyframe every half second might work fine for a talking head and not so well for a pan following a race car. Data rate: If you start with DV you're working with files that grow by 3.6 MBps. If you compress to DVD (MPEG-2), you're down to between 2000-9000 kpbs, roughly. This data rate can be handled on DVD Video disks and at the mid-point by cable and satellite with a set top box to decompress it on the fly. For high speed Internet, 300-700 kbps is the norm, and handled by the receiving computer well or not so well depending on a variety of factors. You get to a lower data rate by compressing your source material. You select that data rate according to your target audience; DVD, CD, Internet. I hope that moves toward answering your questions. Feel free to pursue the subject off-line or on, if no one objects. David Hurdon At 08:34 AM 4/6/2005 -0700, you wrote: Wow David, That was a great explanation and I saw the differences in the examples at the link. Of course now, you know some of us would some explanation of some of the points that you made... I should say that I was trying to shrink the overall size of a 6 min avi file to something that would fit on cd, so a client could upload to a server for streaming.. I was in the export setting box, but it sounds like the same principles are involved... Frame Rate: I thought if I changed the frame to something lower it have the effect of changing the duration, and/or the playback speed. I mean, if I taped at 30fps, what happens if I encode at 15fps? How will it affect quality of playback, and how will it affect the final size of the file? Keyframing: What's that all about ? I know how it works in editing, but how does it work in encoding? Data Rate: How does the data rate effect playback and size? Is higher better? of lower? should I "recompress" always, or what? Maintain data rate? LOL I'm totally lost in this area.. I appreciate any help you can give me on this. If there is some link you know with this information, I would appreciate that as well. Thanks a lot (I'll definitely be saving this answer you gave about encoding for the net) -Frank www.Time-LineProductions.com --------------------------------- 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 the Yahoo! Terms of Service. [Non-text portions of this message have been removed] 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/
