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What is the most efficient compression format for ISO files created from DVD movies?

I wouldn't mind compressing them one at a time or a whole group of them, whatever would save me the most space on my storage device.

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3 Answers

up vote 1 down vote accepted

Don't bother. First of all, the movies are already compressed. (What do you think MPEG-2, h.264, etc. are?) They're not going to compress very much at all. Second of all, even if the data were compressible, the result of them being put into an ISO filesystem makes them much less compressible than they would normally be. That's not to say that ISOs don't compress very well, just normally not as well as the raw data would.

You're talking about tons of overhead to save, maybe, a few MB per ISO.

If you really want to save space, convert the movies to a more space-efficient format, like XviD (MPEG-4 ASP) or preferably h.264 (MPEG-4 AVC).

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First, lossless movie formats don't really exist.

Attempting to capture 640x480 pixels at 24-bit color 30-times every second would result in ~27MB/second of raw video. It is very unrealistic to store that on most forms of portable media (DVD/portable players/etc.), especially when you stop to consider video at hidef resolutions like 1080p.

It only gets exponentially worse. Typically, for most DVD formats you are using an MPEG format (MPEG 2) which has a pretty good quality to loss ratio. It uses similar compression schemes to the JPEG image format.

A lot of new streaming media makes use of other compression schemes (they're still lossy compression) like h.264. Such formats are not typically readable by your home DVD player. They're still not "lossless" compression.

Additionally, moving from one compression scheme to another, will typically result in additional loss in quality.

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640x480 @ 30fps = 27MB/sec 1080p @24 fps (minimum blue-ray 1080p resolution)= 145.8 MB/sec --- With a RAW format for blue-rays at 2 hours... that's > 1TB of raw data. –  TheCompWiz Apr 15 '11 at 17:19
There's plenty of lossless video codecs. Linky However, they're generally only used for mastering or archival, not distribution due to the size and storage space required. –  afrazier Apr 15 '11 at 17:33
You are right, but in the "home-production" and "general-consumption" arenas, it's highly unlikely you will ever use them. Still "Usagi" had already mentioned that they were dvd-format. I was merely trying to point out that his description of "lossless" was incorrect. –  TheCompWiz Apr 15 '11 at 18:15
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VOB files, which are the bulk of the data on a DVD are already compressed, you will gain very little space by compressing the ISO file.

I did a sample compression of just one VOB file I had,

  • Original size: 555 MB (582,238,208 bytes)
  • Compressed with WinRar lossless compression 539 MB (565,308,348 bytes)

Roughly a 3% size reduction.

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