mirror of
https://gitlab.freedesktop.org/gstreamer/gstreamer.git
synced 2024-11-23 10:11:08 +00:00
109 lines
4.2 KiB
Text
109 lines
4.2 KiB
Text
Stream Status
|
|
-------------
|
|
|
|
This document describes the design and use cases for the stream status
|
|
messages.
|
|
|
|
STREAM_STATUS messages are posted on the bus when the state of a streaming
|
|
thread changes. The purpose of this message is to allow the application to
|
|
interact with the streaming thread properties, such as the thread priority or
|
|
the threadpool to use.
|
|
|
|
We accommodate for the following requirements:
|
|
|
|
- Application is informed when a streaming thread is about to be created. It
|
|
should be possible for the application to suggest a custom GstTask.
|
|
- Application is informed when the status of a streaming thread is changed.
|
|
This can be interesting for GUI application that want to visualize the status
|
|
of the streaming threads (playing/paused/stopped)
|
|
- Application is informed when a streaming thread is destroyed.
|
|
|
|
We allow for the following scenarios:
|
|
|
|
- Elements require a specific (internal) streaming thread to operate or the
|
|
application can create/specify a thread for the element.
|
|
- Elements allow the application to configure a priority on the threads.
|
|
|
|
|
|
Use cases
|
|
~~~~~~~~~
|
|
|
|
* boost the priority of the udp receiver streaming thread
|
|
|
|
.--------. .-------. .------. .-------.
|
|
| udpsrc | | depay | | adec | | asink |
|
|
| src->sink src->sink src->sink |
|
|
'--------' '-------' '------' '-------'
|
|
|
|
- when going from READY to PAUSED state, udpsrc will require a streaming
|
|
thread for pushing data into the depayloader. It will post a STREAM_STATUS
|
|
message indicating its requirement for a streaming thread.
|
|
|
|
- The application will usually react to the STREAM_STATUS messages with a sync
|
|
bus handler.
|
|
|
|
- The application can create and configure a custom GstTask to manage the
|
|
streaming thread or it can ignore the message which will make the element
|
|
use its default GstTask.
|
|
|
|
- The application can react to the ENTER/LEAVE stream status message to
|
|
configure the thread right before it is started/stopped. This can be used to
|
|
configure the thread priority.
|
|
|
|
- Before the GstTask is changed state (start/pause/stop) a STREAM_STATUS
|
|
message is posted that can be used by the application to keep track of
|
|
the running streaming threads.
|
|
|
|
|
|
Messages
|
|
~~~~~~~~
|
|
|
|
The existing STREAM_STATUS message will be further defined and implemented in
|
|
(selected) elements. The following fields will be contained in the message:
|
|
|
|
- "type", GST_TYPE_STREAM_STATUS_TYPE
|
|
|
|
- a set of types to control the lifecycle of the thread:
|
|
GST_STREAM_STATUS_TYPE_CREATE: a new streaming thread is going to be
|
|
created. The application has the chance to configure a custom thread.
|
|
GST_STREAM_STATUS_TYPE_ENTER: the streaming thread is about to enter its
|
|
loop function for the first time.
|
|
GST_STREAM_STATUS_TYPE_LEAVE: the streaming thread is about to leave its
|
|
loop.
|
|
GST_STREAM_STATUS_TYPE_DESTROY: a streaming thread is destroyed
|
|
|
|
- A set of types to control the state of the threads:
|
|
GST_STREAM_STATUS_TYPE_START: a streaming thread is started
|
|
GST_STREAM_STATUS_TYPE_PAUSE: a streaming thread is paused
|
|
GST_STREAM_STATUS_TYPE_STOP: a streaming thread is stopped
|
|
|
|
- "owner", GST_TYPE_ELEMENT
|
|
The owner element of the thread. The message source will contain the pad
|
|
(or one of the pads) that will produce data by this thread. If this thread
|
|
does not produce data on a pad, the message source will contain the owner
|
|
as well. The idea is that the application should be able to see from the
|
|
element/pad what function this thread has in the context of the
|
|
application and configure the thread appropriatly.
|
|
|
|
- "object", G_TYPE, GstTask/GThread
|
|
A GstTask/GThread controlling this streaming thread. This can be NULL when
|
|
the object controlling the streaming thread is not yet created.
|
|
|
|
- "flow-return", GstFlowReturn
|
|
A status code for why the thread state changed. when threads are created
|
|
and started, this is usually GST_FLOW_OK but when they are stopping it
|
|
contains the reason code why it stopped.
|
|
|
|
- "reason", G_TYPE_STRING
|
|
A string describing the reason why the thread started/stopped/paused.
|
|
Can be NULL if no reason is given.
|
|
|
|
|
|
|
|
Events
|
|
~~~~~~
|
|
|
|
|
|
|
|
|
|
|