Compression question / problem
alex at tweedly.net
Wed Jan 12 13:09:25 CST 2005
Richard Miller wrote:
> Looking for the simplest and quickest solution to a compression
> problem. The goal is to take 50 jpeg images (highly compressed)
> starting on a Mac, move them to our directory on a hosted web server,
> then have them downloaded and displayed on a Windows XP machine.
> Transmission time (over the Internet) is a very big factor here.
I already replied with a "detailed" suggestion - but I also want to give
a personal opinion on the overall problem.
using Rev's compress (or any other standard lossless compression
available today) is unlikely to give you very much benefit on JPG files
- it's rare to see as much as 4 or 5 % decrease in file size, and you're
unlikely to get better than 3% average on a large number of files.
I'd focus my time and energy on making good use of either the "load URL"
/ cachedURLs commands or perhaps libURL. Getting a suitable number of
transfers happening in parallel is your best hope of achieving results
you like. Exactly what "good use" means will vary depending on the
context (number of files, what's being done with them at the receiving
end, etc.). If they are photos being displayed in a gallery / slide
show, then you probably want to start with just one transfer (to get the
first one to display asap), but then build up to 4 or 6 in parallel; in
other cases you should simply start up N immediately - where N would
vary depending on photo sizes / connection speeds / wind direction (?) /
I'm sure that various people on this list would be willing to suggest
things if you can describe that part of the problem.
If "simple" is important as well as "best" result - set off all the
"load URL"s in parallel and use the resulting URLs as they become
available; let Rev's library deal with how many it emits in parallel.
[This depends on there being only 50 files to retrieve - if you have
hundreds, you perhaps shouldn't do this, certainly not without testing
it .... - but I have done upwards of 50 without problems; I didn't test
to see how many actually happened in parallel].
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