17 replies to this topic

[lyallp]

How about being able to generate Compressed CD Images and mount them without having to uncompress them in their entirity?

I am sure some people would be willing to sacrifice some of that 200x speed increase for smaller CD images

...Lyall

[zamiel]

Hi. There's been a couple of posts regarding image compression a wee while back. Though it sounds like it could've been considered once upon a time in:

http://forum.alcohol...?showtopic=5797

Phoenix's post in the review section probably can answer why its not made an appearance as yet:

Having no image compression in Alcohol also lost a few points, but this is a small thing as there is very little to gain from having a built in Compression, as little space is saved and an image can not be run compressed.

You can read that here:

http://forum.alcohol...?showtopic=4451

[lyallp]

After a bit of reading, I would like to comment on using NTFS or FS compression.

I have my images on a FAT32 filesystem (I use the FS as a share point to Linux).

FS compression is not an option for me, whilst I appreciate it may be for others.

What I was thinking of doing was 'backing up' my Images less frequently used images to a DVD, multiple to a DVD. The theory is that I might be able to fit an extra Image if they where all compressed.

The theory is (since disk space is a bit short) that I would insert the DVD with the relevant image on it and then use Alcohol120 to mount the image.

The image backup to DVD has become more important to me since the concept of CD rot has started making itself known.


Anyway, thanks for your fast response.

....Lyall

Edited by lyallp, 13 May 2004 - 11:40 AM.

[mrtchandler]

Why would compression of an image be small, when I compress my image files and uncompress them when I want to use them. I'm getting typically >50% compression (using 7 zip) and decompressing does not take that long, admittedly on a high end machine but 6 second delay whilst the image is uncompressed does not seem to be too much of an issue.

I use a script to uncompress the image, mount the image and another to then unmount and delete the uncompressed image. Not the cleanest, but if Alcohol had built in on the fly decompression, surely that would not be an issue if it was an option. (7 zip is supposed to run at 20-30MB/s on 2GHz machine which is at least 10 times spead improvement over a cd, if cpu load is reduced to effect the software in a compressed image, surely this is not to much of an issue, other than the coding)

Regards
Tony

[Andareed]

It depends on contents of disc. I would generally expect that installer itself cmopresses files fairly well. So I think that any further compression would be minimized to around 20%. Anyway, you can try using ntfs compression - it saves ~10-20% or so.

[MrCrowley]

NTFS compression sucks!!

I have a folder on my hard drive that is compressed using NTFS compression it contains 21 cd images, total size is 9.5 gigs compressed size is 8.5 gigs its almost worthless!

I think the best idea for compression would be as mrtchandler says, by running a script to quickly decompress/mount in 1 swoop. 7zip and rar are probably the best candidates.

[Jito463]

MrCrowley: You should do your math before you speak. Compressing from 9.5GB to 8.5GB is ~11-12% compression. I used WinRar 3.3 with maximum compression to shrink down my WarCraft III mds/mdf images, and got ~11% compression. So, I wouldn't say NTFS compression sucks since it got about the same amount as WinRar did. CD images can't be compressed that much, as there's not a lot of free space as it is.

[MrCrowley]

I used WinRar 3.3 with maximum compression to shrink down my WarCraft III mds/mdf images, and got ~11% compression.

Yes well really i guess it depends on the contents of the cd image, Newer pc games are already very heavily compressed as games get bigger the demand for compressing the data on the cd gets higher so when you try to compress the image with anything the results are not so good. All i can say is my folder contains mostly older games, most of which require to load data from the cd to play (so they contain uncompressed data).

A better way to compare compression would be something like a playstation cd image which contains uncompressed data. Rar does a much better job of compression in this case.

Also theres cdda which barely even compresses at all no matter what you use to compress it with, for which i had the idea in this thread: http://forum.alcohol...showtopic=13053 but no-one answered me when i asked simply is it possible?

[Andareed]

If you have 2048 bps image, you will find it can't compress much. If you have raw 2352 or 2448 bps image, it will compress much more. This is because you get repeated characters (namely 00's and FF's) frequencly.

[Iwo]

I vote for bzip2`ed images support. bzip2 is fast, powerful enough (more than zip), sourcecode is given. I mean at least decompressing - e.g. 7-zip can compres using bzip2. Usage could be e-z - just compress image.iso (or .bin etc.) using bzip2-compatible program and mount image.iso.bz2 using Alcohol.

[Mat]

I did a little comparison of compression of 3 different types of Alcohol image:

1) Website backup, mostly html with some images

806 megs original
581 megs NTFS compressed (28% compression)
412 megs zipped (49% compression)
362 megs bzip2 (55% compression)

2) Development tools, exes, zips, etc.

