The pool orphaning function was colling internal _stop() virtual function
implementation. This is not thread safe, as a private lock inside the buffer
pool is supposed to be held. Fix this by keeping delayed _stop() and orphaning
the GstV4L2Allocator instead (REQBUFS(0)).
Then, protect the orphaned boolean with the object lock for the case a buffer
is being released after we have orphaned the buffer. That would otherwise
cause a QBUF to happen while the queue is no longer owned by the buffer pool.
This boolean is otherwise used and set from the streaming lock, or after
threads have been stopped (final cleanup).
Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-good/-/merge_requests/648>
v4l2 plugins
============
The idea is a bit the same as the idea for the v4l1 plugins. We want
one generic v4l2element, and a few child objects (probably only two:
v4l2src and v4l2sink):
/-------- v4l2src
v4l2element ---=
\-------- v4l2sink
Both v4l2src and v4l2sink have a uncompressed and a compressed
recording-/playback-mode. Since this is all part of v4l2, the 'client'
of these elements, i.e. an application using v4l2src/v4l2sink, will
hardly notice this. All capsnego stuff is done inside, and the plugin
knows which formats are compressed and which are not.
Please note that the v4l1 and the v4l2 plugins are *not* compatible
concerning properties. Naming has been kept the same where possible,
but in some cases, properties had to be removed or added to make
full use of v4l2.
V4L2 API: http://linux.bytesex.org/v4l2/.
http://v4l2spec.bytesex.org/
/usr/include/linux/videodev2.h or
Kernel patches available from
http://dl.bytesex.org/patches/.
Articles:
http://lwn.net/Articles/203924/
ca61a76987