Setting overlay parameters on v4l2sink fails

[Nicolas Dufresne]

The overlay support in v4l2sink was designed by TI
before V4L2_BUF_TYPE_VIDEO_OUTPUT_OVERLAY was added. Contribution are
welcome, as long as it's backward compatible.

Nicolas

p.s. isn't those thing deprecated in favour of G_SELECTION now ? what
does vivid do ?

Le vendredi 22 janvier 2016 à 14:12 +0100, Andreas Naumann a écrit :
> Hi,
> 
> i observed positioning of video overlays using the v4l2sink
> parameters 
> like 'overlay-left' doesnt work. Digging a little I found out the 
> VIDIOC_G_FMT/VIDIOC_S_FMT ioctl's dont reach the overlay-driver due
> to 
> being filtered in the kernels v4l2 ioctl dispatcher functions because
> my 
> driver is not a VFL_DIR_RX but TX type.
> 
> After reading the Linux for Video API docu, it seems that the
> S/G_FMT 
> function are indeed intended for the Capture/Rx part of the Video 
> Overlay Interface. Somehow I cant image such a device but anyway,
> the 
> code that checks for RX is in place since 2012.
> 
> Now, the gstreamer v4l2sink does need a TX device doesnt it? So with 
> current kernels, the video-overlay ioctls cant ever work, or what am
> I 
> missing?
> 
> Digging further I came across another type, that is 
> V4L2_BUF_TYPE_VIDEO_OUTPUT_OVERLAY. This is per API doc intended for 
> output and shares the data structures for S/G_FMT ioctls with 
> V4L2_BUF_TYPE_VIDEO_OVERLAY. So I tried telling my driver that he 
> supports such an interface and redirected the existing s/g_fmt
> function 
> pointers (as I saw in some other implementation, I think omap).
> On v4l2sink side its a oneliner to change to using that interface ( 
> gst_v4l2sink_sync_overlay_fields()).
> 
> Voila, the positioning works!
> 
> Now, is this the way to go or what do the experts think?
> 
> 
> cheers,
> Andreas
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