Bug 26463 - -march=pentium4 causes hissing/white noise in OGG audio playback
Bug#: 26463 Product:  Gentoo Linux Version: unspecified Platform: x86
OS/Version: Linux Status: RESOLVED Severity: minor Priority: P2
Resolution: FIXED Assigned To: sound@gentoo.org Reported By: hypnos75@gmail.com
Component: GCC Porting
URL: 
Summary: -march=pentium4 causes hissing/white noise in OGG audio playback
Keywords:  
Status Whiteboard: 
Opened: 2003-08-11 23:50 0000
Description:   Opened: 2003-08-11 23:50 0000 
I recently upgraded to GCC3 (3.2.3), and rebuilt libvorbis in the process,
going
from ebuild 1.0-r2 to 1.0-r3.  The latter does not filter out "-march=*" flags,
and this caused a problem with rock music, which has some jarring higher
frequency sounds like cymbal crashes and electric guitar harmonics.  So I
changed my CFLAGS from "-march=pentium4 -Os -pipe" to "-mcpu=i686 -Os -pipe"
and
now my OGG tracks sound nominal.

My recommendation is to retain the "-march=*" filter in the libvorbis ebuilds.


Reproducible: Always
Steps to Reproduce:
1. (see "Details")

------- Comment #1 From Martin Schlemmer (RETIRED) 2003-08-12 06:48:59 0000 ------- 
Whoever does libvorbis please.

------- Comment #2 From J. Ellis 2003-08-15 23:39:01 0000 ------- 
Can you retest with -r4. If it is still an issue we can filter pentium4 out.

------- Comment #3 From Hypnos 2003-08-16 02:50:14 0000 ------- 
There is some improvement, but still not acceptable.  Going from
"-march=pentium4" to "-march=pentium3" doesn't help; "-mcpu=*" is works fine,
as before.

This Forums thread suggests that "-march=*" is untenable for AMD architectures
as well:

http://forums.gentoo.org/viewtopic.php?t=73292&highlight=libvorbis

------- Comment #4 From J. Ellis 2003-08-16 03:37:29 0000 ------- 
Understood. I'll add something to filter march in r4. Thanks.

------- Comment #5 From J. Ellis 2003-08-16 04:38:34 0000 ------- 
Now filtering -march=pentium?. Let me know if this works.

I'm not convinced that the athlon-zp problem is the same. Reading into the forum post i'd guess that -sse +3dnow results in the simd patch not being applied and consequently everything being okay.

If this is the case then perhaps the patch could be applied if (sse || 3dnow), but i have no idea if that will result in any improvement on althon-xp.

Anyway, that bug will wait for another day; i don't have an athlon box to experiment with.

------- Comment #6 From Hypnos 2003-08-16 04:54:36 0000 ------- 
Where are you filtering?  I'm not seeing any changes after "emerge rsync" nor
through the CVS browser on Gentoo.org.

Anyway, I'm hitting the sack soon -- let me know when you commit the changes,
and I'll try out the ebuild to make sure it works.

------- Comment #7 From Hypnos 2003-08-16 08:34:13 0000 ------- 
Revised -r4 has propagated, and works fine.