[FFmpeg-devel] H.264 + PAFF: BBC HD recording shows extreme interlacing artefacts

Michael Niedermayer michaelni
Sun Oct 28 11:03:31 CET 2007


On Sun, Oct 28, 2007 at 10:07:32AM +0100, Reinhard Nissl wrote:
> Hi,
> Michael Niedermayer schrieb:
> >> Strange is that splitting the image into images which just contain odd
> >> or even lines respectively doesn't give you two "crisp" images. After
> >> splitting the odd lines image for example once again, I've got a crisp
> >> image and one which looks like luma and chroma don't match.
> >>
> >> This leads me to the conclusion that there might still be a decoding
> >> issue with H.264 + PAFF.
> >>
> >> Shall I upload this recording for further investigation?
> > 
> > no, there is no problem with decoding, the problem is in the yv12->rgb
> > convertion, the fields have to be converted seperately not like a frame
> Just to clarify, this sounds like taking the snapshot as PNG is buggy.
> But the same artefacts are also visible when using libxv (by xine's
> option -V xv) which does the colorspace conversion in hardware.
> Is it that libxv must be informed about how to do the colorspace
> conversion or must hardware colorspace conversion be turned off in such
> a case respectively?

yes, either inform xv (if xv supports that at all) or do it in software

> As the image looks still wrong when using -V xshm, which should do the
> colorspace conversion in software, it seems that this part of code needs
> some work, too.
> > you can eiher send us a CLEAN patch which changes ffmpeg.c / ffplay.c
> > to support that or better implement it in libavfilter
> > 
> > to see some example on how to do it see libmpcodec/vf_scale.c in mplayer
> > svn
> MPlayer dev-SVN-r24824-4.2.1 (C) 2000-2007 MPlayer Team
> [snip]
> VDec: vo config request - 1440 x 1080 (preferred colorspace: Planar YV12)
> VDec: using Planar YV12 as output csp (no 0)
> Movie-Aspect is 1.82:1 - prescaling to correct movie aspect.
> VO: [xv] 1440x1080 => 1964x1080 Planar YV12
> Mplayer shows the same issue, at least when using xv. I assume that the
> above suggested changes are only meant for getting a PNG image, isn't it?

you need -vf scale=0:0:1 with mplayer and that will work with any vo which
doesnt support yuv (that is it will work with -vo x11)

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Freedom in capitalist society always remains about the same as it was in
ancient Greek republics: Freedom for slave owners. -- Vladimir Lenin
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