In roll-up mode, when no more timed text comes in, the closed
captions may remain displayed on screen indefinitely (unless the
decoder implements a timeout, but that is not mandatory).
Expose a property to erase the display memory after a configurable
amount of time has elapsed instead.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-rs/-/merge_requests/754>
There is no point to that, the code is already factored in such
a way that erase_display_memory is inserted at the correct time,
including while loading the next pop-on captions in non displayed
memory.
Locking order of state and settings was inconsistent, and causing
deadlocks. Fix and document it, consistently drop locks before
chaining up events / pushing and avoid sequentially unlocking /
relocking settings in the same local code path.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-rs/-/merge_requests/539>
In roll-up modes, we open new lines when the last column is reached.
This commit implements lookahead on a word basis, in order to avoid
splitting words unless absolutely necessary (when a word won't fit
on a full row)
Up to now, tttocea608 supported text/utf8, and no interface to
control the positioning of closed captions apart from new lines
in the input text.
CEA 608 supports a larger set of features than that, such as
positioning CC precisely in its 32 x 15 grid, styling text,
switching from one mode to another, resetting the base row
in roll-up mode etc ..
A custom, JSON-based format is now supported by the element
(caps application/x-json, format=cea608), allowing users to
control those features in a pretty advanced manner.
A side effect of this is that the approach previously used
by the element to ensure frame-accurate CC display is now
untenable: where we knew before that an input buffer would
at most span 74 buffers and calculate a somewhat reasonable
latency based on that, this is no longer possible. Instead
we pick the approach most CC encoders seem to pick, and
accept a certain latency at display time: for example the
flipping of the back buffer to the display buffer for a
10-character text buffer will occur 7 frames after its
PTS. This has obvious benefits in terms of code complexity
and should generally be acceptable.
+ Removes a now irrelevant test, updates other tests
+ Extracts the Mode enum to the root of the crate, it will
be used by another element in a follow-up commit
