Re: impostor yv12

On Thu, Feb 05, 2004 at 01:21:29AM +0200, Ivan Kalvachev wrote:
> D Richard Felker III said:
> > On Wed, Feb 04, 2004 at 02:42:04AM +0200, Ivan Kalvachev wrote:
> >> Hello,
> >> I had send few patches and few mails to xvid people
> >> regarding their handling of YV12 format.
> >> In short they claimed that it is reversed and they swaped the UV
> >> planes. I had tracked a bug in DSHOW and VfW handling of
> >> IYUV - they had mapped it to yv12, while IYUV is the same as I420.
> >> Few weaks ago I checked the image.c routines and noticed that
> >> the thing are unchanged, but later i found out that the VfW/DShow issues
> >> have been sorted.
> >>
> >> So,
> >> In short the YV12 format is not the format that mplayer claims it is.
> >> YV12 is in fact YVU / YCrCb /, that is in no way the default MPEG
> >> standart
> >> color format. As you know in MPEG 0,1,2,3 blocks are Y, Cb is #4 block,
> >> Cr
> >> is #5 block.
> >> Yes, I know that all code over mplayer-g1 use IMGFMT_YV12 as YUV, but in
> >> fact this format is the I420 or IYUV format. The real conversion is done
> >> at vo_xv (in draw_slice around line 488). Same for vo_directx and
> >> probably
> >> all that support planar formats. I should say that now I see the reason
> >> mplayer to have always U as plane[1] and V as plane[2].
> >>
> >> Well, I don't want to change all IMGFMT_YV12 to I420, or to IMGFMT_YUV,
> >> as it is a too global change. But we should make G2 in the right way.
> >> Of cource if it is not already done.
> >
> > RTFM, this is all nonsense. MPlayer does not care about plane order,
> > except when allocating or exporting buffers for crappy external
> > codecs/filters/vo's that care.
> I DO RTFM and RTFS
> Thx for you both explaining me things I know and explain too.
> This what I say is that we always have Y U V order in planes
> and YV12 should be with flag SWAPPED set becouse it have
> its plains in YVU order.
> I would like to avoid referencing to yv12 as defalut and normal standart.

In G1, I420 gets the "swapped" flag and YV12 is "normal". I agree this
is backwards, but it doesn't particularly matter.

G2 cares even less about plane order; it's just there so that codecs
or vo's which have the "common plane" stride restriction will have it
honored.

Rich