Is anyone using GMC?

[kurt]

I wonder if anyone uses GMC regularly. There seems to be a bug with GMC on sse2 machines in the 1.2 tree but not many people noticed this. See here for more informations: http://celticdruid.no-ip.com/phpBB2/viewtopic.php?t=206&postdays=0&postorder=asc&start=15

Now the question: do you ues it? and if so in whitch cases? Or is it completely sensless to turn on?

[raeltheimperialaerosolkid]

I don't use ti simply because I always need to encode in a format that can be read from stand alone players.

[xyloy]

Always, along with QPEL if it's a high XviD quality encode.

But since I have a standalone divx/divxpro player, I will only use QPEL(and 2 B-frames if the player can handle it) and no GMC since DivX's GMC is different(and rather useless) if I'm doing an .AVI file(wich has not happened for a lot of time ^^U).

[kypec]

I don't use ti simply because I always need to encode in a format that can be read from stand alone players.

Same reasons apply to me.

[Romario]

I never use GMC.

[Sharktooth]

GMC is quite useless unless you disable B-Frames...

[squid_80]

Quick fix for the sse2 gmc problem.
gmc_mmx.asm, line 194
GMC_8_SSE2

movd xmm4, [esp +20]
pshuflw xmm4, xmm4, 01010101b ; Rounder (bits [16..31])
punpckldq xmm4, xmm4
mov eax, [esp + 4] ; Dst

[skal]

Hi,

Quick fix for the sse2 gmc problem.
gmc_mmx.asm, line 194
GMC_8_SSE2

movd xmm4, [esp +20]
pshuflw xmm4, xmm4, 01010101b ; Rounder (bits [16..31])
punpckldq xmm4, xmm4
mov eax, [esp + 4] ; Dst


hey? what's the problem exactly? (whilst the fix looks ok
to me, except it didn't show up on xvid-devel :) )

Skal

[kurt]

the problem is one can't use GMC on sse2 machines. 2nd pass breaks up immediately with current cvs release (1.2 tree, celtic_druid latest build). I think he could explain better the situation :)

for some time a gcc version of xvidcore.dll did the trick, but it doesn't work anymore....

Could be related to:
2006/06/17 - Enabled Skal's new SIMD optimizations for GMC

esp. since 2006.06.08 buld seems to work fine.

Debug build just exits, same as release, no crash.

Odd that encraw works though.

[ilovejedd]

...need to encode in a format that can be read from stand alone players.
Same here. Since I work mostly with episodic dvds, it's nice to be able to cram a whole show into just 1 disc (26-episode, 30-minute anime series) so I don't have to change discs all the time. For those who are already cringing at the picture quality, an avi with 640x480px at XviD 1000kbps with no QPEL, GMC, etc. shows no noticeable artifacts when viewed on a 27" CRT TV from across my room. Although pixelation and ringing are quite obvious using a PC with a 15" LCD monitor...

[skal]

the problem is one can't use GMC on sse2 machines. 2nd pass breaks up immediately with current cvs release (1.2 tree, celtic_druid latest build). I think he could explain better the situation :)


ah! looks like something completely different: a missing 'emms' for instance!

thanks for the report, will try to commit a fix for that

Skal

[kurt]

nice to hear! :)

[seewen]

I don't use ti simply because I always need to encode in a format that can be read from stand alone players.

same here

[SeeMoreDigital]

GMC is quite useless unless you disable B-Frames...Indeed... along with cropping away any black mattes.

It's not an implementation I'd recommend using. I reckon the MPEG-4 ASP world would be an easier place to understand without it... Did I say that out-loud?


Cheers

[unmei]

I used to use GMC when i still encoded DVD rips with XviD.

Today i use XviD only for real-time capturing from the TV Card and in that scenario i use fastest-possible settings and therefore no GMC.

From own experience i never really questioned GMC, but seeing how it is no longer present in AVC i probably would think twice before using it again if i ever were to use Xvid in a final backup encode again. Not because of SAPs, i don't care about those, but simply because AVC not supporting it is a hint that is maybe wasn't as effective as they (MPEG) first thought.

[squid_80]

hey? what's the problem exactly? (whilst the fix looks ok
to me, except it didn't show up on xvid-devel :) )
Skal

Some compilers don't keep the stack aligned to 16-byte boundaries. Hence "pshuflw xmm4, [esp+20], 01010101b" causes an unaligned memory error.

[kurt]

The GMC bug is finally solved (tried celtic_druids todays compile), thx to all people who are involved in this :)