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

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)

/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.