On 2025-09-04 22:28, Paul Gevers wrote:
Hi Trupti,
On Fri, 22 Aug 2025 10:57:12 +0530 Trupti <[email protected]> wrote:
I've investigated this build failure on ppc64el and have confirmed the
root cause is a bug in the Altivec code within libx264.
While recompiling libx264 with assembly disabled (--disable-asm) fixes
the build, it's not a viable solution due to a massive performance
regression. A benchmark I ran showed that the:
6.9s with Altivec and 54.3s without Altivec .
Given the performance impact, how would you recommend we proceed with
resolving this?
I am not involved in libx264 maintenance, I'm lurking as a Release
Team member. Reporting upstream sounds like a smart move, maybe
upstream already even found and fixed the issue, if not they may be
helpful. I guess somebody with knowledge of ppc64el assembly needs to
have a look and come up with a patch. Seems like a fitting job for a
porter.
An alternative route is to check for newer upstream versions. This
library hasn't seen a Debian update since one year ago. Might be that
the problem is already fixed.
Paul
Hello,
Thanks for your suggestion.
I tried compiling FFmpeg with the new version of libx264. The test video
no longer shows any artifacts, but it is not using Altivec
optimizations, so the conversion takes more time.
I will look into this further.
