See #2611
When transitioning to PLAYING we call IDeckLinkInput::StartStreams() (via GstDecklinkInput::start_streams). This can
fail for various reasons, including if the hardware device is already in use.
Previously, we logged StartStreams() failure as an element error but otherwise continued to successfully transition to
PLAYING. Now, if StartStreams() returns an error we fail the state change.
If StartStreams() fails then a subsequent call to StopStreams(), when transitioning PAUSED to READY, will also fail.
Previously, if StopStreams() failed then the state change also failed. Unfortunately this prevented the element from
later being disposed, which in turn meant the associated hardware resources was never freed. Consequently, if a
decklinkvideosrc failed to transition PAUSED to READY, then the associated hardware device could not subsequently be
used by any other decklinkvideosrc.
Now, we log an element error if StopStreams() fails but otherwise consider the state change to have succeeded. This
means that the element can be disposed and the associated hardware resource released.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/9578>
aee742223c