lossless compression of still images - recommendations?

Robert Heller heller at deepsoft.com
Mon Feb 20 01:28:45 UTC 2017


At Sun, 19 Feb 2017 15:51:21 -0800 "Ubuntu user technical support,  not for general discussions" <ubuntu-users at lists.ubuntu.com> wrote:

> 
> On Sun, 19 Feb 2017 23:37:49 +0100
> Ralf Mardorf <silver.bullet at zoho.com> wrote:
> 
> > Data compression might be useless, if the data is needed for work and
> > not just for archiving data.
> > 
> > 17,280 photos a day = every 5 seconds one photo = 6,307,200
> > photos/year
> > 
> > Assuming each photo should have a size of 10 MiB it would be
> > 63,072,000 MiB / 1024 = 61594 GiB
> >                         61594 GiB / 1024 = 60 TiB
> > 
> > That is a lot of HDD space. Assuming it should be possible to compress
> > such an amount of data a lot, then another issue does arise.
> > 
> > How long does it take
> > 
> >   1. to compress the data?
> > 
> > and much more important
> > 
> >   2. to extract the data for usage?
> > 
> >   3. What amount of uncompressed data is required for the work?
> > 
> > IOW it might happen, that for using the data, a lot of data anyway is
> > required, in a non-compressed format. Compressing data and extracting
> > data might take very long.
> > 
> > Regards,
> > Ralf
> > 
> > 
> 
> That's pretty much the size analysis I did Ralf, except for an image
> size closer to 2.6 MiB. The device produces .jpgs and so far that's all
> the testing I've done. I can tell you that running 1750 images (so a
> tenth of a day) through ffmpeg gives 149 MiB of .mp4 so there's some
> serious compression going on there (having started with 4GiB).

Both jpeg and mpeg are *lossy* compression. A lot of data is actually being
tossed. It is expected that the *human* brain will reconstruct the lost data.
(The human brain is really good at that. Computers are not so very good at
that.)

> 
> The length of time for compression and extraction are not critical
> features. Trying the previous suggestion of tap+bz2 gace a small
> reduction in file size and took a lot longer than tar.gz (by a factor
> of about ten). So really not very worthwhile. I'll try some other
> compression options.
> 
> D
> 
> 

-- 
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