Fixes https://gitlab.freedesktop.org/gstreamer/gst-plugins-bad/-/issues/1410
Created a new plugin 'webrtchttp' to implement all the
WebRTC HTTP protocols under /net/webrtc-http directory.
WhipSink wraps around 'webrtcbin' with HTTP capabilites
to exchange SDP offer/answer so an ICE/DTLS session can
be established between the encoder/media producer (WHIP client)
and the broadcasting ingestion endpoint (Media Server).
Once the ICE/DTLS session is set up, the media will
flow unidirectionally from the WHIP client to the
broadcasting ingestion endpoint (Media Server).
Spec:
https://www.ietf.org/archive/id/draft-ietf-wish-whip-04.html
The encoding of ONVIF metadata is always UTF-8. ONVIF metadata may
or may not be encoded with gzip, but we don't see a use case for
transporting compressed ONVIF metadata between elements for now.
The code tried to do this before but didn't consider the case where the
first pad has a valid running time, in which case the buffer with the
invalid running time would never be dequeued and the muxer would never
output anything.
Using callgrind with the standalone test showed opportunities for
improvements for sub tasks addition and drain.
All sub task additions were performed after making sure we were
operating on a Context Task. The Context and Task were checked
again when adding the sub task.
Draining sub tasks was perfomed in a loop on every call places,
checking whether there were remaining sub tasks first. This
commit implements the loop and checks directly in
`executor::Task::drain_subtasks`, saving one `Mutex` lock and
one `thread_local` access per iteration when there are sub
tasks to drain.
The `PadSink` functions wrapper were performing redundant checks
on the `Context` presence and were adding the delayed Future only
when there were already sub tasks.
Implement a test that initializes pipelines with minimalistic
theadshare src and sink. This can help with the evaluation of
changes to the threadshare runtime or with element
implementation details. It makes it easy to run flamegraph or
callgrind and to focus on the threadshare runtime overhead.
The aggregator was consuming meta buffers too greedily, causing
potential interleaving starvation upstream. Refactor to consume
media and meta buffers synchronously
Also expect parsed=true metadata caps (requiring an upstream
onvifmetadataparse element).
By moving sync on buffer ts to `try_next`, the resulting delay
can be cancelled when a state transition occurs.
To prevent item loss, this requires first peeking the incoming
item from the channel without popping it. After the delay has
elasped, we can pop the item as the last await point in
`try_next`: either it will be cancelled before popping or the
popped item will be passed on to `handle_item`.
Also add `flush` which was missing from `stop` and `flush_start`
transition actions.
Previous Task iteration model suffered from the following
shortcomings:
- When an iteration was engaged it could be cancelled at
await points by Stop or Flush state transitions,
which could lead to inconsistent states.
- When an iteration was engaged it could not be cancelled
by a Pause state transition so as to prevent data loss.
This meant we couldn't block on the Pause request because
the mechanism couldn't guarantee Paused would be reached
in a timely manner.
This commit split the Task iteration into:
- `try_next`: this function returns a future that awaits
for a new iteration to begin. The regular use case is
to return an item to process. The item can be left to
`()` if `try_next` acts as a tick generator. It can
also return an error. This function can be cancelled at
await points when a state transition request occurs.
- `handle_item`: this function is called with the item
returned by `try_next` and is guaranteed to run to
completion even if a transition request is received.
Note that this model plays well with the common Future
cancellation pitfalls in Rust.
