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Compression issues using iMovie.
October 15, 2004 4:27 AM   Subscribe

When I went with iMovie's "web compression" option -- 240x180, 12 frames a second, unspecified level of compression and "medium-quality" stereo sound -- for a recent 5.5 minute DV clip I shot, I got a 6MB .mov that I felt had serious compression issues. My first swipe at using the "expert" compression settings, conversely, gave me a 230MB file for the same resolution; a second pass was "only" 54MB but the nature of the "better" compression scheme made it look worse. And in my experience, making it an .mpg only makes it bigger. And yet I've seen TV episodes that look reasonably good full-screen and are only 350MB .avi files. I feel like I should be able to get 1 MB/minute of 240x180 video at great quality -- I've downloaded streaming video that would back up that assumption. Can someone point me toward wisdom?
posted by blueshammer to Computers & Internet (9 answers total)
 
The videohelp.com mac forum. I was all set to post some suggestions until I realized that you were using a Mac and Quicktime, both of which I'm fairly ignorant.
posted by Mayor Curley at 4:35 AM on October 15, 2004


Tips on doing the same in Windows would be appreciated by others (eg, me), I'm sure. I have similar problems going from DV down to something acceptable at a smallish file size.
posted by humuhumu at 5:21 AM on October 15, 2004


mencoder, the encoder part of mplayer, should do you fine. I'm pretty sure it's available for mac, linux and windows.

The avi's you speak of are DivX avi's most likely (or mpeg4). Mencoder makes these just fine. I routinely get full length movies at full DVD resolution down to about 1500 megs.

The subtleties of getting good divx encodings are many, but here's a good place to start.

mencoder -vf scale=720:480 -spuaa 4 -oac mp3lame -ovc divx4 -o ./inputfile ./output.avi

This takes the input, inputfile, which can be anything that mplayer can play (almost anything) and produces a divx4 output file named output.avi. The -vf scale option it to set it to DVD resolution: set that to whatever you like. The -spuaa 4 is a guassian blur sort of thing, which I usually add to most encodings that require scaling. -oac mp3lame means the output audio codec is mp3, -ovc dvx4 means the output video codec is divx4. Mencoder has many MANY options for these but I find these acceptable.

I think it has some way to reduce the frames/s, I don't really know.
posted by RustyBrooks at 7:13 AM on October 15, 2004




And if you want an explanation why these full-screen AVI files are so much smaller and higher quality than what you're able to make from iMovie, the reason is that those AVI files are likely using a better codec than you are. There are plenty from which to choose.
posted by majick at 7:44 AM on October 15, 2004


Is there a good divx/etc. plug-in for the major browsers so that people can watch this on the 'net without having to download it and opening VLC?
posted by blueshammer at 8:50 AM on October 15, 2004


I asked a similar question here a while back and got some great advice from filmgeek on the matter. All my problems were solved (on a pc though) by getting hold of Sorenson Squeeze
posted by gravelshoes at 9:12 AM on October 15, 2004


Wisdom, thy name is Sorrenson 3.

Best size/quality ratio I've found, but then I tend to lean toward quality, size be damned. Still, I've spent hours crouched over calculators, trying to find that compression sweet spot, and Sorrenson is the best codec I've found. You see it around a lot, too, in releases by professional operations.

3ivx D4 is pretty good. For 320x240 30fps, 700mB/min is pretty good. I don't know about smaller frame rates and resolutions. There are codec calculators that you can play with on versiontracker.com.

QT's version of the MPG-1 codec is merely okay. There are several Windows versions that rock. I can't wait until MPEG-4 is ubiquitous, because it rocks. For now, it's not very supported.
posted by squirrel at 9:31 AM on October 15, 2004


On Windows you can use Gordian Knot to create XviD/DivX. That seems to be how most of the TV shows passed around the net are done. See www.doom9.org for info.

Is there a good divx/etc. plug-in for the major browsers so that people can watch this on the 'net without having to download it and opening VLC?

As long as you have the right codecs your normal video player plugin should work (Quicktime Player, Windows Media Player). On OS X you can use 3ivx for the codecs. On Windows you can just download the original DivX and XviD distributions.
posted by mcguirk at 9:07 AM on October 16, 2004


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