[FFmpeg-devel] [PATCH 3/6] Add AV_PIX_FMT_NV12T.

[Alexis Ballier]

On Fri, 21 Nov 2014 10:50:42 +0100
Jean-Baptiste Kempf <jb at videolan.org> wrote:
> > Now, if I want to use the fimc device to apply some effects I can't
> > because the decoder is magically using it behind my back.
> 
> How is that relevant? Just block it.

Block what ? automatic conversion ? what fmt should i advertise if
NV12T is the only supported output ?

> > If I want to use s5p-tv to display the decoded video over HDMI,
> > then I have post-processed the frame with fimc for nothing since
> > NV12MT is accepted.
> 
> Then maybe, in those cases, FFmpeg is not the right tool, and you
> should do a HWAccel.

Besides that this belongs more to the lavd outdev, you may or may not
have the tv driver loaded & working. And this would be very specific to
socs with m2m codecs, m2m filters and v4l2 outdev, while the current
code tries to keep everything well separated: one device per "context"
so that it can work with various setups. This is probably increasing
work at application level though, but HWAccel always requires
application specific support afaik.

> > > > MFCv6 and newer don't even understand nv12mt and can output
> > > > standard nv12:
> > > > http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/drivers/media/platform/s5p-mfc/s5p_mfc_dec.c#n35
> > > 
> > > This is yet another good reason to NOT introduce a new weird
> > > pix-fmt that will stay in FFmpeg for the next 10 years.
> > 
> > It will be in kernel headers and kernel ABI for like forever, so I
> > don't understand why this is so much of a problem.
> 
> The linux kernel is not the only one around here.

you'll never get to see this format in an application outside of the
linux kernel, and probably never outside of samsung socs :)

Alexis.