The pseudo buffer pool code was using gst_buffer_is_writable()
alone to try and figure-out if cached buffer could be reused.
It needs to check for memory writability too. Also check map
result and fix map flags.
https://bugzilla.gnome.org/show_bug.cgi?id=734264
Most important part here is special-casing "device busy" so the application
is able to provide better feedback when another application is using the
device.
* Make the driver write directly into each GstBuffer to avoid memcpy().
* Don't memset() the buffer before reusing it.
* Recycle memory by keeping two spare buffers. Two because the sink
downstream may keep a ref to the previous buffer.
Note that we align buffers on highest possible byte boundary (4096) so we
don't have to take into account what kind of alignment the driver requires.
Original commit message from CVS:
* configure.ac:
* sys/Makefile.am:
* sys/winks/Makefile.am:
* sys/winks/gstksclock.c:
* sys/winks/gstksclock.h:
* sys/winks/gstksvideodevice.c:
* sys/winks/gstksvideodevice.h:
* sys/winks/gstksvideosrc.c:
* sys/winks/gstksvideosrc.h:
* sys/winks/kshelpers.c:
* sys/winks/kshelpers.h:
* sys/winks/ksvideohelpers.c:
* sys/winks/ksvideohelpers.h:
New plugin for low-latency video capture on Windows (#519935).
Uses Kernel Streaming, the lowest level API for doing video capture
on Windows (more or less just raw ioctls).
