Hey all.
I’ve been trying to .zip a rather large media file that’s in .avi format in order to get it to CD-size. It seems that .avi doesn’t compress much. Assuming I can find shareware that will allow me to convert it into different formats, what format compresses the best?
There isn’t much you can do with an AVI file. The AVI file format already has compression in it, so when you try to compress it even further, you don’t get a whole lot out of it.
Generally, MPGs tend to be slightly better on compression than AVIs, but the difference is not large.
One that isn’t already compressed. 
How big is the file? And is this for archiving or do you want to play it from CD? Anyway, have a look at http://www.vidomi.com/viewtopic.php?topic=6844&forum=1 as you might find some of their suggestions useful.
Okay, now that I’m browsing, I’m seeing mentions of CD-R’s that hold more than 700 meg. Do these exist?
(Sorry, I’m kinda clueless when it comes to tech / hardware)
Yep. They go up to 870 Megs (99 Minutes). There’s also an 800 Meg/90 Minutes version. I’ve only used 700 Meg/80 Min CD-Rs, but I’ve seen the other ones in stores. Any decent computer supply store should have 'em.
If you have a lot of time on your hands (and don’t mind wasting a lot of it getting things right) you can re-encode your avi files to be smaller. However, it’s not easy to do, and, depending on your processor speed and size of the media file in question, it can take a looooong time to re-encode.
Encode time will vary depending on your computer speed and what encoder you’re using. To give you an idea, I can convert AVIs containing MPEG-4-based codecs (e.g. Divx,Xvid) to MPEG-1 VCD a bit faster than realtime. It takes me about 15 minutes to convert a 22-minute TV show. And once you have your files in MPEG-1 VCD, you can use a regular CD burner to burn them to Video CDs that are playable on most DVD players.
Whoops. I meant to add in that post that I’m running an Athlon 1800 and using TMPGenc to convert.
Media files (video, audio, and still images) are usually compressed using some form of “lossy” compression, which is generally much more efficient than lossless compression like ZIP. But any sort of good compression will generally leave you with a file that can’t be compressed any further (if it could be, then the original compression routine would have already done that). Since the lossy compression is so much more efficient than the lossless compression, it’s usually best to just use the lossy compression.
Many forms of lossy compression will have different settings for how much you want to compress the file, but higher compressions will result in lower quality. The defaults are usually set to where it’s very difficult to notice the loss of quality, but go too much further, and it’ll start to be noticeable.
You can convert AVI to MPG and the file size will be smaller but you will not recover the original AVI. There is no way to gain anything using non-lossy compression such as Winzip on a file which has already been compressed.
Sometimes yes, sometimes no. It depends not only on the bitrate of the input AVI, but also on what bitrate you specify for the output MPEG. From what I’ve seen on the Internet, most people using Divx stick with a bitrate significantly lower than the MPEG-1 VCD spec of 1150kbps, so an MPEG conversion generally means a larger file size.
Okay, so as tangent to the thread, I’ve decided to just go after an 800Mb CD-R. Now, my friend tells me that not all CD-R drives can handle them. Any way to check / know for certain before I blow cash on the CDs?
Find your burner on this list.
The largest size of CD-R that is allowed under ISO CD-R specifications is 700MB. Burning more data to a disc, even if supported by the disc and your drive, will prevent some drives from reading the disc. The more you burn, the fewer drives that will be able to read the disc.
If you burn in ISO Mode 2, you’ll get 800MB per 80minute CD-R. This is the mode the Audio CDs, VCDs, and SVCDs are burned in. The only downside is that you lose error correction, so scratches, dirt, or even fingerprints can result in data loss.
Most AVIs are compressed with a variant of the MPEG4 video compression format (such as DivX or XviD). This is currently the best video compression technology available, and offers vastly superior compression to the MPEG1 format used in .mpg files.