queue
Data is queued until one of the limits specified by the max-size-buffers, max-size-bytes and/or max-size-time properties has been reached. Any attempt to push more buffers into the queue will block the pushing thread until more space becomes available.
The queue will create a new thread on the source pad to decouple the processing on sink and source pad.
You can query how many buffers are queued by reading the current-level-buffers property. If you set notify-levels to TRUE, you can track changes by connecting to the notify::current-level-buffers signal (which like all signals will be emitted from the streaming thread). The same applies to the current-level-time and current-level-bytes properties.
The default queue size limits are 200 buffers, 10MB of data, or one second worth of data, whichever is reached first.
As said earlier, the queue blocks by default when one of the specified maximums (bytes, time, buffers) has been reached. You can set the leaky property to specify that instead of blocking it should leak (drop) new or old buffers.
The underrun signal is emitted when the queue has less data than the specified minimum thresholds require (by default: when the queue is empty). The overrun signal is emitted when the queue is filled up. Both signals are emitted from the context of the streaming thread.
Hierarchy
GObject ╰──GInitiallyUnowned ╰──GstObject ╰──GstElement ╰──queue
Factory details
Authors: – Erik Walthinsen
Classification: – Generic
Rank – none
Plugin – coreelements
Package – GStreamer
Pad Templates
Signals
overrun
overrun_callback (GstElement * queue, gpointer udata)
def overrun_callback (queue, udata):
#python callback for the 'overrun' signal
function overrun_callback(queue: GstElement * queue, udata: gpointer udata): {
// javascript callback for the 'overrun' signal
}
Reports that the buffer became full (overrun). A buffer is full if the total amount of data inside it (num-buffers, time, size) is higher than the boundary values which can be set through the GObject properties.
Parameters:
queue
–
the queue instance
udata
–
Flags: Run First
pushing
pushing_callback (GstElement * queue, gpointer udata)
def pushing_callback (queue, udata):
#python callback for the 'pushing' signal
function pushing_callback(queue: GstElement * queue, udata: gpointer udata): {
// javascript callback for the 'pushing' signal
}
Reports when the queue has enough data to start pushing data again on the source pad.
Parameters:
queue
–
the queue instance
udata
–
Flags: Run First
running
running_callback (GstElement * queue, gpointer udata)
def running_callback (queue, udata):
#python callback for the 'running' signal
function running_callback(queue: GstElement * queue, udata: gpointer udata): {
// javascript callback for the 'running' signal
}
Reports that enough (min-threshold) data is in the queue. Use this signal together with the underrun signal to pause the pipeline on underrun and wait for the queue to fill-up before resume playback.
Parameters:
queue
–
the queue instance
udata
–
Flags: Run First
underrun
underrun_callback (GstElement * queue, gpointer udata)
def underrun_callback (queue, udata):
#python callback for the 'underrun' signal
function underrun_callback(queue: GstElement * queue, udata: gpointer udata): {
// javascript callback for the 'underrun' signal
}
Reports that the buffer became empty (underrun). A buffer is empty if the total amount of data inside it (num-buffers, time, size) is lower than the boundary values which can be set through the GObject properties.
Parameters:
queue
–
the queue instance
udata
–
Flags: Run First
Properties
current-level-buffers
“current-level-buffers” guint
Current number of buffers in the queue
Flags : Read
Default value : 0
current-level-bytes
“current-level-bytes” guint
Current amount of data in the queue (bytes)
Flags : Read
Default value : 0
current-level-time
“current-level-time” guint64
Current amount of data in the queue (in ns)
Flags : Read
Default value : 0
flush-on-eos
“flush-on-eos” gboolean
Discard all data in the queue when an EOS event is received, and pass on the EOS event as soon as possible (instead of waiting until all buffers in the queue have been processed, which is the default behaviour).
Flushing the queue on EOS might be useful when capturing and encoding from a live source, to finish up the recording quickly in cases when the encoder is slow. Note that this might mean some data from the end of the recording data might be lost though (never more than the configured max. sizes though).
Flags : Read / Write
Default value : false
Since : 1.2
leaky
“leaky” Queue-leaky *
Where the queue leaks, if at all
Flags : Read / Write
Default value : no (0)
max-size-buffers
“max-size-buffers” guint
Max. number of buffers in the queue (0=disable)
Flags : Read / Write
Default value : 200
max-size-bytes
“max-size-bytes” guint
Max. amount of data in the queue (bytes, 0=disable)
Flags : Read / Write
Default value : 10485760
max-size-time
“max-size-time” guint64
Max. amount of data in the queue (in ns, 0=disable)
Flags : Read / Write
Default value : 1000000000
min-threshold-buffers
“min-threshold-buffers” guint
Min. number of buffers in the queue to allow reading (0=disable)
Flags : Read / Write
Default value : 0
min-threshold-bytes
“min-threshold-bytes” guint
Min. amount of data in the queue to allow reading (bytes, 0=disable)
Flags : Read / Write
Default value : 0
min-threshold-time
“min-threshold-time” guint64
Min. amount of data in the queue to allow reading (in ns, 0=disable)
Flags : Read / Write
Default value : 0
notify-levels
“notify-levels” gboolean
Whether to emit notify:property-name signals on levels changes or not
Default: FALSE
Flags : Read / Write
Default value : false
Since : 1.26
silent
“silent” gboolean
Don't emit queue signals. Makes queues more lightweight if no signals are needed.
Flags : Read / Write
Default value : false
Named constants
Queue-leaky
Buffer dropping scheme to avoid the queue to block when full.
Members
no (0) – Not Leaky
upstream (1) – Leaky on upstream (new buffers)
downstream (2) – Leaky on downstream (old buffers)
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