[CELT-dev] Question on new release.

[Jean-Marc Valin]

Hi John,

On 10-11-15 07:10 PM, John Ridges wrote:
> First, I just wanted to point out that the link on the download page to 
> download 0.9.1 actually points to the 0.9.0 tarball. I'm pretty excited 
> to try it out.

Sorry about that. Just fixed it. Please want for the mirrors to update.

> Second, I was wondering if you could tell us what the ENABLE_POSTFILTER 
> conditional compilation flag actually does?

Essentially, this flag enables a new prefilter/postfilter contributed by
Raymond Chen from Broadcom. This post-filter produces a small (but
noticeable) improvement on speech and a large improvement on highly
tonal single instruments (e.g. trumpet). The reason it's disabled by
default is that there is a patent involved in this. Broadcom has stated
that they would give everyone a license to use the related patents in
the Opus codec (which is a superset of CELT) once it becomes an IETF
standard. Until that happens, I thought it was safer for people not to
use that post-filter in commercial applications, which is why it's off
by default. That being said, I encourage people to test it and report
any success/problems.

Cheers,

	Jean-Marc