skip_try_fmt_probes is set to TRUE for v4l2src to skip interlace-mode and
colorimetry when probe caps. gst_v4l2_object_set_format_full() will add
colorimetry back to caps when iterating over the negotiated caps. There is
one case that v4l2src is first in preview state then starts recording.
v4l2src caps will change with an additional interlace-mode structure after
renegotiation, then v4l2src needs to reset. But this camera driver can't
orphan buffer pool, it causes require buffer failed as streaming is still
in active state.
To fix this, also need to add interlace-mode back to caps for camera to
avoid reset.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-good/-/merge_requests/961>
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/
5e932395a4