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,
I tested the issue described earlier using x264 r3222 (upstream new
version) with FFmpeg 7.1.1 on Debian Trixie (ppc64el).
The artifacts in video encoding still persist when using:
ffmpeg -i vtest.avi -vcodec libx264 -to 2 out_h264.mkv
I will report this issue upstream.
This is just an update to confirm the issue remains in the newer
version.
Thanks and Regards,
Trupti
