[Bug 712754] v4l2: add support for multi-planar V4L2 API

[GStreamer (bugzilla.gnome.org)]

https://bugzilla.gnome.org/show_bug.cgi?id=712754
  GStreamer | gst-plugins-good | git

--- Comment #27 from Julien Isorce <julien.isorce at gmail.com> 2013-11-26 14:49:09 UTC ---
(In reply to comment #26)

> Actually it doesn't, it would return 1 (ARGB, RGB, UYVY), 2 (NV12) and 3
> (I420). GST_VIDEO_INFO_N_COMPONENTS() returns the values I mentioned above.
> 
> Sorry if I'm a bit pedantic about that comment, I'm just afraid that there's
> some further confusion that could cause incorrect usage of the API in the code.
> 
> There are 3 different concepts here: the number of components, the number of
> planes and the number of memory areas. In this code you only care about the
> last two.

Sorry I confused myself :)
Is the following comment ok ?

/* n_gst_planes is the number of planes
 * (RGB: 1, YUY2: 1, NV12: 2, I420: 3)
 * It's greater or equal than the number of v4l2 planes. */

> Yes, I'm just wondering if we should print a warning if meta->vplanes[i].length
> != GST_VIDEO_FORMAT_INFO_SCALE_HEIGHT (finfo, i, height).
> 

You mean GST_VIDEO_FORMAT_INFO_SCALE_HEIGHT (finfo, i, height) * stride[i] ?

Well not sure about the warning because it's a normal behaviuor. There is the
.bytesused for that actually, that I set (the user has to set it for OUTPUT
devices).
What I understand is that length >= bytesused because the device may use
aligned memory or any other reason.


> > 
> > I added a FIXME/comment, is it ok ?
> 
> Check with git blame who added that specific code and why, maybe they can tell
> you how to reproduce the reason for this code. It's probably uvch264 related :)
> If it seems safe to ignore in your case, a FIXME should be fine.

ok. I let the FIXME.

For log:

http://cgit.freedesktop.org/gstreamer/gst-plugins-good/commit/sys/v4l2/gstv4l2bufferpool.c?id=2e80c0d2c08d1fbda3286bfe397153ec65661322

http://cgit.freedesktop.org/gstreamer/gst-plugins-good/commit/sys/v4l2/gstv4l2bufferpool.c?id=b1378f159accd4fd574c2a24883eef27196fac09

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