[MPlayer-dev-eng] [PATCH] Fix inverted colours when capturingYV12 in V4L2 mode

[Luc Gallant]

I noticed the commit. Thanks for taking time to look at my point of view.

Luc Gallant

On 12/16/05, Jindrich Makovicka <makovick at kmlinux.fjfi.cvut.cz> wrote:
> Luc Gallant wrote:
> > On 12/16/05, Jindrich Makovicka <makovick at kmlinux.fjfi.cvut.cz> wrote:
> >
> >>Luc Gallant wrote:
> >>
> >>>In this case, this is my point. When I put outfmt=yv12, tvi_v4l2 requests
> >>>this format from my driver, and my driver agrees to send it in.
> >>
> >>No. MPlayer requests fcc_mp2vl(IMGFMT_YV12), which is V4L2_PIX_FMT_YUV420.
> >>
> >
> > In the V4L2 API Spec, it says that V4L2_PIX_FMT_YVU420  == ('YV12')
> > http://v4l2spec.bytesex.org/spec-single/v4l2.html
>
> I know what these formats are.
>
> > According to me, it was broken and set to YUV420, causing part of the
> > problem.
>
> If tvi_v4l* does VIDIOC_S_FMT(V4L2_PIX_FMT_YUV420) and you subsequently
> return the YVU image, you have a problem. I agree with that.
>
> > Now, YV12 and I420 are distinct formats. There is a part in
> > the patch that resets this. Basically, in the mplayer code, because of
> > the following statements in different parts of the code:
> >
> >      case V4L2_PIX_FMT_YUV420:        return IMGFMT_I420;
> >
> > AND
> >
> >     case IMGFMT_YV12: return V4L2_PIX_FMT_YUV420;
> >
> > YV12 was defined as equaling I420, which to me is a problem.
>
> Grrrr... that's why the plane swapping code is there. Once more: If
> outfmt=YV12 is used, tvi_v4l* requests I420 from the card (the same when
> you used outfmt=i420), and it swaps the u/v planes when copying it. So
> everything works fine.
>
> Or, as I see now, this is how it worked before 1.28 tvi_v4l2 commit,
> which made this hack useless because now YV12 is in fact not used even
> for output :)
>
> So I'll probably apply your patch to make things clear.
>
> --
> Jindrich Makovicka
>
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