[MPlayer-dev-eng] [PATCH] Fix inverted colours when capturing YV12 in V4L2 mode

[Luc Gallant]

On 12/16/05, Jindrich Makovicka <makovick at kmlinux.fjfi.cvut.cz> wrote:
> Luc Gallant wrote:
> > I am using a virtual v4l2 driver that I created (ported from v4l1
> > actually). I can send in whatever file type I want, and in this case I
> > send in YV12/YVU420. When I send in that file type, the colours are
> > inverted. When I send in I420/YUV420 and tell mplayer about this, it
> > works fine...
>
> MPlayer never asks for YV20/YVU420. So why do you send it? You'll
> obviously get inverted colours when MPlayer requests I420 and you send YV12.
>
If Mplayer never asks for YV12/YVU420, then why can you put an
outfmt=xxx flag in the TV options? In my specific case, I put this
outfmt flag in the tv options, so I expect it to ask for that. I will
look at the S_FMT commands issued later to see what it asks for.


> > It is ok that the bt8x8 was unable to produce YV12/YVU420 natively. In
> > my opinion, mplayer should try to set an image format, and if the
> > driver responds with something that it doesn't have that image format,
> > then too bad. In the way that mplayer is right now, if a device is
> > actually sending in YV12, it will display inverted, and the user has
> > to use -of swapuv or something like this.
> >
> > Like it says in the code in tvi_v4l2.c, "// YV12 uses
> > VIDEO_PALETTE_YUV420P, but the planes are swapped", this goes back to
> > V4L1 and the fact that back then YV12 == YUV420P, which is completely
> > inverted. With V4L2, it is now correct.
>
> No, YV12 was never YUV420P. MPlayer just uses YUV420 ~ YV12 for
> convenience, because YV12 is sort of "default" colorspace, and later
> swapped the planes when copying the buffer. I might as well remove this
> code, but as long as it works and there is negligible overhead, I'd
> prefer to let it be until I hear real bugreports.
>
> > Let me know if there are any more issues or something I missed. Thanks.
>
> There are no issues. Everything works as expected. I only suppose that
> your driver (or just your approach) is bogus.
>
> Regards,
> --
> Jindrich Makovicka
>
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