[oi-dev] libjpeg-turbo and VLC

[Bob Friesenhahn]

On Wed, 2 Dec 2015, Aurélien Larcher wrote:

> Hi,
> ABI 6b, 7 and 8 are apparently backward compatible but not 9.

The ABI for 6b, 7, 8, and 9 are all different.  There is a way to 
compile libjpeg-turbo to provide either a 6b or 8 ABI.  I don't think 
it actually offers any more features when built to emulate IJG JPEG 8 
since it does not provide the additional features added by IJG JPEG 8 
(only interface structures are changed).

> So should I start by adding a libjpeg-turbo component and add possibly a symlinks like libjpeg.so.8.0.0 and libjpeg8.so (could do
> that to tell which lib to use given an ABI) ?

It should be possible for the existing libjpeg and libjpeg8.so to 
co-exist, but only one can be used for development.

Please note that the results from IJG JPEG and libjpeg-turbo are not 
always identical and libjpeg-turbo has had some issues with edge-cases 
(e.g. small accesses outside of initialized or even allocated memory) 
in the past, and possibly the present.  As a result, I can't use 
libjpeg-turbo when doing memory testing (valgrind or ASAN) under Linux 
for GraphicsMagick tests since these tests exercise edge cases.

Bob
-- 
Bob Friesenhahn
bfriesen at simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/