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

[Nicolas Pomarède <npomarede@xxxxxxxxxxxx>]

Le 09/11/2014 16:56, Eero Tamminen a écrit :
> 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.

Hi

patch looks fine to me, but maybe the option could be "--avi-png-level" 
instead, in case we later add more codecs, each one could have its own 
compression's level parameter.

Or --avi-codec could be <x>[,n] with x =png or bmp and n is an optional 
compression level ?

Also, you could apply the png compression to screenshots too maybe ? (or 
leave it to 9, as it's not that cpu intensive as recording a video)

> 	- 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.

I'm more in favor of doing lossless compression in Hatari (bmp or png) 
and then leave it to external programs (ffmpeg or others) to further 
compress the resulting video.
But if someone feels like adding jpg compression, why not, but we might 
end with many dependancies.


Nicolas