This enables a use case for preparing slow to start up sources
ahead of time in a live cueing system, where a stream is scheduled
to start at some point in the future, and the application wants to
make sure it is ready for prime time by that time, instead of
spinning it up at the last moment and waiting for the stream to
actually come up.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-rs/-/merge_requests/515>
When only the backup pad is receiving buffers, and the primary
pad is a bit slow to start up (eg network source with buffering),
it makes for a better UX to output buffers from the backup pad
while waiting for the network source to make its move.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-rs/-/merge_requests/515>
This new element puts together some of the elements we've written
in recent times (awstranscriber, tttocea608, textwrap, cccombiner)
into a convenience high-level element.
The design of the element is AV in -> AV (+ CC metas) out.
The element exposes property to set and unset a "passthrough" mode,
during which the transcriber element's state is set to NULL but kept
in the bin, in order for the user to be able to set properties on
sub elements no matter what the current mode is, using the
GstChildProxy interface.
In addition, the element ensures that the latency it reports stays
fixed so that playback continues uninterrupted.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-rs/-/merge_requests/528>
As awstranscriber might in theory push out gap events without
any flow of input data, it needs to send its mandatory events
(stream-start, caps, segment) independently.
In addition, track a start time and use it to offset the 0-based
timestamps returned by AWS in order to output buffers timestamped
in the running-time domain, and perform item timing adjustment
only when dequeuing, instead of when queuing.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-rs/-/merge_requests/525>
and use 0 instead of -1 to disable accumulation. In practice 0
already had the same effect, and this lets us get rid of unsafe
code that actually breaks inspection of the element.
<https://aws.amazon.com/blogs/machine-learning/amazon-transcribe-now-supports-partial-results-stabilization-for-streaming-audio/>
Amazon seem to have realized the previous iteration of their API
made it difficult to identify items from one result to the next,
which made the element much more complicated than it should have
been. With that new "stability" option, we can enqueue items as
soon as they stabilize, and simply rely on the current index in
the transcript to output them exactly once.
This also means the "use_partial_results" is now useless, as there
will be no difference in accuracy between a non-partial result and
and of its stable items that might have been pushed from previous
partial versions of the result.
The property is removed, instead a new option is exposed to let
users control how fast results should stabilize.
This greatly simplifies the code, and also improves the output as
punctuation doesn't need to be randomly discarded anymore.
As stated in the spec:
> In addition, the user must have the capability to select a black
> background over which the captioned letters are displaced.
The property is MUTABLE_PLAYING
It rejects code such as:
```rust
if state
.start_ts
.zip(accumulate_time)
.map_or(false, |(start_ts, accumulate_time)| {
start_ts + accumulate_time < pts
})
```
because it looks like:
```rust
if { true }
```
csound-sys can detect the system lib using either pkg-config or using
the CSOUND_LIB_DIR env variable.
The former case just work but the second is trickier as we need to
ensure that CSOUND_LIB_DIR is defined when building.
So we no longer try to detect the lib using find_library() if user
didn't define the env variable as the build will fail later.
Also explicitly pass the env variable to cargo so user can now call
'CSOUND_LIB_DIR=/usr/lib64 meson build && ninja -C build'
and have it work without repassing the env variable to ninja.
Using ubuntu 20.04, the build was failing with version
cargo 0.47 / rustc 1.47.
Following this discussion:
https://github.com/rust-lang/cargo/issues/9340
it appears that rustc 1.52 is the minimum version.
