[Dorian Gray]

Hi folks,

I have a 713.7 MB MPEG-4 file, compressed by yours truly a long time ago from Motion JPEG sources that I have long since discarded. I would like to send this to someone on a CD, i.e. 702.8 MB. Using OS X's ZIP archive creator the file size drops to 709.4 MB. Is it likely that any file compression app could get it down to 702.8 MB?

The alternatives are:

(1) encode the video again from MPEG-4, which would reduce the quality a lot and take a long time
(2) split the file in two with QuickTime Pro and burn two CDs
(3) use a file compression app to split the file into two and burn the two parts to two CDs

The second option is an acceptable solution this time, but I often come across this problem (e.g. fitting large files into 10 MB email limits, etc.) so I'd be interested in other file compression apps, particularly ones that are significantly more efficient than ZIP and/or can split archives into multiple files (preferably with an easy GUI).

Ta very much!

[ghoti]

Since you're trying to compress data that is already quite well compressed, you will just have to try out a few compression programs and see which one happens to shave off those few percent from this particular file. You could try gzip --best, do zip from the command line (with -9 to get the most compression), rar, etc.

Or you could simply burn the movie onto a DVD

[chucker]

bzip2, RAR or LZMA (7-zip) typically yield the best results. zip is a very weak compression scheme and mainly used today for performance and ubiquity, not efficiency.

7zx and EZ 7z will help you compress to LZMA.

[Dorian Gray]

Appreciate the tips ghoti, but there is the little matter of my not having a DVD burner! I'm still not comfortable with the command line, but I'll try that as a last resort.

chucker: I don't suppose you have a copy of either of those apps, preferably EZ 7z? I can't find somewhere to download them.

[chucker]

http://sixtyfive.thesneaky.com/contents/7zX_1.6.4.dmg works for me.

[Banana]

Someone correct me on this, but aren't there CD with 750MB or something like that?

[Dorian Gray]

There may be Banana, but 7zX has solved my problem beautifully. That is a fantastic app. I am very impressed. Dead easy to use, dramatically better compression than OS X's ZIP archive creator, and useful options such as splitting an archive into multiple files. Highly recommended.

That said, it is seriously CPU and memory intensive. It took my 1.33 GHz G4 over half an hour to compress the MPEG-4 file I mentioned in my post, using normal compression efficiency mode (there are also maximum and ultra compression levels!). This compares to about 2 or 3 minutes for OS X to create a ZIP from the same file. But 7zX is much more efficient: the final file size is 670.9 MB. Impressive.

[Banana]

Glad it all worked out.

[Dorian Gray]

Gah! I compressed the wrong fecking file! (One of 677 MB.) How I managed to do that I don't know, but suffice to say the compression ratio isn't anywhere nearly as good as it appeared due to that error.

In ultra compression mode my computer cranked out the right file in about an hour, resulting in a file size of 706.2 MB. (Performance was nearly identical on high and low processor settings, suggesting a front-side bus bottleneck. RAM usage was astronomical in ultra, consuming around 700 MB of real memory!) This is an improvement over OS X's built-in ZIP (709.4 MB), but in my opinion, the small improvement would only be worth the exponentially longer compression time in rare circumstances. And it doesn't quite get under the 702.8 MB limit I'm looking for.

Nevertheless, I do still feel 7zX is a very nice little app, and it gives me an easy way to break the file into two for burning to two CDs. And perhaps it performs very well with normal data, i.e. not an already compressed MPEG-4 file. But it's not as magic as it first appeared. Indeed, I should have been suspicious of that result.

[chucker]

Well, there's rzip if you want to go extreme. That's gonna use a lot of RAM though.

[ghoti]

I would have been very suprised if 7zip had been that much better than zip, especially given the source file. I don't think you will be able to go much below those 706 MB, certainly not below 702. While there may be significant differences between compression algorithms for text files etc., things are quite different when your source file already contains almost no redundancies to begin with.

Could you split the file so the bigger part just fits onto the CD, and then send the the remaining few MB by email?

[Dorian Gray]

chucker, I downloaded "large-corpus/archive", mentioned on that rzip page, and compressed it with 7zX on ultra mode: the resulting compression ratio was 6.88, i.e. even better than rzip (which got 6.03).

ghoti, good idea about emailing the remnant. In fact, that is what I shall do. Problem solved.

Thanks to everyone for the very useful discussion.