Re: PNG coding

From	BartC <bc@freeuk.com>
Newsgroups	comp.lang.c
Subject	Re: PNG coding
Date	2016-11-18 11:56 +0000
Organization	A noiseless patient Spider
Message-ID	<o0mq7i$67c$1@dont-email.me> (permalink)
References	(3 earlier) <58044c2b-c4d4-cfd7-7142-2b5ca73a6c28@verizon.net> <o0g2tk$ou4$1@dont-email.me> <20161116152343.8f327ba657c914b38a9a8492@g{oogle}mail.com> <o0hoim$hra$1@dont-email.me> <o0maak$tva$1@news.albasani.net>

Show all headers | View raw

On 18/11/2016 07:24, BGB wrote:

> a lot of my other formats have a more complicated interface and
> implementation, but mostly for other reasons of speed. PNG remained
> simple, partly as earlier on I have basically given up on making it
> fast. some aspects of PNG's design basically make fast decoding (much
> past around 40-50 megapixels/second) essentially a road-block.

That doesn't sound too bad. The fastest C jpeg decoder I've tried took 6 
seconds for an 80 Mpixel image (IIRC), so some 13Mpix/second. (Although 
that image had full chroma resolution so more info than normal.)

> I had tried before, but just couldn't really manage to get it much
> faster than this.
>
> some of my other codecs can generally be a lot faster (faster ones
> getting 300-400 Mpix/sec per thread for decoding, *), but at the cost of
> a lot of hair, and frequently lackluster quality/bitrate.

Again that's very good unless you're talking about something like 
uncompressed BMP where it depends on how fast you can load a file into 
memory. (But BMP is lossless so probably not.)

Doing a test now, of simply reading an 80MB file and expanding each byte 
to three, to end up with 240MB in memory (and doing nothing more with 
the result), took 0.27 secs so an upper limit of just under 
900MB/second, using gcc-O3, and even that takes advantage of the file 
already being cached.

With your figures, what size of input file does 300-400Mpix represent? 
(I guess this will be video rather than still images.)

-- 
Bartc

Thread

PNG coding ruben safir <ruben@mrbrklyn.com> - 2016-11-15 14:40 -0500
  Re: PNG coding "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-11-15 12:02 -0800
    Re: PNG coding ruben safir <ruben@mrbrklyn.com> - 2016-11-15 15:20 -0500
      Re: PNG coding "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-11-15 12:25 -0800
  Re: PNG coding "James R. Kuyper" <jameskuyper@verizon.net> - 2016-11-15 15:34 -0500
    Re: PNG coding Popping mad <rainbow@colition.gov> - 2016-11-15 20:57 +0000
      Re: PNG coding "James R. Kuyper" <jameskuyper@verizon.net> - 2016-11-15 16:12 -0500
      Re: PNG coding jadill33@gmail.com - 2016-11-15 14:00 -0800
        Re: PNG coding Jorgen Grahn <grahn+nntp@snipabacken.se> - 2016-11-20 11:14 +0000
    Re: PNG coding Richard Heathfield <rjh@cpax.org.uk> - 2016-11-15 21:45 +0000
      Re: PNG coding "James R. Kuyper" <jameskuyper@verizon.net> - 2016-11-15 17:15 -0500
        Re: PNG coding Richard Heathfield <rjh@cpax.org.uk> - 2016-11-15 22:41 +0000
          Re: PNG coding Melzzzzz <mel@zzzzz.com> - 2016-11-15 23:49 +0100
          Re: PNG coding Anton Shepelev <anton.txt@g{oogle}mail.com> - 2016-11-16 15:23 +0300
            Re: PNG coding Richard Heathfield <rjh@cpax.org.uk> - 2016-11-16 13:57 +0000
              Re: PNG coding BGB <cr88192@hotmail.com> - 2016-11-18 01:24 -0600
                Re: PNG coding BartC <bc@freeuk.com> - 2016-11-18 11:56 +0000
                Re: PNG coding BGB <cr88192@hotmail.com> - 2016-11-18 12:48 -0600
                Re: PNG coding BartC <bc@freeuk.com> - 2016-11-19 00:21 +0000
                Re: PNG coding BGB <cr88192@hotmail.com> - 2016-11-19 01:50 -0600
        Re: PNG coding Melzzzzz <mel@zzzzz.com> - 2016-11-15 23:42 +0100
        Re: PNG coding BGB <cr88192@hotmail.com> - 2016-11-15 17:53 -0600
          Re: PNG coding "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-11-15 16:25 -0800
        Re: PNG coding raltbos@xs4all.nl (Richard Bos) - 2016-11-18 08:15 +0000
          Re: PNG coding jameskuyper@verizon.net - 2016-11-18 09:35 -0800
          Re: PNG coding supercat@casperkitty.com - 2016-11-20 14:34 -0800
      Re: PNG coding BartC <bc@freeuk.com> - 2016-11-16 19:38 +0000
        Re: PNG coding Richard Heathfield <rjh@cpax.org.uk> - 2016-11-16 22:16 +0000
  Re: PNG coding "Mr. Man-wai Chang" <toylet.toylet@gmail.com> - 2016-11-16 21:14 +0800
  Re: PNG coding Jean-marc Lienher <jean-marc.lienher@bluewin.ch> - 2016-11-16 20:55 +0100
    Re: PNG coding BartC <bc@freeuk.com> - 2016-11-16 20:31 +0000
    Re: PNG coding Richard Heathfield <rjh@cpax.org.uk> - 2016-11-16 22:24 +0000

csiph-web