Re: [hatari-devel] [patch] AVI recording PNG compression level

[Eero Tamminen <oak@xxxxxxxxxxxxxx>]

Hi,

On sunnuntai 09 marraskuu 2014, Troed Sångberg wrote:
> JPG should only be used for photos with "natural content"
> PNG should be used for clipart, computer graphics etc
>
> (The algorithms used by JPG assumes things about the content in the same
> way as MP3 assumes things about the nature of sound & ears)

Sure, but you can disable the lossy part and still get
some compression from cosine transformation & LZ.


	- Eero
 
> /Troed
> 
> On Sun, Nov 9, 2014 at 4:56 PM, Eero Tamminen <oak@xxxxxxxxxxxxxx> wrote:
> > Hi,
> > 
> > Douglas commented that depending on (Falcon screen) content,
> > AVI recording performance can drastically change:
> > http://www.atari-forum.com/viewtopic.php?f=68&t=26775&p=261461#p261358
> > 
> > Attached is patch allowing to specify PNG compression
> > level from command line, in case someone wants to
> > experiment with it.
> > 
> > According to png.h header, levels 3-6 would offer nearly
> > same compression for PNGs as Hatari's default (9, highest),
> > but potentially with significantly lower CPU overhead.
> > 
> >         - Eero
> > 
> > PS. When we were (nearly decade ago) testing different
> > image format libraries for ARM and optimizing them, JPG
> > compression and decompression were in general clearly faster
> > than PNG.  PNG was better just in not losing details from
> > images with high contrast / few colors.  C-code for JPG
> > handling was also much more natural fit for SIMD
> > optimizations.
> > 
> > -> Especially for recording Falcon hi-color demos,
> > 
> >    JPG compression could be better fit than PNG.