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From Markus Schaber <>
Subject RE: Proposal: new fsfs.conf properties
Date Tue, 11 Jul 2017 12:53:45 GMT

(Sorry, it seems my previous message was sent _very_ prematurely :-(

From: Pavel Lyalyakin []
> Hello Paul,
> On Sat, Jul 8, 2017 at 2:51 AM, Paul Hammant <> wrote:
> >
> > 1. compression-exempt-suffixes = mp3,mp4,jpeg
> >
> > 2. deltification-exempt-suffixes = mp3,mp4,jpeg
> >
> > Regardless of the setting of 'compression-level', #1 above two mean certain
> things can skip the compression attempt.  It must give up at a certain point
> right?
> >
> > Same for deltification re #2
> >
> > I'm assuming debate happens now. Then y'all let me go off and diligently
> file a Jira ticket for this feature request, or I slink away suitably
> admonished...
> >
> > - Paul
> I'm not sure whether this is going to be useful. How do you expect these
> exemptions to help Subversion users? What's the story?

I agree partly. Skipping compression for known "incompressible" formats like mpX, png or gif
can come with performance benefits, saving some CPU cycles (see the recent performance disccussions
on this list)

However, I'm not sure whether the same amounts for deltification. There are editing tasks
which do not reencode the whole image / movie, and they can profit from deltification, for

- Lossless rotation / cropping of jpeg images.
- Editing / stripping the EXIF data of jpeg images.
- Embedding / dropping the preview thumbnail of jpeg images.
- Lossless MP3 editing (e. G. via mp3DirectCut).
- Editing MP3 meta data (e. G. Song Title)
(... and more...)

In all those cases, skipping deltification can drastically increase storage.

Best regards

Markus Schaber

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