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Old 11th September 2018, 11:46   #905  |  Link
SmilingWolf
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Join Date: Aug 2018
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Quote:
Originally Posted by LigH View Post
@SmilingWolf: I'll keep an eye on it, as soon as MABS passes in both branches again. But for now, there is a greater evil breaking the building of ffmpeg. If the API for AV1 was ever "frozen", it seems to melt already.
Well TBF they froze the bitstream and released a "stable" version 1.0, such issues are to be expected when using an old and moving codebase that needs some cleaning up after many different iterations.
Shouldn't take much more than removing lines 741-744 from libavcodec/libaomenc.c
This one's on FFMPEG, and will probably be fixed in a day or so

What bothers me much more is the same as the second part of your post, the inertia over months-long periods of time in the AOM tracker

Quote:
Originally Posted by LigH View Post
And yes, I shared one of the issues of GCC 8.2.0 creating unaligned RAM access when vector optimization is enabled, several weeks ago, and apart from adding more CC's, not much happened about it.
Regarding this, they are evaluating using the patch I suggested in comment 8 as a short term fix. BUT now it can't be tested with GCC 8.2 on master, because there is another couple of access violations of various nature happening at different optimization levels because of (as far as I've been able to test) some unholy interaction between GCC 8.2 and AVX code

Side note: unaligned memory access is fine AS LONG AS the ASM instructions emitted take into account memory could be unaligned. In this instance GCC 8.2 -O3 emits instructions that expect memory to be aligned to a 16-byte boundary (movdqa and movaps), while GCC 8.2 -O3 -fno-tree-slp-vectorize emits instructions fit for unaligned memory access (movdqu and movups)

My advice is to stay on GCC 7.3 for AV1 for the time being. I found the laptop I was using back in june to build A/V stuff with an old toolchain, if you want I can zip it up and upload

Last edited by SmilingWolf; 11th September 2018 at 11:59.
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