Ticket #265 (closed defect: fixed)
MMX2 yuv420p10 → yuv444p scaler produces vertical undithered(?) lines with GCC 4.6
| Reported by: | lachs0r | Owned by: | michael |
|---|---|---|---|
| Priority: | normal | Component: | swscale |
| Version: | git | Keywords: | yuv420p10, yuv444p, mmx2 |
| Cc: | Blocked By: | ||
| Blocking: | Reproduced by developer: | no | |
| Analyzed by developer: | no |
Description
I know this might be a PITA to reproduce since it only happens with GCC 4.6, but I’ll report it anyway.
Background: I’ve been trying to play yuv420p10 video with my patched MPlayer2 builds for Windows ( http://mplayer2.srsfckn.biz/mplayer2-high-bit-depth-latest.7z).
MPlayer2 apparently chooses the yuv420p10 → yuv444p scaler by default.
That is probably fine, but there’s a problem: The MMX2 version of that scaler seems to break with GCC 4.6.0, causing vertical lines of what seems to be undithered luma (can’t tell for sure since I didn’t actually investigate that in detail, but I’ll attach a screenshot).
The C version works fine.
This can be reproduced with for example:
ffmpeg -i test10bit.mkv -pix_fmt yuv444p -vcodec ffv1 out.mkv
Attachments
-
ffmpeg-dither-h10p.png
(96.9 KB) -
added by lachs0r 2 years ago.
- vertical lines in dithered yuv444p output
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swscale-test-results.tar.xz
(1.3 MB) -
added by lachs0r 2 years ago.
- swscale-test results for linux, win32 and win32 without assembly optimization
Change History
Changed 2 years ago by lachs0r
-
attachment
ffmpeg-dither-h10p.png
added
comment:1 Changed 2 years ago by lachs0r
Update: It only breaks with MinGW targets (even using GCC 4.5.x), which makes it even more of a PITA to debug. This is probably a MinGW/GCC bug rather than an FFmpeg bug. Sorry if I’m wasting your time here.
Edit: 3DNOW and MMX versions are also affected.
Just a hunch (I have no clue about assembly language at all), but maybe it’s a problem with the memalign hack (which is needed for MinGW)? Even though that only breaking one part of swscale wouldn’t make much sense to me…
comment:2 follow-up: ↓ 3 Changed 2 years ago by michael
maybe comparing the output from swscale-test between mingw and linux could help
Changed 2 years ago by lachs0r
-
attachment
swscale-test-results.tar.xz
added
swscale-test results for linux, win32 and win32 without assembly optimization
comment:3 in reply to: ↑ 2 Changed 2 years ago by michael
Replying to michael:
maybe comparing the output from swscale-test between mingw and linux could help
which versions did you use to generate these?
also how did you force enable mmx* 3dnow, they are autodetected in recent swscale.
thanks
comment:4 Changed 22 months ago by rogerdpack
Just ran into this too, with this version
ffplay version git-N-30610-g1929807, built on Jun 7 2011
however this version:
ffplay version N-31706-g335bbe4, built on Jul 31 2011
seems to no longer exhibit the problem for me (it was showing striated lines in mplayer with any software scaler selected, which also appears fixed now with a newer build).
vertical lines in dithered yuv444p output