564 megs original
502 megs NTFS compressed (11% compression)
470 megs zipped (17% compression)
466 megs bzip2 (17% compression)

3) Game backup (SafeDisc 2)

752 megs original
639 megs NTFS compressed (15% compression)
596 megs zipped (21% compression)
590 megs bzip2 (22% compression)

Overall:

2122 megs original
1722 megs NTFS compressed (19% compression)
1478 megs zipped (30% compression)
1418 megs bzip2 (33% compression)

So for the tested images NTFS compression isn't too bad and i'll certainly enable it. Although i only tested one game, if they all compress like that the advantage of having some built in zip compression in Alcohol isn't that great over regular NTFS compression.

Edited by Mat, 15 September 2004 - 03:30 PM.

[Iwo]

Could you test also bzip2? Just use 7-zip for example (www.7-zip.org) and pack using bzip2

[Mat]

Sure, i've added bzip2 to the post above. Although bzip2 just beat zip in compression, bzip2 was unbearably slow. I should have timed them all but the zip and NTFS compression took less than 2 minutes on each file, possibly under a minute whereas bzip2 took over 10 minutes for each and it was agonising waiting for it to finish! These compression timings roughly agree with those in the table at the end of the page here.

I used 7zip for the bzip2 compression on its default settings and Directory Opus for the zips on its default settings (normal compression in both cases). I think the only practical compression method would be zip on a low compression (ie. fast) setting. These tests were on a 3ghz machine so i dread to think how slow they would be on other machines.

Edited by Mat, 15 September 2004 - 03:35 PM.

[Iwo]

Could you add time of compression?

Under PIII 800MHz bzip2 gains 0.5mb/sec, ZIP really maximum level for ZIP: 0.4mb/sec, ZIP fast: arounf 4-6x faster than bzip2

BZIP2 decompression speed under PIII 800: 1.45 mb/sec

ZIP is too weak, bzip2 has better compression ratio. Also decompression speed for ZIP depends very slightly on compression level. More compressed file => faster decompression (sic!) for each format with same dictionary size. Since bzip2 is free (ZIP also?) i think that Alcohol could handle them both Not too much code to add!

[ejallison]

What about NTFS sparse files?

Addendum: Or...
You could have Alcohol use a swapfile [or allocate RAM, which would probably faster] and have it read the entire iso and temporarily decompress whatever it needed. I think some Linux liveCDs [Knoppix in particular] use that; you could integrate that with Alcohol [use Cygwin or something]. Big pain in the neck from how it sounds, but it'd be worth it ... if you wanted it.

Edited by ejallison, 08 October 2004 - 04:33 AM.

[Iwo]

You could use LZMA algorithm. There is good SDK: {no external links please - mod} - my test shows that LZMA "fast" (dictionary 32kb, word size 32) has slightly better compression speed and also slightly better ratio than bzip2.

LZMA features:

    * Compressing speed: 500 KB/s on 1 GHz CPU
    * Decompressing speed:
          o 8-12 MB/s on 1 GHz Intel Pentium 3 or AMD Athlon.
          o 500-1000 KB/s on 100 MHz ARM, MIPS, PowerPC or other simple RISC CPU.
    * Small memory requirements for decompressing: 8-32 KB
    * Small code size for decompressing: 2-8 KB (depending from speed optimizations)

LZMA decoder uses only integer operations and can be implemented in any modern 32-bit CPU (or on 16-bit CPU with some conditions).

[dillbilly]

Since I use Alcohol primarily for backing up my audio CD's, and not programs, compressed images would be a great asset to me. Currently I have my CD's compressed as lossless APE files, so to mount them I have to uncompress them then mount the WAV/CUE in order to listen to them or rip a track. The ability to mount the APE file directly from the CUE sheet, or to have some sort of built in compression so my images were smaller when I ripped them would be a huge improvement (for me at least. I doubt there are many other people who do it that way)

[mrtchandler]

Should have looked at the replies sooner, but to add a few comments, most of the stuff I'm doing is related to Aviation Content DVDs, and most software supplied on DVDs seems to use very little compression. I get on average a 3.8GB goes down to 1.9 GB, some go as low as 1 GB, the highest (image maps) 3.0 GB.

Now admittedly these do take some time to compress (~20 minutes per Disk on a Athlon 64 system max compression) but only take about 30 seconds to decompress, again all using 7-zip.

NTFS compression is okay, but, having Alcohol do inline compression, and has been posted there are various options, all freely available, would be excellant, mileage will vary, but the benefits are surely worth it.

Typical from other posts, CD's seem to compress anywhere between 5-60%, typical is 10-25%, but!!! for DVD's and sorry I only have my testing for this, compression is anywhere between 10-75%, typical is 20-50%.

Maybe a wrapper, such as Daemon-scripts could be used to take/filter compressed images rather than directly in Alcohol, just a thought, anyone?