[FFmpeg-devel] PATCH grab.c, adding support for hardware based VIDIOSFPS
Mon Jun 4 19:56:40 CEST 2007
Trent Piepho writes:
> On Mon, 4 Jun 2007, Benoit Fouet wrote:
> > mmh wrote:
> > > >
> > > > this is wrong.
> > > > from my videodev2.h:
> > > > #define VIDIOC_S_RDS _IOWR ('V', BASE_VIDIOC_PRIVATE+11,
> > > > struct v4l2_radio_rds_set)
> > > >
> > > > i can (if i want) change the BASE_VIDIOC_PRIVATE+11 by
> > > > BASE_VIDIOC_PRIVATE+20
> > > > this ioctl will be defined, but will not do what you want...
> > > >
> > > > moreover, it can just return without any error, and lead you to believe
> > > > that framerate is accepted by the camera, even though this is not true...
> Not exactly. The size of the argument to the ioctl (struct
> v4l2_radio_rds_set) is part of the ioctl number. You could assign two
> different ioctls to BASE_VIDIOC_PRIVATE+20 and they won't be the same if
> the size of the arugment and the direction (R, W, WR) doesn't match.
> > > #ifndef VIDIOSFPS
> > > #define VIDIOSFPS _IOW('v',BASE_VIDIOCPRIVATE+20, int) /* Set fps */
> > > #endif
> > >
> > yes, i really think this should be removed
> > and, FWIW, syntax in v4l2 is, most of the time, as follows:
> > VIDIOC_S_*
> > i don't know if it's planned to add such a feature in future videodev
> > version, though...
> This isn't a v4l2 ioctl, but a v4l1 ioctl. V4L2 uses the ioctl range 'V',
> while v4l1 uses 'v'. Notice the case difference. Also BASE_VIDIOCPRIVATE
> is the base for v4l1 private ioctls and BASE_VIDIOC_PRIVATE is the base for
> v4l2. It should still be VIDIOCSFPS to have correct v4l1 naming
> The whole ioctl name clash thing isn't solved by just removing the #define
> from the ffmpeg code. What happens if someone compiles on a kernel where
> 'v',private+20 is SFPS and then runs on a kernel where it's something else?
> This is why changing ioctls once they make it into the kernel isn't
Thanks for explaining this to me.
Then can I for this device which support this particular behavior
integrate this type of functionality. The only thing which I'm clear
on is that what I have done is not the correct thing to do... If
someone has a suggestion for this I would like to here it.
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