Hi, On Mon, Nov 7, 2011 at 12:46 PM, Reinhard Tartler <[email protected]> wrote: > On Mo, Nov 07, 2011 at 18:20:50 (CET), Måns Rullgård wrote: > >> Reinhard Tartler <[email protected]> writes: >> >>> tags 647824 upstream >>> stop >>> >>> On So, Nov 06, 2011 at 17:53:30 (CET), Harald Dunkel wrote: >>> >>>> Package: libav >>>> Version: 4:0.7.2-1 >>>> >>>> If I build the current xbmc snapshot, then it dies at runtime when >>>> creating thumbnails for wmv files. See http://trac.xbmc.org/ticket/11789 >>>> for more details >>>> >>>> http://article.gmane.org/gmane.comp.video.ffmpeg.devel/134444 >>>> >>>> provides a workaround. Do you think this could be included in the >>>> libav and libav-extra packages? >>>> >>> >>> That patch does not apply to Debian's libav package. In fact, it seems >>> that this bug is still present in the master branch. >>> >>> I was able to reproduce the segmentation fault using the following >>> command in libav *master* (inspired by >>> https://ffmpeg.org/trac/ffmpeg/ticket/397): >>> >>> ./ffmpeg -v 9 -loglevel 99 -i >>> /srv/scratch/fate-suite/amv/MTV_high_res_320x240_sample_Penguin_Joke_MTV_from_WMV.amv >>> -sws_flags fast_bilinear -vf "scale=640:480" -vframes 1 -vcodec png >>> output.png >>> >>> Unforutnately, this (adapted) patch does not seem to fix the >>> segmentation fault: >>> >>> diff --git a/libswscale/x86/swscale_template.c >>> b/libswscale/x86/swscale_template.c >>> index 5e7df5c..51ea303 100644 >>> --- a/libswscale/x86/swscale_template.c >>> +++ b/libswscale/x86/swscale_template.c >>> @@ -1657,6 +1657,11 @@ static void RENAME(hyscale_fast)(SwsContext *c, >>> int16_t *dst, >>> DECLARE_ALIGNED(8, uint64_t, ebxsave); >>> #endif >>> >>> + // HACK: gcc 4.6 no longer decrements esp, >>> + // use this to make it reserve space for the call >>> + // return address >>> + void *dummy; >> >> The real problem here comes from hiding a call inside inline asm. > > That sounds pretty plausible. > > To make matters more complicated, I've tried disabling the MMX2 version > of hyscale_fast with this patch: > > diff --git a/libswscale/x86/swscale_template.c > b/libswscale/x86/swscale_template.c > index 5e7df5c..b7a75b1 100644 > --- a/libswscale/x86/swscale_template.c > +++ b/libswscale/x86/swscale_template.c > @@ -1843,7 +1843,7 @@ static av_cold void RENAME(sws_init_swScale)(SwsContext > *c) > if (c->srcBpc == 8 && c->dstBpc <= 10) { > // Use the new MMX scaler if the MMX2 one can't be used (it is faster > than the x86 ASM one). > #if COMPILE_TEMPLATE_MMX2 > - if (c->flags & SWS_FAST_BILINEAR && c->canMMX2BeUsed) > + if (c->flags & SWS_FAST_BILINEAR && c->canMMX2BeUsed && 0) > { > c->hyscale_fast = RENAME(hyscale_fast); > c->hcscale_fast = RENAME(hcscale_fast); > > AFAIUI, this makes swscale fallback to the slower hyScale() function and > avoid this buggy implementation. Unfortunately, I get another > segmentation fault here:
That's not right, scaling coefficients are different so you need to account for that. I'll have a look at this... I'm not against removing hscale_fast altogether, including the scale coefficient specialcase handling etc. Ronald _______________________________________________ libav-devel mailing list [email protected] https://lists.libav.org/mailman/listinfo/libav-devel
